necessarily represent the decisions or the stated policy of the United Nations Environment Programme, the International Labour Organization, or the World Health Organization.
Concise International Chemical Assessment Document 47
ARSINE: HUMAN HEALTH ASPECTS
Please note that the layout and pagination of this pdf file are not necessarily identical to the printed hard copy
First draft prepared by S. Czerczak, The Nofer Institute of Occupational Medicine, Lodz, Poland; second draft prepared by L. Fishbein, Fairfax, Virginia, USA
Published under the joint sponsorship of the United Nations Environment Programme, the International Labour Organization, and the World Health Organization, and produced within the framework of the Inter-Organization Programme for the Sound Management of
Chemicals.
World Health Organization
Geneva, 2002
Organization (ILO), and the World Health Organization (WHO). The overall objectives of the IPCS are to establish the scientific basis for assessment of the risk to human health and the environment from exposure to chemicals, through international peer review processes, as a prerequisite for the promotion of chemical safety, and to provide technical assistance in strengthening national capacities for the sound management of chemicals.
The
Inter-Organization Programme for the Sound Management of Chemicals (IOMC) wasestablished in 1995 by UNEP, ILO, the Food and Agriculture Organization of the United Nations, WHO, the United Nations Industrial Development Organization, the United Nations Institute for Training and Research, and the Organisation for Economic Co-operation and Development (Participating Organizations), following recommendations made by the 1992 UN Conference on Environment and Development to strengthen cooperation and increase coordination in the field of chemical safety. The purpose of the IOMC is to promote coordination of the policies and activities pursued by the Participating Organizations, jointly or separately, to achieve the sound management of chemicals in relation to human health and the environment.
WHO Library Cataloguing-in-Publication Data Arsine: Human health aspects.
(Concise international chemical assessment document ; 47)
1.Arsenic - toxicity 2.Arsenic - poisoning 3.Arsenic - physiology 4.Occupational exposure 5.Environmental exposure 6.Hazardous substances - adverse effects
I.International Programme on Chemical Safety II.Series
ISBN 92 4 153047 2 (NLM Classification: QV 294) ISSN 1020-6167
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iii
FOREWORD...1
1. EXECUTIVE SUMMARY...4
2. IDENTITY AND PHYSICAL/CHEMICAL PROPERTIES ...5
3. ANALYTICAL METHODS...5
4. SOURCES OF HUMAN AND ENVIRONMENTAL EXPOSURE...6
5. ENVIRONMENTAL TRANSPORT, DISTRIBUTION, AND TRANSFORMATION...6
6. ENVIRONMENTAL LEVELS AND HUMAN EXPOSURE...6
6.1 Environmental levels ...6
6.2 Human exposure ...7
7. COMPARATIVE KINETICS AND METABOLISM IN LABORATORY ANIMALS AND HUMANS ...8
7.1 Animal studies...8
7.2 Human studies ...9
7.3 Biological monitoring ...9
8. EFFECTS ON LABORATORY MAMMALS AND IN VITRO TEST SYSTEMS...10
8.1 Single exposure ...10
8.2 Repeated exposure...11
8.3 Carcinogenicity ...12
8.4 Skin and eye irritation and sensitization ...12
8.5 Reproductive toxicity...12
8.6 Genotoxicity...12
8.7 Mechanisms of toxicity/mode of action...12
9. EFFECTS ON HUMANS...13
9.1 Acute poisoning ...13
9.1.1 Immediate effects...13
9.1.2 Late effects...14
9.2 Long-term exposure ...14
9.3 Effects on individual organs ...14
9.3.1 Blood and haematopoietic tissue ...14
9.3.2 Kidneys...15
9.3.3 Liver...15
9.3.4 Nervous system ...16
9.3.5 Respiratory and circulatory systems ...16
9.4 Reproductive toxicity...16
9.5 Carcinogenicity ...16
iv
10. EFFECTS EVALUATION ...16
10.1 Evaluation of health effects...16
10.1.1 Hazard identification and dose–response assessment ...16
10.1.2 Criteria for setting guidance values for arsine ...17
10.1.3 Sample risk characterization...17
10.1.4 Uncertainties in the hazard characterization...18
11. PREVIOUS EVALUATIONS BY INTERNATIONAL BODIES...18
REFERENCES...19
APPENDIX 1 — SOURCE DOCUMENTS...22
APPENDIX 2 — CICAD PEER REVIEW ...22
APPENDIX 3 — CICAD FINAL REVIEW BOARD...23
INTERNATIONAL CHEMICAL SAFETY CARD ...24
RÉSUMÉ D’ORIENTATION...26
RESUMEN DE ORIENTACIÓN ...28
FOREWORD
Concise International Chemical Assessment Documents (CICADs) are the latest in a family of publications from the International Programme on Chemical Safety (IPCS) — a cooperative programme of the World Health Organization (WHO), the International Labour Organization (ILO), and the United Nations Environment Programme (UNEP). CICADs join the Environmental Health Criteria documents (EHCs) as authoritative documents on the risk assessment of chemicals.
International Chemical Safety Cards on the relevant chemical(s) are attached at the end of the CICAD, to provide the reader with concise information on the protection of human health and on emergency action. They are produced in a separate peer-reviewed procedure at IPCS.
CICADs are concise documents that provide sum- maries of the relevant scientific information concerning the potential effects of chemicals upon human health and/or the environment. They are based on selected national or regional evaluation documents or on existing EHCs. Before acceptance for publication as CICADs by IPCS, these documents undergo extensive peer review by internationally selected experts to ensure their completeness, accuracy in the way in which the original data are represented, and the validity of the conclusions drawn.
The primary objective of CICADs is characteri- zation of hazard and dose–response from exposure to a chemical. CICADs are not a summary of all available data on a particular chemical; rather, they include only that information considered critical for characterization of the risk posed by the chemical. The critical studies are, however, presented in sufficient detail to support the conclusions drawn. For additional information, the reader should consult the identified source documents upon which the CICAD has been based.
Risks to human health and the environment will vary considerably depending upon the type and extent of exposure. Responsible authorities are strongly encour- aged to characterize risk on the basis of locally measured or predicted exposure scenarios. To assist the reader, examples of exposure estimation and risk characteriza- tion are provided in CICADs, whenever possible. These examples cannot be considered as representing all possible exposure situations, but are provided as guidance only. The reader is referred to EHC 170.1
1International Programme on Chemical Safety (1994) Assessing human health risks of chemicals: derivation of guidance values for health-based exposure limits. Geneva, World Health Organization (Environmental Health Criteria 170) (also available at http://www.who.int/pcs/).
While every effort is made to ensure that CICADs represent the current status of knowledge, new informa- tion is being developed constantly. Unless otherwise stated, CICADs are based on a search of the scientific literature to the date shown in the executive summary. In the event that a reader becomes aware of new informa- tion that would change the conclusions drawn in a CICAD, the reader is requested to contact IPCS to inform it of the new information.
Procedures
The flow chart on page 2 shows the procedures followed to produce a CICAD. These procedures are designed to take advantage of the expertise that exists around the world — expertise that is required to produce the high-quality evaluations of toxicological, exposure, and other data that are necessary for assessing risks to human health and/or the environment. The IPCS Risk Assessment Steering Group advises the Coordinator, IPCS, on the selection of chemicals for an IPCS risk assessment based on the following criteria:
• there is the probability of exposure; and/or
• there is significant toxicity/ecotoxicity.
Thus, a priority chemical typically
• is of transboundary concern;
• is of concern to a range of countries (developed, developing, and those with economies in transition) for possible risk management;
• is significantly traded internationally;
• has high production volume;
• has dispersive use.
The Steering Group will also advise IPCS on the appropriate form of the document (i.e., EHC or CICAD) and which institution bears the responsibility of the document production, as well as on the type and extent of the international peer review.
The first draft is based on an existing national, regional, or international review. Authors of the first draft are usually, but not necessarily, from the institution that developed the original review. A standard outline has been developed to encourage consistency in form.
The first draft undergoes primary review by IPCS to ensure that it meets the specified criteria for CICADs.
The second stage involves international peer review by scientists known for their particular expertise and by scientists selected from an international roster compiled by IPCS through recommendations from IPCS national Contact Points and from IPCS Participating Institutions.
Adequate time is allowed for the selected experts to undertake a thorough review. Authors are required to take reviewers’ comments into account and revise their
CICAD PREPARATION FLOW CHART
Selection of priority chemical, author institution, and agreement
on CICAD format
9
Preparation of first draft
9
Primary acceptance review by IPCS and revisions as necessary
9
Selection of review process
9
Peer review
9
Review of the comments and revision of the
document
9
Final Review Board:
Verification of revisions due to peer review comments, revision, and approval of the document
9
Editing
Approval by Coordinator, IPCS
9
Publication of CICAD on web and as printed text
Advice from Risk Assessment Steering Group
Criteria of priority:
$ there is the probability of exposure;
and/or
$ there is significant toxicity/ecotoxicity.
Thus, it is typical of a priority chemical that
$ it is of transboundary concern;
$ it is of concern to a range of countries (developed, developing, and those with economies in transition) for possible risk management;
$ there is significant international trade;
$ the production volume is high;
$ the use is dispersive.
Special emphasis is placed on avoiding duplication of effort by WHO and other international organizations.
A prerequisite of the production of a CICAD is the availability of a recent high-quality national/regional risk assessment document = source document. The source document and the CICAD may be produced in parallel. If the source document does not contain an environ- mental section, this may be produced de novo, provided it is not controversial. If no source document is available, IPCS may produce a de novo risk assessment document if the cost is justified.
Depending on the complexity and extent of controversy of the issues involved, the steering group may advise on different levels of peer review:
$ standard IPCS Contact Points
$ above + specialized experts
$ above + consultative group
draft, if necessary. The resulting second draft is submitted to a Final Review Board together with the reviewers’ comments. At any stage in the international review process, a consultative group may be necessary to address specific areas of the science.
The CICAD Final Review Board has several important functions:
• to ensure that each CICAD has been subjected to an appropriate and thorough peer review;
• to verify that the peer reviewers’ comments have been addressed appropriately;
• to provide guidance to those responsible for the preparation of CICADs on how to resolve any remaining issues if, in the opinion of the Board, the author has not adequately addressed all comments of the reviewers; and
• to approve CICADs as international assessments.
Board members serve in their personal capacity, not as representatives of any organization, government, or industry. They are selected because of their expertise in human and environmental toxicology or because of their experience in the regulation of chemicals. Boards are chosen according to the range of expertise required for a meeting and the need for balanced geographic repre- sentation.
Board members, authors, reviewers, consultants, and advisers who participate in the preparation of a CICAD are required to declare any real or potential conflict of interest in relation to the subjects under discussion at any stage of the process. Representatives of nongovernmental organizations may be invited to observe the proceedings of the Final Review Board.
Observers may participate in Board discussions only at the invitation of the Chairperson, and they may not participate in the final decision-making process.
1. EXECUTIVE SUMMARY
The first draft of this CICAD on human health aspects of arsine was prepared by Dr S. Czerczak from the Nofer Institute of Occupational Medicine, Lodz, Poland. The literature searches performed cover data identified up to June 2000. The US Environmental Protection Agency’s Integrated Risk Information System document (US EPA, 1994b) and the German MAK document (Greim, 2001) were used as additional source documents. The source documents and their peer review are described in Appendix 1. The peer review of this CICAD is described in Appendix 2. This CICAD was approved as an international assessment at a meeting of the Final Review Board, held in Monks Wood, England, on 16–19 September 2002. Participants at the Final Review Board meeting are listed in Appendix 3. The International Chemical Safety Card for arsine (ICSC 0222), produced by the International Programme on Chemical Safety in a separate, peer-reviewed process (IPCS, 2001b), has also been reproduced in this document.
The information presented in this CICA D focuses on effects associated with short-term exposure to arsine.
Within the body, arsine is oxidized to other arsenic species. Effects (notably cancer and genotoxic effects) associated with exposure to arsenic and arsenic com- pounds have been recently reviewed by IPCS (2001a).
Arsenic and arsenic compounds are carcinogenic to humans and induce genotoxic effects in experimental systems and in humans.
Arsine (CAS No. 7784-42-1) is a colourless, non- irritating gas with a mild, garlic-like odour. Arsine is generated whenever nascent hydrogen is released in the presence of arsenic or by the action of water on a metallic arsenide. Arsine is a strong reducing agent, deposits arsenic on exposure to light and moisture, and is easily transformed into other oxidized arsenic forms (e.g., As(III), As(V)). Arsine vapour is heavier than air and accumulates close to the surface, which makes distant ignition possible in the presence of flame or spark.
For the determination of arsine in air at the work- place, the air sample is collected in a charcoal tube equipped with a cellulose filter to eliminate aerosols of arsenic compounds. The measurement is done by graphite furnace atomic absorption spectrometry after nitric acid desorption and using nickel as a matrix modifier. The working range of the method is 1–
200 µg/m3 in a 10-litre air sample. Commercial con- tinuously recording instruments with specified sensi- tivity of 1 µg/m3 are available.
Arsine may be formed by microorganisms by bio- transformation of non-volatile arsenic compounds, such as arsenites and arsenates.
The main anthropogenic sources of arsine include formation from reaction of acids with reducing metals containing arsenic impurities, which occurs primarily as a by-product of the refining of non-ferrous metals, such as zinc, copper, and cadmium. It is predicted that arsine can be formed in the environment in such places as hazardous waste deposits.
Arsine is extensively used in the semiconductor industry for epitaxial growth of gallium arsenide, as a doping agent for silicon-based solid-state electronic devices, and in the manufacture of light-emitting diodes.
In the environment, arsine is transformed into other arsenic compounds.
There are no reports on concentrations of arsine in the environment, and reports on the levels of occupa- tional exposure to arsine are scarce.
In humans and animals, arsine is absorbed via the lungs and mucous surface of the respiratory tract. After exposure, the concentration of arsine increases rapidly in blood, whereas the distribution to liver, kidneys, and other organs is much slower.
In humans and animals, arsine is metabolized to trivalent arsenic (As(III)) as well as pentavalent arsenic (As(V)). As(III) is methylated to monomethylarsonate and dimethylarsinate. Arsine metabolites are mainly excreted via urine.
The acute toxicity of arsine in different species, including humans, is high. The target organ of arsine poisoning is the haematopoietic system, in particular the erythrocytes. Arsine induces haemolysis, causing haemo- globinuria and subsequent kidney damage; a large number of fatal intoxications in humans have been described, and they continue to occur. The LC50 for mice is 250 mg/m3 for a 10-min exposure. Inhalation of arsine by mice caused an increase in the relative spleen weight after a 6- h exposure to 16 mg/m3 and a decrease in haematocrit value after a 1-h exposure to 30 mg/m3. Histopatholog- ical changes observed included haemosiderosis and extramedullary haematopoietic activity in the spleen.
No studies or relevant data are available on the irri- tant effects of arsine on skin or eyes or on the sensitizing activity of arsine.
Repeated exposure to arsine caused persistent splenomegaly and slight suppression of bone marrow erythroid precursors in rats and mice at concentrations of =1.6 mg/m3 and in Syrian Golden hamsters at
concentrations of =8.1 mg/m3. Methaemoglobinaemia was observed in mice exposed to arsine at a concen- tration of 8.1 mg/m3. In rats, mice, and Syrian Golden hamsters, a lowest-observed-adverse-effect level (LOAEL) for haematological effects of 1.6 mg/m3 was observed. A no-observed-adverse-effect level (NOAEL) was established at 0.08 mg/m3, recognizing that a reversible, compensatory change in mean corpuscular volume (MCV), not considered to be adverse, was observed in mice even at the lowest exposure level studied.
In the only study available, arsine did not induce developmental toxicity in mice or rats at exposure levels that induced splenomegaly.
In humans, arsine induces haemolysis with an increase in plasma haemoglobin, iron, and potassium concentrations and subsequent anaemia and kidney damage. No reliable information is available on expo- sure levels at which these effects occur. Myocardial and pulmonary failures are other causes of death. Severe liver lesion is rare.
Anaemia is observed to varying degrees, accom- panied by Heinz-Ehrlich corpuscles and increased leukocytosis. Haemoglobin, haemosiderin, erythrocytes, proteins, and casts are found in the urine.
Effects of long-term exposure to low levels of arsine are not well characterized. There are no data on the carcinogenicity or mutagenicity of arsine to humans or experimental animals. Exposure to other arsenic com- pounds to which arsine is metabolized can induce lung, bladder, kidney, and skin cancer in humans.
From the NOAEL of 0.08 mg/m3, using an overall uncertainty factor of 300 and adjusting for the exposure pattern, a guidance value of 0.05 µg/m3 can be derived.
2. IDENTITY AND PHYSICAL/CHEMICAL PROPERTIES
Arsine (CAS No. 7784-42-1) (AsH3) is a colourless, extremely flammable gas with a garlic-like odour (an odour threshold of about 1.5 mg/m3 has been reported;
Stokinger, 1981). The gas is heavier than air and accumulates close to the surface, which makes distant ignition possible in the presence of flame or spark.
Explosive limits are 4.5–78% in air. The most common synonyms for arsine are arsenic hydride, arsenic tri- hydride, hydrogen arsenide, and arsenous hydride. The relative molecular mass of arsine is 77.95. Its boiling point is –62 °C, and its vapour pressure at 20 °C is 1043 kPa. Arsine is soluble in benzene and chloroform
and slightly soluble in alcohol and alkalis. Its solubility in water is 200 ml/litre. Additional physical/chemical properties are presented in the International Chemical Safety Card (ICSC 0222) included in this document.
The conversion factors1 for arsine in air (20 °C, 101.3 kPa) are as follows:
1 mg/m3 = 0.309 ppm 1 ppm = 3.24 mg/m3
3. ANALYTICAL METHODS
Numerous methods have been developed to deter- mine arsine in atmospheric and workplace air (i.e., in workers’ breathing zones). The most widely applied include colorimetric methods, spectrophotometry (Mazur et al., 1983), graphite furnace atomic absorption spectrometry (Denyszyn et al., 1978; NIOSH, 1985, 1994), and X-ray fluorescence spectrometry (Keech &
West, 1980).
The method of Mazur et al. (1983) is based on the reaction of arsine with molybdenum reagent and deter- mination of the blue-coloured reaction product by spectrophotometry at a wavelength of 800 nm. The air sample is collected into a bubbler with potassium permanganate and sulfuric acid. The detection limit is 0.05 mg/m3. However, this method does not allow specific analysis of arsine.
In the graphite furnace atomic absorption spectro- metric methods, Matsumura (1988) used synthetic resin active carbon for the sample collection, whereas Denyszyn et al. (1978) and NIOSH (1985, 1994) used activated charcoal. All three desorbed arsine in nitric acid and analysed it with graphite furnace atomic absorption spectrometry, using nickel as a matrix modi- fier. NIOSH (1985, 1994) used a cellulose filter to prevent aerosols of arsenic compounds from entering the adsorbent. The limits of detection were 1 µg/m3 for the method of Matsumura (1988) and 2 µg/m3 in a 15-litre air sample for the method of Denyszyn et al. (1978); the
1 In keeping with WHO policy, which is to provide measurements in SI units, all concentrations of gaseous chemicals in air will be given in SI units in the CICAD series.
Where the original study or source document has provided concentrations in SI units, these will be cited here. Where the original study or source document has provided concentrations in volumetric units, conversions will be done using the con- version factors given here, assuming a temperature of 20 °C and a pressure of 101.3 kPa. Conversions are to no more than two significant digits.
working range of the NIOSH (1985, 1994) method was 1–200 µg/m3 in a 10-litre air sample.
The content of arsine in workplace air can be deter- mined by X-ray fluorescence spectrometry. Arsine gas was collected on a filter paper impregnated with silver nitrate and then subjected to X-ray fluorescence analysis.
The limit of detection of the method for a 60-litre air sample was 4 µg/m3 (Keech & West, 1980).
Commercial continuously recording instruments with specified sensitivity of 1 µg/m3 are available (G.
Franz, personal communication, 2002).
Arsenic concentrations in urine, blood, hair, and nails have been used for the biological monitoring of arsenic exposure. However, these measures are not specific to arsine exposure, and exposure to other arsenic species may confound the findings. Extensive descrip- tion of these methods has been presented in the Environmental Health Criteria document on arsenic (IPCS, 2001a).
4. SOURCES OF HUMAN AND ENVIRONMENTAL EXPOSURE
Arsine may be generated from other arsenic com- pounds by some fungi and bacteria (Cheng & Focht, 1979; Tamaki & Frankenberger, 1992). Cheng & Focht (1979) studied the production of arsine from some arsenical substrates (arsenate, arsenite, monomethyl- arsonate, and dimethylarsinate) added to three different soils. Both Pseudomonas and Alcaligenes reduced arsenate and arsenite to arsine under anaerobic con- ditions. Many microorganisms isolated from anaerobic sewage sludge have also been reported to produce arsine (Michalke et al., 2000). However, the liberation of arsine from dimethylarsinate and monomethylarsonate from silty clay was a very minor degradation pathway (<0.4%
in 70 days) compared with mineralization, which was the major degradation pathway for these arsenic species (3–87%) (Gao & Burau, 1997).
The main anthropogenic sources of arsine include its accidental formation, particularly in the chemical and non-ferrous (e.g., zinc, copper, and cadmium) metallur- gical industries, and production or use of the gas itself during manufacture of semiconductors as a doping agent (Wald & Becker, 1986; Badman & Jaffe, 1996;
Aposhian, 1997; Winski et al., 1997) and in battery production as an alloy with lead (Wald & Becker, 1986).
Arsine intoxications are often unexpected, since even very small amounts of arsenic present as an impurity can produce dangerous quantities of arsine (Johnson, 1953).
Arsine may also be produced in the use of lead and
batteries (Marr & Smaga, 1987). It is predicted that arsine can be formed in the environment in such places as hazardous waste deposits.
In investigating a possible relationship between exposure to arsine and sudden infant death syndrome, Richardson (1990) detected the generation of arsine from polyvinyl chloride-covered cot mattresses. The fungus Scopulariopsis brevicaulis could be cultivated from all mattresses studied, and it was suggested that 10,10'-oxybisphenoxyarsine used in plasticized poly- vinyl chloride as the preservative was converted to arsine by these arsine-tolerant organisms (Richardson, 1990).
Arsine is produced commercially by the reaction of aluminium arsenide with water or hydrochloric acid or as a result of electrochemical reduction of arsenic com- pounds in acid solutions. Arsine is manufactured in the USA, Belgium, Italy, and Germany (IARC, 1980).
Arsine is extensively used in the semiconductor industry for epitaxial growth of gallium arsenide and as a dopant for silicon-based electronic devices (Zukauskas
& Gavriusinas, 2002). Arsine is also used in organic synthesis (Lewis, 1993), as an agent in the manufacture of light-emitting diodes, and for manufacturing certain glass dyes (HSDB, 1999). Arsine has been investigated as a chemical warfare agent, but no such use has been documented (Lewis, 1993; Suchard & Wu, 2001).
5. ENVIRONMENTAL TRANSPORT, DISTRIBUTION, AND TRANSFORMATION
No data are available on the environmental transport or distribution of arsine between media. Arsine decom- poses on exposure to light or when it comes into contact with moisture in the air, depositing shiny black arsenic (Windholz, 1983); in water, it rapidly hydrolyses to other arsenic compounds (HSDB, 1999).
6. ENVIRONMENTAL LEVELS AND HUMAN EXPOSURE
6.1 Environmental levels
No data are available on the occurrence of arsine per se in the environment. Environmental levels of arsenic can be found in IPCS (2001a).
Table 1: Workplace conditions that may lead to arsine exposure.a
Workplace Particular conditions References
Slag-washing plant Process of washing arsenic-contaminated slag during copper–aluminium alloy production. From this slag, arsine can be generated by:
- hydrolysis of aluminium arsenide;
- the production of nascent hydrogen by finely separated aluminium in an alkaline medium; or - an electrolytic action between the revolving iron drum and the aluminium.
Kipling &
Fothergill, 1964
Chemical manufacturing company
An antifreeze concentrate containing water, caustic, and sodium arsenate was loaded into an aluminium tank. A worker periodically placed his head into the dome opening to check the fill level.
Arsine was evolved in a reaction between antifreeze concentrate and the aluminium tank.
Konzen &
Dodson, 1966 Trucking company An aluminium tank trailer was cleaned with a phosphoric acid solution. The tank had been used
previously for storage of sodium arsenite solution. Most probably, arsenic was deposited on the aluminium and was converted to arsine when acid was added.
Elkins & Fahy, 1967 Handling and
transporting cylinders containing arsenic compounds
A solution containing sodium hydroxide and arsenic trioxide was removed from an aluminium tank by workers who entered the tank and flushed out the residue with water for about 30 min. Most probably, arsine was evolved in the reaction of the aluminium wall of the tank with sodium hydroxide and arsenic trioxide.
Muehrcke &
Pirani, 1968
Chemical plant, in which a herbicide was synthesized by reacting methyl chloride with sodium arsenite
An aluminium ladder was placed into a tank with a moist mixture containing sodium arsenite. The three ingredients necessary for the evolution of arsine gas were present in the tank: arsenic, water and/or acid, and aluminium. The workers saw “bubbling” at the foot of the ladder.
De Palma, 1969
Copper smelting and refinery
A galvanized bucket was accidentally used instead of a plastic one to transfer sulfuric acid containing both arsenic and antimony impurities. It was estimated that the interior of the galvanized pail could produce 2300 mg of arsenic (in the form of arsine) as a result of reaction with sulfuric acid solution.
Pinto, 1976
“Bronzing” process During the technological process of bronze plating, the alloy containing zinc was by mistake placed in the bronzing solution, instead of brass. The solution was composed of arsenic and ferric chlorides in concentrated hydrochloric acid. This reaction led to arsine formation.
Clay et al., 1977
Chemical company
— cleaning a clogged drain
Arsine was formed by the action of a drain cleaner containing sodium hydroxide, sodium nitrate, and aluminium chips on an arsenic residue. It is not clear whether the arsenic came mainly from the liquid in the storage tank (1% solution arsenical herbicide) or from arsenic residue in the drain, which had collected arsenic trioxide.
Parish et al., 1979
Transistor industry The valve on one of the cylinders containing arsine was half opened and leaking during its delivery to a semiconductor division and the process of unloading the cylinders.
Kleinfeld, 1980 Zinc metallurgical
plants
Arsine was generated in a zinc refining furnace and during furnace repair. Braszczynska et al., 1983 Blackening opera-
tions on zinc/alu- min ium alloy parts
Arsine was formed when zinc/aluminium alloy parts ware treated with acid solutions. Marchiori et al., 1989
Transmission repair shop
Aluminium transmission casings of trucks used for arsenical herbicide applications were cleaned in a hot acidic detergent bath. Arsenic-containing pesticides were deposited on the casings after spraying. The acidic detergent caused rapid evolution of arsine gas.
Risk & Fuortes, 1991
Ferrous metal foundry
An immediate increase of arsine concentration was recorded when hot dross, which contained arsenical impurity, was coated with water.
Mora et al., 1992 Burnishing of
metals
Small zinc–tin alloy components were treated with solutions containing hydrochloric acid and arsenous anhydride. Arsenic compounds were reduced to arsine in the presence of nascent hydrogen in an acid environment.
Romeo et al., 1997
a Quantitative data are not available for the incidents described; rather, they are illustra tive of situations where arsine exposures have been so high that acute intoxications have been produced.
6.2 Human exposure
No quantitative data are available on arsine expo- sures except at work; even information on occupational exposures is very limited. Table 1 illustrates a number of workplace conditions and localities where exposures to arsine have occurred, usually at levels sufficient to cause acute arsine intoxication. Studies where information is available on exposure levels are briefly described below.
Unintentional formation of arsine can occur princi- pally in the metallurgical industry as a result of arsenic contamination of many ores, such as zinc, lead, copper, cadmium, antimony, gold, silver, and tin. When acid comes into contact with these arsenic-bearing ores or metals, arsine is formed (Stokinger, 1981; Suess et al., 1985). Many processes, including electrolytic refining, galvanizing, soldering, etching, lead plating, metal smelting, and extraction, may expose workers to toxic concentrations of arsine.
Workers in the electronics industry using gallium arsenide to manufacture gallium arsenide optoelectronic, microwave, and integrated circuit products are poten- tially exposed to arsine (Sheehy & Jones, 1993). Arsine has also been demonstrated to be formed from gallium arsenide in the presence of hydrochloric acid (Scott et al., 1989). Evaluation of arsenic and arsine levels was conducted in three electronics industry facilities according to NIOSH Method 6001 (NIOSH, 1985, 1994). Personal samples collected for arsenic (or arsine) analysis indicated that there was exposure to both particulate and gaseous arsenic species; quantification of arsine and other arsenic species was not reported (Sheehy & Jones, 1993).
In a factory involved with bronzing of brass
products, the concentration of arsine in the bronzing tank was 2.6 mg/m3. The concentration was similar at the lip of the bronzing tank when the lid was opened and the work was started, but dropped to 0.28 mg/m3 during the work. The concentration in the breathing zone of the bronzing workers was 0.08 mg/m3 (Clay, 1977).
Measurements of arsine in the workroom air breathing zone of a lead battery manufacturing plant found concentrations ranging from non-detectable to 49 µg/m3 (8-h time-weighted average). The greatest arsine exposure was recorded during electrical formation as a result of contact between lead–arsenic alloy and battery acid (Landrigan et al., 1982).
Jones & Gamble (1984) reported arsine concen- trations in five plants involved in the manufacturing of lead acid storage batteries. Arsine was detected in the charging and forming areas, where its concentrations in area samples ranged from non-detectable to 0.18 mg/m3 (average 43 µg/m3).
Mora et al. (1992) reported arsine concentrations in a ferrous metal foundry. To determine arsine concentra- tions in the work environment, continuous measure- ments were performed using Dräger pipes. The arsine concentration in the dry atmosphere was 0.2–0.8 mg/m3; after water was poured onto the slag, the concentration rose momentarily to 200 mg/m3. The highest concen- tration in the breathing zone of the workers, as a 1- to 1.5-h average, was 0.081 mg/m3.
Arsine poisoning was suspected in some workers employed at a leaching operation for the recovery of cadmium as a secondary output of zinc smelter opera- tions. Several tests for arsine in the ambient air were positive. Urinary arsenic concentrations in workers who were suspected to be arsine poisoned were 0.6, 0.7, 1.0, 1.0, 1.0, and 2.0 mg/litre. The urinary arsenic levels of the employees on other shifts were usually between 0.05 and 0.20 mg/litre (for health effects observed in this study, see section 9.2) (Johnson, 1953).
Uldall et al. (1970) reported a case of acute poison- ing of three workers employed in the metallurgical industry that involved the cleaning of tanks with zinc sulfide solution. Arsine was probably released when the tank was opened and zinc added. Arsenic levels were 1.6–8.2 mg/kg in nails and 2–8 mg/kg in hair of the poisoned workers. Hair arsenic concentration was measured in one non-exposed person from the same factory and was 1 mg/kg. Although the concentrations were measured after an acute poisoning, previous incidents of arsine poisoning had been observed in the same facility, and it is likely that exposure to arsine was not limited to a single short-term incident.
7. COMPARATIVE KINETICS AND METABOLISM IN LABORATORY ANIMALS
AND HUMANS
Only limited quantitative information is available on the kinetics and metabolism of arsine in experimental animals and humans. It should be pointed out that tissues and urine were mostly analysed for total arsenic in older human studies.
7.1 Animal studies
In an old but carefully controlled study, an average of 64% of inhaled arsine was absorbed in mice exposed by inhalation at concentrations of 25–2500 mg/m3 for periods ranging from 0.40 min to 24 h (Levvy, 1947).
Blair et al. (1990b) measured the arsenic content in liver after exposure of rats (both males and females) to arsine at concentrations of 0.08, 1.6, and 8.1 mg/m3 for 6 h/day for 90 days. The arsenic concentration in liver increased with airborne arsine concentration and was higher in females than in males. The arsenic level in liver 3–4 days after a 90-day exposure at the concentra- tion of 8.1 mg/m3 was 6–8 µg/g (compared with approx- imately 1.5 µg/g in the controls).
After arsine exposure of rabbits, high arsenic con- centrations were found in liver, lungs, and kidneys.
Following a 5-min exposure at 940 mg arsine/m3, the following arsenic levels were measured: 4.6 mg/kg (liver, wet weight), 3.6 mg/kg (lungs), and 1.2 mg/kg (kidneys). The corresponding values for arsenic con- centrations following a 20-min exposure to arsine at 960 mg/m3 were 22 mg/kg (liver), 9.9 mg/kg (lungs), and 8.9 mg/kg (kidneys) (Levvy, 1947).
The main route of arsine excretion is via urine after metabolism. The elimination of arsenic in arsine- exposed mice was compared with that resulting from
exposure to sodium arsenite. It was found that arsenic from arsenite administered intravenously was excreted monoexponentially; after 24 h, less than 10% of the dose remained. On the other hand, arsenic arising from arsine (inhalation exposure to 180 mg/m3 for 20 min) was excreted more slowly; after 24 h, about 45% remained in the exposed mice (Levvy, 1947).
When rats were exposed to 4–80 mg arsine/m3 for 1 h, the major metabolites were As(III), As(V), mono- methylarsonate, and dimethylarsenate. Importantly (see section 7.2), no arsenobetaine was observed. As the exposure exceeded 60 mg/m3, the proportional urinary excretion increased, indicating saturation of arsine/
arsenic binding (Buchet et al., 1998).
7.2 Human studies
Arsine is rapidly absorbed into blood through the respiratory tract; quantitative information in humans is not available (Thienes & Haley, 1972; Venugopal &
Luckey, 1978).
In the first days after arsine poisoning, arsenic can be detected in blood. In persons fatally poisoned with arsine, the highest quantities of arsenic were found in liver, kidney, and spleen, and smaller amounts of arsenic were also found in hair of workers occupationally exposed to arsine (Lazariew, 1956).
The presence of arsenic was detected in the tissues, blood, and urine of workers in the petroleum industry who were poisoned with arsine. In cases of fatal poison- ing, the following arsenic levels were found: in lungs, 400 µg/litre (probably means µg/kg); in urine, 260 µg/li- tre; and in blood, 434 µg/litre. No arsenic was detected in the gastric contents. Neither doses nor exposure times were specified in this study (Teitelbaum & Kier, 1969).
In a fatal case of arsine poisoning involving a worker at a zinc plant, arsenic was found in the liver at a concentration of 11.8 mg/g, in the spleen at 7.9 mg/g, in the kidneys at 3.2 mg/g, in the brain at 0.6 mg/g, and in the urine at 0.6 mg/g; trace amounts were also found in blood (Fowler & Weissberg, 1974).
The analysis of a case of lethal arsine poisoning showed the presence of arsenic in the liver at concentra- tions as high as 15 mg/kg; concentrations above 1 mg arsenic/kg were also found in kidneys and spleen (Macaulay & Stanley, 1956).
Inhaled arsine was rapidly dissolved in body fluids and oxidized to As(III) (Pershagen et al., 1982). Part of As(III) is further oxidized to As(V), as indicated by the appearance of As(V) in urine of humans exposed to arsenic 1–2 days following exposure (Romeo et al.,
1997). Trivalent arsenic is methylated to monomethyl- arsonate and dimethylarsinate.
Various forms of arsenic are excreted mainly via urine (about 60% in 24 days) (Apostoli et al., 1997).
Information on possible sequestration of arsenic in the human body after exposure to arsine is not available.
After an acute occupational intoxication with arsine, the highest urinary excretion occurred in the first 5 days after exposure. The urinary clearance equalled 7.8 ml/h per kg body weight; through other routes (non-renal excretion), it was 5.27 ml/h per kg body weight. As in experimental animals, after exposure to inorganic arsenic species, the following arsenic species are usually found in urine: dimethylarsinate, monomethylarsonate, As(III), and, to a lesser extent, As(V) (Apostoli et al., 1997; Romeo et al., 1997). Apostoli and co-workers (1997) also reported the presence of arsenobetaine in the urine of a person after an acute arsenic poisoning; it is not excluded, however, that this was from dietary origin.
In a driver who was poisoned when unloading cylinders containing arsine (approximate exposure time about 1–2 min), the level of total arsenic in his urine amounted to 0.72 mg/litre on the day of exposure, decreasing to 0.01 mg/litre by the fourth day (Kleinfeld, 1980).
Parish et al. (1979) described acute arsine poisoning in two workers employed at cleaning clogged drains who used a cleaner containing sodium hydroxide and alumin- ium chips. Both workers were hospitalized because of rapid acute haemolytic anaemia and kidney failure.
Arsenic concentrations in the urine of the patients, analysed within 3 days after the incident (but after exchange transfusion and dialysis), were 0.85 and 0.97 mg/kg, and in blood, 0.18 mg/kg and 0.20 mg/kg; in two persons working near the gutter, arsenic was found at concentrations of 0.30 and 0.12 mg/kg in urine and
<0.082 and <0.96 mg/kg in blood.
7.3 Biological monitoring
Arsenic concentrations in urine, blood, hair, and nails have been used for the biological monitoring of arsenic exposure. However, these measures are not specific to arsine exposure, and exposure to other arsenic species may confound the findings (Vahter, 1988; Aitio et al., 1996).
The arsenic concentration in urine has been conven- tionally used as an indicator of occupational exposure to arsine. Positive correlations between urinary elimination of arsenic in individuals exposed to arsine and the level of their occupational exposure have been reported (Elkins & Fahy, 1967; Landrigan et al., 1982; Apostoli et al., 1997). Speciation of arsenic in the urine is a
prerequisite for the meaningful interpretation of the results in biological monitoring (Aitio et al., 1996).
A close relationship was observed between urinary arsenic concentrations and arsine exposure level (N = 47, r = 0.84, P = 0.0001) among employees at a lead acid battery manufacturing factory (Landrigan et al., 1982).
From this correlation, it was estimated that concentra- tions of arsine in air above 15.6 µg/m3 are associated with total arsenic concentrations in urine in excess of 0.67 µmol/litre.
Blood arsenic concentration is a poor indicator of exposure to arsine. Since most arsenic compounds contained in human blood disappear quickly, the arsenic level in blood reflects exposure to arsine for a short period only (Romeo et al., 1997).
Since the trivalent form of arsenic accumulates in hair, as a result of its binding to the thiol group of the scleroprotein keratin, the arsenic content in hair may be used for monitoring long-term exposures to arsine (compared with the arsenic content in urine, which reflects relatively short-term exposures only). The determination of arsenic levels in hair as an indicator of exposure to arsenic in the atmosphere is limited, how- ever, since there is no reliable method to distinguish hair arsenic adsorbed as a result of external exposure from that absorbed and metabolized in the individual.
Increased arsenic concentrations in pubic hair and toenails were observed in individuals exposed to arsenic and arsine in workplace atmospheres. Two cases of arsine poisoning were reported in workers employed at bronzing of brass products, where the arsine level in the breathing zone of the bronzing workers was 0.08 mg/m3 for sampling times of 35–40 min (Clay et al., 1977). The concentrations of arsenic were 10.8–76.1 mg/kg in hair, 8.6–63.1 mg/kg in pubic hair, 15–188 mg/kg in finger- nails, and 37.1–60.9 mg/kg in toenails. In workers employed at bronzing of brass products in other depart- ments, where no cases of arsine poisoning had been reported, arsenic concentrations were lower: 3.33–
16.0 mg/kg in hair, 5.61–38.5 in pubic hair, 9.03–
53.3 mg/kg in fingernails, and 1.06–5.79 in toenails. In adults not exposed to arsenic at work, concentrations of arsenic in hair are usually <1 mg/kg, whereas those in nails are <3 mg/kg (Vahter, 1988).
8. EFFECTS ON LABORATORY MAMMALS AND IN VITRO TEST SYSTEMS
8.1 Single exposure
The acute toxicity of inhaled arsine is summarized in Table 2, and the relationship between the LC50 value and duration of exposure is shown in Table 3.
Table 2: Acute toxicity of inhaled arsine in different species.
Species Parameter
Exposure concentration
(mg/m3)
Duration of exposure
(min)
Rat LC50 390 10
Mouse LC50 250 10
Dog LC50 350 30
Rabbit LC50 650 10
Table 3: Dependence of acute inhalation LC50 of arsine on the duration of exposure in mice. a
LC50 (mg/m3) Duration of exposure (min)
2500 0.40
1000 1.18
500 2.4
250 12
100 50
25 1440
a From Levvy (1947).
The acute toxicity of arsine in animals is attributable chiefly to its haemolytic effects. Arsine also induces haemolysis in vitro (see section 8.6); approximately 20%
haemolysis was observed after a 2-h incubation of rat and dog erythrocytes in the presence of 0.56 mmol arsine/litre (Hatlelid et al., 1995).
Morgan (1992) studied the acute toxicity of arsine in Fischer-344 rats, B6C3F1 and C57BL/6 mice, and Syrian Golden hamsters. One hundred per cent mortality was observed in all these species when they were exposed for 6 h to 81 mg arsine/m3.
Peterson & Bhattecharyya (1985) studied the haematological responses of mice to exposure for 1 h at 16–84 mg arsine/m3. The decrease in haematocrit at 24 h was linear with increasing exposure concentration and statistically significant for exposures =30 mg/m3; the changes in numbers of erythrocytes paralleled changes in haematocrit.
In B6C3F1 mice, no changes in body weight gain were observed in either sex exposed to arsine by inhala- tion for 6 h at concentrations of 1.6, 8.1, or 16 mg/m3. Significant exposure-related increases in relative spleen weights occurred in both sexes in all exposure groups.
Female mice exposed to 16 mg arsine/m3 for 6 h had significantly enlarged spleens after 2 days (Blair et al., 1990b).
8.2 Repeated exposure
In repeated-exposure studies in animals, similarly to acute arsine poisoning, blood is mainly affected, as shown by haemolysis, decrease in erythrocyte count, and changes in haemoglobin level (Stokinger, 1981).
A series of studies at the National Institute of Environmental Health Sciences in the USA (Hong et al., 1989; Rosenthal et al., 1989; Blair et al., 1990a,b,), in which mice, rats, and Syrian Golden hamsters were exposed to arsine by inhalation for 1–90 days, forms the basis of the hazard characterization of arsine (see section 10.1.1).
In a study in mice, in which only peripheral blood was studied as the end-point, mice were exposed for 6 h/day, 5 days/week, for 5–90 days to arsine at concen- trations of 0.08, 1.6, or 8.1 mg/m3 (Blair et al., 1990a).
Moderate anaemia was observed at the highest exposure level, and the reticulocyte count, MCV, and mean cor- puscular haemoglobin (MCH) were increased. With continued exposure, the anaemia was less severe, and the compensatory increase in the reticulocyte count was greater. An increased concentration of methaemo globin was observed in animals exposed to 8.1 mg arsine/m3. In this study, the NOAEL was 1.6 mg/m3, and the LOAEL was 8.1 mg/m3 (Blair et al., 1990a).
Blair et al. (1990b) exposed B6C3F1 mice (14 or 90 days), Fischer-344 rats (14, 28, or 90 days), and Syrian Golden hamsters (28 days) of both sexes to arsine with a regimen of 6 h/day, 5 days/week. The short-term experiments were performed with arsine at concentra- tions of 1.6, 8.1, and 16 mg/m3. In the 90-day studies, arsine at 0.08, 1.6, and 8.1 mg/m3 was used.
Histopathological studies in all species on 29 (males) or 31 (females) organs revealed effects on the bone marrow, liver, and spleen only. A decrease of body weight gain was observed only in male rats exposed to 16 mg arsine/m3 for 28 days. Inconsistent increases in liver weight were observed at exposures of =8.1 mg/m3.
In rats, significant dose-related increases in relative spleen weights were recorded in both sexes (35% in females and 20% in males at 1.6 mg/m3 after 90 days) in groups exposed to arsine at =1.6 mg/m3. Increased haemo siderosis and splenic haematopoiesis and medul- lary hyperplasia were observed in rats exposed to 16 mg/m3.
Anaemia (reduced haemoglobin, haematocrit, red blood cell count) was observed in all exposed groups in
females (4–18% drop in haemoglobin at exposure levels of 0.08–8.1 mg/m3) (but was not observed in two other groups with the low exposure after a recovery period of 3 or 4 days) and in males at exposure levels of
=1.6 mg/m3 (7–16% drop in haemoglobin). MCV, MCH, and erythrocyte aminolevulinate dehydratase activity were elevated in rats exposed to =1.6 mg/m3 (indicating a compensatory increase in the proportion of reticulo- cytes in blood) (Blair et al., 1990b).
Blair et al. (1990b) concluded that a significant anaemia was observed at the lowest exposure level (0.08 mg/m3). This conclusion is based on a decrease of haemoglobin, red blood cell count, and haematocrit of 4–5% (P < 0.05) in female (but not in male) rats exposed for 80–81 days to arsine. However, when a group of female rats was exposed for 90 days and studied 3 days later, no effect on haematocrit was observed. Similarly no effect was observed in a further group exposed for 90 days and analysed after 4 days. Thus, 0.08 mg/m3 is considered to be a NOAEL rather than a LOAEL in rats;
the LOAEL is 1.6 mg/m3.
In mice, significant dose-related increases in relative spleen weights were recorded in males exposed to arsine at =1.6 mg/m3 (20–30% at 1.6 mg/m3). In females, the same was observed after 14 days of exposure; after 90 days of exposure, the increase in spleen weight was significant only for the highest exposure studied, 16 mg/m3 (for the groups studied after 3 days of recov- ery and after 4 days of recovery). Consistent decreases in packed cell volume were observed in animals exposed to
=8.1 mg/m3. Increases in aminolevulinate dehydratase activity were first seen in animals exposed to 1.6 mg/m3 and consistently seen in animals exposed to =8.1 mg/m3. Intracanalicular bile stasis in the liver was observed in mice exposed to 8.1 mg/m3 for 90 days (highest dose studied for 90 days).
In a mechanistic study on female mice (for results of the mechanistic studies, see below) of the same strain, using a similar exposure pattern (14-day inhalation of 1.6, 8.1, or 16 mg/m3 or 12-week inhalation of 0.08, 1.6, or 8.1 mg/m3, 6 h/day, 5 days/week) (Hong et al., 1989), anaemia was similarly observed in animals exposed to 8.1 mg/m3 (highest exposure studied) for 2 or 12 weeks;
this effect subsided in 2 weeks. After an exposure of 12 weeks to 0.08 mg/m3, a 2% (P < 0.05) increase in MCV was also observed. In contrast to the study of Blair et al.
(1990b), an increase in the absolute (24%) and relative (25%) spleen weights (P < 0.05) was observed after a 12-week exposure (and 3-day recovery) to the lowest concentration, 0.08 mg/m3; the spleen weight returned to normal in this group after a further 17-day recovery period. It should be noted that the spleen weight varied markedly in different control groups in the experiment and was low in the referent group for the group with a 12-week exposure and 4-day recovery (but returned to
the common level during the 17-day additional recovery period).
In the mechanistic parts of this study, bone marrow cellularity, granulocyte-macrophage progenitors (CFU- GM), colony-forming unit erythroids (CFU-E) (Hong et al., 1989), and relative abundance of different lympho- cyte populations (Rosenthal et al., 1989) were studied.
No changes were observed in bone marrow cellularity.
CFU-GM showed a =8% dose-dependent decrease after a 14-day exposure to =1.6 mg/m3 (i.e., lowest exposure studied), which was no longer observed after a 12-week exposure. CFU-E showed a similar =11% dose-
dependent decrease after exposure to =1.6 mg/m3, which was reduced in magnitude but did not completely disap- pear when exposure was continued for 12 weeks.
There was no effect on the total number of splenic lymphocytes, but the percentage of lymphocytes of all cells fell in all arsine-exposed groups (from 83.4% in controls to 45.6% in the 16 mg/m3 group). Splenic T-cell percentage was similarly decreased in all arsine-treated groups, but B cells were decreased in the high-dose group only in the 14-day study (Rosenthal et al., 1989).
As the compensatory, reversible 2% increase in MCV (Hong et al., 1989) is not considered adverse and the observed effect on spleen weight at 0.08 mg/m3 in the Hong et al. (1989) study is in striking contrast to the findings of Blair et al. (1990b) (no similar effect at a 20 times higher dose), it is concluded that 0.08 mg/m3 is a NOAEL, rather than a LOAEL, and the LOAEL is 1.6 mg/m3 in mice.
In Syrian Golden hamsters, significant dose-related increases in relative spleen weights were recorded in both sexes exposed to =8.1 mg/m3, and packed cell volume and aminolevulinate dehydratase activity in the erythrocytes showed dose-dependent decreases from the lowest exposure level studied (1.6 mg/m3). The spleen was enlarged and dark in animals exposed to =8.1 mg arsine/m3. A LOAEL of 1.6 mg/m3 is deduced for Syrian Golden hamsters from these studies; as this was the lowest exposure investigated, a NOAEL cannot be identified (Blair et al., 1990b).
In old studies at higher arsine concentrations (Nau, 1948; Lazariew, 1956), haemolytic anaemia with a dose–response relationship was reported in dogs and guinea-pigs.
8.3 Carcinogenicity
No data were identified on the carcinogenicity of arsine in experimental animals. In a study only published as an abstract, administration of sodium arsenate
(500 µg/litre) in drinking-water to C57Bl/6J mice for 26 months led to an increased incidence of tumours in
the intestinal tract, lungs, liver, and, to a smaller extent, other organs. Administration of dimethylarsinate in drinking-water induced a dose-dependent increase in the incidence of urinary bladder tumours in rats (IPCS, 2001a).
8.4 Skin and eye irritation and sensitization No relevant data were available on skin or eye irritation or on sensitizing effects of arsine on skin or respiratory tract in animals.
8.5 Reproductive toxicity
Swiss (CD-1) mice and Fischer-344 rats were exposed to arsine by inhalation at concentrations of 0.08, 1.6, or 8.1 mg/m3 from gestation days 6 through 15. In rats, splenomegaly (in the 8.1 mg/m3 group) and decreased packed red cell volume were detected in dams. No developmental toxicity was observed. In mice, dams dosed with 8.1 mg arsine/m3 developed significant splenomegaly, whereas the number of living fetuses, mean fetal body weight, and the percentages of resorp- tions and malformations per litter did not differ from the findings in controls (Morrissey et al., 1990).
8.6 Genotoxicity
No studies are available regarding the genotoxicity of arsine per se. Inorganic arsenic does not induce point mutations, but it does induce chromosomal abnormal- ities in vitro, including changes in structure and number of chromosomes, endoreduplication, and sister chroma- tid exchange, and it affects methylation and repair of DNA. Limited studies indicate that arsenite is also clastogenic in vivo (IPCS, 2001a).
8.7 Mechanisms of toxicity/mode of action The mechanisms of toxicity and modes of action of arsine in humans and animals have not been fully elab- orated. While some authors have postulated an oxidative stress (Pernis & Magistretti, 1960; Blair et al., 1990a;
Hatlelid et al., 1995, 1996; Hatlelid & Carter, 1997), others have suggested a mechanism dependent on reaction with sulfhydryl groups (Levinsky et al., 1970;
Winski et al., 1997).
Hatlelid & Carter (1997) postulated that the haemo- lytic activity of arsine is connected with oxidative stress through the formation of hydrogen peroxide and arsine adducts with haemoglobin, according to the following sequences:
H2As–H + HbO2 ? H2As* + Hb–O2–H These products may then react to form methaemoglobin and arsine peroxide, or, alternatively, the reaction may
produce hydrogen peroxide and an arsenic adduct such as H2As–Hb or H2As–haem:
H2As* + Hb–O2–H ? adduct + H2O2
Such an adduct may probably damage haemoglobin molecules, leading to the rapid denaturation and precipitation of the proteins (Hatlelid & Carter, 1997).
The denaturation of proteins and the aggregation of precipitated molecules and their binding to the inner surface of red blood cells (Heinz bodies) lead to a redistribution of membrane proteins and increased membrane rigidity. Oxidation of the haem iron induces the formation of haemin, which results in the oxidation of membrane protein sulfhydryl groups, dissociation of membrane skeletal protein, and perturbation of mem- brane ion gradients (Hatlelid et al., 1996). Ultimately, the Heinz bodies and haemins increase the fragility of red blood cell membranes and predispose the cells to fragmentation (Weed & Reed, 1966). In this manner, the degradation of haemoglobin may lead to haemolysis.
Some studies have suggested that the sulfhydryl groups of glutathione prevented haemoglobin oxidation and in this manner are essential for the maintenance of the intact erythrocyte structure (Blair et al., 1990a). In in vitro studies, a decrease in reduced glutathione concen- tration in human red blood cells was found to correlate with the haemolytic action of arsine (Pernis & Magis- tretti, 1960). Blair et al. (1990a) recorded a 60%
decrease in reduced glutathione level in erythrocytes exposed to arsine in vitro. However, later studies of Hatlelid et al. (1995) showed that the depletion of reduced glutathione in red blood cells in dogs neither preceded nor coincided with haemolysis.
According to the hypothesis of the sulfhydryl- dependent mechanism of arsine toxicity (Levinsky et al., 1970), arsine reacts with the sulfhydryl group of Na+K+- ATPase, causing an impairment in the sodium–
potassium pump mechanism, with subsequent red cell swelling and haemolysis. The affinity of trivalent arsenic for the sulfhydryl group is well known. However, dog erythrocytes, which do not have Na+K+-ATPase, were haemolysed when they were exposed to arsine (Hatlelid et al., 1995), which may suggest that Na+K+-ATPase is only partially responsible for red cell damage (Hatlelid et al., 1995; Winski et al., 1997).
Winski et al. (1997) observed immediate profound abnormalities in membrane ultrastructure and in red blood cell volume, which were manifested by potassium leakage, sodium influx, and increases in haematocrit in arsine-exposed red cells. Additionally, ATP levels did not significantly decrease, and ATPase was not inhibited by arsine. Winski et al. (1997) then suggested that haemolysis in arsine-exposed red cells depended on
membrane disruption caused by arsine–haemoglobin metabolites, which are the ultimate toxic species.
Although it is generally held that the kidney failure in arsine intoxication is due to the effects of free haemoglobin and degradation products, arsine has also been demonstrated to have a direct toxic effect on kidney glomeruli and tubules (Ayala-Fierro et al., 2000).
9. EFFECTS ON HUMANS
The toxicity to humans of arsine was demonstrated dramatically in 1815 when a German chemist, in the course of an experiment, inhaled arsine vapour, became ill within an hour, and soon died (Vallee et al., 1960).
Following this demonstration of the toxicity of arsine, 454 cases of poisoning were reported by 1974 (Elkins &
Fahy, 1967; Guajardo et al., 1970; Levinsky et al., 1970;
Fowler & Weissberg, 1974; Wilkinson et al., 1975); of 207 cases of arsine toxicity reported between 1928 and 1974 (4.5 cases per year), 25% were fatal (Fowler &
Weissberg, 1974). Prior to 1974, anuria was a common cause of death following short-term exposure to high concentrations of arsine. Between 1974 and 1986, there were an additional approximately 30 cases reported (2.5 cases per year), with no fatalities (Guajardo et al., 1970; Hocken & Bradshaw, 1970; Levinsky et al., 1970;
Wilkinson et al., 1975; Conrad et al., 1976; Frank, 1976;
Pinto, 1976; Levy et al., 1979; Parish et al., 1979;
Rathus et al., 1979; Kleinfeld, 1980; Williams et al., 1981; Dlhopolcek et al., 1982; Gosselin et al., 1982;
Rogge et al., 1983; Phoon et al., 1984; Togaybayev et al., 1984; Hesdorffer et al., 1986; Wald & Becker, 1986;
Marchiori et al., 1989; Hotz & Boillat, 1991; Mora et al., 1992; Pairon et al., 1992; US EPA, 1994a,b; Romeo et al., 1997).
The data on arsine concentrations in the workplace atmosphere are relatively scant (see section 6). A case report indicated that exposure to arsine by inhalation for a few hours at a concentration of 10–32 mg/m3 might induce symptoms of poisoning, whereas exposure to 810 mg/m3 for 30 min might be fatal (Steel & Feltham, 1950). Morse & Setterlind (1950) reported that concen- trations of 230–970 mg arsine/m3 were associated with fatalities.
9.1 Acute poisoning 9.1.1 Immediate effects
A number of reports indicated that clinical manifes- tations of arsine intoxication appeared within 1–24 h of exposure (usually within a few hours). The period of
