Nickel (EHC 108, 1991)

INTERNATIONAL PROGRAMME ON CHEMICAL SAFETY

ENVIRONMENTAL HEALTH CRITERIA 108

NICKEL

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

First draft prepared by Dr. R.F. Hertel,
Dr. T. Maass and Ms V.R. Muller,
Fraunhofer Institute of Toxicology and Aerosol Research, Germany

World Health Orgnization
Geneva, 1991

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 the 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.

WHO Library Cataloguing in Publication Data

Nickel.

(Environmental health criteria ; 108)

1.Nickel-adverse effects 2.Nickel-toxicity 3.Environmental exposure
I.Series

ISBN 92 4 157108 X (NLM Classification: QV 290)
ISSN 0250-863X

The World Health Organization welcomes requests for permission
to reproduce or translate its publications, in part or in full.
Applications and enquiries should be addressed to the Office of
Publications, World Health Organization, Geneva, Switzerland, which
will be glad to provide the latest information on any changes made
to the text, plans for new editions, and reprints and translations
already available.

^(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. All rights reserved.

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

ENVIRONMENTAL HEALTH CRITERIA FOR NICKEL

1. SUMMARY AND CONCLUSIONS
1.1. Identity, physical and chemical properties, and
analytical methods
1.2. Sources of human and environmental exposure
1.3. Environmental transport, distribution, and transformation
1.4. Environmental levels and human exposure
1.5. Kinetics and metabolism in human beings and animals
1.6. Effects on organisms in the environment
1.7. Effects on experimental animals and in vitro test systems
1.8. Effects on human beings

2. IDENTITY, PHYSICAL AND CHEMICAL PROPERTIES, ANALYTICAL METHODS
2.1. Identity, physical and chemical properties of nickel and
nickel compounds
2.1.1. Nickel carbonate hydroxide
2.1.2. Nickel carbonyl
2.1.3. Nickel chloride and nickel chloride hexahydrate
2.1.4. Nickel hydroxide
2.1.5. Nickel nitrate
2.1.6. Nickel oxide
2.1.7. Nickel sulfate
2.1.8. Nickel sulfide
2.1.9. Nickel subsulfide
2.2. Analytical methods
2.2.1. Determination of trace amounts
2.2.2. Sample collection
2.2.3. Sample pretreatment
2.2.4. Analytical methods

3. SOURCES OF HUMAN AND ENVIRONMENTAL EXPOSURE
3.1. Natural occurrence
3.1.1. Rocks
3.1.2. Soils
3.1.3. Water
3.1.4. Fossil fuels
3.1.5. Air
3.2. Man-made sources
3.2.1. Production, use, and disposal
3.2.1.1 Primary production
3.2.1.2 Intermediate products and end-use
3.2.1.3 World production levels and trends
3.2.1.4 Emissions from the primary nickel
industry
3.2.1.5 Emissions from the intermediate nickel
industry
3.2.1.6 Emissions from the combustion of fossil
fuels
3.2.1.7 Emissions from sewage sludge and waste
incineration
3.2.1.8 Miscellaneous emission sources
3.2.1.9 Waste disposal

4. ENVIRONMENTAL TRANSPORT, DISTRIBUTION, AND TRANSFORMATION
4.1. Transport and distribution between media
4.1.1. Air
4.1.2. Water
4.1.3. Rocks and soil
4.1.4. Vegetation and wildlife
4.2. Uptake and bioaccumulation
4.2.1. Terrestrial organisms
4.2.2. Aquatic organisms
4.3. Biomagnification

5. ENVIRONMENTAL LEVELS AND HUMAN EXPOSURE
5.1. Environmental levels
5.1.1. Air
5.1.2. Drinking-water
5.1.3. Food
5.1.4. Terrestrial and aquatic organisms
5.2. General population exposure
5.2.1. Oral
5.2.2. Inhalation
5.2.3. Dermal
5.3. Iatrogenic exposure
5.4. Occupational exposure

6. KINETICS AND METABOLISM
6.1. Absorption
6.1.1. Absorption via the respiratory tract
6.1.1.1 Particulate nickel
6.1.1.2 Nickel carbonyl
6.1.2. Absorption via the gastrointestinal tract
6.1.2.1 Experimental animals
6.1.2.2 Human beings
6.1.2.3 Factors influencing gastrointestinal
absorption
6.1.3. Absorption through the skin
6.1.3.1 Experimental animals
6.1.3.2 Human beings
6.1.4. Other routes of absorption
6.1.4.1 Experimental animals
6.1.4.2 Human beings
6.1.5. Transplacental transfer
6.1.5.1 Experimental animals
6.1.5.2 Human beings
6.1.6. Nickel carbonyl
6.2. Distribution, retention, and elimination
6.2.1. Transport
6.2.2. Tissue distribution
6.2.2.1 Experimental animals
6.2.2.2 Kinetics of metabolism
6.2.2.3 Nickel carbonyl
6.2.2.4 Nickel levels in human beings
6.2.2.5 Pathological states influencing nickel
levels
6.3. Elimination and excretion
6.3.1. Experimental animals
6.3.2. Human beings

7. EFFECTS ON ORGANISMS IN THE ENVIRONMENT
7.1. Microorganisms
7.2. Aquatic algae and plants
7.3. Aquatic invertebrates
7.4. Fish
7.5. Terrestrial organisms
7.5.1. Plants
7.5.2. Animals
7.5.3. Essentiality of nickel for bacteria and plants
7.6. Population and ecosystem effects

8. EFFECTS ON EXPERIMENTAL ANIMALS AND IN VITRO AND OTHER TEST
SYSTEMS
8.1. Animals
8.1.1. Essentiality
8.1.1.1 Nickel deficiency symptoms
8.1.2. Acute exposures
8.1.2.1 Nickel carbonyl
8.1.2.2 Other nickel compounds
8.1.2.3 Possible mechanisms of acute nickel
toxicity
8.1.3. Short- and long-term exposures
8.1.3.1 Effects on the respiratory tract
8.1.4. Relationship of nickel toxicity and mixed metal
exposure
8.1.5. Endocrine effects
8.1.6. Cardiovascular effects
8.1.7. Effects on the immune system
8.1.8. Skin and eye irritation and contact hypersensitivity
8.1.8.1 Skin and eye irritation
8.1.8.2 Contact hypersensitivity
8.1.9. Reproduction, embryotoxicity, and teratogenicity
8.1.9.1 Effects on the male reproductive system
8.1.9.2 Effects on the female reproductive system
8.1.10. Embryotoxicity and teratogenicity
8.2. Mutagenicity and related end-points
8.2.1. Mutagenesis in bacteria and mammalian cells
8.2.2. Chromosomal aberration and sister chromatid
exchange (SCE)
8.2.3. Mammalian cell transformation
8.3. Other test systems
8.4. Carcinogenicity
8.4.1. Inhalation
8.4.2. Oral
8.4.3. Other routes
8.4.4. Interactions with known carcinogens
8.4.5. Possible mechanisms of nickel carcinogenesis
8.4.6. Factors influencing nickel carcinogenesis

9. EFFECTS ON HUMAN BEINGS
9.1. Systemic effects
9.1.1. Acute toxicity - poisoning incidents
9.1.1.1 Nickel carbonyl
9.1.1.2 Other nickel compounds

9.1.2. Short- and long-term exposure
9.1.2.1 Respiratory effects
9.1.2.2 Renal effects
9.1.2.3 Cardiovascular effects
9.1.2.4 Other effects
9.2. Skin and eye irritation and contact hypersensitivity
9.2.1. Skin and eye irritancy
9.2.2. Contact hypersensitivity
9.3. Reproduction, embryotoxicity and teratogenicity
9.4. Genetic effects in exposed workers
9.5. Carcinogenicity
9.5.1. Epidemiological studies
9.5.1.1 Nickel refining industry
9.5.1.2 Nickel alloy manufacturing
9.5.1.3 Nickel plating industry
9.5.1.4 Welding
9.5.1.5 Nickel powder
9.5.1.6 Nickel-cadmium battery manufacturing
9.5.1.7 Case-control studies
9.5.2. Carcinogenicity of metal alloys in orthopaedic
prostheses

10. EVALUATION OF HUMAN HEALTH RISKS AND EFFECTS ON THE ENVIRONMENT
10.1. Exposure
10.2. Human health effects
10.3. Environmental effects

11. RECOMMENDATIONS

12. PREVIOUS EVALUATIONS BY INTERNATIONAL BODIES

REFERENCES

RESUME ET CONCLUSIONS

RESUMEN Y CONCLUSIONES

WHO TASK GROUP ON NICKEL

Members

Professor D.A. Calamari, Institute of Agricultural Entomology,
University of Milan, Milan, Italy

Dr R.F. Hertel, Fraunhofer Institute of Toxicology and Aerosol
Research (ITA), Hanover, Germany (Rapporteur)

Professor S.M. Hopfer, University of Connecticut School of
Medicine, Farmington, Connecticut, USA

Professor B.A. Katsnelson, Occupational Health Research
Institute, Sverdlovsk, USSR

Professor Yasushi Kodama, Department of Environmental Health,
School of Medicine, University of Occupational and Environmental
Health, Kitakyushu City, Japan

Professor V. Yu. Kogan, Occupational Health Research Institute,
Erevan, USSR (Vice-Chairman)

Ms V.R. Müller, Fraunhofer Institute of Toxicology and Aerosol
Research (ITA), Hanover, Germany

Dr G.D. Nielsen, Department of Environmental Medicine, Odense
University, Odense, Denmark

Professor T. Norseth, National Institute of Occupational Health,
Oslo, Norway (Chairman)

Dr J. Pastuszka, Institute of Environmental Protection, Katowice,
Poland

Professor J. Peto, Section of Epidemiology, Institute of Cancer
Research, Belmont, Surrey, United Kingdom

Dr E.A. Soyombo, Environmental and Occupational Health Division,
Federal Ministry of Health, Lagos, Nigeria

Dr S.H.H. Swierenga, Genetic Toxicology Section, Bureau of Drug
Research, Health Protection Branch, Health and Welfare Canada,
Tunney's Pasture, Ottawa, Ontario, Canada

Dr A.P. Tossavainen, Institute of Occupational Health, Helsinki,
Finland

Representatives of nongovernmental organizations

Professor N. Izmerov, Institute of Industrial Hygiene and
Occupational Diseases, Moscow, USSR, representing the International
Commission on Occupational Health (ICOH)

Observers

Professor A. Horie, Department of Environmental Health, School of
Medicine, University of Occupational and Environmental Health,
Kitakyushu City, Japan

Dr J. Ishmael, Central Toxicology Laboratory, ICI plc,
Macclesfield, Cheshire, United Kingdom

Professor M.I. Mikheev, Institute for Advanced Medical Studies,
Leningrad, USSR

Dr L.G. Morgan, INCO Europe Limited, Swansea, United Kingdom

Dr M. Richold, Unilever Research, Colworth Laboratory, Bedford,
United Kingdom

Professor A.V. Roscin, Central Institute for Advanced Medical
Studies, Moscow, USSR

Secretariat

Dr A. Aitio, International Agency for Research on Cancer, Lyon,
France

Dr E. Smith, International Programme on Chemical Safety, Division
of Environmental Health, World Health Organization, Geneva,
Switzerland

NOTE TO READERS OF THE CRITERIA DOCUMENTS

Every effort has been made to present information in the
criteria documents as accurately as possible without unduly
delaying their publication. In the interest of all users of the
environmental health criteria documents, readers are kindly
requested to communicate any errors that may have occurred to the
Manager of the International Programme on Chemical Safety, World
Health Organization, Geneva, Switzerland, in order that they may be
included in corrigenda, which will appear in subsequent volumes.

* * *

A detailed data profile and a legal file can be obtained from
the International Register of Potentially Toxic Chemicals, Palais
des Nations, 1211 Geneva 10, Switzerland (Telephone no.
7988400/7985850).

ENVIRONMENTAL HEALTH CRITERIA FOR NICKEL

A WHO Task Group on Environmental Health Criteria for Nickel
met at the Leningradskaya Hotel, Moscow, USSR, from 17 to 21 April
1989, under the auspices of the USSR State Committee for
Environmental Protection, Centre for International Projects. Dr
S.N. Morozov welcomed the participants on behalf of the host
institution and Dr E. Smith opened the meeting on behalf of the
three cooperating organizations of the IPCS (ILO/UNEP/WHO). The
Task Group reviewed and revised the draft criteria document and
made an evaluation of the health risks of exposure to nickel.

The first draft of this document was prepared by Dr R.F.
Hertel, Dr J. Maass, and Ms V. Müller, Fraunhofer Institute of
Toxicology and Aerosol Research, Hanover, Germany. This draft was
reviewed in the light of international comments by a Working Group
comprising Dr V. Bencko, Prague, Czechoslovakia, Dr M. Piscator,
Stockholm, Sweden, and Dr F.W. Sunderman, Farmington, Connecticut,
USA, with the assistance of Dr R.F. Hertel, Ms V. Müller and Dr G.
Rosner. The revised draft resulting from this Working Group was
submitted for the Task Group review. Dr E. Smith, IPCS Central
Unit, was responsible for the overall scientific content of the
document and for the organization of the meetings, and Mrs M.O.
Head of Oxford, England, was responsible for the editing.

The efforts of all who helped in the preparation and
finalization of the document are gratefully acknowledged.

* * *

Financial support for the Task Group was provided by the United
Nations Environment Programme, through the USSR Commission for
UNEP. Partial 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.

1. SUMMARY AND CONCLUSIONS

1.1. Identity, physical and chemical properties, and analytical
methods

Nickel is a metallic element belonging to group VIIIb of the
periodic table. It is resistant to alkalis, but generally
dissolves in dilute oxidizing acids. Nickel carbonate, nickel
sulfide, and nickel oxide are insoluble in water, whereas nickel
chloride, nickel sulfate, and nickel nitrate are water soluble.
Nickel carbonyl is a volatile colourless liquid that decomposes at
temperatures above 50 °C. The prevalent ionic form is nickel (II).
In biological systems, dissolved nickel may form complex components
with various ligands and bind to organic material.

The most commonly used methods for the analysis of biological
and environmental materials are atomic absorption spectroscopy and
voltammetry. In order to obtain reliable results, especially in
the ultratrace range, specific procedures have to be followed to
minimize the risk of contamination during sample collection,
storage, processing, and analysis. Depending on sample
pretreatment, extraction and enrichment procedures, detection
limits of 1-100 ng/litre can be achieved in biological materials
and water.

1.2. Sources of human and environmental exposure

Nickel is a ubiquitous trace metal and occurs in soil, water,
air, and in the biosphere. The average content in the earth's
crust is about 0.008%. Farm soils contain between 3 and 1000 mg
nickel/kg. Levels in natural waters have been found to range from
2 to 10 µg/litre (fresh water) and from 0.2 to 0.7 µg/litre
(marine). Atmospheric nickel concentrations in remote areas range
from <0.1 to 3 ng/m³.

Nickel ore deposits are accumulations of nickel sulfide
minerals (mostly pentlandite) and laterites. Nickel is extracted
from the mined ore by pyro- and hydro-metallurgical refining
processes. Most of the nickel is used for the production of
stainless steel and other nickel alloys with high corrosion and
temperature resistance. Nickel alloys and nickel platings are used
in vehicles, processing machinery, armaments, tools, electrical
equipment, household appliances, and coinage. Nickel compounds are
also used as catalysts, pigments, and in batteries. Global mining
production of nickel was approximately 67 million kg in 1985. The
primary sources of nickel emissions into the ambient air are the
combustion of coal and oil for heat or power generation, the
incineration of waste and sewage sludge, nickel mining and primary
production, steel manufacture, electroplating, and miscellaneous
sources, such as cement manufacturing. In polluted air, the
predominant nickel compounds appear to be nickel sulfate, oxides,
and sulfides, and to a lesser extent, metallic nickel.

Nickel from various industrial processes and other sources
finally reaches waste water. Residues from waste-water treatment

are disposed of by deep well injection, ocean dumping, land
treatment, and incineration. Effluents from waste-water treatment
plants have been reported to contain up to 0.2 mg nickel/litre.

1.3 Environmental transport, distribution, and transformation

Nickel, which is emitted into the environment from both natural
and man-made sources, is circulated throughout all environmental
compartments by means of chemical and physical processes, and is
biologically transported by living organisms.

Atmospheric nickel is considered to exist mainly in the form of
particulate aerosols containing different concentrations of nickel,
depending on the source. The highest nickel concentrations in
ambient air are usually found in the smallest particles. Nickel
carbonyl is unstable in air and decomposes to form nickel oxide.

The transport and distribution of nickel particles to, or
between, different environmental compartments is strongly
influenced by particle size and meteorological conditions.
Particle size distribution is primarily a function of the emitting
sources. In general, particles from man-made sources are smaller
than natural dust particles.

Nickel is introduced into the hydrosphere by removal from the
atmosphere, by surface run-off, by discharge of industrial and
municipal waste, and also following natural erosion of soils and
rocks. In rivers, nickel is mainly transported in the form of a
precipitated coating on particles and in association with organic
matter; in lakes, it is transported in the ionic form, also mainly
in association with organic matter. Nickel may also be absorbed on
to clay particles and via uptake by biota. Absorption processes
may be reversed leading to release of nickel from the sediment.
Part of the nickel is transported via rivers and streams to the
ocean. Riverine suspended particulate input is estimated to be 135
x 10⁷ kg/year.

Depending on the soil type, nickel may exhibit a high mobility
within the soil profile finally reaching ground water and, thus,
rivers and lakes. Acid rain has a pronounced tendency to mobilize
nickel from the soil. Terrestrial plants take up nickel from soil
primarily via the roots. The amount of nickel uptake from soil
depends on various geochemical and physical parameters including
the type of soil, the soil pH and humidity, the organic matter
content of the soil, and the concentration of extractable nickel.
The best known example of nickel accumulation is the increased
nickel levels, in excess of 1 mg/kg dry weight, found in a number
of plant species ("hyperaccumulators") growing on relatively
infertile serpentine soils. Nickel levels above 50 mg/kg dry
weight are toxic for most plants. Accumulation and toxic effects
have been observed in vegetables grown on sewage sludge-treated
soils and in vegetation close to nickel-emitting sources. High
concentration factors have been found in aquatic plants.
Laboratory studies showed that nickel had little capacity for
accumulation in all the fish studied. In uncontaminated waters,

the range of concentrations reported in whole fish (on a wet-weight
basis) ranged from 0.02 to 2 mg/kg. These values could be up to 10
times higher in fish from contaminated waters. In wildlife, nickel
is found in many organs and tissues, due to dietary uptake by
herbivorous animals and their carnivorous predators. However,
there is no evidence for the biomagnification of nickel in the food
chain.

1.4 Environmental levels and human exposure

Nickel levels in terrestrial and aquatic organisms can vary
over several orders of magnitude. Typical atmospheric nickel
levels for human exposure range from about 5 to 35 ng/m³ at rural
and urban sites, leading to a nickel uptake via inhalation of 0.1-
0.7 µg/day. Drinking-water generally contains less than 10 µg
nickel/litre, but occasionally nickel may be released from the
plumbing fittings, resulting in concentrations of up to 500 µg
nickel/litre.

Nickel concentrations in food are usually below 0.5 mg/kg fresh
weight. Cocoa, soybeans, some dried legumes, various nuts, and
oatmeal contain high concentrations of nickel. Daily intake of
nickel from food will vary widely, because of different dietary
habits, and can range from 100 to 800 µg/day; the mean dietary
nickel intake in most countries is 100-300 µg/day. Release of
nickel from kitchen utensils may contribute significantly to oral
intake. Pulmonary intake of 2-23 µg nickel/day can result from
smoking 40 cigarettes a day.

Dermal exposure in the general environment is important for the
induction and maintenance of contact hypersensitivity caused by
daily skin contact with nickel-plated objects or nickel-containing
alloys (e.g., jewellery, coins, clips).

Iatrogenic exposure to nickel results from implants and
prostheses made from nickel-containing alloys, from intravenous or
dialysis fluids, and from radiographic contrast media. An
estimated average intravenous nickel uptake from dialysis fluids is
100 µg per treatment.

In the working environment, airborne nickel concentrations can
vary from a few µg/m³ to, occasionally, a few mg/m³, depending on
the process involved and the nickel content of the material being
handled.

Throughout the world, millions of workers are exposed to
nickel-containing dusts and fumes during welding, plating and
grinding, mining, nickel refining, and in steel plants, foundries,
and other metal industries.

Dermal exposure to nickel may occur in a wide range of jobs,
either by direct exposure to dissolved nickel, e.g., in refining,
electroplating, and electroforming industries or by handling
nickel-containing tools. Wet cleaning work may involve exposure to
nickel, because of the amounts of nickel that become dissolved in
the washing water.

1.5 Kinetics and metabolism in human beings and animals

Nickel can be absorbed in human beings and animals via
inhalation or ingestion, or percutaneously. Respiratory absorption
with secondary gastrointestinal absorption of nickel (insoluble and
soluble) is the major route of entry during occupational exposure.
A significant quantity of inhaled material is swallowed following
mucociliary clearance from the respiratory tract. Poor personal
hygiene and work practices can contribute to gastrointestinal
exposure. Percutaneous absorption is negligible, quantitatively,
but is important in the pathogenesis of contact hypersensitivity.
Absorption is related to the solubility of the compound, following
the general relationships nickel carbonyl > soluble nickel
compounds > insoluble nickel compounds. Nickel carbonyl is the
most rapidly and completely absorbed nickel compound in both
animals and human beings. Studies in which nickel was administered
via inhalation are limited. Studies on hamsters and rats with
insoluble nickel oxide showed poor absorption, with retention of
much of the material in the lung after several weeks. In contrast,
absorption of soluble nickel chloride or amorphous nickel sulfide
was rapid. Nickel is transported in the blood, principally bound
to albumin.

Gastrointestinal absorption of nickel is variable and depends
on the composition of the diet. In a recent study on human
volunteers, absorption of nickel was 27% from water compared with
less than 1% from food. All body secretions are potential routes
of excretion including urine, bile, sweat, tears, milk, and
mucociliary fluid. Non-absorbed nickel is eliminated in the
faeces. Transplacental transfer has been demonstrated in rodents.
Following parenteral administration of nickel salts, the highest
nickel accumulation occurs in the kidney, endocrine glands, lung,
and liver: high concentrations are also observed in the brain
following administration of nickel carbonyl. Data on nickel
excretion suggest a two-compartment model. Nickel concentrations
in the serum and urine of healthy non-occupationally exposed adults
are 0.2 µg/litre (range: 0.05-1.1 µg/litre) and l.5 µg/g creatinine
(range: 0.5-4.0 mg/g creatinine), respectively. Increased
concentrations of nickel are seen in both of these fluids following
occupational exposure. The body burden of nickel in a non-exposed,
70-kg adult is 0.5 µg.

1.6 Effects on organisms in the environment

In microorganisms, growth was generally inhibited at nickel
concentrations in the medium of 1-5 mg/litre in the case of
actinomycetes, yeast, and marine and non-marine eubacteria and at
levels of 5-1000 mg/litre in filamentous fungi. In algae, no growth
was observed at approximately 0.05-5 mg nickel/litre. Abiotic
factors, such as the pH, hardness, temperature, and salinity of the
medium and the presence of organic and inorganic particles,
influence the toxicity of nickel.

Nickel toxicity in aquatic invertebrates varies considerably
according to species and abiotic factors. A 96-h LC₅₀ of 0.5 mg
nickel/litre has been found for Daphnia spp., while, in molluscs,
96-h LC₅₀ values were around 0.2 mg/litre in two freshwater snail
species and 1100 mg/litre in a bivalve.

In fish, 96-h LC₅₀ values generally fall within the range of
4-20 mg nickel/litre, but can be higher in some species. Long-term
studies on fish, and fish development, in soft water demonstrated
some effects on rainbow trout at levels as low as 0.05 mg
nickel/litre. In terrestrial plants, nickel levels above 50 mg/kg
dry weight are usually toxic. Copper was found to act
toxicologically in a synergistic way, whereas calcium reduced the
toxicity of nickel. Data on the effects of nickel on terrestrial
animals are limited.

Earthworms seem to be relatively insensitive to nickel, if the
medium is rich in microorganisms and organic matter, thus, making
the nickel less available to the earthworms. Nickel has not been
considered as a broad scale global contaminant; however, ecological
changes, such as decreases in the number and diversity of species,
have been observed near nickel-emitting sources. Microecosystem
studies have shown that addition of nickel to soil disturbs the
nitrogen cycle.

1.7 Effects on experimental animals and in vitro test systems

Nickel is essential for the catalytic activity of some plant
and bacterial enzymes. Slow weight gain, anaemia, and decreased
viability of offspring have been described in some animal species
after dietary deprivation of nickel.

The most acutely toxic nickel compound is nickel carbonyl, the
lung being the target organ; pulmonary oedema may occur within 4 h
following exposure. The acute toxicity of other nickel species is
low.

Though contact allergy to nickel is very common in human
beings, experimental sensitization in animals is only successful
under special conditions. Long-term inhalation exposure to
metallic nickel, nickel oxide, or nickel subsulfide caused mucosal
damage and inflammatory reaction in the respiratory tract in rats,
mice, and guinea-pigs. Epithelial hyperplasia was observed in rats
after inhalation exposure to aerosols of nickel chloride or nickel
oxide.

High-level, long-term exposure to nickel oxide led to gradually
progressive pneumoconiosis in rats. Inflammatory reaction,
sometimes accompanied by slight fibrosis, was observed in rabbits
after high-level exposure to nickel-graphite dust. Pulmonary
fibrosis was seen in rats exposed to nickel subsulfide.

Nickel salts, administered parenterally, induced a rapid
transitory hyperglycaemia in rats, rabbits, and chickens. These
changes may be associated with effects on alpha and beta cells in
the islets of Langerhans. Nickel also decreased the release of
prolactin. Nickel chloride, given orally or by inhalation, has
been reported to decrease iodine uptake by the thyroid.

Nickel salts, given intravenously, decreased blood flow in the
coronary arteries in the dog; high concentrations of nickel
decreased the contractility of dog myocardium in vitro.

Nickel chloride affects the T-cell system and suppresses the
activity of natural killer cells. Parenteral administration of
nickel chloride and nickel subsulfide have been reported to cause
intrauterine mortality and decreased weight gain in rats and mice.
Inhalation exposure to nickel carbonyl caused fetal death and
decreased weight gain, and was teratogenic in rats and hamsters.
Information on maternal toxicity was not given in any of these
studies. Nickel carbonyl has been reported to cause dominant
lethal mutations in rats.

Several inorganic nickel compounds were tested for mutagenicity
in various test systems. Nickel compounds were generally inactive
in bacterial mutagenesis assays, except where fluctuation tests
were used. Mutations were observed in several cultured mammalian
cell types. Nickel compounds inhibited DNA synthesis in a wide
variety of organisms. In addition, nickel compounds induced
chromosomal aberrations and sister chromatid exchange (SCE) in both
mammalian and human cultured cells. Chromosomal aberrations, but
not sister chromatid exchange (except in one study on electrolysis
workers), were observed in human beings, occupationally exposed to
either insoluble or soluble nickel compounds. Nickel induced cell
transformation in vitro.

In an inhalation study, nickel subsulfide induced benign and
malignant pulmonary tumours in rats. A few pulmonary tumours were
seen in rats in a series of inhalation studies with nickel
carbonyl. There was no significant increase in lung tumours in
rats in an adequate inhalation study with metallic nickel.
Inhalation exposure to black nickel oxide did not induce lung
tumours in Syrian golden hamsters (a species resistant to lung
carcinogenesis). Adequate carcinogenicity studies on inhalation
exposure to other nickel compounds were not available. However,
nickel subsulfide, metallic nickel powder, and an unspecified
nickel oxide induced benign and malignant lung tumours in rats
after repeated intratracheal instillations.

Nickel carbonyl, nickelocene, and a large number of slightly
soluble or insoluble nickel compounds, including nickel subsulfide,
carbonate, chromate, hydroxide, sulfides, selenides, arsenides,
telluride, antimonide, various unidentified oxide preparations, two
nickel-copper oxides, metallic nickel, and various nickel alloys,
induced local mesenchymal tumours in a variety of experimental
animals after intramuscular, subcutaneous, intraperitoneal,
intrapleural, intraocular, intraosseous, intrarenal, intra-articular,
intratesticular or intra-adipose administration. No local
carcinogenic response was seen in single-dose studies with some
nickel alloys, colloidal nickel hydroxide, or with two specimens of
nickel oxide, especially prepared for carcinogenicity testing by
calcining at 735 °C or 1045 °C.

Nickel sulfate and nickel acetate, but not nickel chloride,
induced tumours of the peritoneal cavity in rats after repeated
intraperitoneal administration.

Metallic nickel and a very large number of nickel compounds
have been tested for carcinogenicity by parenteral routes of
administration; with few exceptions, they caused local tumours.

Only nickel subsulfide has been shown convincingly to cause
cancer after inhalation exposure. However, the number of adequate
inhalation studies is very small.

In studies using repeated intratracheal instillation, nickel
powder, nickel oxide, and nickel subsulfide caused pulmonary
tumours.

When nickel sulfate and nickel chloride, which had not induced
local tumours in intramuscular studies, were tested using repeated
intraperitoneal administration, they elicited a carcinogenic
response.

1.8 Effects on human beings

In terms of human health, nickel carbonyl is the most acutely
toxic nickel compound. The effects of acute nickel carbonyl
poisoning include frontal headache, vertigo, nausea, vomiting,
insomnia, and irritability, followed by pulmonary symptoms similar
to those of a viral pneumonia. Pathological pulmonary lesions
include haemorrhage, oedema, and cellular derangement. The liver,
kidneys, adrenal glands, spleen, and brain are also affected.
Cases of nickel poisoning have also been reported in patients
dialysed with nickel-contaminated dialysate and in electroplaters
who accidentally ingested water contaminated with nickel sulfate
and nickel chloride.

Chronic effects such as rhinitis, sinusitis, nasal septal
perforations, and asthma have been reported in nickel refinery and
nickel plating workers. Some authors reported pulmonary changes
with fibrosis in workers inhaling nickel dust. In addition, nasal
dysplasia has been reported in nickel refinery workers. Nickel
contact hypersensitivity has been documented extensively in both
the general population and in a number of occupations in which
workers were exposed to soluble nickel compounds. In several
countries, it has been reported that 10% of the female population
and 1% of the male population are sensitive to nickel. Of these,
40-50% have vesicular hand eczema, which, in some cases, can be
very severe and lead to loss of working ability. Oral nickel
intake may aggravate vesicular hand eczema and, possibly, also
eczema arising on other parts of the body where there has not been
any skin contact with nickel.

Prostheses, or other surgical implants, made from nickel-
containing alloys have been reported to cause nickel sensitization
or to aggravate existing dermatitis.

Nephrotoxic effects, such as renal oedema with hyperaemia and
parenchymatous degeneration, have been reported in cases of
accidental industrial exposure to nickel carbonyl. Transient
nephrotoxic effects have been recorded after accidental ingestion
of nickel salts.

Very high risks of lung and nasal cancer have been reported in
nickel refinery workers employed in the high-temperature roasting
of sulfide ores, involving substantial exposure to nickel
subsulfide, oxide, and, perhaps, sulfate. Similar risks have been
reported in processes involving exposure to soluble nickel
(electrolysis, copper sulfate extraction, hydrometallurgy), often
combined with some nickel oxide exposure, but with low nickel
subsulfide exposure. The risk to miners and other refinery workers
has been reported to be much lower. Cancer rates have generally
been close to normal in stainless steel welding and nickel-using
industries, with the exception of those involving exposure to
chromium, particularly electroplating. However, nickel/cadmium
battery workers exposed to high levels of both nickel and cadmium
may have suffered a slightly increased risk of lung cancer.

Excesses of various cancers other than lung and nasal cancers,
such as renal, gastric, or prostatic cancer, have occasionally been
reported in nickel workers, but none has been found consistently.

The epidemiological data can be used to address two important
questions: (i) whether specific nickel compounds have been shown to
be carcinogenic; and (ii) whether low-exposure cohorts provide
upper limits of risk at specified exposure levels.

(a) Soluble nickel

There was evidence of a cancer hazard in workers exposed to
soluble nickel concentrations of the order of 1-2 mg/m³, both in
electrolysis and in the preparation of soluble salts. These
workers were also exposed to other nickel compounds, but often at
lower levels than in other high-risk processes. In the absence of
historical exposure measurements it is impossible to draw
unequivocal conclusions, but the evidence that soluble nickel is
carcinogenic is certainly strong. Refinery dust sometimes contains
a substantial proportion of nickel sulfate in addition to nickel
subsulfide. This raises the possibility that the very high cancer
risk observed in workers employed in the high-temperature oxidation
of nickel subsulfide may be partly due to soluble nickel.

(b) Nickel subsulfide

In refinery areas where cancer risks were high, exposure to
nickel subsulfide almost always occurred together with exposure to
the oxide and, perhaps, sulfate (see above). Thus, it is difficult
to demonstrate from epidemiological data alone, that nickel
subsulfide is carcinogenic, though this seems likely.

Nickel oxide was present in almost all circumstances in which
cancer risks were elevated, together with one or more other forms
of nickel (nickel subsulfide, soluble nickel, metallic nickel). As
for nickel subsulfide, it is difficult to either demonstrate or
disprove its suspected carcinogenicity on the basis of
epidemiological data alone.

(d) Metallic nickel

No increased cancer risk has been demonstrated in workers
exposed exclusively to metallic nickel. The combined data on
nickel alloy workers and gaseous diffusion workers, all of whom
were exposed to average concentrations of the order of 0.5 mg
nickel/m³, show no excess risk, though the total number of lung
cancers in these cohorts was too small to exclude a small increase
in risk at this level.

(e) Conclusion

Although some, and perhaps all, forms of nickel may be
carcinogenic, there is little or no detectable risk in most sectors
of the nickel industry at current exposure levels; this includes
some processes that were associated, in the past, with very high
lung and nasal cancer risks. Long-term exposure to soluble nickel
at concentrations of the order of 1 mg/m³ may cause a marked
increase in the relative risk of lung cancer, but the relative risk
among workers exposed to average metallic nickel levels of about
0.5 mg/m³ is approximately 1. The cancer risk at a given exposure
level may be higher for soluble nickel compounds than for metallic
nickel and, possibly, than for other forms as well. The absence of
any marked lung cancer risk among nickel platers is not surprising,
as the average exposures to soluble nickel are very much lower than
those in electrolytic refining or nickel salt processing.

2. IDENTITY, PHYSICAL AND CHEMICAL PROPERTIES, ANALYTICAL METHODS

2.1. Identity, and physical and chemical properties of nickel and
nickel compounds

Nickel is a silvery white metal belonging to Group VIIIb of the
periodic table. Nickel is slightly more resistant to oxidation than
iron and cobalt, with a standard potential of -0.236 V relative to
the hydrogen electrode (Stoeppler, 1980). Several hundreds of
nickel compounds have been identified and characterized. Nickel has
a specific density of 8.90 g/cm³, a melting point of 1555 °C, and
a boiling point of 2837 °C (Table 1). It is insoluble in water,
soluble in dilute nitric acid and aqua regia, and slightly soluble
in hydrochloric and sulfuric acid. Nickel usually has an oxidation
state of two, but also occurs as relatively stable tri- and
tetravalent ions (Stoeppler, 1980). Several binary nickel compounds
are commercially and environmentally significant. A brief
description of the chemistry of some of these compounds is given
below. Physical and chemical properties of nickel and its compounds
are summarized in Table 1.

Nickel forms complexes (chelates) that are insoluble in water,
but soluble in organic solvents. These compounds are often very
stable and play an important role in trace analysis. For example,
nickel dimethylglyoxime is the compound that makes possible the
separation of nickel from cobalt, which is similar in its chemical
and analytical behaviour (Stoeppler, 1980). Divided nickel (Raney
nickel) absorbs up to seventeen times its volume of hydrogen and
can act as an catalyst (Lewis & Ott, 1970).

2.1.1. Nickel carbonate hydroxide

Nickel carbonate hydroxide (2NiCO₃ x 3Ni(OH)₂ x 4H₂O) is
insoluble in water, but soluble in ammonia and in dilute acids.
The composition of basic nickel carbonate can vary. The most
common forms range from 2NiCO₃ x 3Ni(OH)₂ x XH₂O to NiCO₃ x Ni(OH)₃
x XH₂O. The tetrahydrate occurs in nature as zaratite. It is used
in nickel plating, as a catalyst for the hardening of fats, and in
colours and glazes for ceramics (Windholz et al., 1983). High
purity nickel carbonate is used in electronic components (IARC, 1976).

2.1.2. Nickel carbonyl

Nickel carbonyl (Ni(CO)₄) is a colourless volatile liquid and
is formed when nickel powder is treated with carbon monoxide at
about 50 °C. It is used for the production of pure nickel by
thermal deposition at atmospheric pressure and at 200-250 °C
(Stoeppler, 1980). The carbonyl is insoluble in water, but soluble
in most organic solvents (Windholz et al., 1983).

Table 1. Physical properties of nickel and nickel compounds^a
_____________________________________________________________________________________________________
Name Chemical Relative Appearance Density Melting Boiling Solubility
formula molecular (g/cm³) point point (water; other
mass (°C) (°C) solvents)
_____________________________________________________________________________________________________
Nickel Ni 58.70 lustrous, white, 8.90 1555 2837 insoluble
face-centered cubic 1455^b
crystals

Nickel Ni(CH₃CO₂)₂ 176.80 green crystalline 1.744 -^c - soluble;
acetate mass or powder soluble
in alcohol

Nickel Ni₃(AsO₄)₂ 453.97 yellow-green powder 4.982 - - insoluble;
arsenate soluble
in acids

Nickel NiBr₂ 218.53 yellow-green, - loses - soluble;
bromide deliquescent crystals H₂O - soluble
at 200 in alcohol

Nickel 2NiCO₃ 118.70 light-green crystals - decomposes - insoluble;
carbonate soluble
in acids

Nickel Ni(CO)₄ 170.73 colourless, volatile 1.318 -19.3 43 insoluble;
carbonyl liquid (17 °C) soluble in
organic
solvents

Nickel NiCl₂ 129.61 yellow, deliquescent 3.55^d 987^d soluble
chloride crystals

Nickel NiCl₂ x 237.70^d green, monoclinic, - - - soluble;
chloride 6H₂O deliquescent crystals soluble
hexahydrate in alcohol
_____________________________________________________________________________________________________

Table 1 (contd.)
_____________________________________________________________________________________________________
Name Chemical Relative Appearance Density Melting Boiling Solubility
formula molecular (g/cm³) point point (water; other
mass (°C) (°C) solvents)
_____________________________________________________________________________________________________
Nickel NiF₂ 96.69 yellow-green, 4.72 - - slightly
fluoride tetragonal crystals soluble

Nickel Ni(OH)₂ 92.72 green powder - decomposes - insoluble;
hydroxide above 200 soluble in
acids and
ammonia

Nickel 2NiCO₃ x 587.67^b green powder - - - insoluble;
hydroxy- 3Ni(OH)₂ x soluble in
carbonate 4H₂O acids
tetrahydrate

Nickel Ni(NO₃)₂ 182.72 green, deliquescent 2.05 56.7 137 soluble;
nitrate crystals soluble
in alcohol

Nickel NiO 74.69 green or black 6.67^d 1990^d - insoluble;
oxide powder soluble in
acid

Table 1 (contd.)
_____________________________________________________________________________________________________
Name Chemical Relative Appearance Density Melting Boiling Solubility
formula molecular (g/cm³) point point (water; other
mass (°C) (°C) solvents)
_____________________________________________________________________________________________________
Nickel Ni₃(PO₄)₃ 366.07 light-green powder - - - insoluble;
phosphate soluble in
acid

Nickel NiSO₄ 154.77 alpha blue-green, - 53.3(a-b) - soluble
sulfate tetragonal crystals loses
beta green, water soluble
monoclinic crystals at 280

beta-Nickel NiS 90.77^d trigonal crystals^e 5.3^d 797^d - insoluble
sulfide

Nickel Ni₃S₂ 240.26^b pale, yellowish 5.82^b 790^b - insoluble;
subsulfide bronze metallic^b soluble in
nitric acid^b
_____________________________________________________________________________________________________
^a From: Windholz et al. (1983).
^b From: Weast (1981).
^c Data not available.
^d From: Blankenstein & Starck (1979).
^e From: Neumüller (1985).
2.1.3. Nickel chloride and nickel chloride hexahydrate

Nickel chloride (NiCl₂) and nickel chloride hexahydrate
(NiCl₂ x 6H₂O) are both soluble in water. The anhydrate salt is used
as an absorbent for ammonia in gas masks and in nickel plating
(Windholz et al., 1983).

2.1.4. Nickel hydroxide

Nickel hydroxide (Ni(OH)₂) is insoluble in water but soluble in
acids (Windholz et al., 1983). When dissolved in ammonia it forms
complexes. It is used as electrode material for secondary cells
(Blankenstein, 1979).

2.1.5. Nickel nitrate

Nickel nitrate (Ni(NO₃)₂) dissolves easily in water and
alcohol. It is used in nickel plating and nickel-cadmium batteries
(Neumüller, 1985).

2.1.6. Nickel oxide

Nickel oxide (NiO) includes several nickel-oxygen compounds,
which differ in stoichiometry, and chemical and physical properties
(see Table 32 in section 8.4.3). The different nickel oxides, and
also the nickel-copper oxides present in the nickel refining
industry, have different biological properties (Sunderman et al.,
1987a).

Nickel oxide is insoluble in water. The solubility in acids
and other properties depend on the method of preparation. Nickel
oxide is an important raw material for smelting and alloy-producing
processes. It is also used as a catalyst and in glass colours
(Blankenstein & Starck, 1979). Nickel oxide exists in two forms.
Black nickel oxide is chemically reactive and forms simple salts in
the presence of acids. Green nickel oxide is an inert and
refractory material. It is used primarily in metallurgical
operations.

2.1.7. Nickel sulfate

Nickel sulfate (NiSO₄), which exists as a hexahydrate in the
alpha-form, changes into the beta-form at 53.3 °C (Windholz et al.,
1983). It is produced by dissolving nickel oxide or hydroxide in
sulfuric acid (Neumüller, 1985). It is the main component of the
electrolyte solution in electrolytic refining and is a raw material
for the production of catalysts. It is also used in fabrication of
jewellery.

2.1.8. Nickel sulfide

Nickel sulfide (NiS) occurs naturally as millerite. It is
insoluble in water and is of importance in catalyst production and
in the hydrogenation of sulfur compounds in the oil industry
(Blankenstein, 1979).

2.1.9. Nickel subsulfide

Nickel subsulfide (Ni₃S₂) exists at high-temperatures in a
bronze-yellow form (beta-Ni₃S₂). At lower temperatures, it
transforms to the green beta-form, which is stable at normal
temperature, and may be formed electrolytically. The grey mineral
heazlewoodite is the same modification, but has been named alpha-
nickel subsulfide. Nickel subsulfide may be formed during the
production of nickel from sulfide ores.

2.2. Analytical methods

A variety of methods has been used to determine nickel
concentrations in different media. Methods are summarized in
Table 2.

2.2.1. Determination of trace amounts

The use of very sensitive instrumental methods has shown that
detection limits are not so much set by the capabilities of the
instrument as by contamination from different sources. Sources of
contamination include laboratory air, laboratory equipment and
construction material, reagents and the analyst. In order to
obtain reliable results, especially when determining trace (mg/kg)
and ultratrace (µg/kg) amounts, specific procedures concerning
contamination control during sample collection, storage, processing,
and analysis must be adhered to.

Besides contamination control during sample processing, the
establishment of the level of accuracy of the analytical procedure
is of great importance. Thus, analysis of certified reference
materials is recommended. Recovery experiments to check the
analytical procedure include the spiking of samples with known
amounts of nickel.

2.2.2. Sample collection

Great care must be taken to minimize the risk of contamination
during sample collection by the use of suitable procedures (Nieboer
& Jusys, 1983; Boyer & Howitz, 1986). Persons who handle samples
should wear talc-free gloves to avoid nickel contamination from
sweat. When collecting liquid samples, e.g., sea water, fresh
water, or urine, acid-washed polyethylene containers should be
used. As stainless steel is a source of nickel contamination,
Teflon^(R), intravenous catheters are recommended for blood
collection. Tissues should be dissected with plastic forceps and
obsidian scalpels (Sunderman et al., 1985).

Collection of airborne particulate nickel involves pumping a
known volume of air through a membrane filter, which usually
consists of cellulose, PVC, or glass fibre (Mackenzie Peers, 1986).
Equipment of the air sampling system with a cyclone, cascade, or
cascade impactor allows sampling of respirable particulate nickel
(Roy, 1985).

Table 2. Analytical methods for nickel determination^a
_________________________________________________________________________________________________________
Medium Sample treatment Analytical method Detection Comment Reference
limit
_________________________________________________________________________________________________________
Biological materials

Serum, urine sampling in analysis of extract 0.4 µg/ suitable for monitoring Mikac-Devic
urine PE-bottles; blood by EAAS, with litre occupational exposure; et al. (1977)
collection with graphite atomizer, interference from high
PE-catheter and using a deuterium iron contents possible
PE-syringe; wet background corrector
digestion;
extraction as
furildioxime into
MIBK

Liver, wet digestion; analysis of extract by ns removal of iron and copper Dornemann
kidney evaporation to EAAS, with graphite as N-nitrosophenylhydr- & Kleist
(animal) dryness; atomizer oxylamine-chelates (1980)
dissolution;
extraction as
hexamethylenedi-
thiocarbamate-
chelate into
diisopropylketone
and xylene

Food filtration; wet analysis of extract by 1 ng/ rapid and inexpensive Pilhar et
digestion DPV, with HMDE litre method; higher sensitivity al. (1981)
extraction as than AAS
DMG-chelate

Tissues, wet digestion; analysis of extract ns good agreement between Szathmary
body evaporation to and of digested sample results from EAAS & Daldrup
fluids dryness; by EAAS, with graphite determination and results (1982)
extraction as atomizer; analysis of from GC-determination
DDTC-chelate into extract by GC with FID
MIBK
_________________________________________________________________________________________________________

Table 2 (contd.)
_________________________________________________________________________________________________________
Medium Sample treatment Analytical method Detection Comment Reference
limit
_________________________________________________________________________________________________________
Whole wet digestion; analysis of extract by 0.1 ng/ suitable for routine Ostapczuk
blood, evaporation to DPV, with HMDE litre determination in a variety et al.
urine, dryness and of biological materials (1983)
saliva, dissolution;
liver, extraction as
nails DMG-chelate

Hair washing in analysis by AAS ns more convenient for Bencko et
redistilled sampling and storage than al. (1986)
acetone, then in other biological materials
deionized water
and again in
redistilled acetone;
repeat twice

Serum, blood collection analysis by EAAS, with 0.05 µg/ suitable for routine Sunderman
whole with PE-cannula Zeeman background litre determination et al.
blood and PP-syringe; corrector (1984a)
wet digestion

Body wet digestion; analysis by SWV at ns more sensitive method Ostapczuk et
fluids, extraction as DMG- HMDE compared with DPV al. (1985a)
tissues chelate

Tissue sampling with analysis of sample by 10 ng/g minimal nickel Sunderman
plastic forceps EAAS, with Zeeman dry weight contamination et al.
and obsidian background corrector (1985)
scalpel; wet
digestion

Urine sampling in PE- analysis of extract ns suitable for monitoring Long-zhu
bottles; wet by EAAS, with graphite occupational exposure & Zhe-ming
digestion using atomizer (1985)
nitric acid,
perchloric acid,
and ascorbic acid;
extraction as APDC-
chelate into MIBK
_________________________________________________________________________________________________________

Table 2 (contd.)
_________________________________________________________________________________________________________
Medium Sample treatment Analytical method Detection Comment Reference
limit
_________________________________________________________________________________________________________
Urine filtration; automated 0.1 ng/ convenient for Bond et al.
acidification; determination by 10 µlitre determination of (1986)
complexation with electrochemical sample multimetals (normal
HPDC within determination, to occupational
automated following separation exposure levels)
analytical system by HPLC (reversed after direct injection
phase) of sample

Urine sampling in PE- analysis by EAAS, 0.45 µg/ direct analysis of Sunderman
bottles; with Zeeman background litre sample et al.
acidification; corrector (1986a)
centrifugation

Plasma dilution of sample analysis by EAAS, with 0.09 µg/ no sample pretreatment Andersen et
with nitric acid Zeeman background litre necessary al. (1986)
and Triton X-100 corrector

Lung freeze drying analysis by EAAS, with lower suitable method for the Baumgardt et
tissue following graphite atomizer ng/g routine determination al (1986)
collection; wet amounts of trace elements
digestion;
evaporation to
dryness; dilution

Blood, enzymatic analysis by EAAS, with 0.1 µg/ lower risk of Christensen
serum, digestion of blood Zeeman background litre contamination with & Pedersen
sweat, and serum; corrector pretreatment method used (1986)
urine ultrasonic
treatment of urine
and sweat
_________________________________________________________________________________________________________

Food- wet digestion; analysis of extract 0.048- interference by high Evans et al.
stuffs dilution; by FAAS 0.061 copper content (1978)
extraction as APDC- mg/kg
DDDC-chelate into
n-methylpentane-
2-one

Fish freeze-drying; analysis of dissolved ns Ikebe &
shell- low temperature sample by FAAS Tanaka (1979)
fish ashing

Food- wet digestion; analysis of extract ns accurate and inexpensive Valenta et
stuffs evaporation to by DPASV, with HMDE method al. (1981)
dryness;
dissolution;
extraction as
DMG-chelate

Dried dry ashing; analysis of diluted 5 ng/ sensitive and accurate Meyer &
milk extraction as extract by DPV, with sample method, less interference Neeb (1985)
powder DMG-chelate; HMDE compared with FID-GC
dilution

Dried dry ashing; analysis of solution 100 ng/ interference by higher Meyer &
milk extraction as Na- by GC, with FID µlitre iron content in presence Neeb (1985)
powder FDEDTC-chelate in sample of low copper content is
chloroform; possible
evaporation and
dissolution in
chloroform
_________________________________________________________________________________________________________

Table 2 (contd.)
_________________________________________________________________________________________________________
Medium Sample treatment Analytical method Detection Comment Reference
limit
_________________________________________________________________________________________________________
Citrus wet digestion; analysis of extract µg/g simultaneous determination Ichinoki &
leaves, extraction as HMDE by HPLC of nickel, molybdenum, Yamazaki
rice chelates into zinc, and copper (1985)
flour chloroform
(both
standard
reference
materials)

Water

Sea extraction with analysis of extract ns probably only ionic form Danielsson
water APDC and DDTC into by EAAS with graphite of total nickel is et al. (1978)
Freon TF and back- atomizer using a measured; stability of
extraction into deuterium background extract is good
nitric acid corrector

Sea PE bottles or analysis of extract concentration factor 200 Bruland &
water Teflon-coated PVC by EAAS with graphite Franks (1979)
ball-valve furnace
samplers;

a) double extraction 10 ng/
with APDC and DDTC litre
into chloroform; (instrumental
back extraction detection
into nitric acid; limit)
evaporation of
back-extract and
redissolution into
nitric acid
_________________________________________________________________________________________________________

Table 2 (contd.)
_________________________________________________________________________________________________________
Medium Sample treatment Analytical method Detection Comment Reference
limit
_________________________________________________________________________________________________________
Sea b) concentration on 15 ng/ inefficient concentration Bruland &
water Chelex-100 resin litre factor by Chelex-100 Franks (1979)
(contd.) (instru-
mental
detection
limit)

Sea PVC samplers; analysis of ns probably only ionic form Frache et al.
water storage in PE extract by FAAS of total nickel is measured (1980)
containers;
filtration;
extraction with
ADPC into MIBK

Sea adsorption on analysis of resin 0.077 µg/ rapid and inexpensive Yoshimura et
water PAN-resin phase by ion-exchange litre method al. (1980)
calorimetry

Fresh 0.34 µg/
water litre

Fresh buffered analysis of extract 2 µg/ suitable for routine water Flora &
water, extraction as by DPP, with HMDE litre analysis Nieboer
drink- DMG-chelate (1980)
ing
water

Sea UV-irradiation; analysis of extract 1 µg/ rapid and inexpensive Pilhar et
water, extraction as by DPV, with HMDE litre method; high sensitivity al. (1981)
fresh DMG-chelate
water,
waste
water
_________________________________________________________________________________________________________

Table 2 (contd.)
_________________________________________________________________________________________________________
Medium Sample treatment Analytical method Detection Comment Reference
limit
_________________________________________________________________________________________________________
Fresh UV-irradiation; analysis of ns enrichment factor Wilson &
water enrichment by electrolyte by FAAS decreases at higher DiNunzio
(river) Donnan dialysis calcium concentration (1981)

Aqueous extraction as analysis of extract 1-2 µg/ in case of high copper and Gemmer-Colos
solution heptoxime-chelate; by DPP with HMDE litre iron concentrations, et al. (1981)
evaporation and extraction with NH₄OH is
redissolution in necessary to prevent
toluene/methanol/ interference
LiCl

Sea preconcentration analysis of diluted 0.05 mg/ concentration factor 200 Watanabe et
water by complexation extract by ICP-AES litre al. (1981)
with 8-hydroxy-
quinoline;
adsorption on
C₁₈-bonded silica
gel; evaporation of
eluate to dryness,
dissolution in
nitric acid

Sea preconcentration analysis by EAAS with ns concentration factor 50 Sturgeon et
water by complexation graphite furnace al. (1982)
with 8-hydroxy-
quinoline;
adsorption on
C₁₈-bonded silica
gel; evaporation of
eluate to dryness,
dissolution in
nitric acid
_________________________________________________________________________________________________________

Table 2 (contd.)
_________________________________________________________________________________________________________
Medium Sample treatment Analytical method Detection Comment Reference
limit
_________________________________________________________________________________________________________
Indus- complexation with separation of chelate 0.5 ng suitable for automated Bond &
trial APDC and DDTC with by HPCC (reversed (electro- monitoring of nickel and Wallace
plant automated phase) followed by chemical) copper (1983)
solu- analytical system electrochemical and 0.1 ng
tions spectrophotometric (spectro-
detection within photo-
automated system metric)

Sea preconcentration analysis of eluate 1 µg/ 50-fold preconcentration McLaren et
water by adsorption on by ICP-MS litre al. (1985)
immobilized
8-hydroxyquinoline

Sea coprecipitation analysis of dissolved 60 ng/ 200-fold preconcentration, Akagi et al.
water with gallium precipitate by ICP-AES litre appropriate for multi- (1985b)
element analysis

Fresh filtration; analysis by DPCSV, 0.4 µg/ elimination of Weidenauer
water oxidative UV- with HMDE litre interference caused by & Lieser
river photolysis dissolved organic matter (1985)
by UV-photolysis

Drink- evaporation onto analysis by PIXE 1.2 µg/ suitable for multi-element Ali et al.
ing cellulose matrix, litre analysis (1985)
water grinding and
pelletizing of
residue

Waste dilution; ion-chromatographic ns Tanaka (1985)
water, separation of analysis, with anion
plating metal ions as separator
solution EDTA-complexes
_________________________________________________________________________________________________________

Table 2 (contd.)
_________________________________________________________________________________________________________
Medium Sample treatment Analytical method Detection Comment Reference
limit
_________________________________________________________________________________________________________
Sea extraction with analysis of diluted 17 µg/ inexpensive method; Carvajal &
water DDTC into extracts by GC, with litre to appropriate for multimetal Zienius
(synth.) chloroform FID by GC with ECD 0.2 µg/ analyses (1986)
litre
(depending
on type of
column)

Rain filtration; analysis by DPSV, 0.24 mg/ rapid, inexpensive and Vos et al.
water acidification; with HMDE litre sensitive method for (1986)
extraction as DMG- multielement analysis
chelate

Soil

Rock wet digestion with analysis of extract 5-200 mg/ appropriate for iron, Sanzolone
material HF and HNO₃; by FAAS kg molybdenum, and calcium- et al. (1979)
(stand- extraction as rich geological materials
ard DDTC-chelate into
refer- MIBK
ence
material)

River wet digestion; analysis of diluted 0.1 mg/ elimination of Abo-Rady
sedi- filtration and sample by FAAS using kg interference of matrix (1979a)
ments, dilution a deuterium background effects by use of
rock corrector deuterium background
material, detector
plants

Soil wet digestion; analysis of 4 mg/kg concentration factor 5; Schmidt &
extraction as re-extracts by EAAS re- reduction of interference Dietl (1981)
APDC-chelate into with zirconium coated extract by re-extraction
MIBK; re- graphite atomizer
extraction with
nitric acid
_________________________________________________________________________________________________________

Soil wet digestion; analysis by ASWV 0.08 µg/ more sensitive and rapid Ostapczuk
extraction as ml analyte method for determination et al.
DMG-chelate solution of heavy metals than DPV (1985b)

Air

Air adsorption on analysis by FAAS 1 µg/ suitable for determining US NIOSH
cellulose ester sample occupational exposure (1977b)
membrane filter;
wet digestion

Air adsorption on analysis by ICP-AES 1 µg/ suitable for simultaneous Mackenzie
cellulose ester sample multielement analysis Peers (1986)
membrane filter;
wet digestion;
evaporation to
dryness; dilution

Air adsorption in analysis by 1 µg/m³ nickel carbonyl is Stedman
alcoholic iodine colorimetry measured, interference by (1986a)
solution; gaseous nickel compounds
extraction as
furildioxime
chelate into
chloroform

Air direct sampling analysis by 0.2 µg/m³ allows continuous Stedman
into chemilumin- chemiluminescence measuring of nickel (1986b)
escence detector; carbonyl
mixing of sampling
with carbon
monoxide
_________________________________________________________________________________________________________

Steel extraction as analysis by DPP, 1 µg/kg Copper can be determined Weinzierl
DMG-chelate; with HMDE simultaneously Umland (1982)
complexation of
Fe³⁺ and Mn²⁺ with
triethanolamine
solution

City wet digestion; analysis by ICP-AES 25 µg/ multistep digestion Taylor et al.
waste evaporation to litre procedure necessary (1985)
incin- near dryness; analyte because of difficult
erator dilution solution matrix
ash filtration
(standard
reference
material)
_________________________________________________________________________________________________________
^a Abbreviations:

APDC ammonium pyrolidinedithiocarbamate GC gas-chromatography
ASWV adsorption square wave voltammetry HMDE hanging mercury drop electrode
DDDC diethylammonium diethyldithiocarbamate HPLC high-performance liquid chromatography
DDTC diethyldithiocarbamate ICP-AES inductively coupled plasma atomic
DMG dimethylgyoxime emission spectroscopy
DPASV differential pulse aniodic stripping ICP-MS inductively coupled plasma mass
voltammetry spectroscopy
DPCSV differential pulse cathodic stripping MIBK methyl isobutyl ketone
voltammetry NaFDEDTC natrium (ditrifluorethylene)dithio-
DPP differential pulse polarography carbamate
DPV differential pulse voltammetry ns not specified
EAAS electrothermal atomic absorption PAN [1-(2-pyridylazo)-2-naphthol]
spectrometry PE polyethylene
ECD electron-capture detector PIXE particle-induced X-ray emission
FAAS flame atomic absorption spectroscopy PP polypropylene
FID flame ionization detector PVC polyvinyl chloride
TPP tetraphenylporphine
Volatile nickel compounds, such as nickel carbonyl, can be
absorbed in an alcoholic iodine solution through which the air
being sampled is passed (NIOSH, 1977a; Stedman, 1986a).

2.2.3. Sample pretreatment

Prior to the determination of nickel in biological and
environmental materials, the organic constituents must be oxidized
or removed to avoid interference during analysis. The most common
methods include wet digestion, i.e., oxidation of organic matter by
reagents, such as nitric acid, sulfuric acid, perchloric acid, or
hydrogen peroxide, or combinations of these compounds, and dry
ashing, which ensures oxidation of organic matter by the action of
oxygen and high temperatures. Puchyr & Shapiro (1986) developed an
extraction method for food samples that involved low-temperature
HCl/HNO₃-leaching followed by filtration. This method proved to be
very efficient and less hazardous and less time-consuming than
common wet or dry digestion techniques. Organic substances,
dissolved in natural waters, and certain liquid foods are
successfully decomposed by oxidative ultraviolet (UV) photolysis
(Pilhar et al., 1981; Weidenauer & Lieser, 1985).

As nickel concentrations are often low in relation to
analytical detection limits, preconcentration steps are introduced,
which may also separate nickel from substances interfering with
analysis. Techniques very frequently employed include chelate
extraction with dithiocarbamates, dimethylglyoxime, furildioxime,
or 8-hydroxyquinoline into organic non-polar solvents. Tanaka
(1985) used EDTA as a complexing agent prior to determination of
nickel in waste water and plating solution: Gemmer-Colos et al.
(1981) reported complete extraction of nickel-heptoxime from an
aqueous nickel solution at low pH values. Interfering cobalt and
iron ions were eliminated by treatment of the extract with ammonia.
Another preconcentration technique, prior to analysis of nickel in
fresh and sea water, is the use of chelating ion-exchanged resins,
e.g., Chelex 100^(R), (Bruland et al., 1979) or 1-(2-pyridylazo)-2-
naphthol (PAN) (Yoshimura et al., 1980). Brajter & Slonawska
(1986) considered Chelex-P^(R), a dibasic phosphate ester of
cellulose, as very efficient for the preconcentration of nickel in
water samples. A less time-consuming method for the
preconcentration of nickel in sea water was developed by Watanabe
et al. (1981), Sturgeon et al. (1982), and McLaren et al. (1985).
It involved complexation of the trace metals by 8-hydroxyquinoline
followed by adsorption on C₁₈ chemically bonded silica gel. Wan et
al. (1985) achieved a greater enrichment factor, smaller sample
volume, and removal of interfering humic substances when
preconcentrating nickel and other trace metals in natural waters on
XAD-7 regions (cross-linked polymer of methylmethacrylate) in a
two-step procedure at two different pH values. A very efficient
preconcentration method was developed by Burba & Willmer (1985) in
which trace metals in natural waters were enriched on metal
hydroxide coated cellulose, using iron hydroxide and indium
hydroxide. The use of gallium hydroxide as a coprecipitation agent
for multi-element determination in sea water, and zirconium
hydroxide as a coprecipitation agent for multi-element

determination in sea and fresh water has been described (Akagi et
al., 1985a,b). Zirconium caused spectral interferences in the
inductively coupled plasma atomic emission spectrometry, whereas
coprecipitation with gallium proved to be more efficient with lower
limits of detection in subsequent analysis.

2.2.4. Analytical methods

The two most commonly used analytical methods for nickel are
atomic absorption spectroscopy and voltammetry.

In biological samples, such as tissues and body fluids, nickel
concentrations are routinely determined by electrothermal atomic
absorption spectroscopy (EAAS). Acid digestion is required before
analysis of biological samples, which is commonly followed by an
enrichment step. The IUPAC Subcommittee on the Environmental and
Occupational Toxicology of Nickel (Sunderman, 1980) developed a
reference method for the determination of nickel in serum or urine
by EAAS, after acid digestion and the subsequent extraction of
nickel with ammonium pyrrolidine dithiocarbamate (APDC) into methyl
isobutyl ketone (MIBK).

The introduction of a Zeeman-compensated system improved
background compensation and permitted a more rapid and direct
determination of nickel levels with considerably lower detection
limits, which was suitable for routine use. Sunderman et al.
(1984a, 1985) applied EAAS with Zeeman background correction for the
direct determination of nickel in acid-digested serum (detection
limit, 0.05 µg/litre), in whole blood, and in acid-digested tissue
homogenates (detection limit, 10 ng/g dry weight). The suitability
of this method for the direct determination of nickel in acidified
urine with a detection limit of 0.5 µg/litre has been demonstrated
(Sunderman et al., 1986a). Andersen et al. (1986a) presented an
even more direct method, which only required dilution of the human
plasma prior to quantification by Zeeman-corrected EAAS. The limit
of detection was 0.09 µg/litre. Recent progress in voltammetry has
made this method the most sensitive. Ostapczuk et al. (1983) used
a new voltammetric method for the determination of nickel in a
variety of biological materials following acid digestion of the
sample. The method was based on the application of differential
pulse voltammetry (DPV) after prior interfacial accumulation by an
adsorption layer of nickel-dimethylglyoxime chelate at the hanging
mercury drop electrode (HMDE). The measurement of nickel
concentrations as low as 1 ng/litre was possible using this method,
which was also suitable for analysing food samples (Meyer & Neeb,
1985). Though it requires time-consuming sample digestion
procedures, voltammetry is more sensitive, more rapid, and less
costly than EAAS (Ostapczuk et al., 1983). An isotope dilution gas
chromatography-mass spectrometric method for the detection of
nickel in biological materials at the ng/litre level was recently
introduced by Aggarwal et al. (1988). The method depends on the
preparation of a thermally stable and volatile chelate (chelating
agents: sodium diethyldithiocarbonate or lithium
bis(trifluoroethyl) dithiocarbamate) followed by on-column
injection into a gas chromatographic column and electron
ionization of the eluted chelate in the mass spectrometer.

Analysis for nickel in natural water is frequently performed by
EAAS following preconcentration. Large concentration factors
(200:1) provide detection limits as low as 10 ng/litre in sea-water
analysis (Bruland et al., 1979). Inductively-coupled plasma atomic
emission spectroscopy (ICP-AES) is gaining importance in
simultaneous multi-element determination. Provided that there is
sufficient enrichment, nickel concentrations as low as 60 ng/litre
can be determined in natural waters (Akagi et al., 1985a).

Pilhar et al. (1981) presented DPV-HMDE with prior chelate
adsorption at the electrode as a simple, rapid, and inexpensive
procedure for determining nickel levels in natural waters and waste
water, with a detection limit of 1 ng/litre. This method is also
suitable for determining the nickel contents of various kinds of
food (Valenta et al., 1981; Meyer & Neeb, 1985). Particle-induced
X-ray emission makes possible the detection of various trace metals
in water at the ng/litre level (Ali et al., 1985).

Atomic absorption spectroscopy is the most widely used method
of analysis for nickel in soil. The sample must undergo acid
digestion and may be submitted to enrichment procedures. Detection
limits are in the mg/kg range (Abo-Rady, 1979a; Sanzolone et al.,
1979; Schmidt & Dietl, 1981) . Voltammetry, which has been
successfully used for the determination of nickel in a variety of
biological samples, has also been applied in the analysis of acid-
digested soil samples, using square wave voltammetry as the more
efficient method (Ostapczuk et al., 1985b).

Determination of nickel in air samples has been performed using
different methods (NIOSH, 1977b). However, flame atomic absorption
spectroscopy (FAAS) is the most commonly used analytical technique
for measuring the nickel concentration in air samples. Following
an acid digestion procedure, 1 µg of nickel in 1 ml sample can be
detected by this method. Interference by a 100-fold excess of
iron, manganese, chromium, copper, cobalt or zinc can be minimized
by proper burner elevation and the use of an oxidizing flame.

A technique suitable for the simultaneous determination of
several metals in air has been reported (Mackenzie Peers, 1986).
Following acid digestion of the absorbing cellulose ester membrane
filter the extracted sample was analysed by ICP-AES with a
detection limit of 1 µg/sample.

Volatile nickel carbonyl in air can be determined by
colorimetry, as a coloured furildioxime-chelate (Stedman, 1986a),
or directly, by photometric detection of chemiluminescence
(Stedman, 1986b). Detection limits are 1 µg/m³ and 0.2 µg/m³,
respectively.

Electron microscopy and X-ray microanalysis can be used for the
determination of nickel in single dust particles, such as welding
fumes and grinding dusts.

3. SOURCES OF HUMAN AND ENVIRONMENTAL EXPOSURE

3.1. Natural occurrence

Nickel is a ubiquitous element and has been detected in
different media in all parts of the biosphere. It is the fifth
most abundant element by weight after iron, oxygen, magnesium, and
silicon, and the 24th most abundant element in the earth's crust.
However, the average concentration of nickel in the earth's crust
is only about 0.008% (Mason, 1952). Meteorites have been found to
contain 5-50% nickel. Nickel-enriched nodules have been discovered
on the ocean floor (NAS, 1975).

3.1.1. Rocks

Most nickel occurs in the ferromagnesium minerals of igneous
and metamorphic rocks, e.g., olivine [(MgFe)₂ x SiO₄]. Normal nickel
concentrations in igneous rocks range from 2 to 60 mg/kg (acidic
rocks), 50-200 mg/kg (basic rocks), and 10-2000 mg/kg (ultramafic
rocks) (Boyle, 1981). Among the major sedimentary rocks, shale and
carbonate rocks contain an average of 50 mg nickel/kg; sandstone
contains only 1 mg nickel/kg (NAS, 1975).

The most commercially important nickel ore deposits are
accumulations of nickel sulfide minerals in ultramafic igneous
rocks. Such deposits are found in Australia, Canada, and the USSR.
The ores are composed almost entirely of pentlandite [(Fe,Ni)₉S₈],
chalcopyrite (CuFeS₂), and pyrrhotite (Fe_xS_x+1), and usually
contain 1-4% nickel (Duke, 1980). Other nickel ore deposits are
formed by the weathering of ultramafic ferromagnesium silicate
rocks in humid tropical areas. The residual soil (laterite)
developing during the weathering process may contain up to 10 times
the amount of nickel in the original rock (Duke, 1980). The
nickeliferous lateritic weathering profile is characterized by two
deposits, an upper oxide zone and a silicate zone, both varying in
proportion. The oxide zone is composed of iron oxides containing
nickel in solid solution. In the silicate zone, also called the
garnierite zone, nickel is found in the mineral serpentine
Mg₃Si₂O₅(OH)₅ substituting for magnesium. The nickel content of
lateritic ores is approximately 1-3% (Duke, 1980). Important
deposits are located in Brazil, Cuba, Dominican Republic,
Guatemala, Indonesia, New Caledonia, and the Philippines.

3.1.2. Soils

In glacial areas, nickel-containing components may have been
dispersed over wide areas; thus, the nickel contents of the soil
can differ considerably from the nickel content of the underlying
bedrock.

In unweathered glacial sediments, nickel occurs in the same
mineral phases as those in which it is found in the rocks, i.e.,
sulfides and silicates. Weathering of rocks and soils leads to
nickel release from nickeliferous minerals. The nickel released is

largely retained in the weathered material in association with clay
particles and therefore not considered to be very mobile in the
superficial environment (Duke, 1980).

Nickel can exist in soils in several forms (Hutchinson et al.,
1981) including:

(a) inorganic crystalline minerals or precipitates (e.g., in the
lattice of aluminium silicates);

(b) complexed or adsorbed on organic cation surfaces (e.g., organic
matter) or on inorganic cation exchange surfaces (e.g., clay
minerals); and

In a soil-water system, nickel may form complexes with
inorganic ligands (Cl^-, OH^-, SO₄^2-, or NH₃) (Richter & Theiss,
1980) and organic ligands (e.g., humic or fulvic acids) (Nriagu,
1980). Agricultural soils of the world contain between 3 and 1000
mg nickel/kg (NAS, 1975). In forest floor samples collected from
78 sites in 9 states in the northeastern USA, nickel was present at
concentrations in the range of 8.5-15 mg/kg (Friedland et al., 1986).

3.1.3. Water

Nickel occurs in aquatic systems as soluble salts adsorbed on
clay particles or organic matter (detritus, algae, bacteria), or
associated with organic particles, such as humic and fulvic acids
and proteins.

Nickel may enter surface waters from three natural sources
(Boyle, 1981), i.e., as particulate matter in rainwater, through
the dissolution of primary bedrock minerals, and from secondary
soil phases.

The fate of nickel in freshwater and sea water is affected by
several factors including pH, pE, ionic strength, type and
concentration of organic and inorganic ligands, and the presence of
solid surfaces for adsorption (Snodgras, 1980).

In natural waters, at a pH range of 5-9, the divalent ion Ni²⁺
(Ni(H₂O)₆²⁺) is the dominant form. In this pH range, nickel may
also be adsorbed on iron and manganese oxides, or form complexes
with inorganic ligands (OH^-, SO₄^2-, Cl^- or NH₃) (Richter & Theiss,
1980).

If sulfate concentrations are sufficiently high, nickel sulfate
may be the predominant soluble form; under anaerobic conditions,
sulfide is the major factor controlling the solubility of nickel
(Richter & Theiss, 1980). Nickel concentrations of 0.228-0.693
µg/litre, determined for a vertical open-ocean water profile, were
considered to reflect the actual nickel concentration in this

medium (Bruland et al., 1979). Concentrations of nickel in
freshwater systems are generally less than 2-10 µg/litre (Stokes,
1981). For nickel levels in drinking-water see section 5.1.2.

3.1.4. Fossil fuels

Nickel occurs in both coal and crude oil in minor quantities,
originating from vegetation and from percolating waters containing
nickel leached from rocks. The average value in some Canadian
coals was found to be 15 mg nickel/kg (Hawley, 1955). The nickel
contents in some Western Canadian crude oils, analysed by Hodgson
(1954), were in the range of 0.09-76.6 mg/kg.

3.1.5. Air

Atmospheric nickel is considered to exist mainly in the form of
aerosols with different nickel concentrations in particles
depending on the type of source (Schmidt & Andren, 1980). Major
natural sources include the aerosols constantly produced by the
oceanic surface, windblown soil dusts, and volcanic ash. Nickel is
released from plants during growth, at different levels, depending
on soil composition. Forest fires produce nickel-containing smoke
particles. A part of atmospheric nickel originates from meteoric
dusts.

Atmospheric nickel concentrations for remote areas that are
considered to be relatively free from man-made nickel emissions are
in the range of <0.1-1 ng/m³ (marine) and 1-3 ng/m³ (continental)
(Schmidt & Andren, 1980). The wide variation in ambient nickel
concentrations reflects the influence of nickel emissions from
distant sources being transported by means of meteorological
processes.

Nickel from natural sources, excluding volcanic dust and forest
fires, is probably in the form of the oxide (Barrie, 1981).

3.2. Man-made sources

3.2.1. Production, use, and disposal

3.2.1.1 Primary production

The methods for the extraction and refining of nickel minerals
depend on the mineralogical and geological characteristics of the
ore. To date, nickel has mainly been extracted from sulfide and
laterite ores.

Nickel sulfide ores are mostly mined underground using
drilling, blasting, and other techniques. Milling procedures
include liberation, flotation, and magnetic separation. Liberation
of the sulfides from the gangue includes grinding of the rock
material. Then the sulfides are concentrated by flotation
processes. Flotation involves streaming air bubbles through an
aqueous slurry of the ore particles in a flotation cell. The
particles that are not wetted by the liquid adhere to the air

bubbles, rise to the surface of the slurry, and can be removed.
The addition of different chemicals to the flotation medium allows
the selective flotation of nickel- and copper-rich fractions.

Most of the pyrrhotite (both lump ore and ground ore) can be
separated magnetically, because of its magnetic properties.

Laterite nickel deposits are mined from surface pits using
earth-moving equipment.

Both sulfide ore concentrates and laterite ores are subjected
to pyro- and hydrometallurgical processes. The pyrometallurgical
processing basically involves three operations, i.e., roasting,
smelting, and converting.

During roasting, the concentrate is oxidized by hot air. Most
of the iron is oxidized, while nickel, copper, and cobalt remain
combined with sulfur. Part of the sulfur is removed as gaseous
sulfur dioxide.

The roasted product is smelted in a furnace together with a
siliceous flux to obtain two immiscible phases, an iron-rich
silicate slag and a nickel-rich sulfide matte, which also contains
iron, copper, and cobalt.

The matte is treated in a "converter" where more sulfur is
driven off and the remaining iron is oxidized and removed as slag.
The matte is allowed to cool and treated in different ways. It may
be, for example, cast into anodes for electrolytic refining or
cooled slowly to facilitate crystallization to nickel sulfide,
copper sulfide and a nickel-copper alloy containing the desired
metals. These three phases can then be separated by flotation and
magnetic separation. The species of nickel likely to be present
during roasting, smelting, and converting include the ore, nickel
subsulfides, nickel copper sulfides, nickel oxides, nickel-copper
oxides, arsenides, and anhydrous nickel sulfate. The extraction of
nickel from laterite ores is similar to the extraction of nickel
from sulfide ores with the exception that sulfur (commonly gypsum)
has to be added. The molten matte is charged into a converter
where the iron is oxidized and the sulfur combines with nickel to
form Ni₃S₂.

Smelting to ferronickel is essentially the same as matte
smelting, except that no sulfur is added. It is often applied to
laterite ores. The resulting iron-nickel alloy contains 20-50%
nickel (Duke, 1980).

Most of the nickel matte obtained from sulfide or laterite ore
smelting undergoes further refining techniques, such as electro-,
vapo-, or hydrometallurgical refining, but a part of the matte is
roasted to marketable nickel oxide sinter.

Hydrometallurgical refining can be applied both to laterite ore
and sulfide ore or sulfide ore concentrates. Soluble nickel amines
are formed during pressure leaching of the sulfide ore concentrate
with strong ammoniacal solution at a moderately elevated

temperature. The saturated solution is boiled to drive off ammonia
and precipitate copper as sulfide. Sulfur is oxidized. Nickel and
cobalt are recovered as pure metal powders by reduction with
hydrogen under pressure.

Laterite ores must first be reduced. The reduced ore is
leached with an ammonia-ammonium carbonate solution. Nickel
dissolves as nickel amine. The saturated solution is heated by
steam, ammonia is driven off, and nickel is precipitated as a basic
carbonate.

Pure nickel (99.9%) can be produced by electrolytic refining.
Generally, an impure metal anode (produced by reducing nickel
oxide) and a cathode starting sheet are placed in an acidic
electrolytic solution. When a current flows, nickel and other
metals are dissolved from the anode. The electrolyte is then
removed, purified and returned to the cathode compartment, where
nickel is deposited on the cathode.

During vapometallurgical refining, impure metal obtained by the
reduction of nickel oxide is subjected to the action of carbon
monoxide forming volatile nickel carbonyl [Ni(CO)₄] (carbonyl or
Mond process). This reaction is reversed by heat and the nickel
carbonyl decomposes to pure nickel metal and carbon monoxide. The
carbonyl process produces the purest nickel (99.97% or more).

The smelting and refining processes yield various marketable
forms of nickel of different purities (Table 3).
Table 3. Commercial forms of primary nickel^a
------------------------------------------------------------------------------------------------
Type Composition (%)
Nickel Carbon Copper Iron Sulfur Cobalt Oxygen Silicon Chromium
------------------------------------------------------------------------------------------------
Pure unwrought nickel

Cathode >99.9 0.01 0.005 0.002 0.001 - - - -

Pellets >99.97 <0.1 0.001 0.0015 0.0003 5 x 10^-5 - - -

Powder 99.74 <0.1 - <0.1 <0.01 - <0.15 - -

Briquettes 99.9 0.01 0.001 0.002 0.0035 0.03 - - -

Rondelles 99.25 0.022 0.046 0.087 0.004 0.37 0.042 - -

Ferronickel^b 20-50^c 1.5-1.8 - Rest <0.3 -^c - 1.8-4 1.2-1.8

Nickel oxide 76.0 - 0.75 0.3 0.006 1.0 Rest - -
------------------------------------------------------------------------------------------------
^a Modified from: Corrick (1977).
^b Ranges used to denote variable grades produced.
^c Cobalt included with nickel (1-2%).
3.2.1.2 Intermediate products and end-use

Most of the nickel produced is used in the production of alloys
(Table 4). In the production of nickel steel alloys, steel scrap,
limestone, iron oxide ore, and nickel are charged into a furnace
(open-hearth furnace, electric arc furnace and cupola) where the
steel and iron alloys are melted. After final adjustment of the
carbon and alloy contents, the steel is cast into moulds. Non-
ferrous melting is commonly performed in a reverberatory furnace.

Table 4. Consumption of nickel by
intermediate product and end-use industry in
1985 in the USA
---------------------------------------------
Index Consumption^a
(% of total)
---------------------------------------------
Intermediate product

Stainless and alloy steels 42
Nonferrous alloys 36
Electroplating 18

End-use industry

Transportation 23
Chemical industry 15
Electrical equipment 12
Construction 10
Fabricating metal products 9
Petroleum 8
Household appliances 8
Machinery 8
Other 7
---------------------------------------------
^a Data from: US Bureau of Mines (1986).

The forming and shaping of ingots, after the casting of the
alloy, is performed by hot-working, grinding, and welding. Hot-
working includes the reduction of the cross section, e.g., by
forging or rolling. The resulting product may be cut and then
extruded to the desired form. Grinding is necessary to condition
the metal surface for further processing, e.g., welding. Welding
techniques, such as electric-arc, electric-spot oxyacetylene-torch,
or furnace-brazing, are used to fabricate assembled shapes. In
special cases, forming of parts may also be performed by sintering,
e.g., by sintering nickel powder from the Mond process.

The addition of nickel to steel and cast iron yields an alloy
with increased strength and toughness and resistance to corrosion.
Stainless steel is used in the chemical and food-processing
industries. Because of their ferromagnetic properties, iron-nickel
alloys are important materials for the electrical industry.

Various medical devices, such as prostheses or orthopaedic
implants, are made from stainless steel.

Nickel-copper alloys exhibit the highest mechanical strength
and resistance to corrosion and are used in the chemical and
machine industries (pipes, nozzles, machine parts for the food and
textile industries). Their high resistance to corrosion makes
these alloys a valuable material for the shipbuilding industry.
The nickel-copper alloy containing 77-63% nickel is known as Monel
metal.

Nickel alloys containing chromium, molybdenum, aluminium,
cobalt, titanium, or combinations of these elements are of special
industrial importance, because of their high-temperature
resistance.

Nickel-chromium alloys are used for jet engine components, in
nuclear reactors, and for turbine blades. Superalloy is an
extremely high-temperature resistant alloy containing 10-20%
cobalt. It is used in turbine blades and other engine components
of jets, ships, and racing vehicles, where extreme mechanical and
high-temperature resistance is required.

In plating, nickel gives a hard, tarnish resistant surface that
can be polished, which makes the finished product suitable for
consumer items, such as automobile components, household furniture,
and plumbing fixtures. Normally nickel-plated consumer items are
covered with a thin layer of chromium plating.

Other important uses of nickel are in nickel-cadmium batteries,
electronic equipment, and computers. Nickel compounds are used as
catalysts in the manufacture of organic chemicals, petroleum
refining, and edible oil hardening. They are also constituents of
pigments and colours for ceramics and glassware, and of marine
anti-fouling paint. In the glass industry, nickel is used in
moulds for bottles. Nickel compounds are also used as a coating
for pressure sensitive papers. In the United Kingdom, "silver"
coinage (5 p, 10 p, and 20 p) is based on cupro-nickel alloys
containing approximately 20% nickel. Coinage from other countries
contains higher levels, e.g., Canadian 10 cents (99.8% nickel), and
French 1 and 2 francs (99.8-99.9% nickel).

The production of secondary nickel in the form of scrap
recovery is a major source of nickel. Recycled scrap is generally
melted and refined and subsequently used for the production of
steels and alloys, similar in composition to those in which it
entered the recycling process. Thus, scrap recycling processes are
analogous with those used in primary production.

3.2.1.3 World production levels and trends

The development of global mine production during this decade is
shown in Table 5.

Table 5. Global mine production of nickel, by country^a,b (short tonnes of nickel)
--------------------------------------------------------------------------------------------------------
Country or territory 1980 1981 1982 1983^c 1984^d 1985^d
--------------------------------------------------------------------------------------------------------
Albania (content of ore)^d 6 100 6 200 6 400 6 400 6 600 6 600
Australia (content of concentrate) 81 927 81 963^e 96 510 84 465 82 900 81 000
Botswana (content of matte) 17 022 18 200 19 573 20 079 19 300 19 000
Brazil (content of ore) 2 504^e 2 573^e 5 306 11 840 12 100 12 000
Burma (content of speiss) 15 22 22^d 22^d 22 -
Canada^f 203 709 176 642 97 824 134 300 192 000 195 000
China^d 12 000 12 000 13 200^e 14 300^e 15 400 16 000
Colombia (content of ferroalloys) - - 1 100 15 000 15 400 10 000
Cuba (content of oxide, sinter, sulfide) 40 338 42 489 39 790 41 500^d,e 35 050 40 000
Dominican Republic 18 019 20 601 5 838 23 369 26 698^g 27 000
Finland (content of concentrate) 7 199 7 566 6 852 5 418 5 500 6 000
German Democratic Republic^d 3 000 3 000 2 800 2 400 2 300
Greece (recoverable content of ore)^h 16 796 17 200 5 500^d,e 18 500^d,e 18 400 16 000
Guatemala 7 650 - - - - -
Indonesia (content of ore)^h 58 738 53 848 50 578 54 430 68 900 70 000
Morocco (content of nickel ore and 148 144^e 140 - -
cobalt ore)
New Caledonia (recoverable content or ore) 95 451 86 079 66 250 43 542 45 200 44 000
Norway (content of concentrate)^d 2 200^e 7 700^e 3 900^e 4 000^e 3 900^e
Philippines 51 934 32 239 22 183 17 522 18 300 25 000
Poland (content of ore)^d 2 300 2 300 2 300 2 300 2 300 -
South Africa, Republic of 28 239 29 100 24 250^d 22 600^d 27 600 27 000
USSR (content of ore)^d 170 000 174 000 182 000 187 000 192 000 197 000
USA (content of ore shipped) 14 653 12 099 3 203 - 14 540^g 6 900
Yugoslavia (content of ore)^d 2 200 4 400 4 400^e 3 300^e 4 400 3 000
Zimbabwe (content of concentrate) 16 617 14 350 14 671 11 186 11 080 11 000
--------------------------------------------------------------------------------------------------------
Total 858 850^e 804 715^e 674 590 723 473 819 890 821 000
--------------------------------------------------------------------------------------------------------
^a From: US Bureau of Mines (1985; 1986).
^b As far as possible, this table represents recoverable mine production of nickel. Where data relate
to some more highly processed form of nickel, the figure given has been used in place of an
unreported actual mine output, to provide some indication of the magnitude of mine output. See notes
in parentheses and footnotes.
^c Preliminary.
^d Estimated.
^e Revised.
^f Refined nickel and nickel content.
^g Reported figure.
^h Includes a small amount of cobalt not reported and not recovered separately.
The nickel market weakened considerably from 1981 to 1983,
because of a reduction in demand arising from a recession in the
economy. In 1984, production and demand increased again. From a
1983 base, the US Bureau of Mines (1986) estimated that there would
be an increase in the average annual demand of about 2.5%, up
to 1990.

The identified world deposits with an average nickel content of
approximately 1% or more, contain 143 million tonnes of nickel (US
Bureau of Mines, 1986). In addition, there are extensive deep-sea
resources of nickel in manganese nodules, particularly in the
Pacific Ocean (US Bureau of Mines, 1986).

At present, there are only a few actual and potential
substitutes for nickel, e.g., aluminium, coated steel, titanium,
and plastic for industrial purposes, and platinum, cobalt, and
copper for catalytic uses. However, the use of these substitutes
results in increased costs and a lower quality end-product (US
Bureau of Mines, 1986).

3.2.1.4 Emissions from the primary nickel industry

Data on the loss of nickel into the environment during
production are limited. The smelting and roasting stages of ore
refining and alloy production may be considered as the more
important sources of nickel emission, because these processes
generate flue dust, i.e., fine particulate matter that is swept
from roasters and reverberatory furnaces by air and combustion
gases that pass through these units.

During an environmental study initiated by the Ontario Ministry
of Environment, trace metal emission rates from two nickel smelters
were calculated on the basis of the results of chimney stack
emission tests (Chan & Lusis, 1986).

The annual emissions of nickel during the study period are
given in Table 6. Annual emissions from a 381-m stack of one
smelter that emits particulates and gases from pyrometallurgical
smelting processes are listed in Table 7. This was considered the
most significant emission source.

Data on the chemical forms of nickel released into the
atmosphere from production processes are practically non-existent.
In most cases, statements are based on assumptions.

Species of nickel emitted into the air from mining garnierite
and processing it to produce ferronickel at a facility in the USA,
were assumed to be in the form of silicates, as in the ore, but
were expected to be minimal (Radian Corporation, 1984). Depending
on the temperature reached during drying and calcining, some nickel
on the surface of ore fragments may become oxidized and emitted as
iron-nickel oxide (Radian Corporation, 1984). Emissions during
roasting and smelting would probably be in the form of nickel oxide
combined with iron oxide as a ferrite (Radian Corporation, 1984;
Warner, 1984).

Table 6. Yearly emission (in tonnes)
of nickel (Sudbury Basin, Canada) for
the period 1973-81^a,b
______________________________________
Source Variation Nickel
______________________________________
INCO 381-m stack Maximum 342
Average 228
Minimum 53

INCO 194-m stack Maximum 226
Average
Minimum

INCO Smelter Maximum 40
(low level) Average 31
Minimum 15

Falconbridge Maximum
93-m stack Average 9.6
Minimum
______________________________________
^a From: Chan & Lusis (1986).
^b Basis: 365 x 24 h/day production.

Table 7. Average measured emissions
of nickel from a 381-m stack (Canada)
(in kg/h)^a
______________________________________
Year Emission
______________________________________
1973 48
1974 55
1975 15
1976 22
1977 33
1978 20
1979 12
1980 44
Average 31
______________________________________
^a From: Chan & Lusis (1986).

When producing nickel from the sulfide ore,