IPCS INTERNATIONAL PROGRAMME ON CHEMICAL SAFETY
Health and Safety Guide No. 57
FORMALDEHYDE
HEALTH AND SAFETY GUIDE
UNITED NATIONS ENVIRONMENT PROGRAMME
INTERNATIONAL LABOUR ORGANISATION
WORLD HEALTH ORGANIZATION
WORLD HEALTH ORGANIZATION, GENEVA 1991
This is a companion volume to Environmental Health Criteria 89:
Formaldehyde
Published by the World Health Organization for the International
Programme on Chemical Safety (a collaborative programme of the United
Nations Environment Programme, the International Labour Organisation,
and the World Health Organization)
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
WHO Library Cataloguing in Publication Data
Formaldehyde : health and safety guide.
(Health and safety guide ; no. 57)
1. Formaldehyde- standards I. Series
ISBN 92 4 151057 9 (NLM Classification: QV 225)
ISSN 0259-7268
(c) World Health Organization 1991
Publications of the World Health Organization enjoy copyright protection
in accordance with the provisions of Protocol 2 of the Universal
Copyright Convention. For rights of reproduction or translation of WHO
publications, in part or in toto, application should be made to the
Office of Publications, World Health Organization, Geneva, Switzerland.
The World Health Organization welcomes such applications.
The designations employed and the presentation of the material in this
publication do not imply the expression of any opinion whatsoever on the
part of the Secretariat of the World Health Organization concerning the
legal status of any country, territory, city or area or of its
authorities, or concerning the delimitation of its frontiers or
boundaries.
The mention of specific companies or of certain manufacturers' products
does not imply that they are endorsed or recommended by the World Health
Organization in preference to others of a similar nature that are not
mentioned. Errors and omissions excepted, the names of proprietary
products are distinguished by initial capital letters.
CONTENTS
INTRODUCTION
1. PRODUCT IDENTITY AND USES
1.1. Identity
1.2. Physical and chemical properties
1.3. Analytical methods
1.4. Composition
1.5. Uses
2. SUMMARY AND EVALUATION
2.1. Human exposure
2.2. Uptake, metabolism, and excretion
2.3. Effects on organisms in the environment
2.4. Effects on experimental animals
2.5. Effects on human beings
3. CONCLUSIONS AND RECOMMENDATIONS
3.1. Conclusions
3.1.1. Exposure
3.1.2. Health effects
3.2. Recommendations
3.2.1. General
3.2.2. Workplaces
3.2.3. Cosmetics
3.2.4. Disinfection
3.2.5. Pathology
3.2.6. Laboratories
4. HUMAN HEALTH HAZARDS, PREVENTION AND PROTECTION, EMERGENCY ACTION
4.1. Main human health hazards, prevention and protection,
first aid
4.1.1. Human health hazards, prevention and protection
4.1.2. First aid
4.2. Advice to physicians
4.3. Explosion and fire hazards
4.3.1. Explosion hazards
4.3.2. Fire hazards
4.4. Storage
4.5. Transport
4.6. Spillage and disposal advice
4.6.1. Spillage
4.6.2. Disposal
5. HAZARDS FOR THE ENVIRONMENT AND THEIR PREVENTION
6. SUMMARY OF CHEMICAL SAFETY INFORMATION
7. CURRENT REGULATIONS AND GUIDELINES
7.1. Exposure limit values
7.2. Specific restrictions
7.3. Labelling, packaging, and transport
BIBLIOGRAPHY
INTRODUCTION
The Environmental Health Criteria (EHC) documents produced by the
International Programme on Chemical Safety include an assessment of the
effects on the environment and on human health of exposure to a chemical
or combination of chemicals, or physical or biological agents. They
also provide guidelines for setting exposure limits.
The purpose of a Health and Safety Guide is to facilitate the
application of these guidelines in national chemical safety programmes.
The first three sections of a Health and Safety Guide highlight the
relevant technical information in the corresponding EHC. Section 4
includes advice on preventive and protective measures and emergency
action; health workers should be thoroughly familiar with the medical
information to ensure that they can act efficiently in an emergency.
Within the Guide is a Summary of Chemical Safety Information which
should be readily available, and should be clearly explained, to all who
could come into contact with the chemical. The section on regulatory
information has been extracted from the legal file of the International
Register of Potentially Toxic Chemicals (IRPTC) and from other United
Nations sources.
The target readership includes occupational health services, those in
ministries, governmental agencies, industry, and trade unions who are
involved in the safe use of chemicals and the avoidance of environmental
health hazards, and those wanting more information on this topic. An
attempt has been made to use only terms that will be familiar to the
intended user. However, sections 1 and 2 inevitably contain some
technical terms. A bibliography has been included for readers who
require further background information.
Revision of the information in this Guide will take place in due course,
and the eventual aim is to use standardized terminology. Comments on
any difficulties encountered in using the Guide would be very helpful
and should be addressed to:
The Manager
International Programme on Chemical Safety
Division of Environmental Health
World Health Organization
1211 Geneva 27
Switzerland
THE INFORMATION IN THIS GUIDE SHOULD BE CONSIDERED AS A STARTING POINT
TO A COMPREHENSIVE HEALTH AND SAFETY PROGRAMME
1. PRODUCT IDENTITY AND USES
1.1. Identity
Common name: formaldehyde
Chemical formula: CH2O [HCHO]
Chemical structure:
H
'
C = O
'
H
CAS registry number: 50-00-0
RTECS registry number: LP 8925000
UN numbers: 1198, 2209, 2213
EC numbers: 605-001-01-2 (solution 5% to 25%)
605-001-02-X (solution 1% to 5%)
605-001-00-5 (solution 25%)
IUPAC name: methanal
Common synonyms: formic aldehyde, methyl oxide, methylene
oxide, oxymethylene, methyl aldehyde,
oxomethane, fannoform, formalith, karsan
Common names for
solutions of formaldehyde: formalin, formol
Relative molecular mass: 30.03
1.2 Physical and Chemical Properties
Formaldehyde is a flammable, colourless, reactive, and readily
polymerized gas at normal temperature and pressure. The heat of
combustion for formaldehyde gas is 4.47 kcal/g. It forms explosive
mixtures with air and oxygen at atmospheric pressure. Flammability is
reported to range from 12.5 to 80% by volume, a 65-70% formaldehyde-air
mixture being the most readily flammable.
Formaldehyde is present in aqueous solutions as a hydrate and tends to
polymerize. At room temperature and with a formaldehyde content of 30%
and more, the polymers precipitate, making the solution turbid.
Formaldehyde decomposes into methanol and carbon monoxide at
temperatures above 150°C, though uncatalysed decomposition is slow at
temperatures below 300°C.
Under atmospheric conditions, formaldehyde is readily photooxidized by
sunlight to carbon dioxide. It reacts relatively quickly with trace
substances and pollutants in the air, and its half-life in urban air,
under the influence of sunlight, is short. In the absence of nitrogen
dioxide, the half-life of formaldehyde is approximately 50 min during
the day; in the presence of nitrogen dioxide, it is about 35 min.
1.3 Analytical Methods
The most widely used methods for the determination of formaldehyde are
based on spectrophotometry. Depending on the method used, sensitivities
of between 0.0036 and 0.3 mg/litre can be achieved.
Other available methods include colorimetry, fluorimetry, high pressure
liquid chromatography (HPLC), polarography, gas chromatography, infrared
detection, and gas detector tubes. HPLC is the most sensitive method.
In all these methods, other inorganic and organic chemicals, such as
sulfur dioxide, other aldehydes, and amines, cause interference.
The method of sampling and the treatment of the sample before analysis
are important factors in the accuracy of the determination.
Gas detector tubes or infrared analysers are often used for monitoring
workplace atmospheres, and the sensitivity of these is generally around
0.5-0.6 mg/litre.
1.4 Composition
Formaldehyde is most commonly available, commercially, as a 30-50% (by
weight) aqueous solution. Methanol or other substances are usually
added to the solution as stabilizers, to reduce intrinsic
polymerization. The concentration of methanol can be as high as 15%,
while that of other stabilizers is of the order of several hundred
mg/litre. Concentrated liquid formaldehyde-water systems containing up
to 95% formaldehyde are obtainable, but the temperature necessary to
maintain solution and prevent separation of the polymer increases from
room temperature to 120°C, as the concentration in solution increases.
In solid form, formaldehyde is marketed as trioxane (CH2O)3, and its
polymer, paraformaldehyde, with 8-100 units of formaldehyde.
Paraformaldehyde is technologically important.
1.5 Uses
The uses of formaldehyde cover a wide spectrum. Some examples are given
below:
(a) Animal nutrition and agriculture
In animal nutrition, formaldehyde may be added to feed to protect
dietary protein from deamination by ruminal microorganisms in ruminants.
In the USA, formaldehyde is used as a food additive, to improve the
handling characteristics of animal fat and oilseed cattle food mixtures,
by producing a dry free-flowing product. Urea-formaldehyde fertilizer is
used in farming, as a source of nitrogen, to improve the biological
activity of the soil.
(b) Aminoplastics (urea formaldehyde resins and melamine formaldehyde
resins)
Reaction of formaldehyde with urea or melamine yields urea formaldehyde
(UF) or melamine formaldehyde (MF) (condensation process). Various
concentrations of these synthetic resins are then used, in solution or
powder form, for further processing.
In the Federal Republic of Germany, about 70% of the total amount of
aminoplastics produced, i.e., 170 000 tonnes of formaldehyde per annum,
is used as glue in the manufacture of particle boards. These boards are
mostly manufactured from urea formaldehyde resins.
About 10% of the aminoplastic glues used are melamine-urea-formaldehyde
resins, i.e., products in which melamine and urea are co-condensed with
formaldehyde. Melamine resins are more damp-proof than urea resins, but
they are also more expensive.
Condensed aminoplastics of very low relative molecular mass serve as
textile treatments, to make cotton and fabrics containing synthetic
fibres creaseproof and permanently pressed. In the USA, it is estimated
that approximately 85% of all fabrics used in the clothing industry have
been treated in this way. Extremely stable aminoplastics are used, in
order to ensure that they will not degrade during the lifetime of the
articles.
Compounds similar to those used in finishing textiles are used in the
tanning of leather. Others are used in electrical engineering, e.g., in
light switches, sockets, and in parts of electric motors, in mechanical
engineering, in the motor-vehicle industry, for household articles,
e.g., camping dishes, parts of electrical household appliances, lamps,
and plumbing components.
Aminoplastics are used in the paint industry as binding agents in
special types of lacquer and paint, e.g., for cars. In agriculture, they
are used as preservatives. Aminoplastics in the form of foam resin are
also used in carpet cleaning agents.
(c) Phenolic plastics (phenol formaldehyde resins)
Phenolic plastics are synthetic resins in which formaldehyde is
condensed with phenols. Phenol, resorcinol, and cresols are among the
phenolic components. The wood-working industry is a major consumer.
Other major areas of application are: in the production of hard
materials, similar to those produced from aminoplastics; as a moulding
material; and as a binder in enamel, paints, and lacquers.
Phenolic plastics are used as binding agents in the production of
insulating materials from rock-wool or glass fibres, in brake-linings,
abrasive materials, and moulded laminated plastics. They also serve as
binding agents for moulding sand in foundries.
(d) Polyoxymethylene (polyacetal plastics)
Polyoxymethylenes (POM) are another group of plastics produced by
polymerizing formaldehyde. They are used for parts of motor vehicles
and machines that are subjected to mechanical or thermal stress, in
precision and communication engineering, in household appliances, and in
plumbing fixtures.
(e) Chemical intermediate
Formaldehyde is an important raw material in the industrial synthesis of
a number of organic compounds, e.g., 1,4-butane diol, pentaerythritol,
methylenediphenyldiisocyanate, trimethylolpropane, neopentylglycol,
hexamethylenetetramine, and chelating agents (NTA, EDTA). It is also
used in the production of dyes, dispersion products, pesticides,
perfumes, and vitamins.
(f) Pharmaceutical products
Products containing formaldehyde are now rarely used for disinfecting
the skin and mucous membranes, but formaldehyde may be added to some
pharmaceutical products as a preservative.
Formaldehyde kills viruses, bacteria, fungi, and parasites, and has
found wide use as a fumigant. It is a disinfectant with a broad
efficiency, and its virucidal properties make it extremely useful for
disinfection in the clinical field.
Root canal-filling sealants containing paraformaldehyde are used in
dental surgery.
(g) Cosmetics
Formaldehyde is used as a preservative in cosmetics and in
nail-hardening agents. Traces can also be found in cosmetics resulting
from the disinfection of apparatus used in their manufacture. Products
containing formaldehyde are used for other purposes, e.g.,
antiperspirants, skin-hardening agents, dry-skin lotion, shampoos, and
bubble bath oil.
(h) Other consumer goods
Formaldehyde at a concentration of <1% is also used as a preservative
in a variety of other consumer goods, such as household cleaning agents,
dish-washing liquids, fabric softeners, shoe-care agents, car shampoos
and waxes, and carpet-cleaning agents.
2. SUMMARY AND EVALUATION
2.1 Human Exposure
Air concentrations of formaldehyde, near the ground in coastal,
mountain, and oceanic areas, were found to range from 0.05 to
14.7 µg/m3, the majority of concentrations being within the range of
0.1-2.7 µg/m3. In the presence of man-made sources of formaldehyde,
but away from any industrial plants, mean values ranged from 7 to
12 µg/m3, with a few peaks up to 60-90µg/m3. Data from different
parts of the world were in good agreement.
Rain-water contains 110-174 µg formaldehyde/litre, with peaks as high as
310-1380 µg/litre.
Emissions of formaldehyde from industrial processes vary widely,
according to the type of industry. A considerable amount of
formaldehyde comes from the exhaust emission of motor vehicles, but this
varies greatly, according to country and the quality of fuel.
There is some natural formaldehyde in raw food, levels ranging from
1 to 90 mg/kg. Accidental contamination of food may occur during
fumigation. Formaldehyde is sometimes used as a preservative, or it may
be produced during cooking.
Indoor air levels (non-industrial) depended on several factors, but
mainly on the age of the building and the building materials, the type
of construction, and the ventilation. Tobacco smoke as well as
ureaformaldehyde foam insulation and formaldehyde-containing
disinfectants are all important sources of indoor formaldehyde. Indoor
levels varied widely in different situations, most being within the
range of 10-4000 µg/m3. In some cases, low values were found in rooms
with substantial sources of formaldehyde emission. Area disinfection in
hospitals produced the highest levels of up to 20 000 µg/m3.
However, persons carrying out such disinfection wear protective equipment
and the areas are not occupied until the formaldehyde levels have fallen
to 1200 µg/m3 (1 ppm) or less. Levels in rooms in which there is
tobacco smoking can exceed 100 mg/m3.
The contribution of various atmospheric environments to the average
human daily intake has been calculated to be 0.02 mg/day for outdoor
air, 0.5-2 mg/day for indoor conventional buildings, 1-10 mg/day for
buildings with sources of formaldehyde, 0.2-0.8 mg/day for workplaces
where formaldehyde is not used, 4 mg/day for workplaces in which
formaldehyde is used, and 0-1 mg/day for environmental tobacco smoke.
Smoking 20 cigarettes per day corresponds to an intake of 1 mg
formaldehyde/day, through inhalation.
The formaldehyde concentration in drinking-water is generally about
0.1 mg/litre, resulting in a mean daily intake of 0.2 mg/day. The
quantity of formaldehyde ingested in food depends on the composition
of the meal and, for an average adult, may range from 1.5 to 14 mg/day.
2.2 Uptake, Metabolism, and Excretion
Formaldehyde is readily absorbed via the respiratory and
gastrointestinal routes. Dermal absorption of formaldehyde appears to
be very slight. Increases in blood concentrations of formaldehyde were
not detected in rats or human beings exposed to formaldehyde through
inhalation, because of rapid metabolism. Absorbed formaldehyde is
metabolized rapidly to formate, or enters the one-carbon pool to be
incorporated into other molecules. There are two pathways of final
elimination, namely, in exhaled air or via the kidneys.
2.3 Effects on Organisms in the Environment
Formaldehyde is used as a disinfectant to kill viruses, bacteria, fungi,
and parasites, but it is only effective at relatively high
concentrations.
Algae, protozoa, and other unicellular organisms are relatively
sensitive to formaldehyde, with acute lethal concentrations ranging from
0.3 to 22 mg/litre. Aquatic invertebrates showed a wide range of
responses; some crustaceans were the most sensitive, with median
effective concentration (EC50) values ranging from 0.4 to
20 mg/litre. In 96-h tests on several fish species, the LC50 of
formaldehyde for adults ranged from a minimum of about 10 mg/litre to a
maximum of several hundred mg/litre; most species showed LC50 values
in the range of 50-100 mg/litre. The responses of various species of
amphibians are similar to those of fish, with median acute lethal
concentrations (LC50) ranging from 10 to 20 mg/litre for a 72-h
exposure.
No data are available on long-term aquatic studies.
Eggs and larvae of some cattle parasites are killed by formaldehyde
solution (1-5%) and some nematodes by a 37% solution, whereas other
nematodes are unaffected. In ruminant mammals, formaldehyde protects
dietary protein from microbial proteolysis in the rumen and increases
the efficiency of utilization of amino acids.
Few data are available on the effects of formaldehyde on plants.
However, from the agricultural use of urea-formaldehyde fertilizers, it
appears that, at recommended concentrations, formaldehyde does not alter
nitrogen and carbohydrate metabolism in plants, but that high doses have
negative effects on soil metabolism. Formaldehyde impairs pollen
germination.
Formaldehyde undergoes rapid decomposition, and does not accumulate in
the environment or in food chains.
2.4 Effects on Experimental Animals
Acute inhalation exposure of rats and mice to formaldehyde at very high
concentrations (120 mg/m3) produced salivation, dyspnoea, vomiting,
spasms, and death. At a concentration of 1.2 mg/m3, eye irritation,
decreased respiratory rate, increased airway resistance, and decreased
compliance appeared. Mice were more sensitive than rats.
Short-term, repeated exposures (7-25 mg/m3) of rats produced
histological changes in the nasal epithelium, such as cell degeneration,
inflammation, necrosis, squamous metaplasia, and increased cell
proliferation.
There is evidence that it is the concentration rather than the dose that
determines the cytotoxic effects of formaldehyde on the nasal mucosa of
rats; concentrations below 1 mg/m3 do not lead to cell damage and
hyperplasia.
Dose-related lesions, observed with long-term, repeated inhalation
exposure (2.4, 6.7, or 17.2 mg/m3), were dysplasia and squamous
metaplasia of the respiratory and olfactory epithelia, which regressed,
to some extent, after cessation of exposure.
Formaldehyde is carcinogenic in rats and mice. It produced nasal
squamous cell carcinomas in rats exposed to high concentrations
(17.2 mg/m3), which also caused severe tissue damage. The
concentration-response curve was extremely non-linear with a
disproportionate increase in tumour incidence at higher concentrations.
A low, but not statistically significant, incidence of nasal tumours
occurred at 6.7 mg/m3. No tumours were found at other sites. Mice
developed squamous cell carcinomas of the nasal cavity with long-term
exposure to 17.2 mg formaldehyde/m3, but this finding was not
statistically significant. No tumours were found at other sites. No
tumours were found in hamsters.
Long-term oral administration of formaldehyde (0.02-5% in the
drinking-water) was found to induce papillomas in the forestomach of
rats.
Several skin initiation/promotion studies on formaldehyde in mice did
not produce evidence of skin carcinogenicity; the results, with regard
to promotion, were either negative or inconclusive.
The International Agency for Research on Cancer has concluded that there
is sufficient evidence for the carcinogenicity of formaldehyde in
animals.
2.5 Effects on Human Beings
Formaldehyde has a pungent odour, detectable at low concentrations, and
its vapour and solutions are known skin and eye corrosives or irritants
(depending on the concentration) in human beings. The common effects of
formaldehyde exposure are various symptoms caused by irritation of the
mucosa in the eyes and upper airways. In the non-industrial indoor
environment, sensory reactions are typical effects, but there are large
individual differences in the normal population and between
hyperreactive and sensitized people.
There are a few case reports of asthma-like symptoms caused by
formaldehyde. However, none of these conformed to classical asthma, and
were neither Type I nor Type IV reactions. Irritation of the airways
was considered to be the primary cause. Skin sensitization is induced
only by direct skin contact with formaldehyde solutions at
concentrations higher than 2%. The lowest patch-test challenge
concentration in an aqueous solution, reported to produce a reaction in
sensitized persons, was 0.05% formaldehyde.
Formaldehyde does not have any adverse effects on reproduction, and is
not teratogenic.
In in vitro studies, formaldehyde interfered with DNA repair in human
cells, but there are no data relating to mutagenic outcomes.
The International Agency for Research on Cancer has concluded that there
is limited evidence for the carcinogenicity of formaldehyde in human
beings.
3. CONCLUSIONS AND RECOMMENDATIONS
3.1 Conclusions
3.1.1 Exposure
Formaldehyde occurs naturally and is a product of normal metabolic
pathways in many species. It is a widely produced industrial chemical.
Major sources of formaldehyde are automobile and aircraft exhaust
emissions, tobacco smoke, natural gas, fossil fuels, waste incineration,
and oil refineries.
Formaldehyde exposure varies widely, because of local variations in
emissions from natural and man-made sources. Significant levels of
formaldehyde have been reported in indoor air arising from tobacco
smoking, building and furnishing materials, and the use of
formaldehyde-containing disinfectants. In workplaces, exposure can
occur during the production, or handling, of formaldehyde, or products
containing formaldehyde.
3.1.2 Health effects
The most prominent features of formaldehyde vapour are its pungent odour
and its irritant effects on the mucosa of the eyes and upper airways.
Odour-detection thresholds are in the range of
0.1-0.3 mg/m3. Thus, some individuals can smell formaldehyde at very
low concentrations.
Eye and respiratory-tract irritation can occur at levels of about
1 mg/m3, but discomfort has been reported at much lower levels.
Direct contact with formaldehyde solutions at concentrations of 1-2% can
cause skin irritation in some individuals. In general, solutions
containing between 5% and 25% are irritant, those containing more than
25% formaldehyde are corrosive; below 5%, irritancy decreases with
decreasing concentration. Long-term exposure of the skin can lead to
allergic contact dermatitis, but this has been demonstrated only for
formaldehyde solution and not for gaseous formaldehyde.
Reversible obstruction of the airways has been produced by irritant
concentrations of formaldehyde, and long-term exposure to formaldehyde
at levels as low as 0.5 mg/m3 may cause a slight elevation in airway
resistance. Formaldehyde-related asthma is unusual, despite widespread
population exposure to formaldehyde.
In dental surgery, in order to avoid adverse reactions, root canal
sealants should not be extruded beyond the apex.
There is no convincing evidence that formaldehyde is teratogenic, in
either animals or human beings; it has not produced any adverse effects
on reproduction in test animals or in human beings.
Formaldehyde is positive in a wide range of mutagenicity test systems in
vitro; results of in vivo test systems are conflicting. It has been
shown to form DNA-protein cross-links in vitro and in vivo in rat
nasal mucosa. In vivo, this occurred at an exposure concentration of
1.1 mg/m3. Formaldehyde interferes with DNA repair in human cells in
vitro.
Following inhalation exposure at levels causing cell damage, a
significant incidence of squamous cell carcinomas of the nasal cavity
was induced in two strains of rat. Nasal tumours in mice have also been
reported, but the incidence was not statistically significant. There
were no tumours at other sites.
A limited number of forestomach papillomas were reported in rats
following the administration of formaldehyde in the drinking-water.
In human beings, though an increased risk for a number of cancers has
been reported, the causal role of formaldehyde is considered likely only
for nasal and nasopharyngeal cancer.
3.2 Recommendations
3.2.1 General
Human exposure to formaldehyde should be controlled.
It is recommended that consumer goods containing formaldehyde should be
labelled, in order to protect persons with a formaldehyde allergy.
3.2.2 Workplaces
Personal protective clothing should be required only under exceptional
circumstances. Normally, plant design and operating procedures should
make the use of personal protection unecessary. Work procedures must
always be planned so that skin contact with formaldehyde solutions is
avoided. Washing facilities should be readily available so that
contaminated skin can be washed immediately with ample quantities of
water.
Any work involving formaldehyde or paraformaldehyde should, whenever
possible, be carried out using enclosed systems. Pipes carrying
formaldehyde should be distinctly and durably marked. Flange
connections should be equipped with a splash guard.
The release of formaldehyde into workplace atmospheres should be
prevented during filling or emptying operations, for example, by the use
of the gas pendulum method or suitable suction devices, and the
introduction of formaldehyde via ports. Areas in which formaldehyde is
handled must be well ventilated. Normally, mechanical ventilation is
necessary.
For sampling, open contact with formaldehyde should be avoided by using
sampling ports, closed sampling vessels, or vacuum samplers.
Work procedures must always be planned so that skin contact with
formaldehyde solutions is avoided. Washing facilities should be readily
available to enable contaminated skin to be washed immediately with
ample quantities of water.
Where the release of formaldehyde from processes cannot be prevented by
technical measures, suction devices at the release points or adequate
ventilation should be used, to ensure the safe removal of gaseous
formaldehyde.
When exhaust gases from equipment or rooms containing formaldehyde are
vented to the atmosphere, the installation of purification or
destruction units may be required.
3.2.3 Cosmetics
Cosmetics (creams) containing formaldehyde should be suitably labelled,
giving the concentration. Levels in oral health products should be
strictly limited.
The concentration of formaldehyde, used as a preservative agent in
cosmetics, should not exceed 0.2%, except in the case of nail hardeners,
which may contain up to 5% formaldehyde.
3.2.4 Disinfection
Because of the sensitizing potential, skin contact with
formaldehyde-containing disinfectants should be avoided by wearing
impermeable gloves. Thermal procedures are preferred for disinfection
or sterilization. If instruments are disinfected using formaldehyde,
closed containers should be used. Incubators for babies, endoscopes, and
tubes (e.g., endotracheal, gastric) should not be sterilized with
formaldehyde.
Appropriate laundering procedures are preferred for the disinfection of
clothing. Any "tub-disinfection" of clothing in formaldehyde solution
should be exceptional and, if used, the "tub" must be closed with a
tight-fitting lid. Gloves (and, if necessary, respirators) should be
worn for the initial handling of formaldehyde-disinfected clothing.
Steam disinfecting is the method of choice for mattresses; spraying with
disinfectants is considered obsolete. However, mattresses covered with
synthetic materials can be disinfected by wiping with formaldehyde
solution, but this should only be performed under well-ventilated
conditions.
Care should be taken when using formaldehyde solutions for area
disinfection. Wiping or scrubbing is recommended and the spraying of
formaldehyde solutions should be confined to inaccessible places.
Direct contact with the formaldehyde solution should be avoided by the
use of gloves and suitable protective clothing. Large-area disinfection,
e.g., of laboratories, should be done after working hours. Good
ventilation during and after disinfection is mandatory.
3.2.5 Pathology
Fixation of tissues in formalin baths should be performed in closed
containers, under an exhaust hood. Fixed tissue slices should then be
washed with water to remove superfluous formaldehyde, before viewing
them under the microscope.
3.2.6 Laboratories
In all laboratories, any work using formaldehyde or paraformaldehyde
should be carried out under an exhaust hood, using enclosed equipment.
4. HUMAN HEALTH HAZARDS, PREVENTION AND PROTECTION, EMERGENCY ACTION
4.1 Main Human Health Hazards, Prevention and Protection, First Aid
4.1.1 Human health hazards, prevention, and protection
Workers must be informed of the possible dangers associated with the
handling of formaldehyde, and instructed on safety precautions. When a
risk to workers handling formaldehyde cannot be ruled out by technical
means, personal protective equipment must be made available and used.
Individuals with an allergy to formaldehyde should not work with it.
Some technical protective measures are described in section 3.2.
Working clothes and personal protective equipment, including protective
clothing that has been contaminated with formaldehyde or
paraformaldehyde, must be changed and either thoroughly cleaned or
destroyed.
Storage of food, eating, drinking, and smoking, should not take place in
workplaces where formaldehyde is used.
If there is a risk of inhaling toxic concentrations of formaldehyde, for
example, during open sampling or repair work, under uncontrolled working
conditions, or in emergencies, breathing masks should be worn. As the
effectiveness of gas filters is extremely limited, they should only be
used if the total atmospheric contaminant concentration, including
formaldehyde, is 1% (by volume) or less, and the oxygen content of the
air is not less than 17% (by volume).
At higher concentrations of formaldehyde, or with prolonged exposures to
formaldehyde-containing atmospheres, or under uncertain conditions,
self-contained breathing apparatus or an independent air supply must be
used. A full face-mask provides additional eye and face protection.
When working with formaldehyde solutions or paraformaldehyde, safety
glasses (framed spectacles with side protection) must be worn. If eye
irritation is expected, full goggles must be used.
During work involving a risk of skin contact with formaldehyde solutions
or paraformaldehyde, well-fitting full goggles, suitable protective
gloves, boots, and, possibly, an impermeable safety suit should also be
worn.
4.1.2 First aid
All persons handling formaldehyde or paraformaldehyde should be informed
about the health risks and given instructions on the actions to take in
case of accident.
If formaldehyde poisoning is suspected, the affected person must be
removed from the danger area immediately. First-aid and rescue
personnel must protect themselves against contact with formaldehyde (for
example, breathing protection, protective gloves). Medical advice
should be sought without delay and the physician given details
concerning both the exposure and the first-aid measures applied.
Advice on first-aid measures is given in the Summary of Chemical Safety
Information (section 6).
4.2 Advice to Physicians
There is no specific antidote. If formaldehyde has been ingested, a
stomach lavage can be performed, providing that full precautions are
taken against inadvertent inhalation. In all cases of formaldehyde
poisoning, maintain electrolyte balance, treat pain, and combat shock.
4.3 Explosion and Fire Hazards
Formaldehyde gas is flammable with a flash-point of 50°C. Formaldehyde
and formaldehyde solutions will burn above the flash-point, if exposed
to flames or sparks. The flash-point depends on the concentration of
methanol, and can vary between 50°C and 85°C. When formaldehyde is
heated above its flash-point, it explodes (autoignition temperature,
430°C).
4.3.1 Explosion hazards
Work areas where formaldehyde is present, or can be present, in such
quantities that the lower explosion limit (7% volume) is reached, should
be considered as fire and explosion risk areas.
Rooms in which aqueous formaldehyde solutions and paraformaldehyde are
stored or handled at normal temperature (below the flash-point) are not
explosion risks.
4.3.2 Fire hazards
There is a fire risk in rooms in which aqueous formaldehyde solutions
and paraformaldehyde are stored at normal temperature. Smoking, open
flames, and lights are prohibited. Electrical installations must be
explosion-proof. The same restrictions apply to rooms in which work is
carried out using aqueous methanol-containing formaldehyde solutions or
paraformaldehyde heated beyond the ignition point.
Foam, carbon dioxide, and water are suitable for putting out fires.
Powder extinguishers are of limited use, except in the case of small
fires. Keep drums or containers of formaldehyde cool by spraying with
water.
4.4 Storage
Containers of stainless steel, pure aluminium, polyethylene, and
polyester reinforced with glass fibre are suitable for the storage and
shipping of formaldehyde solutions. Normal steel containers with a
corrosion-proof lining, e.g., phenol-formaldehyde resin or asphalt
varnish, or with a rubber inner coating can also be used. Aluminium is
extremely prone to corrosion by formaldehyde, at temperatures above 60
C. Containers made of ordinary steel, copper, nickel, or zinc
compounds, with unprotected surfaces, are unsuitable.
To avoid precipitation of paraformaldehyde, minimum storage temperatures
for formaldehyde solutions of various concentrations are specified by
the manufacturers. Do not store at temperatures below 15°C.
During the filling of containers, exhaust air should be purified or
recycled, using the gas pendulum method. Hoses used for the transfer of
formaldehyde should not be used for any other substances.
4.5 Road Transport
In case of accident, stop the engine. Remove all sources of ignition.
Keep bystanders at a distance and mark the road.
In case of spillage or fire, use the methods advised in sections 4.6 and
4.3, respectively. In case of poisoning, follow the advice in section
4.1.2 and in the Summary of Chemical Safety Information (section 6).
4.6 Spillage and Disposal Advice (based on the IRPTC waste disposal file)
4.6.1 Spillage
Before cleaning up spilled formaldehyde solutions, workers should put on
breathing equipment and suitable protective clothing (protective
goggles, protective gloves, rubber boots, safety suit).
Use absorbent paper to mop up spilled material. Follow by washing
surfaces well with soap and water. Seal all wastes in vapour-tight
plastic bags for eventual disposal. Larger quantities should be
collected by pumping into containers, or by the use of sorbents (e.g.,
kieselguhr or exfoliated mica). Solutions containing formaldehyde are
water-contaminating and should be disposed of safely.
Formaldehyde-containing absorbents, or soil contaminated with
formaldehyde, should be disposed of in a suitable manner.
Working clothes and personal protective equipment, including protective
clothing contaminated with formaldehyde or paraformaldehyde, must be
changed and either cleaned or destroyed.
If transported, formaldehyde waste should be clearly labelled.
4.6.2 Disposal
The International Register of Potentially Toxic Chemicals provides the
following advice on waste treatment and disposal methods:
"Recommendable: incineration, oxidation, discharge to sewer.
Not Recommendable: evaporation, alkaline hydrolysis.
Dissolve in a combustible solvent, thence spray the solution into
a furnace with afterburner.
Dilute formaldehyde waste with a large amount of water and treat
the solution by hypochlorite solution. Concentration of
formaldehyde on the solution should be below 2%, in order to avoid
excess exothermic reaction heat.
Formaldehyde is a powerful reducing agency and many oxidants can be
used but may react violently (must be diluted).
Alkaline hydrolysis may be dangerous because of exothermic
reaction."
5. HAZARDS FOR THE ENVIRONMENT AND THEIR PREVENTION
Formaldehyde is widely present in the environment, as a result of
natural processes and from man-made sources. Most of the formaldehyde
enters the atmosphere, where it is rapidly degraded by photolysis and
photo-oxidation by hydroxyl radicals. Formaldehyde in soil and water is
also biodegraded in a relatively short time. In water, one pathway of
degradation is rapid hydration to methylene glycol.
Formaldehyde is toxic for several aquatic organisms, but its ready
biodegradability, low bioaccumulation, and the ability of organisms to
metabolize it indicate that the impact of formaldehyde on the aquatic
environment is limited, except in the case of major pollution. Similar
considerations apply to the atmosphere and the terrestrial environment
where hazards will only occur when massive discharges or releases lead
to major local pollution. The non-persistence of formaldehyde means
that effects will not be permanent.
The main feature in the prevention of hazards for the environment is the
control of the emissions, release, and disposal of formaldehyde.
6. SUMMARY OF CHEMICAL SAFETY INFORMATION
This summary should be easily available to all health workers
concerned with, and users of, formaldehyde. It should be displayed at,
or near, entrances to areas where there is potential exposure to
formaldehyde, and on processing equipment and containers. The summary
should be translated into the appropriate language(s). All persons
potentially exposed to the chemical should also have the instructions
in the summary clearly explained.
Space is available for insertion of the National Occupational Exposure
Limit, the address and telephone number of the National Poison Control
Centre, and local trade names.
FORMALDEHYDE
Methanal, methylene oxide, oxymethylene, methylaldehyde, oxomethane, formalin (solution), formol (solution)
PHYSICAL PROPERTIES OTHER CHARACTERISTICS
Gas
Relative molecular mass 30.03 Colourless gas at normal temperature and
Melting point (°C) -118 pressure; pungent odour, detectable at low
Boiling point (°C) at ambient pressure concentrations
(3.33kPa or 25 mmHg) -19.2
Water solubility at 30°C (g/100 ml water) 55
Vapour pressure (kPa at -19°C) 101.3
(kPa at -33°C) 52.6
Flash-point (°C) 300
Explosivity range in air (g/m3) 87-910 (7-73%)
Solution
Aqueous solution (37-50% formaldehyde
with varying amounts of methanol)
Boiling point (°C) 97
Freezing point (C) without methanol -15
Flash-point (°C) without methanol 85
Flash-point (°C) with 15% methanol 50
HAZARDS/SYMPTOMS PREVENTION AND PROTECTION FIRST AID
Formaldehyde is a suspected human
carcinogen by the inhalation route
SKIN: Vapour is irritant; solutions Handle mechanically, where possible, Remove contaminated clothing immediately;
may be corrosive or irritant, in proper enclosures or cabinets wash contaminated skin thoroughly with
depending on formaldehyde with exhaust ventilation; where running water and soap; continue for
concentration; redness of skin, appropriate, wear clean impervious at least 10 minutes; protect from heat
burns, scaly and brittle nails gloves and apron to deflect loss; obtain medical advice
splashes; wear freshly laundered
clothes; remove and wash clothes
thoroughly after contamination
EYE: Vapour is irritant and Ensure vapour concentrations are Irrigate eyes with potable water or
lacrimatory; solutions may be below occupational exposure limits; sterile eyewash solution for at
corrosive or irritant, depending wear chemical goggles or face visor least 15 minutes; obtain medical advice
on formaldehyde concentration when handling solutions
INGESTION: Formaldehyde solutions Do not eat, drink, or smoke while Do not induce vomiting; obtain medical
may irritate the upper gastro- handling chemicals; use good advice; water can be sipped (dilution
intestinal tract or have corrosive work and personal hygiene practices effect); milk can be sipped (protein
effects, depending on formaldehyde binds with formaldehyde)
concentration; abdominal pain,
nausea, vomiting, diarrhoea,
convulsions, coma
INHALATION: Irritation, which Remove from danger zone to the fresh
may be severe, possibility of oedema; air; absolute rest; if unconscious,
sore throat, shortness of breath, maintain three-quarter prone position;
laboured breathing, congling protect against heat loss; give oxygen;
bronchospasm, nausea, dizziness, if breathing stops, commence artificial
loss of consciousness respiration, if possible with
respirator; obtain medical advice
HAZARDS/SYMPTOMS PREVENTION AND PROTECTION FIRST AID
ENVIRONMENT: Half-life in the Industrial emissions, discharges, and
environment is short; formaldehyde waste disposal should be minimized
is toxic for aquatic organisms; and regulated
should not pose an environmental
risk, except in the case of major
discharges, when there could be
local, but not persistent, effects
SPILLAGE STORAGE FIRE AND EXPLOSION
SOLUTIONS: Wear rubber gloves Store in a cool dark place in
and boots; absorb on paper, earth, light-proof containers
sand, or equivalent, and shovel into
a sealable container; dispose of
drummed material as hazardous
chemical waste
WASTE DISPOSAL NATIONAL INFORMATION LABELLING
Incineration; oxidation National Occupational Exposure UN: Hazard Class 3 : Flammable liquid
Limit: (applies to flammable formaldehyde
solutions)
National Poison Control Centre:
Hazard Class 9 : Miscellaneous dangerous
substances; and
Local trade names: Packing Class III : Substance presenting minor
danger (applies to formaldehyde solutions)
7. CURRENT REGULATIONS, GUIDELINES, AND STANDARDS
The information given in this section has been extracted from the
International Register of Potentially Toxic Chemicals (IRPTC) legal
file. A full reference to the original national document from which
the information was extracted can be obtained from IRPTC. When no
effective date appears in the IRPTC legal file, the year of the
reference from which the data are taken is indicated by (r).
The reader should be aware that regulatory decisions about chemicals,
taken in a certain country, can only be fully understood in the
framework of the legislation of that country. The regulations and
guidelines of all countries are subject to change and should always be
verified with appropriate regulatory authorities before application
7.1 Exposure Limit Values
Some exposure limit values are given on pages 39 to 43.
7.2 Specific Restrictions
In the Federal Republic of Germany, emissions of formaldehyde are
controlled. Formaldehyde is included in Class 1, in which the air
emissions of organic compounds must not exceed (as the sum of all
compounds in one class) a mass concentration of 20 mg/m3, at a mass
flow equal to, or greater than, 0.1 kg/h.
In the European Economic Community, formaldehyde, in quantities equal
to, or greater than, 50 tonnes (at concentrations greater than 90%) is
listed as a dangerous substance in the 1988 Directive on the Major
Accident Hazards of Certain Industrial Activities.
In the United Kingdom, formaldehyde is classified as a poisonous
substance and its sale is subject to restrictions.
The USA designates formaldehyde, and any isomers, hydrates, and
solutions and mixtures containing formaldehyde, as hazardous
substances for the purposes of discharge (including spillage and
leakage), under the 1981 Federal Water Pollution Control Act. Unless
in compliance with a specified permit or procedure, the USA Government
must be notified of any discharge of formaldehyde in, or on, navigable
waters, adjoining shorelines, or the contiguous zone, in an amount
equal to, or more than, 454 kg in any 24-h period. Permits are
required for the discharge of formaldehyde from any point source into
USA national waters. Formaldehyde in outfalls must be reported. Even
if not required in the permit, discharge of formaldehyde must be
reported, if it exceeds the highest concentration of 100 µg/litre,
five times the maximum concentration reported in the permit
application, or the level established by the US EPA Director. Any
solid waste containing formaldehyde must be listed as hazardous waste
and subject to handling, transport, treatment, storage, and disposal
regulation, permit, and notification requirements, unless it is found
that the waste cannot pose a threat to human health or the
environment, when improperly managed. Certain specified industrial
solid wastes containing formaldehyde are classified as hazardous
wastes. According to the US EPA hazard-ranking system for the
identification of hazardous waste facilities, formaldehyde is assigned
a toxicity value of 3 (on a 0-3 scale), a persistence value of 0, an
ignitability value of 2, and a reactivity value of 2.
7.3 Labelling, Packaging, and Transport
In the European Economic Community, formaldehyde is classified for
labelling purposes in accordance with the concentration of the
solution. Solutions containing 25% or more formaldehyde are labelled:
Toxic by inhalation, in contact with skin and if swallowed;
causes burns; possible risk of irreversible effects; may cause
sensitization by skin contact.
Solutions containing between 1% and 5% formaldehyde are labelled:
Possible risk of irreversible effects; may cause sensitization
by skin contact.
In the United Kingdom, for road tankers transporting formaldehyde
solutions with a flash-point below 60.5°C, the required label is:
Other hazardous substance..
For the purposes of marine transportation, the International Maritime
Organization (IMO) classifies formaldehyde in Hazard Class 3.3 -
Flammable Liquid-; Packing Group II - Substance Presenting Medium
Danger (applies to solutions). For solutions of formaldehyde with a
flashpoint above 60°C (closed-cup), the IMO classification is Hazard
Class 9 - Miscellaneous Dangerous Substances-; Packing Group III -
Substance Presenting Minor Danger.
The United Nations transport classification for non-flammable
formaldehyde solutions is Hazard Packing Group III - Substance
Presenting Minor Danger; For flammable formaldehyde solutions, the
classification is Hazard Class 3 - Flammable Liquid.
In Canada, formaldehyde solutions with a flash-point greater than 61°C
are subject to transport restrictions in the category of miscellaneous
dangerous goods. The maximum amount per package that may be
transported on a passenger aircraft, train, or road vehicle, is
100 litres; on a cargo aircraft, the maximum amount per package is
200 litres. Solutions with a flash-point of less than 61°C, in
containers having a water capacity not greater than 454 litres, are in
the category of flammable liquid, hazardous to the environment, and
Packing Group II (Medium Danger). The maximum amount per package that
may be transported on a passenger aircraft, train, or road vehicle is
5 litres; on a cargo aircraft, the maximum amount per package is
60 litres. Where the containers have a capacity greater than
454 litres, the maximum amount per package that may be transported on
a passenger aircraft, train, or road vehicle, is 60 litres; on a cargo
aircraft, the maximum amount per package is 220 litres.
EXPOSURE LIMIT VALUES
Medium Specification Country/ Exposure limit description Value Effective
organization (mg/m3) datea
AIR Occupational Australia Threshold limit value (TLV) 1985
- Time-weighted average (TWA) 1.5
- Short-term exposure limit (STEL) 3.0
(Suspected carcinogenic potential for man)
Belgium Threshold limit value (TLV) 1989
- Time-weighted average (TWA) 1.5
- Short-term exposure limit (STEL) 3.0
(Suspected carcinogenic potential for man)
Brazil Allowable limit (AL) 1982
- Time-weighted average (TWA) 2.3
(48 h/week)
Canada Threshold limit value (TLV)
- Time-weighted average (TWA) 1.5 1980
- Short-term exposure limit (STEL) 3.0
(Suspected human carcinogen)
Czechoslovakia Maximum allowable concentration (MAC) 1985
- Time-weighted average (TWA) 0.5
- Ceiling value (CLV) 1.0
Finland Maximum permissible concentration (MPC) 1989r
- Short-term exposure limit (STEL) 1.3
Germany, Federal Maximum worksite concentration (MAK) 1989r
Republic of - Time-weighted average (TWA) 0.6
- Short-term exposure limit (STEL) (5-min
ceiling value) 1.2
(local irritant; sensitization; suspected
carcinogenic potential)
Medium Specification Country/ Exposure limit description Value Effective
organization (mg/m3) datea
AIR Occupational Hungary Maximum allowable concentration (MAC) 1985r
- Time-weighted average (TWA) 1.0
- Short-term exposure limit (STEL) 2.0
(30-min)
Italy Threshold limit value (TLV) 1985r
- Time-weighted average (TWA) 1.2
Japan Maximum allowable concentration (MAC) 1988r
- Ceiling limit value (CLV) 2.5
Netherlands Maximum limit (MXL) 1987r
- Time-weighted average (TWA) 1.5
- Short-term exposure limit (STEL) 3.0
Poland Maximum permissible concentration (MPC) 1985r
- Time-weighted average (TWA) 2.0
Romania Maximum permissible concentration (MPC) 1985r
- Ceiling limit value (CLV) 4.0
Sweden Hygienic limit value (HLV) 1988
- Time-weighted average (TWA) 0.6
- Ceiling limit value (CLV) 1.2
(sensitization)
Switzerland Maximum worksite concentration (MAK) 1987r
- Time-weighted average (TWA) 1.2
(sensitizer)
United Control limit (CL) 1986
Kingdom - Time-weighted average (TWA) 2.5
- Short-term exposure limit (STEL) 2.5
(10-min)
Medium Specification Country/ Exposure limit description Value Effective
organization (mg/m3) datea
AIR Occupational *USA (ACGIH) Recommended threshold limit value (TLV)
- Time-weighted average (TWA) 1.2 1990
- Short-term exposure limit (STEL) 2.5
(Suspected carcinogenic potential)
(OSHA) Permissible exposure limit (PEL)
- Time-weighted average (TWA) 3.7 1988
- Ceiling value (CLV) 6.1
- Peak value 12.0
(30-min. during 8-h shift)
USSR Maximum allowable concentration (MAC)
- Ceiling value (vapour) (CLV) 0.5 1989
Yugoslavia Maximum allowable concentration (MAC)
- Time-weighted average (TWA) 1.0 1985r
USA (ACGIH) Recommended threshold limit value (TLV)
- Time-weighted average (TWA) 0.45
(Suspected human carcinogen)
(No short-term exposure limit - STEL)
AIR Ambient USSR Maximum allowable concentration (MAC) 0.035 1984
(once/day)
0.003
daily average)
*Notice of Intended Change, 1989-90
Medium Specification Country/ Exposure limit description Value Effective
organization (mg/m3) datea
SURFACE Environmental USSR Maximum allowable concentration (MAC) 0.05 mg/litre 1985
WATER
SURFACE Environmental USSR Maximum allowable concentration (MAC) 0.25 mg/litre 1982r
WATER
FOR
FISHING
SOIL Environmental USSR Maximum allowable concentration (MAC) 7.0 mg/kg 1980
a r = year of last IRPTC update.
BIBLIOGRAPHY
ACGIH (1986) Documentation of the threshold limit values and
biological exposure indices. Cincinnati, American Conference of
Governmental Industrial Hygienists.
ACGIH (1989) Threshold limit values and biological exposure indices
for 1989-1990. Cincinnati, American Conference of Governmental
Industrial Hygienists.
CLAYTON, G.D. & CLAYTON, F.E. (1981) Patty's industrial hygiene and
toxicology. Vol. 2C. New York, Wiley-Interscience, John Wiley &
Sons.
GOSSELIN, R.E., HODGE, H.C., SMITH R.P., & GLEASON, M.N. (1976)
Clinical toxicology of commercial products. 4th ed. Baltimore,
Maryland, The Williams and Wilkins Company.
DUTCH SAFETY INSTITUTE (1989) Handling chemicals safely. 2nd ed.
Amsterdam, The Netherlands, Dutch Association of Safety Experts, Dutch
Chemical Industry Association, Dutch Safety Institute.
IRPTC (1988) Data profile (legal file). Geneva, International
Register of Potentially Toxic Chemicals.
SAX, N.I. (1984) Dangerous properties of industrial materials. New
York, Van Nostrand Reinhold Company.
US NIOSH (1976) A guide to industrial respiratory protection.
Cincinnati, Ohio, US National Institute for Occupational Safety and
Health.
US NIOSH/OSHA (1981) Occupational health guidelines for chemical
hazards. 3 Vol. Washington, DC, US Department of Health and Human
Services, US Department of Labor (Publication No. DHHS(NIOSH) 01-123).
US NIOSH/OSHA (1985) Pocket guide to chemical hazards. Washington
DC, US National Institute for Occupational Safety and Health,
Occupational Safety and Heath Administration (Publication No. 85.114).
WHO (1989) Environmental Health Criteria 89: Formaldehyde. Geneva,
World Health Organization.