Petroleum products, selected (EHC 20, 1982)

IPCS INTERNATIONAL PROGRAMME ON CHEMICAL SAFETY

ENVIRONMENTAL HEALTH CRITERIA 20

SELECTED PETROLEUM PRODUCTS

This report contains the collective views of an
international group of experts and does not
necessarily represent the decisions or the stated
policy of the United Nations Environment Programme,
the International Labour Organisation, or the World
Health Organization.

Published under the joint sponsorship of
the United Nations Environment Programme,
the International Labour Organisation,
and the World Health Organization

World Health Organization
Geneva, 1982

The International Programme on Chemical Safety (IPCS) is a joint
venture of the United Nations Environment Programme, the International
Labour Organisation, and the World Health Organization. The main
objective of the IPCS is to carry out and disseminate evaluations of
the effects of chemicals on human health and the quality of the
environment. Supporting activities include the development of
epidemiological, experimental laboratory, and risk-assessment methods
that could produce internationally comparable results, and the
development of manpower in the field of toxicology. Other activities
carried out by IPCS include the development of know-how for coping
with chemical accidents, coordination of laboratory testing and
epidemiological studies, and promotion of research on the mechanisms
of the biological action of chemicals.

ISBN 92 4 154080 X

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CONTENTS

ENVIRONMENTAL HEALTH CRITERIA FOR SELECTED PETROLEUM PRODUCTS

1. SUMMARY AND RECOMMENDATIONS FOR FURTHER STUDIES
1.1. Summary
1.1.1. Properties and analytical methods
1.1.1.1 Properties
1.1.1.2 Analytical methods
1.1.2. Sources of environmental pollution
1.1.3. Environmental concentrations and levels of exposure
1.1.3.1 General population exposure
1.1.3.2 Occupational exposure
1.1.4. Effects on experimental animals
1.1.5. Clinical and epidemiological studies in man
1.1.6. Evaluation of health risks
1.1.7. Control measures
1.2. Recommendations for further studies
1.2.1. Analytical aspects
1.2.2. Sources and levels in the environment
1.2.3. Studies on experimental animals
1.2.4. Human studies

2. CRUDE OILS
2.1. Properties and analytical methods
2.1.1. Chemical composition and properties
2.1.2. Methods of sampling and analysis
2.1.2.1 Gases and vapours
2.1.2.2 Aerosols
2.2. Sources of environmental pollution
2.2.1. Natural occurrence
2.2.2. Man-made sources
2.2.2.1 Production
2.2.2.2 Uses
2.2.2.3 Disposal of waste
2.3. Toxicological effects of crude oils
2.3.1. Effects on experimental animals
2.3.2. Effects on man

3. PETROLEUM SOLVENTS
3.1. Properties and analytical methods
3.1.1. Chemical composition and properties
3.1.1.1 Special boiling point solvents (SBPs)
3.1.1.2 White spirits
3.1.1.3 High boiling aromatic solvents
3.1.2. Purity of petroleum solvents
3.1.3. Methods of sampling and analysis

3.2. Sources of environmental pollution
3.2.1. Natural occurrence
3.2.2. Man-made sources
3.2.2.1 Production
3.2.2.2 Uses
3.3. Environmental exposure levels
3.4. Environmental distribution and transformation
3.5. Metabolism
3.5.1. Absorption
3.5.2. Distribution in the body
3.5.3. Biotransformation
3.5.4. Elimination
3.6. Effects on experimental animals
3.6.1. Short-term exposure
3.6.2. Long-term exposure
3.6.3. Mutagenicity, teratogenicity, and carcinogenicity
3.6.3.1 Mutagenicity
3.6.3.2 Teratogenicity
3.6.3.3 Carcinogenicity
3.7. Effects on man
3.7.1. Controlled exposures
3.7.1.1 Effects of dermal exposure
3.7.1.2 Effects of inhalation
3.7.2. Epidemiological studies
3.7.2.1 Occupational exposure
3.7.2.2 General population exposure
3.7.3. Clinical studies
3.7.3.1 Effects of dermal exposure
3.7.3.2 Effects of inhalation
3.7.3.3 Effects of ingestion

4. LUBRICATING BASE OILS AND RELATED OILS, GREASES, AND WAXES
4.1. Properties and analytical methods
4.1.1. Chemical and physical properties
4.1.1.1 Purity of product
4.1.2. Methods of sampling and analysis
4.2. Sources of environmental pollution
4.2.1. Natural occurrence
4.2.2. Man-made sources
4.2.2.1 Production
4.2.2.2 Uses
4.2.2.3 Disposal of waste
4.3. Environmental exposure levels
4.4. Environmental distribution and transformation
4.5. Metabolism
4.6. Effects on experimental animals
4.6.1. Short-term exposure
4.6.1.1 Effects of dermal exposure

4.6.2. Long-term exposure
4.6.2.1 Carcinogenic effects
4.6.2.2 Effects of dermal exposure and
subcutaneous administration
4.6.2.3 Effects of inhalation and intratracheal
exposures
4.6.2.4 Dietary studies
4.7. Effects on man
4.7.1. Occupational exposure
4.7.1.1 Skin disorders
4.7.1.2 Skin carcinogenicity
4.7.1.3 Effects of off mist exposure
4.8. Clinical studies

5. BITUMEN
5.1. Properties and analytical methods
5.1.1. Chemical and physical properties
5.1.2. Methods of sampling and analysis
5.2. Sources of environmental pollution
5.2.1. Natural sources
5.2.2. Man-made sources
5.2.2.1 Production
5.2.2.2 Uses
5.3. Environmental exposure levels
5.4. Environmental distribution and transformation
5.5. Metabolism
5.6. Effects on experimental animals
5.6.1. Short-term exposure
5.6.2. Long-term exposure
5.7. Effects on man
5.7.1. Epidemiological studies
5.7.1.1 Occupational exposure
5.7.1.2 General population exposure
5.7.1.3 High (accidental) exposure
5.7.2. Clinical studies

6. EVALUATION OF HEALTH RISKS FROM EXPOSURE TO CRUDE OILS AND
SELECTED PETROLEUM PRODUCTS
6.1. Crude oils
6.2. Petroleum solvents
6.3. Lubricating base oils, greases, and waxes
6.4. Bitumen

7. CONTROL MEASURES
7.1. General
7.2. Petroleum solvents
7.3. Lubricating base oils, greases, and waxes
7.4. Bitumen

REFERENCES

NOTE TO READERS OF THE CRITERIA DOCUMENTS

While every effort has been made to present information in the
criteria documents as accurately as possible without unduly delaying
theft publication, mistakes might have occurred and are likely to
occur in the future. In the interest of all users of the environmental
health criteria documents, readers are kindly requested to communicate
any errors found to the Division of Environmental Health, World Health
Organization, Geneva, Switzerland, in order that they may be included
in corrigenda which will appear in subsequent volumes.

In addition, experts in any particular field dealt with in the
criteria documents are kindly requested to make available to the WHO
Secretariat any important published information that may have
inadvertently been omitted and which may change the evaluation of
health risks from exposure to the environmental agent under
examination, so that the information may be considered in the event of
updating and re-evaluation of the conclusions contained in the
criteria documents.

WHO TASK GROUP ON ENVIRONMENTAL HEALTH CRITERIA FOR SELECTED PETROLEUM
PRODUCTS

Members

Dr D. A. Akintonwa, Department of Biochemistry, Faculty of Medicine,
University of Calabar, Calabar, Nigeria

Dr L. Boniforti, Department of Contaminants, Laboratory of Toxicology,
Institute of Health, Rome, Italy

Dr K. W. Jager, Shell Internationale Research, Maatschappij B.V., The
Hague, Netherlands (Rapporteur)

Professor L. Jirásek, 1st Dermatological Clinic, Charles University,
Prague, Czechoslovakia

Professor A. A. Kasparov, Institute of Industrial Hygiene and
Occupational Diseases, Academy of Medical Sciences, Moscow, USSR
(Vice-Chairman)

Professor W. O. Phoon, Department of Social Medicine and Public
Health, Faculty of Medicine, University of Singapore, Singapore
(Chairman)

Dr M. Rouhani, Institute of Occupational Safety and Health, Ministry
of Labour and Social Affairs, Teheran, Iran (Present address:
Nice, France)

Dr E. Schmidt, Directorate of Malariology and Environmental
Sanitation, Ministry of Health and Welfare, Caracas, Venezuela

Dr N. K. Weaver, American Petroleum Institute, Washington DC, USA

Representatives of other organizations

Dr P. V. C. Pinnagoda, International Labour Organisation, Geneva,
Switzerland

Professor L. Parmeggiani, Permanent Commission and International
Association on Occupational Health

Dr J. W. Huismans, International Register of Potentially Toxic
Chemicals, United Nations Environment Programme, Geneva,
Switzerland

Mr J. Wilbourn, International Agency for Research on Cancer, Lyons,
France

Secretariat

Dr A. David, Medical Officer, Office of Occupational Health, World
Health Organization, Geneva, Switzerland (Co-Secretary)

Dr M. A. El Batawi, Chief Medical Officer, Office of Occupational
Health, World Health Organization, Geneva, Switzerland

Mrs B. Goelzer, Scientist, Office of Occupational Health, World Health
Organization, Geneva, Switzerland (Co-Secretary)

Dr Y. Hasegawa, Medical Officer, Environmental Health Criteria and
Standards, World Health Organization, Geneva, Switzerland

Dr M. Sharratt, Senior Toxicologist, BP Group Occupational Health
Centre, Middlesex, England (Temporary Adviser)

ENVIRONMENTAL HEALTH CRITERIA FOR SELECTED PETROLEUM PRODUCTS

Further to the recommendations of the Stockholm United Nations
Conference on the Human Environment in 1972, and in response to a
number of World Health Assembly Resolutions and the recommendation of
the Governing Council of the United Nations Environment Programme, a
programme on the integrated assessment of the health effects of
environmental pollution was initiated in 1973. The programme, known as
the WHO Environmental Health Criteria Programme, has been implemented
with the support of the Environment Fund of the United Nations
Environment Programme. In 1980, the Environmental Health Criteria
Programme was incorporated into the International Programme on
Chemical Safety. The result of the Environmental Health Criteria
Programme is a series of criteria documents.

The Office of Occupational Health, WHO, was the unit responsible
for the development of the Environmental Health Criteria document on
Selected Petroleum Products.

The Task Group for this document met in Geneva from 15-19 October
1979. The meeting was opened by Dr M. A. El Batawi, Chief, Office of
Occupational Health, who welcomed the participants and the
representatives of other international organizations on behalf of the
Director-General.

The Task Group reviewed and revised the second draft criteria
document and made an evaluation of the health risks of exposure to
selected petroleum products.

The first and second drafts were prepared by Dr K. W. Jager,
Shell Internationale Research, Maatschappij B. V., The Hague,
Netherlands. Comments on the second draft, which have been
incorporated in this report, were received from the national focal
points for the WHO Environmental Health Criteria Programme in
Australia, the Federal Republic of Germany, Mexico, the United
Kingdom, and the USA, and from the WHO Collaborating Centres of
Occupational Health in: Chile, Finland, Indonesia, Netherlands,
Singapore, Sweden, Switzerland, the United Kingdom, and the USSR.
Additional comments were received from Dr. R. E. Eckardt (USA), Dr M.
Rouhani (Iran), from the International Petroleum Industry
Environmental Conservation Association, and from the American
Petroleum Institute.

The collaboration of these national institutions, international
organizations, and individual experts is gratefully acknowledged. The
Secretariat also wishes to thank Dr K. W. Jager and Dr M. Sharratt for
their invaluable assistance in the final stages of the preparation of
the document.

As the final text of the evaluation could not be distributed at
the meeting, it was circulated to all participants in November 1978.
The comments received were then considered by the Rapporteur and some
members of the Secretariat, and suggested alterations were included.
Later, section 2.1.2, Methods of sampling and analysis, was completely
rewritten by Mr. T. P. C. M. van Dongen of the Shell Laboratory
(Amsterdam) and Dr K. W. Jager, the Rapporteur.

The document has been based, primarily, on original publications
listed in the reference section. However, several recent reviews of
health aspects of petroleum products have also been used, including:
Petroleum Handbook (1966); API Toxicology Reviews (API, 1965, 1967,
1969); US DHEW (1970); and Lazarev & Levina (1976).

The purpose of this document is to review and evaluate available
information on the biological effects of some petroleum products, and
to provide a scientific basis for decisions aimed at the protection of
human health from the adverse consequences of exposure to these
substances in both the occupational and general environments.

It was only feasible to discuss several groups of related
products, and to select priorities among them. Thus, non-fuel products
derived from crude oils are considered in three broad groups, i.e.,
petroleum solvents, lubricating base-oils, and bitumens. These have
been selected as priorities, because of their widespread use and
because large sub-groups of the population may come into close contact
with them through occupational or domestic use. Moreover, adverse
health effects are known to occur from occupational exposure to some
of these products.

Base chemicals derived from the cracking of crude oil fractions,
such as ethylene, propylene, and other olefins, and fuels derived from
crude oils ranging from gasoline to heavy fuel oil, are not discussed
in this document. As fuels and non-fuels of a similar boiling range
may have similar effects, e.g., on the skin or, after aspiration, on
the respiratory tract, most toxicological data discussed in this
review are more or less relevant to crude oil-derived fuels of a
similar boiling range. In fact, it is impossible to make a strict
division between data relating to fuels and non-fuels and they have
been considered together, whenever relevant.

The published literature and other available information have
been critically evaluated and where possible, an attempt has been made
to establish whether or not, under certain conditions, a potential
risk to man exists. Suggestions for avoiding established risks and for
further studies have also been made.

The environmental impact, if any, of the products has only been
considered where it is directly related to the health of man.

Details of the WHO Environmental Health Criteria Programme
including some terms frequently used in the document may be found in
the general introduction to the Environmental Health Criteria
Programme published together with the environmental health criteria
document on mercury (Environmental Health Criteria 1, Mercury, Geneva,
World Health Organization, 1976), now also available as a reprint.

Financial support for the publication of this criteria document
was kindly provided by the United States Department of Health and
Human Services through a contract from the National Institute of
Environmental Health Sciences, Research Triangle Park, North Carolina,
USA -- a WHO Collaborating Centre for Environmental Health Effects.

The following conversion factors have been used in the present
document:

benzene 1 ppm = 3.0 mg/m³

gasoline 1 ppm = 4.5 mg/m^3a

heptane 1 ppm = 4.0 mg/m³

hexane 1 ppm = 3.6 mg/m³

octane 1 ppm = 4.85 mg/m³

pentane 1 ppm = 3.0 mg/m³

toluene 1 ppm = 3.75 mg/m³

xylene 1 ppm = 4.35 mg/m³

^a A conversion factor for gasoline of 1 ppm = 4.5 mg/m³ has been
used throughout the document, though this factor normally varies
according to the composition of the gasoline.

1. SUMMARY AND RECOMMENDATIONS FOR FURTHER STUDIES

1.1 Summary

1.1.1 Properties and analytical methods

1.1.1.1 Properties

(a) Crude oils are a complex mixture of straight and branched
chain paraffinic, cycloparaffinic, aromatic and polynuclear aromatic
hydrocarbons together with small amounts of sulfur and nitrogen
compounds. The composition of crude oils varies considerably with
geographical origin. They can be broadly divided into paraffinic,
asphaltic, and mixed crude oils. Paraffinic crude oils provide large
amounts of paraffinic hydrocarbons, paraffin wax, and high grade oils,
while asphaltic crude oils province more cycloparaffins and high
viscosity lubricating oils.

(b) Petroleum solvents, produced by the distillation of crude
oils, are also complex mixtures of hydrocarbons. They are generally
classified on the basis of distillation ranges. Special boiling-point
solvents, such as petroleum ether and rubber solvent, are mixtures of
C-5 to C-9 normal- and branched-chain paraffins and cycloparaffins
with a boiling-range of 30-160°C. With solvents such as Stoddard
solvent, mineral spirits, and low aromatic white spirits, the chain
lengths are longer (C-7 to C-12) and the boiling-range higher
(150-220°C) and they contain various amounts of aromatic compounds.
Higher boiling-point solvents (B.P. 160-300°C) containing more than 9
carbon atoms per molecule are also produced.

(c) Lubricant base oils, greases, and waxes are products with
boiling-points in the range of 300-700°C that are normally produced by
high-vacuum distillation of the residues of the initial distillation.

(d) Bitumen, the solid and semi-solid residue of the
distillation process, varies from a highly viscous liquid to a brittle
solid, at ambient temperatures, and consists of a mixture of
asphaltenes (high relative molecular mass aromatic and heterocyclic
hydrocarbons), resins (polymers formed from unsaturated hydrocarbons
during processing), together with saturated hydrocarbons and aromatic
hydrocarbons containing one or more benzene rings per molecule
(including polynuclear aromatic hydrocarbons).

1.1.1.2 Analytical methods

A vast and specialized literature on sampling methods and
analytical techniques is available for petroleum products. Many
techniques have proved useful, e.g., infrared spectroscopy, thin-layer
chromatography, ultraviolet fluorescent spectrometry, capillary
gaschromatography, and chromatography combined with mass spectrometry.

1.1.2 Sources of environmental pollution

(a) Crude oil is normally transported in large volumes in
tankers and pipelines. Breakdown or leakage of these may cause a major
and sudden environmental hazard. Less significant degrees of pollution
have resulted from the cleaning out of oil tankers. Certain volatile
components, especially hydrogen sulfide but also other sulfur
compounds, acids, and hydrocarbons may contaminate the atmosphere near
oilfields and refineries.

(b) As a rule, petroleum solvents do not present serious
pollution problems for the general population, since they are mainly
used in industry and seldom domestically. Spillage or use in poorly
ventilated rooms or without proper control measures may cause serious
work-place pollution. Solvents containing n-hexane or benzene may
present particular hazards with respect to health.

(c) Because of theft nature and uses, lubricating base oils,
greases, and waxes rarely present problems for the general population
though spillage may create localized environmental problems. However,
in industry, some of these products, especially the metal working
oils, may produce marked contamination of the workplace and equipment.

(d) From the available evidence, it appears that bitumen is not
a significant source of environmental pollution but, under certain
conditions, occupational exposure may occur.

1.1.3 Environmental concentrations and levels of exposure

1.1.3.1 General population exposure

Little information is available concerning the concentrations of
petroleum products in air, water, or food. Most of the crude oils are
produced from deep wells, but natural seepage occurs on land and on
the sea-bed. Natural bitumen and asphalt deposits occur in several
parts of the world. There are not sufficient data available to
estimate the total environmental exposure of human beings to these
petroleum products. On occasions, the general population may be
exposed for short periods to fumes from heated bitumen used in road
building or roofing. Small amounts of hydrocarbons, probably derived
from petroleum hydrocarbons, have been found in shell fish. Volatile
petroleum components may contribute to atmospheric pollution near
refineries, and storage and pumping areas.

1.1.3.2 Occupational exposure

(a) Crude oil is usually handled in closed systems from oil
well to refinery, so that workers are not exposed to it, unless a
serious breakdown or leakage occurs. However, volatile components can
escape at well heads, pump glands, or through vents in storage tanks
and tanks on ships.

(b) Petroleum solvents are extensively manufactured and are
widely used in many occupations. Because of their volatility,
industrial exposure to "special-boiling-point" spirits can sometimes
be high. Excessive exposure has occurred and has caused ill health in
workshops where ventilation was insufficient. With white spirits, skin
contact is usually of greater importance than inhalation, at least at
ambient temperatures. Skin contact is particularly important in
relation to high aromatic solvents, since the aromatic moieties tend
to penetrate skin readily. Both skin contact and exposure to fumes or
mists of high boiling-point aromatic solvents can occur
occupationally.

(c) The extent of occupational exposure to lubricating oils,
greases, and waxes depends on the occupation and on the precautions
adopted. Some lubricants and transformer oils are handled only
occasionally, while work with automatic lathes of old design can
result not only in direct contamination of clothes and exposed skin,
but also in the inhalation of oil mist that may be produced by the
machine and will further contaminate the skin and clothing. Moreover,
other equipment, floors, and even roofs may become contaminated.

(d) Extensive exposure to bitumen may occur in such occupations
as roadbuilding and repairing, roofing, and flooring.

1.1.4 Effects on experimental animals

(a) Crude oil

Toxicological studies on mice and rabbits have shown that, in
general, the tumorogenicity of crude oils is lower than that of some
distilled fractions.

(b) Petroleum solvents

The few data available suggest that solvents are readily absorbed
when inhaled or ingested and that excretion is also rapid. The
metabolic products of benzene and n-hexane are well established but
the metabolism of other petroleum solvents is not well documented.

Animal studies have been complicated by the fact that mixtures
have generally been studied and that the composition of superficially
similar products can vary greatly. However, studies on representative
samples have demonstrated that solvents present a low oral and
percutaneous hazard for rats. Skin is severely damaged only on
prolonged, repeated contact; "short-chain" solvents mainly have a
defatting action, while dermatotoxic effects are found with

"longer-chain" solvents. In general, the higher the aromatic content
of the solvents, the more intense the effects, whatever the route of
exposure. In short-term exposure (4-8 h) of rats, atmospheric
concentrations causing the death of 50% of animals (LC₅₀) ranged
mainly from approximately 1000-15 000 ppm. The main signs of poisoning
were respiratory tract irritation, depression of the central nervous
system (CNS), and coma, followed rapidly by death.

The presence of small volumes of solvent in the respiratory tract
led to chemical pneumonitis in all species tested. The degree of
injury depended on the viscosity rather than on the chemical nature of
the materials; the higher the viscosity, the lower the possibility of
aspiration into the deeper parts of the lungs.

Repeated exposure of rats, cats, and dogs to the vapours of a
wide range of petroleum solvents showed that the toxicity was
consistently low. However, exposure to n-hexane resulted in
pathological changes similar to those associated with peripheral
neuropathy in man. The maximum no-observed-adverse-effect level for
n-hexane is not yet certain. Results of teratogenicity studies on a
wide range of hydrocarbon solvents have been essentially negative.

Benzene and the aromatic extracts are the only well-defined
petroleum solvents for which carcinogenicity has been reported.

These substances are of low acute oral and dermal toxicity,
though high oral doses have a laxative effect.

In long-term studies on mice, rats, guineapigs, and rabbits, it
has been demonstrated that the carcinogenic activity of these products
resides in the polynuclear aromatic hydrocarbon fraction. By suitable
refining, oils, greases, and waxes can be obtained that consistently
give negative results in skin-painting tests. The most potentially
carcinogenic substances have been found among the 4,5, and 6 condensed
ring polynuclear compounds with relative molecular masses ranging from
230 to 330. Experimental evidence suggests that some long-chain
aliphatic, alicyclic, and alkylaromatic hydrocarbons may act as
co-carcinogens, when applied to the skin together with the
carcinogenic fraction.

It has been shown that washing the skin of animals after
application of carcinogenic oils decreases both the number and rate of
appearance of tumours. The degree of reduction is related to the time
between application and washing. A lowering of the frequency of
application of the oils also reduces the rate of tumour development.

Carcinogenic activity has been demonstrated in certain
metal-working and textile oil formulations and there is evidence that
carcinogenic polynuclear aromatic compounds may be produced, when oil
products are subjected to high temperatures.

Aspiration of oils has been shown to induce a foreign body
reaction in animal lungs as well as lipid pneumonia. However, when
animals were exposed to oil mist, very little was retained in the
lungs, and lipid pneumonia did not occur, even at high exposure
levels. From studies on the mouse, rat, hamster, rabbit, and dog, it
would appear that atmospheric exposure to 5 mg/m³ of oil mist is
without risk.

Oral administration of food-grade mineral oils and waxes to rats
did not result in any carcinogenic or chronic toxic effects.

(d) Bitumens

Although some bitumens applied to the skin of mice exhibit
carcinogenic activity, it is low compared with that of coal tar, and
it is generally accepted that the toxicity of bitumens is low.

1.1.5 Clinical and epidemiological studies in man

(a) Crude oils

Many cases of keratotic changes and epithelioma on exposed parts
of the skin have been reported in workers exposed to crude oils. The
relative roles of the oil and of other factors, e.g., sunlight, is
uncertain.

(b) Petroleum solvents

Petroleum solvents with boiling-ranges up to 230°C are primary
irritants, though their irritant and defatting actions decrease as the
boiling-range increases. Solvents of naphthenic origin or with a high
aromatic content tend to be the most irritant. On repeated contact,
the keratin layer of the skin is damaged, making the skin more
susceptible to other irritants, sensitizing agents, and bacteria.

Acute occupational poisoning by gasoline vapour has usually been
the result of entering unpurged gasoline tanks or other premises,
where high concentrations of gasoline vapour have accumulated. With
increasing concentrations of gasoline vapour, exposed subjects may
experience drowsiness, dullness, numbness, and headache followed by
dizziness, ataxia, and nausea. Exposure to higher concentrations of
vapour, or for a longer period, may lead to loss of consciousness
followed by death, which may be preceded by convulsions.

In the last 15 years, an increasing number of cases of
polyneuropathy have been reported in workers exposed to high
concentrations of volatile petroleum solvents, mainly consisting of
technical hexane. Though n-hexane seems to play a major role, the
possibility that other components of the solvents may have a similar
or synergistic action cannot be ruled out.

Ingestion of large volumes of solvent is usually well tolerated,
unless aspiration occurs. Small volumes (1-2 ml) of kerosene will, if
aspirated, cause acute chemical pneumonitis, which is often fatal. The
prognosis of chemical aspiration pneumonitis has improved over the
past years with improved methods of treatment. Where no aspiration
occurs, the symptoms are similar to those following over-exposure to
vapour.

Long-term exposure to low vapour concentrations has been reported
to produce non-specific symptoms such as nervousness, loss of
appetite, and nausea. Other symptoms referable to the peripheral and
central nervous systems, the gastrointestinal tract, the lungs, eyes,
and reproductive system have also been described. No
dose-concentration effect relationships can be derived from present
knowledge either for short-term or long-term exposures. It is
considered probable that blood abnormalities, previously reported
following exposure to solvents, were, in fact, due to the presence of
benzene in the solvents.

Exposure of the skin to these products can induce several types
of disorder including primary irritation, oil ache, hyperkeratosis,
and photosensitivity. The degree of severity of these disorders
depends on the nature of the oil, the integrity of skin, the frequency
and length of contact, and individual susceptibility. In general,
lower-boiling-point materials have a more pronounced defatting effect,
while the higher-boiling-point materials induce the formation of acne.
In many cases, additives or contaminants in the oils are responsible
for the disorders, rather than the oil itself.

Prolonged exposure to non-solvent, refined mineral oils has been
associated with the induction of cancer of the scrotum, e.g., in
machine operators and those involved in spinning operations. Less
frequently, cancer at other sites, including the hand and forearm,
lung, and bronchus have been associated with exposure to oils
containing significant concentrations of polynuclear aromatic
compounds. Results of epidemiological studies have suggested an
association between exposure to oil mist and an increased incidence of
pulmonary cancer. However, the exact levels of exposure to the oils
and polynuclear aromatic compounds in these studies is not known. Very
rarely, cases have been reported of lipid pneumonia associated with
prolonged exposure to high concentrations of oil mist. Whether there
was a causal relationship is uncertain.

(d) Bitumen

Evidence from epidemiological studies on workers in oil
refineries, highway construction, roofing industries, and bitumen
transport firms strongly suggests that petroleum-based bitumens do not
present a significant health hazard.

The possibility that bitumen and the vapours emanating from it
might contribute to the overall incidence of cancer of the skin and of
the respiratory tract has to be considered in view of their content of
polynuclear aromatic compounds, but there are no data to substantiate
this.

1.1.6 Evaluation of health risks

Available information indicates that the health risks for the
general population from the production of crude oil and the
manufacture and use of petroleum products are very low. Under normal
circumstances, there is, at the most, a nuisance because of pollution
of the air and/or water.

The major risks are related to the health of workers involved in
the manufacture or handling of these products.

Exposure to high concentrations of the vapour of petroleum
solvents can produce narcotic effects. Long-term exposures to low
concentrations have been reported to produce non-specific symptoms.
The no-observed-adverse-effect level of exposure has not been
established for these products. Prolonged exposure to n-hexane has
resulted in the development of polyneuropathies most of which have
proved reversible on cessation of exposure. In the case of solvents
containing benzene, the possibility of bone marrow depression and
leukaemogenesis must be borne in mind. Prolonged skin contact with
petroleum solvents can lead to contact irritative dermatitis, but only
rarely to contact allergic dermatitis.

Both types of skin disease occur more frequently in professions
using products derived from base oils, especially metal-working oils.
Such diseases may cause considerable distress, they affect the general
well-being and reduce the capacity to work. Skin cancer has been
described in workers after prolonged and intensive exposure to less
refined base oil derivatives, e.g., the metal-working oils formerly in
use. Practically all these skin diseases appeared in occupations where
hygiene and working conditions were poor. These factors were as
important as the intrinsic toxicity of the oils.

Exposure to low concentrations of mists of highly refined oils
appears to be without serious health hazards; this is not necessarily
the case with less refined oils, which have been reported to cause an
increased incidence of cancer of the respiratory tract, after
prolonged high-level exposure.

There is no evidence to suggest that the production and use of
bitumens presents a health hazard for the general population and for
workers (other than burns from splashes of hot bitumen).

1.1.7 Control measures

Every effort should be made to avoid the contamination of
workers, the workplace, or the general environment with petroleum
products. This can be achieved by appropriate technological measures
and good work practice.

As far as possible, products containing highly toxic compounds
should be avoided and alternatives sought.

Where contact is unavoidable, suitable protective equipment
should be used. Health education of employers and workers should be
promoted emphasizing the necessity for maintaining high standards of
personal hygiene. When necessary, pre-employment, and regular periodic
medical examinations should be carried out on exposed workers.

Adequate control programmes should be implemented, including the
disposal of many types of waste oil products.

1.2 Recommendations for further studies

1.2.1 Analytical aspects

A major problem in assessing the health hazards of petroleum
products is that the majority have been developed and specified
according to their physical properties such as the boiling-point and
viscosity rather than their chemical composition. Products with the
same physical properties may vary considerably in chemical composition
(e.g., different proportions of isomers) and, hence, biological
properties. It is, therefore, important for future experimental animal
and human studies that analytical methods should be available to
establish the chemical structure of the products to which subjects are
exposed, and research into suitable methods should continue.
Analytical methods suitable for determining low concentrations of
solvents and oil products and their individual components in the
environment should continue to be developed and some consideration
should be given to the development of simple control techniques at the
work-site level.

1.2.2 Sources and levels in the environment

In some cases, the use of aromatic extracts and highly aromatic
base oils should be reconsidered and alternatives sought, where there
might be a risk of carcinogenic effects on the skin and respiratory
tract.

More information is needed on the concentrations of petroleum
products and their constituents in the work-place and the general
environment, especially in the neighbourhood of refineries and
petrochemical plants. Such data would result in more meaningful
epidemiological studies and would be of use in the development of
suitable measures to control pollution and the exposure of the general
population.

There is a need to understand more fully the factors responsible
for the production of oil mists and the importance to health of
inhalation of particles of various sizes. Most oil mists contain
chemical additives and the possible effects of these, when inhaled by
man, must be considered.

Improved methods for quantifying human exposure to petroleum
products in the working environment are required. While inhalation
exposure can be estimated from atmospheric monitoring, the extent of
exposure through skin contact has rarely, if ever, been examined.

International cooperation is needed in the elaboration and
clarification of exposure limits for petroleum products and their
components in water, air, and the working environment. These should be
based on adequate evaluation of their risks.

1.2.3 Studies on experimental animals

More studies are needed of the mechanisms by which petroleum
products produce injury in experimental animals. Little information is
available on the metabolism and pharmacokinetics of the components of
oils. In particular, elucidation of the dose/time/effect relationships
of exposure of animals to n-hexane would be of value in assessing
acceptable human exposure levels. Information on the neurotoxicity of
other components of petroleum solvents and on their ability to act
synergistically with n-hexane should also be sought. The possible
effects of petroleum solvents on aspects of the reproductive
processes, not already studied in depth, should be examined. A quick
and reliable analytical method for determining 4, 5, and 6 condensed
ring polynuclear aromatic compounds needs to be developed and its
predictive value in assessing carcinogenic potential examined.
Similarly, a short-term biological test for carcinogenicity,
applicable to oil products, would be of great value in providing a
method for the rapid assessment of the potential carcinogenicity of
oils.

1.2.4 Human studies

Further studies to determine the dose-effect relationships of
exposure to a wide range of petroleum oil and solvent products would
be of value, particularly in relation to long-term exposure. In such
studies, the possibility that any adverse effect produced by exposure
might be influenced by working conditions (e.g., general work
environment, heat, stress, and noise) should be considered and, if
necessary, investigated. As well as studying general health, possible
specific actions on the cardiovascular, gastrointestinal, and central
and peripheral nervous systems should be considered. Possible
susceptible groups, and factors such as age, sex, state of health, and
genetic background should also be taken into consideration. There is a
need to assess the extent of health problems caused by the use of
petroleum products in the developing countries, where exposure
conditions may be less well controlled; relatively few studies
relating to these problems have been carried out.

Efforts should be made to develop common criteria for the
detection and definition of health effects in order to allow
comparison of findings between different research workers and
institutes throughout the world.

2. CRUDE OILS

2.1 Properties and Analytical Methods

2.1.1 Chemical composition and properties

Crude oils originate from the decomposition and transformation of
aquatic, mainly marine, animals and plants that became buried under
successive layers of mud and silt some 15-500 million years ago; they
are essentially very complex mixtures of many thousands of different
hydrocarbons. Depending on the source, the oils contain various
proportions of straight and branched-chain paraffins, cycloparaffins,
and naphthenic, aromatic, and polynuclear aromatic hydrocarbons. The
younger oils are characterized by their more asphaltic nature. As many
"paraffins" of high relative molecular mass may contain naphthenic
and/or aromatic rings, this should not be understood as a sharp
division between defined chemical entities.

The hydrocarbons may be gaseous, liquid, or solid, under normal
conditions of temperature and pressure, depending on the number and
arrangement of carbon atoms in the molecules. As a general rule, at
ambient temperatures, compounds with molecules containing up to 4
carbon atoms are gaseous; those with 5-20 carbon atoms, liquid; and
those with more than 20 carbon atoms, solid. In crude oil, gaseous and
solid compounds occur dissolved in the liquid fraction. Solidification
of crude oils is caused by the presence of waxy normal paraffins of
high relative molecular mass. Unsaturated hydrocarbons such as olefins
and alkynes do not occur in crude oils.

Crude oils are similar to coal in that they are greatly enriched
in carbon and hydrogen compared with the average composition of the
earth's crust. Both are excellent sources of carbon for chemical
synthesis.

The sulfur content of crude oil ranges from less than 2 to
60 g/kg, depending on the origin of the oil. The sulfur is present not
only as sulfide but also as mercaptans, thiophenes, and more complex
organic sulfur compounds. The level of organic nitrogen compounds in
most crude oils is less than 1 g/kg, but some may occasionally contain
as much as 20 g/kg. Nitrogen compounds in crude oil are complex and
mostly unidentified structures, which, through thermal decomposition
during the distillation process of crude oil, are converted to simpler
structures. Crude oils may also contain some naphthenic acids and
phenolic compounds (Petroleum Handbook, 1966).

As crude oils are the decomposition products of former aquatic
animal and plant organisms, it is not surprising that they contain
most, if not all, of the known elements. These are mainly present in
few small quantities, i.e., only in mg/kg or small fractions of mg/kg.
However, nickel, molybdenum, and mercury levels are sometimes as high
as 10 mg/kg and vanadium levels, 50 mg/kg (Mason, 1966; Bertine &
Goldberg, 1971). More complete coverage of crude oil trace elements
can be found in BP (1975).

Crude oils vary widely in appearance and consistency from country
to country and from field to field. They range from yellowish brown,
mobile liquids to black, viscous semi-solids. The differences are due
to the different proportions of the various molecular types and sizes
of hydrocarbons. One crude oil may contain mostly paraffins, another
mostly naphthenes. Whether paraffinic or naphthenic, one may contain a
large quantity of lower hydrocarbons and be mobile or contain a lot of
dissolved gas; another may consist mainly of higher hydrocarbons and
be highly viscous, with little or no dissolved gas. The nature of the
crude oil governs, to a certain extent, the nature of the products
that can be manufactured from it and their suitability for special
applications. A naphthenic crude oil will be more suitable for the
production of asphaltic bitumen, a paraffinic crude oil for wax. A
naphthenic crude oil, and even more so an aromatic one, will yield
lubricating oils with viscosities that are sensitive to temperature.
However, with modern refining methods there is greater flexibility in
the use of crude oils to produce any desired type of product. Crude
oils are usually classified into three groups, according to the nature
of the hydrocarbons they contain:

(a) Paraffin base crude oils

These contain paraffin wax, but little or no asphaltic matter.
They consist mainly of paraffinic hydrocarbons and usually give good
yields of paraffin wax and high-grade lubricating oils.

(b) Asphaltic base crude oils

These contain little or no paraffin wax, but asphaltic matter is
usually present in large proportions. They consist mainly of
naphthenes and yield lubricating oils that are more viscosity
sensitive to temperature than those from paraffin base crude oils.
These crude oils are now often referred to as naphthene base crude
oils.

These contain substantial amounts of both paraffin wax and
asphaltic matter. Both paraffins and naphthenes are present together
with a certain proportion of aromatic hydrocarbons.

This classification is a rough-and-ready division into types and
should not be used too strictly. Most crude oils exhibit considerable
overlapping of the types described and by far the majority are of the
mixed base type (Petroleum Handbook, 1966).

A useful compilation of the various characteristics and
approximate composition of most relevant crude oils is given in Anon
(1973).

2.1.2 Methods of sampling and analysis

As the methods of sampling and analysis are the same for crude
oils, petroleum solvents, and lubricant base oils, a general
discussion follows.

The petroleum products dealt with in this document are mostly
complex mixtures of closely related chemical compounds, identified as
a product on the basis of certain physical and chemical
characteristics related to their intended use. Because of the complex
nature of these products, only some of the relatively simple,
low-boiling components can be determined individually, and even these
cannot be selectively monitored in the working area without
appreciable expense. Thus monitoring for groups of compounds such as
"total hydrocarbons", etc. is often unavoidable. The objective of the
analysis will, in general, be to determine the concentration of any
particular suspected component class rather than to identify the
product. Moreover, because of differences in the volatility,
solubility, etc. of the components, the product will lose its
"identity" the moment is escapes from its original confinement and
enters the environment.

Potential health hazards associated with handling petroleum
products mainly arise from skin contact and inhalation. By proper
precautionary measures, the risk of skin contact can easily be
controlled. The occurrence of air contaminants, however, quite often
escapes human perception and this section will be devoted to ways of
assessing levels of contaminants in air.

Based on their different toxicological behaviour, 3 classes of
air contaminants can be distinguished, namely: gases and vapours
(from, e.g., solvents, petrol); mists (from, e.g., higher-boiling
refined oils); and fumes (from, e.g., high-boiling aromatic extracts,
bitumens).

Sampling and analysis for these 3 classes will be discussed
separately and particular attention will be given to single components
at present considered to be the most hazardous, such as benzene,
n-hexane, and polycyclic hydrocarbons.

Though, in the context of this Environmental Health Criteria
document, methods for the monitoring of both the air in the workplace
and the ambient air are relevant, only methods for work-place
monitoring will be briefly reviewed. The most sensitive methods for
monitoring work-place air could also be used for monitoring the
generally much lower levels in the ambient air.

The most frequent reason for sampling the air in the workplace is
to measure the concentration of hazardous agents to which the worker
may be exposed. The preferred way of assessing the exposure level is
to determine the time-weighted average (TWA) concentration for a
normal 8-h working day in the breathing zone of an individual worker.
For area monitoring, fixed station or portable monitors are used. Data
obtained in this way are independent of the presence and movement
pattern of the worker.

A detailed description of sampling strategy is given, for
instance, in NIOSH (1977a).

An alternative method for the determination of the amount
absorbed by a worker is biological monitoring, i.e., assessment of the
absorbed substance or its metabolites in biological material (urine,
blood, expired air). Such methods are available for many substances,
but unfortunately not for petroleum products, with the exception of
benzene and its homologues and, to a certain extent, n-hexane. The
principles of biological monitoring have been reviewed by many
authors, e.g., Piotrowski (1977).

The types of pollutants that occur in the work-place can be
divided into 2 broad categories, based on their physical state,
namely: gaseous pollutants and aerosols. Methods for sampling gaseous
pollutants are different from those for aerosols.

2.1.2.1 Gases and vapours

For personal monitoring, sampling and analysis are usually
performed in 2 separate steps. Samples are collected, mostly over a
prolonged period of time, from the breathing zone of the worker by
passing the contaminated air at a flow rate of 50-200 ml per min
(using a personal sampling pump carried by the worker) through a small
tube containing a suitable adsorbent (NIOSH, 1973; Clayton & Clayton,
1978; Voborsky, 1980). For hydrocarbon vapours, activated charcoal is
one of the best adsorbents.

Recently, passive dosimeters, based on diffusion of the substance
into an adsorbing layer, have been developed and marketed. Though
laboratory studies have shown these dosimeters to be as accurate as
adsorbent tubes using sampling pumps, more field data are needed to
prove their validity.

For grab samples, the contaminated air may also be collected in
Tedlar, Mylar, or Saran bags or in gas pipettes. Such samples must be
analysed as soon as possible, because of possible sample losses.

The techniques used for personal monitoring can also be used for
area monitoring. In many instances, however, the high specificity and
accuracy that can be obtained by the sophisticated methods used for
the analysis of personal monitoring samples is not required and
relatively simple, direct reading instruments can often be used when
searching for leakages, when monitoring areas with only a single
substance as a contaminant, or when monitoring areas where the total
hydrocarbon level is generally below the exposure limit for any of the
individual substances of concern.

The most simple direct reading instrument is the colorimetric
indicator tube, usually used with a hand pump, a wide variety of which
are available. However, while it is true that colorimetric indicator
tubes are of low initial cost and simple and convenient to use, there
are distinct limitations and potential errors inherent in this method.
A manual describing the applications and limitations of these devices
is available (AIHA, 1976). Other, commercially available, direct
reading instruments include portable infrared instruments, portable
gas chromatographs, and non-specific analysers, such as total
hydrocarbon analysers (ACGIH, 1978b).

An analytical procedure may, however, include several of the
following steps: sample recovery, concentration, pre-separation,
derivatization, and analysis.

The sample can be recovered from solid collection media by
solvent extraction or by thermal desorption. When a liquid absorbent
is used, a concentration step may be required.

Very many analytical techniques are available. However, as the
quantities of organic material to be determined are generally minute
and concealed in a matrix of many other substances, some analytical
techniques are especially suitable, such as gas chromatography (GC),
gas chromatography and mass spectrometry (GC/MS), and high-pressure
liquid chromatography (HPLC) with ultraviolet or fluorescence
detection.

Criteria for the choice of analytical technique include:
specificity required; quantities involved; ease of operation;
suitability for automation; and cost per analysis.

The principles of the analytical techniques mentioned are
described extensively in many monographs. For example a short
description of all relevant analytical techniques is given in NIOSH
(1973). Thus, only those for total hydrocarbons, n-hexane, and
benzene will be discussed here.

(a) Total hydrocarbons

Colorimetric indicator tubes are available from most
manufacturers for the determination of total hydrocarbons in the
work-place air. These tubes normally cover the range from about
100 ppm to several thousand ppm (corresponding to gasoline levels
ranging from 450 mg/m³ to several grams per m³ if a conversion
factor of 4.5 is applied). Many commercial instruments are also
available (ACGIH, 1978), the most reliable being those based on flame
ionization detection. These methods are generic in nature and the
instruments have to be calibrated, e.g., against methane or
n-octane. The read-out is not absolute, as the detector response
differs according to the composition of the hydrocarbons.

(b) n-Hexane

Depending on the situation, one of the 2 following approaches can
be applied in analysing specifically for n-hexane:

(i) n-Hexane as the main contaminant: direct area monitoring
can be performed using either a flame ionizing detector, without
previous separation (total hydrocarbon detector), or the total
hydrocarbon or low range n-hexane colorimetric indicator tubes
( n-hexane tubes are non-specific and react to all hydrocarbons; the
range is from about 20 mg/m³ upwards).

The NIOSH method S-90 (NIOSH, 1977-79), using the charcoal
tube/carbon disulfide desorption method with GC-analysis on packed
columns is suitable for personal monitoring.

(ii) n-Hexane present as one of the constituents of a
hydrocarbon mixture: In this case the matrix is very complicated. It
is more or less a prerequisite to use capillary GC to obtain a
satisfactory separation. Sample recovery is preferably carried out
with a 2-step thermal desorption, though solvent desorption using a
solvent with a longer retention time on the GC column (e.g., decane)
could be used.

Recently, it has been suggested that the urinary excretion of
hexane metabolites could be used for monitoring occupational exposure
to n-hexane and its isomers (Perbellini et al., 1981).

If benzene is the main pollutant, total hydrocarbon analysers,
or, even better, the benzene colorimetric indicator tubes can be used
(ranges available: from 0.15 to 150 mg/m³, sensitive to other
aromatic compounds, somewhat sensitive to hydrocarbons).

In all cases, the personal monitoring charcoal-tube/carbon-di-
sulfide-desorption/GC-analysis method can be used, i.e., NIOSH method
S-311 (NIOSH, 1977-79).

A detailed description of the determination of benzene in work
environments can be found in CONCAWE (1981a).

Biological monitoring for benzene exposure is carried out by
measuring the elimination of phenol (metabolite of benzene) in urine.
Several colorimetric methods (using 2,6-dibromo- N-chloro-
p-benzoquinoneimine-Gibbs reagent, 2,6-dibromoquinone-4-chlorimide,
diazo- p-nitroaniline or 4-dimethylamino-2,3-dimethyl-l-phenyl-
3-pyrazolin-5-one (4-aminopyrine)) or gas chromatographic methods are
available. A concentration of phenol in urine of more than 25 mg/litre
indicates some exposure to benzene (Truhaut & Murray, 1978).

2.1.2.2 Aerosols

The sampling of aerosols is performed by drawing a measured
volume of air through a filter, an impaction or impingement device, or
an electrostatic or thermal precipitator. The most common method,
especially for personal monitoring, consists of drawing air, at a
well-defined rate, through a filter. For personal monitoring, a
portable pump and a suitable filter in a filter-holder, located in the
worker's breathing zone, is used.

For area monitoring, some direct reading instruments for grab
sampling are also available based on, e.g., light-scattering,
attenuation of beta radiation, and changes in the resonant frequency
of a piezoelectric quartz crystal (ACGIH, 1978).

In some cases, size-selective sampling is necessary. This can be
accomplished by placing a cyclone or elutriator in front of the
sampler, or by the use of special-size selective sampling devices.
When, however, the aerosol also presents a hazard through absorption
via the gastrointestinal tract, total particulate matter should be
sampled.

In many instances, the total particulate concentration in air is
the only information needed, in which case, a gravimetric
determination of the material collected is all that is required.

On the other hand, if it is necessary to determine the
benzene-soluble matter present in the total particulate matter
collected, the collected matter must first be extracted with benzene.
The extract must then be evaporated to dryness and the residue weighed
(NIOSH, 1977-79). When more detail is required concerning the
composition of the aerosol collected, the benzene extract should be
analysed for the substances of concern.

Mists

Aerosols generated from refined oils and oils with a relatively
low aromatic content are often referred to as mists. The methods of
analysis most frequently used for mists consist of drawing air, at a
well-defined rate, through a preweighed and preconditioned glass-fibre
filter and recording the weight gain. If the weight gain indicates
that the total particulate concentration in the work atmosphere is
well below the appropriate exposure limits, no further analytical
action is required for the air sample. However, when concentrations in
excess of such levels are found, investigators invariably require
determination of the oil content of the filter.

For this purpose, the filter is extracted with a suitable solvent
and the oil content of the extract determined, either gravimetrically
(after evaporation of the solvent) or spectrophotometrically, using
ultraviolet or infrared adsorption or fluorescence spectrophotometry
(CONCAWE, 1981b; NIOSH, 1977-79).

The exposure limits for mists are mainly established as total
particulate oil mist and, for general investigations and control work,
it is recommended that sampling should be designed to take this into
account. Nevertheless, there may be some occasions when the
investigator feels it necessary to assess the concentration of
respirable particles in the mist, and special sampling techniques,
e.g., using a cyclone, will need to be employed. Experience, however,
does suggest that, in general, the equivalent diameter of particles '
in oil mists in engineering workshops is well below 5 µm and hence
they may be regarded as respirable. Thus, it is common industrial
practice to sample for total particulate matter.

For area monitoring, one of the direct reading devices mentioned
earlier could also be used.

Fumes

Aerosols generated from high-boiling aromatic extract oils and
bitumens are called fumes.

Where exposure to fumes from materials containing significant
concentrations of polycyclic aromatic hydrocarbons, such as aromatic
extract oils, is likely to occur, some guidance can be gained from the
AGGIH TLV-TWA of 0.2 mg/m³ for particulate polycyclic aromatic
hydrocarbons (as benzene-soluble material BSM). Coal tar pitch
volatiles include the fused polycyclic hydrocarbons that volatilize
from the distillation residues of coal, petroleum, wood, and other
organic matter. In the case of aromatic extract oils, the fact that a
major part of the BSM consists of non-polycyclic aromatic compounds
should be taken into account (NIOSH, 1977b).

With regard to the present standard for BSM, the analytical
method is as follows: total particulate matter suspended in air is
collected on a glass-fibre filter, with a silver membrane back-up
filter. The filter is extracted with benzene, using ultrasonic
agitation. An aliquot of the extract is evaporated to dryness and the
residue is weighed (NIOSH, 1977-79).

If it is felt necessary to characterize more fully the polycyclic
aromatic hydrocarbons (PAHs) present in the benzene extract of the
fume samples. further analysis of these extracts can be performed as
follows:

(a) GC method (Grimmer & Böhnke, 1972; Grimmer, 1979): The filter
extract is treated in several steps to isolate a fraction,
enriched in PAHS. This fraction is then analysed by capillary
GC/MS. For very complex products, the aerosol composition might
be too complicated to obtain a reasonable chromatogram, even
after all the pre-separation steps.

(b) HPLC separation with fluorescence detection (Das & Thomas, 1978;
Belinky, 1980).

The filter extract is evaporated and dissolved in 0.5-1 ml of
benzene. This extract is directly injected into the HPLC
instrument. As the fluorescence detector only records the highly
unsaturated molecules, the larger part of the matrix does not
give any signal at all on the detector. Only the
alkyl-substituted and unsubstituted polycyclic aromatic compounds
give rise to a detector signal.

Specificity for selected substances can be increased
substantially by a proper choice of excitation and emission
wavelengths. For the more volatile polycyclic aromatic
hydrocarbons, like pyrene, some losses may occur during sampling,
due to volatilization. If these more volatile polycyclic aromatic
hydrocarbons are also of interest, the filter collector could be
backed up by a silicagel tube. The silicagel from this tube is
then treated in the same way as the filter.

2.2 Sources of Environmental Pollution

2.2.1 Natural occurrence

Crude oils are exclusively natural products, most of which are
produced from artificial wells. Natural seepage of crude oils occurs
in various parts of the world, not only on land, but also on the
sea-bed; however, this represents only a minor source of environmental
pollution in comparison with man-made sources.

2.2.2 Man-made sources

2.2.2.1 Production

Taking world-wide figures, total crude oil production for 1973
was about 2900 million tonnes, i.e., approximately 10 times the crude
oil production in 1938. The rate of growth of production has declined
since 1973 (the 1979 level was just over 3200 million tonnes), and
very little overall increase, if any, is expected in the near future.

2.2.2.2 Uses

In some areas, e.g., Japan, certain unrefined crude oils are used
as fuels.

Negligible amounts of unrefined oils are used for such
applications as road construction and malaria control.

In some areas, where crude oils come to the surface in natural
seepage, they have been used by the local population, since
prehistoric times, for a number of purposes, but mainly for heating
and lighting.

Nearly. all the crude oil produced is processed in refineries
into various fuel and non-fuel fractions.

An example of an integrated flow scheme for the processing of
crude oil is shown in Fig. 1. The crude oil distillation (a
straightforward distillation process) and subsequent
vacuum-distillation (distillation under high vacuum) of the residues
of the first process splits crude oil into its basic fractions which,
after further treatment, purification, and sometimes blending with
additives, are used as commercial products. The major petroleum
fractions are listed in Table 1 in broad categories according to
increasing boiling-point.

Certain petroleum fractions, such as naphtha or wax can be
submitted to various thermal or catalytic cracking processes and to
other refinery processes such as alkylation, and isomerization. In the
course of these processes, long-chain paraffinic hydrocarbon molecules
are broken down into smaller molecules including unsaturated
(olefinic) compounds. Some of these olefins may stay in the
end-product of the cracking process, others, especially if under the
influence of high temperatures and catalysts, will react among each
other and form more complex structures ranging from iso-octanes to
polynuclear aromatic hydrocarbons (Badger, 1962).

The products obtained from cracking processes can be distilled
into various fractions in a similar way to crude oils, though
obviously the composition of the fractions is different. For instance,
they contain a certain percentage of olefins that are highly valued as
base materials for the chemical industry. By suitable choice of
cracking procedures, the yield of special compounds such as gasoline
components or olefins can be boosted. On the other hand, fractions
derived from the cracking of petroleum products contain a higher
percentage of polynuclear aromatic hydrocarbons than corresponding
straight-run crude oil fractions. The implications of this will be
discussed later.

TABLE 1. Range of major petroleum fractions

Fuels Boiling range Non fuels
(approximate)

natural gas
refinery gas
liquefied petroleum <10 °C
gas (LPG)

gasolines 35 °C petroleum solvents
kerosenes naphtha
gas oils 300 °C

heavy fuel oils 300 °C base oils also used for
lubricating, metal
working and textile oils
petrolatum
700 °C petroleum waxes

>700 °C bitumens, coke

Examples of olefinic base chemicals derived from cracking
processes are: ethylene, acetylene, propylene, butylenes, pentenes,
and higher aliphatic olefins, such as butadiene, isoprene.

It is outside the scope of this review to give further details
and other refining processes.

2.2.2.3 Disposal of waste

In a refining process, the release of oil into refinery effluents
is practically negligible and of a lower order of magnitude than
tanker washings in tankers that do not use the "load-on-top" system.
Waste gas in production fields is generally burnt on the spot. In
refineries and chemical plants, it may be necessary to burn some gas
at a flare for reasons of safety, and some oil and gas is consumed as
refinery fuel. Atmospheric pollutants in and around refineries
basically consist of saturated and unsaturated hydrocarbons, carbon
monoxide, hydrogen sulfide, and sulfur dioxide (Poliansky &
Musserskaja, 1971; Krasovitskaja, 1976). Sulfur dioxide, hydrogen
sulfide, and mercaptan emissions are not discussed in this review and
emissions of hydrocarbon vapours into the atmosphere from storage
terminals, filling stations, and cars will be covered in another
document.

2.3 Toxicological Effects of Crude Oils

As, in this document, crude oils are discussed only to provide
background information for the petroleum solvents, lubricating base
oils, and bitumens derived from them, no detailed discussion will
follow concerning environmental exposure levels, environmental
distribution and transport, physiological factors relating to
mammalian uptake, dose-response relationships, and maximum permissible
levels. Most of the relevant aspects will, however, be covered in the
sections on fractions derived from the crude oils. This also applies
to toxicological effects on experimental animals and man, with the
exception of a very few studies that are related to crude oil exposure
only.

The toxicological and nuisance aspects of hydrogen sulfide and
mercaptans have been reviewed in detail by Miner (1969) and Sullivan
(1969). A review on hydrogen sulfide has been prepared by NIOSH
(1977c) and an Environmental Health Criteria document on hydrogen
sulfide has recently been published (WHO, 1982).

2.3.1 Effects on experimental animals

Leitch (1924) examined 16 untreated crude oils from various parts
of the world for their carcinogenicity by applying them 3 times a week
to the skin of mice and found significant differences in
tumorigenicity among these oils. Similar results were reported by
Hieger & Woodhouse (1952) in skin tests on mice and rabbits. The
tumorigenicity of the crude oils they examined was low in comparison
with that of some of the distilled fractions. Skin tests were also

carried out on mice and rabbits by Antonov & Lints (1960), who found
that Saratov oil possessed weak carcinogenic properties. The main
causes of death in these tests, however, were pneumonia and general
intoxication, probably from absorption of oil components through the
skin. The authors found that rabbits were more sensitive than mice, as
did Hieger & Woodhouse (1952).

Batt-Neal & Wolman (1977) demonstrated skin tumorigenicity and
amyloid deposition following skin exposure of mice to saturated
acetone extracts of various oils collected from beaches.

2.3.2 Effects on man

Examination of 743 oilfield workers exposed to California crude
oil and excessive sunlight revealed that 7 of them had epitheliomas on
exposed parts of the body and that nearly 20% had keratotic changes on
the hands, forearms, face, and neck. Five of the 7 subjects, who
developed epitheliomas, were blonds, though blonds were in the
minority in this group of workers (Schwartz et al., 1947).

During 1938-39, Schwartz saw 189 cases of carcinomas on exposed
parts of the skin; 128 were in males, 71 of whom were oilfield workers
20 others being workers exposed to excessive sunlight only. Emmett
(1975) mentions the strong potentiating effect of UV radiation on
other potentially carcinogenic exposures. In southern Texas, however,
the incidence of skin carcinomas in 330 oilfield workers was low,
which underlines the fact that Texas and Pennsylvania oils are known
to be less carcinogenic than California oil (Twort & Ing, 1928).

In a study on 50 volunteer operators, who had not previously been
in contact with oil and petroleum products, crude oil was applied to
the skin of the inner surface of the forearm, for periods of 3-6 h. An
inflammatory reaction of the skin developed with moderate erythema,
oedema, and slight burning. Changes in the thermosensitive threshold
were noted, as well as an increase in the permeability of the
epidermis (Gusein-Zade, 1975).

3. PETROLEUM SOLVENTS

3.1 Properties and Analytical Methods

3.1.1 Chemical composition and properties

Only solvents consisting of hydrogen and carbon alone and
produced from petroleum will be considered in this review. It should
be noted, however, that similar solvents are also produced from coal.

Petroleum solvents consist of complex mixtures of hydrocarbons
reflecting the hydrocarbon constituents of the crude oil or, more
usually, the intermediate refinery streams from which they are
distilled. Because of their complex nature, classification is a
problem and no standard, worldwide-accepted nomenclature exists.
However, providing that it is recognized that considerable overlapping
and many exceptions occur, they can be classified into 3 broad
subdivisions, based on distillation ranges:

(a) special-boiling-point solvents (SBPs) - grades with narrow or
wide distillation ranges within the main limits of 30-160°C;

(b) white spirits - grades distilling within the main range
150-220°C, the boiling-points of individual grades usually
ranging over more than 20°C;

Benzene, toluene, and the xylene isomers occur as components of
petroleum solvents, but as they fall more naturally into the category
of chemical intermediates, they will be referred to here only in so
far as they are important as components of the mixtures being
discussed.

Two further clarifications can be made. Firstly, it is common
industrial practice to ascribe the name of the predominant isomer
present to the petroleum solvent; thus the descriptions pentane,
isopentane, hexane, isohexane, and heptane are commonly met. However,
in almost all cases, the amount of the named isomer present in an
industrial scale product will not exceed 95% v/v of the solvent and
may be as small as 30% v/v.

Second, most petroleum solvents are marketed on the basis of
typical physical properties rather than on chemical specifications,
because of the limitations during refining of controlling the complex
mixtures of isomers that make up the petroleum solvents. As production
techniques become more sophisticated, greater control is possible and
more properties can be specified within narrower limits. However, even
when such narrow limits are met, the mixture of components present may
vary, because of variations in the types of crude oil being processed
and alterations in conditions in processing units.

To meet the wide range of properties required by the market,
several different processes are used. Distillation is the common
process setting the volatility range. Chemical conversion techniques,
including reforming, alkylation, and hydrogenation, alter the chemical
composition and hence the solvency, as do physical conversion
techniques such as solvent extraction and molecular sieve separation.
Specific treatments such as caustic soda and sulfuric acid washing and
clay percolation are frequently applied to remove odourous substances,
chiefly sulfur compounds.

The reader is referred to Boenheim & Pearson (1973) for detailed
discussions of the chemical and physical composition and uses of
petroleum solvents.

3.1.1.1 Special-boiling-point solvents (SBPs)

These are highly purified naphtha fractions with specially
selected boiling ranges. The boiling range may be narrow or wide, and
generally falls within the limits of 30-160°C: SBPs are classified
according to their boiling range, e.g., SBP 62/82. Petroleum ether,
lighter fluid, spot remover, and rubber solvent are consumer products
in this range. Generally, SBPs consist of a mixture of hydrocarbons in
the C-5 to C-9 range: normal and branched paraffins, cycloparaffins,
and aromatic compounds. They contain only traces of olefins. An
example of the composition of a typical sample of straight run (i.e.,
non-dearomatized) SBP 80/110 is given in Table 2.

3.1.1.2 White spirits

The boiling-range of this group of solvents falls within the
limits 150-220°C (intermediate between gasoline and kerosene). These
solvents can be classified into low-aromatic grades (approximately
15-20% aromatic hydrocarbons) and high-aromatic grades (45% or more
aromatic hydrocarbons). They generally consist of hydrocarbons in the
C-7 to C-12 range, again including normal and branched paraffins as
well as naphthenic (cycloparaffins) and aromatic compounds. Olefins
are present in trace amounts only. Stoddard solvent, mineral spirits,
low-aromatic white spirits (LAWS) and turpentine-substitute are
well-known examples from this range.

3.1.1.3 High-boiling aromatic solvents

Aromatic hydrocarbons occur naturally in certain crude oils in
widely varying concentrations. They are also formed during secondary
processes such as thermal and catalytic reforming. They can be
concentrated and extracted by solvent extraction.

Apart from benzene, toluene, and xylene, which will not be
discussed separately in this review, this group includes solvents with
an aromatic content of 80-100%, and a wide boiling-range from 160 to
300°C. High-boiling aromatic solvents are obtained by distillation or
solvent extraction from refinery fractions such as kerosene and
lubricating base oils, and consist of very complex mixtures of
hydrocarbons with more than 9 carbon atoms per molecule. The
composition of a typical sample of one of these aromatic hydrocarbons
from the middle range (distillation range approximately 192-203°C) is
given in Table 3.

Most aromatic solvents are highly purified "white" solvents.
Those in the higher boiling range, derived from lubricating base oil
stocks by solvent extraction, may be less pure and coloured. They are
often by-products and are used as solvents for various technical
purposes. In many cases, they are referred to as "processing oils"
instead of solvents, and considered under lubricating oils.

3.1.2 Purity of petroleum solvents

In these complex mixtures, impurity is, of course, a matter of
definition. Components that are taken out in the course of the various
refining and treating processes used to obtain the more pure solvents
could be regarded as such. The major impurities would then be sulfur
compounds such as hydrogen sulfide, mercaptans, and thiophens, as well
as, olefins and other reactive unsaturated hydrocarbons.

A second category of impurities includes the hydrocarbons that
have been demonstrated to be carcinogenic in animals and man, such as
benzene, the polynuclear hydrocarbons and related heterocyclic
compounds containing nitrogen or sulfur.

TABLE 2. Composition of typical sample of SBP 80/110^a

Hydrocarbon Hydrocarbon % mass present Boiling
type in sample^b point °C

normal n-pentane 0.2 36.2
paraffins n-hexane 8.2 69.0
n-heptane 17.2 98.4

branched 2 methyl butane T^c 0.1 27.9
paraffins 2,2 dimethyl butane T trace 49.7
2,3 dimethyl butane T 0.3 58.0
2 methyl pentane 1.5 60.3
3 methyl pentane 1.6 63.3
2,2 dimethyl pentane 1.0 79.2
2,4 dimethyl pentane 1.3 80.5
2,2,3 trimethyl butane T 0.3 80.9
2,3 dimethyl pentane 9.7 89.8
3 methyl hexane 9.2 91.9
3 ethyl pentane 3.1 93.5
2,2,4 trimethyl pentane trace 99.2
2,2 dimethyl hexane trace 106.8
2,5 dimethyl hexane 0.6 109.1
3,3 dimethyl hexane T trace 112.0
2,3 dimethyl hexane 0.8 115.66
3,4 dimethyl hexane trace 117.7
3 methyl heptane 0.5 118.9

cyclo C-6 cyclohexane 8.4 80.7
paraffins methyl cyclohexane 14.2 100.9

cyclo C-5 cyclopentane T trace 49.3
paraffins methyl cyclopentane 4.7 71.8
1,1 dimethyl cyclopentane T 2.9 87.9
1-cis-3-dimethyl 1.9 90.8
cyclopentane T

TABLE 2. (contd).

Hydrocarbon Hydrocarbon % mass present Boiling
type in sample^b point °C

cyclo C-5 1-trans-3-dimethyl 2.7 91.7
paraffins cyclopentane T
contd. 1-trans-2-dimethyl 0.5 91.9
cyclopentane T
1-cis-2-dimethyl cyclopentane T 0.5 99.5
ethyl cyclopentane 0.6 103.5
1,1,3 trimethyl cyclopentane T 0.8 104.9
1-trans-2-cis-4-trimethyl 0.4 109.3
cyclopentane T
1-trans-2-cis-3-trimethyl 0.4 110.2
cyclopentane T
1,1,2 trimethyl cyclopentane T 0.3 113.7

unidentified Probably
paraffins 1.1 110.0

aromatic benzene 0.7 80.1
compounds toluene 3.9 110.6

olefins 0.4

^a From: Shell International Petroleum Co., London (unpublished data).
^b Average of duplicate analyses.
^c T = tentative identification.

TABLE 3. Composition of typical sample of Solvesso 150^a

Hydrocarbon % v/v of solvent

n-butylbenzene 2.47
sec-butylbenzene 0.08
tert-butylbenzene 0.05
m-cymene 0.13
o-cymene 0.01
p-cymene 0.52
1.2-diethylbenzene 1.72
1.3-diethylbenzene 1.10
1.4-diethylbenzene 0.56
1.2-dimethyl-3-ethylbenzene 2.86
1.2-dimethyl-4-ethylbenzene 6.64
1.3-dimethyl-2-ethylbenzene 0.71
1.3-dimethyl-4-ethylbenzene 4.17
1.3-dimethyl-5-ethylbenzene 2.80
1.4-dimethyl-2-ethylbenzene 3.26
m-ethyltoluene 0.37
o-ethyltoluene 0.02
p-ethyltoluene 0.01
indane 0.46
isobutylbenzene 0.32
isopropylbenzene 0.01
1-methyl-3-t-butylbenzene 0.76
1-methyl-2-n-propylbenzene 1.26
1-methyl-3-n-propylbenzene 2.08
1-methyl-4-n-propylbenzene 1.93
1-methylindane 0.91
2-methylindane 2.43
4-methylindane 9.28
5-methylindane 2.02
naphthalene 4.03
n-propylbenzene 0.00
1.2,3,4-tetramethylbenzene 3.66
1.2,3,5-tetramethylbenzene 8.84
1.2,4,5-tetramethylbenzene 5.53
toluene 0.02
1.2,3-trimethylbenzene 0.10
1.2,4-trimethylbenzene 0.05
1,3,5-trimethylbenzene 0.01

^a Courtesy Esso Standard Oil Company, New York, N.Y.,
USA (From: Gerarde, 1960).

TABLE 3. (contd).

Hydrocarbon % v/v of solvent

m-xylene 0.05
o-xylene 0.03
p-xylene 0.03
C-11-naphthalenes 0.31
C-11-indanes 3.58
C-11-alkylbenzene 18.27
C-12-alkylbenzene 0.73
C-12-indanes 0.08
C-13-alkylbenzene 0.02
C-10-indenes 0.10
C-11-indenes 0.07
C-12-naphthalenes trace
C-13-naphthalenes
C-12-indenes 0.10
aromatic compounds Total 94.55

Generally, the total sulfur content, the olefin content, and the
total aromatic content are specified for commercial petroleum
solvents. Where special products such as food-grade materials are
concerned, the benzene content is specified as well as the UV
absorption limits at certain wavelengths, as a measure of the
polynuclear aromatic hydrocarbon content.

3.1.3 Methods of sampling and analysis

See section 2.1.2.

3.2 Sources of Environmental Pollution

3.2.1 Natural occurrence

Petroleum solvents do not occur in nature as such, but only as
components of the crude oils from which they are derived.
Environmental pollution is always man-made and related to the use of
the solvents.

3.2.2 Man-made sources

3.2.2.1 Production

Because there is no uniform system of definition and
classification of petroleum solvents, firm statistics concerning the
magnitude of production of this group of materials do not exist. The
best estimate of the world-wide production of the group of solvents
would be 9 million tonnes for the year 1979.

3.2.2.2 Uses

It is not feasible to give more than a general outline of the
uses of the range of petroleum solvents.

(a) SpeciaL-boiling-point solvents (SBPs)

SBPs are mainly used as: solvents and thinners in lacquers and
paints; extraction solvents for perfumes, for vegetable oils and oil
and fats of animal origin; quick-drying solvents in printing-ink,
coatings, and adhesives; lighter fuel; and for dry-cleaning and
degreasing purposes.

(b) White spirits

White spirits are mainly used as: solvents and thinners for
lacquers, paints, resins, and printing-ink; solvents in formulations
of chemical products, e.g., pesticides; and for metal degreasing, wool
degreasing, and dry-cleaning.

The higher-boiling and less-purified aromatic extracts have very
good solvent properties for many polymers and are used as
ex-tender-oils in rubber, plastics, and bitumens, and also as solvents
in printing-ink and pesticide formulations. Furthermore, they can be
used as base-materials in the manufacture of carbon black.

3.3 Environmental Exposure Levels

Specific data are not available concerning levels of petroleum
solvents in air, water, food, or other environmental media. However,
low concentrations of hydrocarbons found in mussels have probably been
derived from petroleum hydrocarbons present in the environment
(Ehrhardt & Heineman, 1975).

Because of the relatively low boiling-range of these solvents,
industrial exposure to vapour may sometimes be high. This is known to
occur, especially in small workshops with insufficient ventilation,
where, for example, adhesives are used routinely. Although a lot of
consumer products may contain these solvents, excessive domestic
exposure would not normally be expected unless neat solvent were used
for cleaning purposes, indoors. Very limited, indirect exposure of the
general population is possible following the use of these solvents as
extractants in the production of food-grade vegetable oils.

Exposure to the higher-boiling and less-purified aromatic
extracts is mainly confined to occupational situations, where
excessive skin-contact may occur, or exposure to vapour in processes
carried out at elevated temperatures or with high-speed machines that
could give rise to fumes or mists. This will be considered in detail
under lubricating base oils.

3.4 Environmental Distribution and Transformation

Data on the distribution between media, environmental
transformation and degradation, interaction with physical, chemical,
or biological factors and bioconcentration, are not available for
petroleum solvents.

However some information exists concerning the behaviour and
degradation of crude oil in water (Floodgate, 1972, Hellmann & Zehle,
1972), and of hydrocarbons in general (Walker et al., 1975), and there
is much information on the microbial degradation of individual
petroleum hydrocarbons (Van der Linden & Thysse, 1965; Haines &
Alexander, 1974).

From these publications it can be seen that the subject is highly
complex and many factors have to be taken into account, such as the
composition of the oil product, the extent of dispersion into the
medium, and climatic conditions.

3.5 Metabolism

3.5.1 Absorption

The kinetics are determined by diffusion rates, solubility in
fat, and the concentration gradients in the individual compartments of
the body.

The highly volatile C-5, C-6, and C-7 paraffins, cycloparaffins,
and aromatic hydrocarbons readily pass across the alveolar membrane
into the bloodstream and are transported within minutes to the central
nervous system. Longer-chain homologues can, to a certain extent, also
pass the alveolar membrane, but their principal effect is local. This
was shown by Gerarde (1963) in studies on rats.

The alveolar air and blood concentrations of white spirit have
been measured in man following inhalation (Åstrand et al., 1975).
Aromatic hydrocarbons were absorbed to a greater extent into the
bloodstream than aliphatic hydrocarbons (approximate values being 62%
and 50%, respectively). Similar uptake values in man were shown for
the aromatic hydrocarbons, benzene and toluene, by Nomiyama & Nomiyama
(1974), for xylene by Sedivec & Flek (1976), Åstrand et al. (1978),
and Riihimäki et al. (1979), and for ethylbenzene by Bardodej &
Bardodejová (1970). Nomiyama & Nomiyama (1974) demonstrated a much
lower pulmonary absorption for n-hexane, the only aliphatic compound
that they tested; it was also rapidly excreted.

The skin is only permeable to hydrocarbons of a certain size.
With paraffinic substances, the maximum chain length appeared to be up
to 14 C-atoms (Scheuplein & Blank, 1971). Aromatic compounds have a
more compact structure and, in studies on guineapigs, Hoekstra &
Phillips (1967) showed that compounds from this group with a higher
number of C atoms could still pass the skin barrier.

The absorption of vapours through the skin is of minor
importance. For example, in man, whole body skin exposure to
2250 mg/m³ (600 ppm) of toluene was equivalent to an inhalation
exposure of less than 37.5 mg/m³ (10 ppm) (Riihimäki & Pfäffli,
1978). However, absorption during immersion in liquid solvents may be
considerable. Percutaneous absorption during immersion of both hands
in pure xylene was equal to an inhalation exposure of 435 mg/m³
(100 ppm) (Engström et al., 1977). The permeation of xylene is thus
about 20 nmol/min per cm² (Engström et al., 1977; Riihimäki, 1979)
and that for toluene, 3 µmol/min per cm² (Cohr & Stockholm, 1979).
Cutaneous exposure was probably a major route of absorption in 2 cases
of acute renal failure with oliguria, caused by exposure to diesel oil
(Barrientos et al., 1977; Crisp et al., 1979).

Data for absorption in the intestinal tract are not available,
but it is presumed that it would resemble absorption in the alveoli
rather than that through the skin.

3.5.2 Distribution in the body

Tissue hexane levels in rats, following inhalation of anaesthetic
concentrations, were measured by Böhlen et al. (1973). The tissue
distribution generally depended on exposure time and was proportional
to the lipid content of an organ until saturation occurred. The liver
was a special case for, as its lipid level changed rapidly, the
saturation level varied. Hexane was also apparently bound to some
blood components.

Women working at conveyor belts gluing parts of rubber footwear
had concentrations of petroleum solvents (no details on
physicochemical properties given) in the blood ranging from 2 . 35 ±
0.4 up to 4.6 ± 0.6 mg/litre at concentrations in the air of
100-300 mg/ m³. The solvent concentration in the blood increased with
increasing length of the working period from 1.6 mg/litre in the first
year to 2.5 mg/litre after 3.5 years and 3.4 mg/litre after 7-8 years
of service.

Wistar rats were exposed to the solvents used in the factory at
concentrations in air of 300-1000 mg/m³ for 30-45 days, 4 h/day. The
concentration of solvent in the blood amounted to 0.45 ± 0.05 -
1.2 ± 0.01 mg/litre (Lipovskij et al., 1977a).

Transfer of petroleum solvents through the placenta was studied
in 85 pregnant women workers in the rubber industry, who came into
contact with petroleum solvents during work (physicochemical
properties of the solvents not defined, concentration in the air of
the operating premises 300 ± 10 mg/m³). The average level of solvents
in the blood of 46 pregnant women, on whom abortion was performed, was
1.27 ± 0.3 mg/litre. A level of 3.29 ± 0.6 mg/kg was found in the
tissue of the embryo. Women giving birth to a child (39 women) had a
level of solvents in the blood of 2.5 ± 0.3 g/litre, while the content
in the blood of the umbilical cord was 3.5 ± 0.3 g/litre. The
concentration of solvents in the blood of the newborn infants was
twice that of the mothers.

Pregnant Wistar rats were exposed to the same solvent at a
concentration of 300 ± 10 mg/m³, for 48 days, 4 h per day. The
solvent was present in the blood, brain, liver, placenta, uterus, and
fetal tissues (Lipovskij et al., 1979).

3.5.3 Biotransformation

In both man and animals, the aliphatic hydrocarbons are generally
considered to be biochemically inert and excreted in the same form
(Williams, 1959). However, it has been shown that some normal alkanes
will, at least in part, be oxidized by the mammalian organism. For
example, Ichihara et al. (1969) demonstrated the oxidation of decane
in animals such as mice and rats, and the oxidative pathway of
n-hexane to hexane-2,5-dione and hexane-2,5-diol via
methyl- n-butylketone has been well established (see for example
Spencer et al., 1978).

As far as the metabolism of the cycloparaffins and aromatic
hydrocarbons is concerned, the half-life, form, and rate of excretion
of each component of the solvent has to be considered. It should be
mentioned, however, that the metabolism of individual compounds will
not be discussed in this document and readers are referred to the
reviews by Williams (1959) and Gerarde (1960).

The carcinogenicity of the solvents is thought to be due to the
presence of benzene and some of the polynuclear aromatic compounds.

3.5.4 Elimination

The elimination of the lower-boiling solvents (SBP type) in both
animals and man is usually rapid and mainly occurs via the respiratory
tract. However, in the case of ingestion of the heavier solvents
(white spirits), elimination mainly takes place with the faeces
(Browning, 1965).

3.6 Effects on Experimental Animals

It has been mentioned in section 3.1.1, that the petroleum
solvents under discussion in this document are more or less complex
mixtures of a range of hydrocarbons. For the commercial products, the
specification given generally includes the specific gravity,
boiling-range, and total content of aromatic hydrocarbons. The
concentrations of individual components vary, within certain limits,
with the source of the crude oil from which the solvent is derived,
and with the processes by which it is produced. These facts should be
kept in mind because:

(a) the toxicity data developed for a certain solvent-specification
indicate the order of magnitude of the toxicity of this type of
product;

(b) in practice it would be impossible and impracticable to carry out
complete toxicity testing on every single solvent on the market.
It is only sensible to develop toxicity data for typical
representative samples of a certain boiling range and within a
certain specification of aromatic content. In the evaluation of
the results, however, the analytical composition of the material
- especially its contents of n-hexane, benzene, and polynuclear
aromatic hydrocarbons should be taken into account.

3.6.1 Short-term exposure

Hine & Zuidema (1970) examined various aspects of the acute
toxicity of 10 samples of petroleum solvents that contained components
representative of the range of hydrocarbons found in commercial
petroleum solvents. Four were aromatic solvents containing at least
98% aromatic hydrocarbons (coded A) and 6 were non-aromatic solvents
containing less than 1% aromatic hydrocarbons (coded S). The boiling
ranges and principal components of the samples examined are given in
Table 4.

Acute oral, inhalation, and percutaneous toxicity and skin and
eye irritancy were examined for all samples. Intratracheal aspiration
was simulated with 2 samples and repeated skin irritation tests were
carried out using 5 of the samples. Undiluted samples were used for
the investigations, all of which were carried out on rats with the
exception of skin and eye irritancy and skin toxicity rests in which
rabbits were used.

TABLE 4. The boiling-range and principal components of solvents examined for
acute toxicity^a

Sample Boiling-range Principal components

A-1 281-286°F (138-141°C) C-8 aromatic compounds (ortho, meta, and
paraxylene; ethyl benzene)
A-2 362-398°F (163-203°C) C-9, C-10 and C-11 aromatic compounds
A-3 364-408°F (188-209°C) C-10 and C-11 aromatic compounds
A-4 384-507°F (196-264°C) C-11 to C-14 aromatic compounds
S-1 149-166°F (65-75°C) C-6 normal and isoparaffins (hexanes) and
naphthenes (cyclohexane, methylcyclopentane)
S-2 196-220°F (91-104°C) C-7 normal and isoparaffins (heptanes) and naphthenes
(methylcyclohexane, dimethylcyclopentane)
S-3 313-356°F (156-180°C) C-9 and C-10 normal and isoparaffins and naphthenes
S-4 368-395°F (187-212°C) C-11 and C-12 normal and isoparaffins and naphthenes
S-5 345-402°F (174-216°C) C-12 isoparaffins
S-6 384-500°F (195-260°C) C-13 to C-16 normal and isoparaffins and naphthenes

^a From: Hine & Zuidema (1970).

The findings of Hine & Zuidema (1970) which are summarized in
Table 5, showed that all the solvents tested could be considered of
low hazard to health unless aspirated or inhaled in extremely high
concentrations. Aromatic solvents were more toxic than non-aromatic
materials, the dose of solvent required to kill 50% of rats, when
administered orally or percutaneously, being lower for aromatic than
for non-aromatic solvents. Skin and eye irritancy were also greater
with aromatic solvents. The toxicity of the vapours could not be
compared, because the volatility of samples varied greatly. All
solvents induced similar toxic effects, whatever the route of

administration, including central nervous system depression
(characterized by incoordination, prostration, and coma) followed by
death. Convulsions sometimes occurred. All solvents caused skin and
eye irritation though, in general, as the chain length of the
non-aromatic solvents increased their irritant properties decreased.
Repeated skin exposure led to skin irritation and necrosis with all
solvents.

Hoekstra & Phillips (1963) found that light mineral oils, when
applied topically to the skin of guineapigs, caused epidermal
hypertrophy, hyperplasia, hyperkeratosis, and depilation. Examination
of the effects of various oil fractions demonstrated that the main
effect of the short-chain volatile paraffins was to defat the skin,
while longer-chain and aromatic hydrocarbons had a dermatoxic effect
that was related to the permeability of the skin to these compounds.
The maximum dermatoxic effect was seen with hydrocarbons containing
14-19 carbon atoms, while a transition to non-dermatoxicity occurred
around 21-23 carbon atoms. This was confirmed with pure n-paraffins,
but variations may exist with other types of hydrocarbons.
Simultaneous application of innocuous long-chain substances together
with irritant short-chain substances greatly reduced their toxicity,
though this effect was less marked with aromatic solvents.

In further studies on the effects of inhaling the vapours of
hydrocarbon solvents (Carpenter et al. 1977a, b, c), the acute (4-h
exposure) LC₅₀ and no-observed-adverse-effect concentrations were
studied in rats cats, and dogs. Results are summarized in Table 6.

These studies confirmed the occurrence of central nervous system
depression and there was also evidence of respiratory tract irritancy.
There were no marked or consistent differences between the species
examined. The major factor determining the acute inhalation hazard was
the volatility of the solvent, those containing 9 or more carbon atoms
tending to be insufficiently volatile to produce concentrations high
enough to be lethal over a short period of exposure. One exception was
a "high naphthenic" solvent, which was peculiar also in that
depression was not preceded by signs of irritation of the respiratory
tract, so that there was no warning of overexposure. Increased
aromatic content did not consistently result in increased inhalation
toxicity, though earlier work (Lazarew, 1929) suggested that the acute
inhalation toxicity of gasoline vapours increased with increasing
contents of cycloparaffins and aromatic hydrocarbons. The narcotic
action was also found to increase in each step by a factor of 3 in the
series - pentane, hexane, heptane, and octane (Fühner, 1921). Swann et
al (1974) found that anaesthesia occurred with these compounds at
concentrations of 32 000 ppm or more and that respiratory tract
irritation increased with chain length. Full anaesthesia can be
produced with gasoline (Haggard, 1921), but anaesthetic concentrations
are little lower than those that cause convulsions and death
(Browning, 1965).

TABLE 5. Toxicity of solvents. Summary of results^a

Test Sample Result Classification

Oral A-1 10.0(7.5-13.3) practically non-toxic
LD₅₀ A-2 4.5(3.0-6.8) slightly toxic
(ml/kg) A-3 13.3(7.5-23.7) practically non-toxic
A-4 12.3(8.1-18.7) practically non-toxic
S-1 >25.0^b relatively harmless
S-2 >25.0^b relatively harmless
S-3 >25.0^b relatively harmless
S-4 >25.0^b relatively harmless
S-5 >25.0^b relatively harmless
S-6 >25.0^b relatively harmless
Vapour A-1 6 350(4 670-8 640) slightly toxice
exposure A-2 >2 450^b SVNTART^d
LC₅₀ in ppm A-3 >580^c SVNTART
for 4 h A-4 >553^c SVNTART
S-1 73 680(66 310-79 940) practically non-toxic
S-2 14 000-16 000 practically non-toxic
S-3 2 000-2 600 slightly toxic
S-4 >710 SVNTART
S-5 >792 SVNTART
S-6 >263 SVNTART
Aspiration A-4 5/10 hazardous
(mortality) S-6 5/10 hazardous
Primary A-1 2.21 moderately irritating
skin A-2 2.04 moderately irritating
irritation A-3 2.17 moderately irritating
A-4 2.79 moderately irritating
S-1 1.92 slightly irritating
S-2 1.13 slightly irritating
S-3 2.38 moderately irritating
S-4 1.04 slightly irritating
S-5 1.29 slightly irritating
S-6 0.75 minimally irritating
Eye A-1 6.33 moderately irritating
irritation A-2 6.0 moderately irritating
A-3 4.33 moderately irritating
A-4 3.67 slightly irritating
S-1 0.33 minimally irritating
S-2 1.0 minimally irritating
S-3 2.0 minimally irritating
S-4 0 minimally irritating
S-5 0 minimally irritating
S-6 0 minimally irritating

TABLE 5. (contd).

Test Sample Result Classification

4-h A-1 approx. 5.0 practically non-toxic
percutaneous A-2 approx. 5.0 practically non-toxic
LD₅₀ rangefind A-3 approx. 5.0 practically non-toxic
(ml/kg) A-4 approx. 5.0 practically non-toxic
S-1 >5.0 practically non-toxic
S-2 >5.0 practically non-toxic^e
S-3 >5.0 practically non-toxic^e
S-4 approx. 5.0 practically non-toxic^e
S-5 5.0 practically non-toxic^e
S-6 5.0 practically non-toxic^e
Repeated benzene 3.6
skin toluene 3.5
irritation^f A-1 3.3

^a From: Hine & Zuidema (1970).
^b Doses above this amount not practical for testing.
^c Maximum concentration obtainable at 25 °C.
^d SVNTART = Saturated vapours not toxic at room temperature.
^e Lowest toxicity classification may be "relatively harmless"
^f Scored according to the method of Draize.

The greatest health hazard arises when hydrocarbon solvents are
aspirated into the lungs. This rapidly induces acute chemical
pneumonitis, which is characterized by pulmonary oedema and
haemorrhage, and is generally fatal (Waring, 1933; Lesser et al.,
1943; Gerarde, 1959). Gerarde (1959) demonstrated that the ratio of
the oral and intratracheal LD₅₀s was 140:1 for kerosene, the
intra-tracheal LD₅₀ being 0.2 ml for rats. This and other evidence
demonstrated that pulmonary injury was caused by direct contact with
the solvent and not by solvent present in the blood, following its
absorption through the gastrointestinal tract.

TABLE 6. Toxicity of solvents^a

Coined Boiling Composition^b Major 4-8h LC₅₀^c 13-wk Inhalation Human data Recommended
name range °C % Constituents mg/litre (ppm) NEL mg/litre (ppm) hygiene
carbon Odour Sensory limit
P N A number rat dog cat rat dog threshold threshold mg/litre
mg/m³ mg/litre (ppm)
(ppm) (