necessarily represent the decisions or the stated policy of the United Nations Environment Programme, the International Labour Organisation, or the World Health Organization.
Concise International Chemical Assessment Document 19
PHENYLHYDRAZINE
First draft prepared by
Mr R. Cary, Health and Safety Executive, Liverpool, United Kingdom,
Dr S. Dobson, Institute of Terrestrial Ecology, Huntingdon, United Kingdom, and Dr I. Brooke, Health and Safety Executive, Liverpool, United Kingdom
Please note that the layout and pagination of this pdf file are not identical to the printed CICAD
Published under the joint sponsorship of the United Nations Environment Programme, the International Labour Organisation, 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, 2000
of the United Nations Environment Programme (UNEP), the International Labour Organisation (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 Phenylhydrazine.
(Concise international chemical assessment document ; 19)
1.Phenylhydrazines - toxicology 2.No-observed-adverse-effect level 3.Risk assessment 4.Environmental exposure I.International Programme on Chemical Safety II.Series
ISBN 92 4 153019 7 (NLM classification: QV 180) ISSN 1020-6167
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FOREWORD . . . 1
1. EXECUTIVE SUMMARY . . . 4
2. IDENTITY AND PHYSICAL/CHEMICAL PROPERTIES . . . 5
3. ANALYTICAL METHODS . . . 5
4. SOURCES OF HUMAN AND ENVIRONMENTAL EXPOSURE . . . 5
5. ENVIRONMENTAL TRANSPORT, DISTRIBUTION, AND TRANSFORMATION . . . 6
6. ENVIRONMENTAL LEVELS AND HUMAN EXPOSURE . . . 6
6.1 Environmental levels . . . 6
6.2 Human exposure . . . 6
7. COMPARATIVE KINETICS AND METABOLISM IN LABORATORY ANIMALS AND HUMANS . . . 7
8. EFFECTS ON LABORATORY MAMMALS AND IN VITRO TEST SYSTEMS . . . 7
8.1 Single exposure . . . 7
8.2 Irritation and sensitization . . . 8
8.3 Short-term exposure . . . 8
8.4 Long-term exposure . . . 9
8.4.1 Subchronic exposure . . . 9
8.4.2 Chronic exposure and carcinogenicity . . . 9
8.5 Genotoxicity and related end-points . . . 10
8.6 Reproductive and developmental toxicity . . . 11
8.7 Immunological and neurological effects . . . 11
9. EFFECTS ON HUMANS . . . 11
10. EFFECTS ON OTHER ORGANISMS IN THE LABORATORY AND FIELD . . . 12
10.1 Aquatic environment . . . 12
10.2 Terrestrial environment . . . 12
11. EFFECTS EVALUATION . . . 13
11.1 Evaluation of health effects . . . 13
11.1.1 Hazard identification and dose–response assessment . . . 13
11.1.2 Criteria for setting guidance values for phenylhydrazine . . . 13
11.1.3 Sample risk characterization . . . 14
11.2 Evaluation of environmental effects . . . 14
12. PREVIOUS EVALUATIONS BY INTERNATIONAL BODIES . . . 15
13. HUMAN HEALTH PROTECTION AND EMERGENCY ACTION . . . 15
13.1 Human health hazards . . . 15
13.2 Advice to physicians . . . 15
13.3 Health surveillance advice . . . 15
iv
14. CURRENT REGULATIONS, GUIDELINES, AND STANDARDS . . . 16
INTERNATIONAL CHEMICAL SAFETY CARD . . . 17
REFERENCES . . . 19
APPENDIX 1 — SOURCE DOCUMENTS . . . 22
APPENDIX 2 — CICAD PEER REVIEW . . . 22
APPENDIX 3 — CICAD FINAL REVIEW BOARD . . . 23
RÉSUMÉ D’ORIENTATION . . . 24
RESUMEN DE ORIENTACIÓN . . . 26
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 Organisation (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.
CICADs are concise documents that provide summaries 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 characterization 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 encouraged to characterize risk on the basis of locally measured or predicted exposure scenarios. To assist the reader, examples of exposure estimation and risk characterization 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 1701 for advice on the derivation of health-based guidance values.
While every effort is made to ensure that CICADs represent the current status of knowledge, new
information 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 information 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 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 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 draft, if necessary. The resulting second draft is submitted to a Final Review Board together with the reviewers’ comments.
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
1 International 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
S E L E C T I O N O F H I G H Q U A L I T Y N A T I O N A L / R E G I O N A L A S S E S S M E N T D O C U M E N T ( S )
CICAD PREPARATION FLOW CHART
F I R S T D R A F T P R E P A R E D
REVIEW BY IPCS CONTACT POINTS/
SPECIALIZED EXPERTS
FINAL REVIEW BOARD 2
FINAL DRAFT 3
EDITING
APPROVAL BY DIRECTOR, IPCS
PUBLICATION SELECTION OF PRIORITY CHEMICAL
1 Taking into account the comments from reviewers.
2 The second draft of documents is submitted to the Final Review Board together with the reviewers’ comments.
3 Includes any revisions requested by the Final Review Board.
REVIEW OF COMMENTS (PRODUCER/RESPONSIBLE OFFICER), PREPARATION
OF SECOND DRAFT 1 P R I M A R Y R E V I E W B Y I P C S (REVISIONS AS NECESSARY)
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
representation.
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
This CICAD on phenylhydrazine was based on a review of human health concerns (primarily occupation- al) prepared by the United Kingdom’s Health and Safety Executive (Brooke et al., 1997) and a report prepared for the German Advisory Committee on Existing Chemicals of Environmental Relevance (BUA, 1995). Hence, this document focuses on exposures via routes relevant to occupational settings but also contains environmental information. Data identified as of December 1993 and December 1994, respectively, were covered. A further literature search was performed up to January 1998 to identify any extra information published since these reviews were completed. Information on the nature of the peer review and availability of the source documents is presented in Appendix 1. Information on the peer review of this CICAD is presented in Appendix 2. This CICAD was approved as an international assessment at a meeting of the Final Review Board, held in Washington, DC, USA, on 8–11 December 1998. Participants at the Final Review Board meeting are listed in Appendix 3. The International Chemical Safety Card (ICSC 0938) for phe- nylhydrazine, produced by the International Programme on Chemical Safety (IPCS, 1993), has also been reproduced in this document.
Phenylhydrazine (CAS No. 100-63-0) exists as yellow to pale brown crystals or as a yellowish oily liquid. It is sparingly soluble in water and is miscible with other organic solvents.
Phenylhydrazine is used worldwide mainly as a chemical intermediate in the pharmaceutical, agrochemi- cal, and chemical industries.
The number of persons potentially exposed to phenylhydrazine or its hydrochloride salt is not known, but it is expected to be small. No personal exposure data were available, although the Estimation and Assessment of Substance Exposure (EASE) model predicted exposure (8-h time-weighted average) to be around 2.3 mg/m3 (0.5 ppm). In practice, the 8-h time-weighted average exposure will be less than this figure.
The limited data on toxicokinetics indicate that phenylhydrazine is well absorbed by inhalation, oral, and dermal routes and binds readily to haemoglobin in red blood cells. Metabolism seems to occur via ring hydroxylation and conjugation, probably with gluc- uronic acid. Excretion is primarily via the urine.
Phenylhydrazine is toxic by single exposure via the oral route (LD50 80–188 mg/kg body weight) and is expected to be toxic by the inhalation and dermal routes (data from these routes of exposure are less clear).
Phenylhydrazine has potential for skin and eye irritation,
and there is evidence that it has skin-sensitizing proper- ties in humans. Exposure to phenylhydrazine may cause damage to red blood cells, potentially resulting in anaemia and consequential secondary involvement of other tissues, such as the spleen and liver. Phenylhydra- zine is mutagenic in vitro, and there is some evidence to indicate that it may express genotoxic activity in vivo.
The substance is clearly carcinogenic in mice following oral dosing, inducing tumours of the vascular system.
The mechanism for tumour formation is unclear, but a genotoxic component cannot be excluded. Hence, it is not considered possible to reliably identify a level of exposure at which there will be no risk of carcinogenic or genotoxic effects.
There are no adequate data available regarding reproductive or developmental effects; hence, it is not possible to evaluate the risk to human health for these end-points.
The level of risk in occupational settings is uncer- tain; as a result, there is a continuing requirement to reduce exposure levels as much as is reasonably prac- ticable with the technology that is currently available.
The lack of available data to serve as a basis for estimation of indirect exposure of individuals to phenyl- hydrazine from the general environment precludes the characterization of potential cancer risks for the general population.
No atmospheric effects are expected given the release of phenylhydrazine predominantly to water, its extremely low volatilization from water to the atmos- phere, and its rapid calculated atmospheric half-life following reaction with hydroxyl radicals.
Phenylhydrazine is degraded photochemically and autoxidizes in water. It is readily biodegradable, and this is expected to be the major route of breakdown in the environment. There is minimal sorption to particulates.
Phenylhydrazine is toxic to aquatic organisms, with the lowest reported no-observed-effect concentration (NOEC) in standard acute fish tests at 0.01 mg/litre; fish are generally more sensitive than either daphnids or bacteria. A NOEC of 0.49 :g/litre has been reported for embryo-larval stages of the zebra fish (Brachydanio rerio).
The risk to aquatic organisms is expected to be low, based on very conservative assumptions.
2. IDENTITY AND PHYSICAL/CHEMICAL PROPERTIES
Phenylhydrazine (C6H8N2; molecular weight 108;
CAS No. 100-63-0; see structural diagram below) exists as yellow to pale brown crystals or as a yellowish oily liquid, with a freezing point of 19.6 °C, a boiling point of 243.4 °C, and a vapour pressure of 133 Pa at 72 °C. It is soluble in water (values ranging from 145 to 837 g/litre at 24 °C have been reported) and is miscible with alcohol, ether, chloroform, benzene, and acetone. The conversion factor for phenylhydrazine is 1 ppm = 4.5 mg/m3 (at 20 °C, 101 kPa). Additional physical/chemical properties of phe- nylhydrazine are presented in the International Chemical Safety Card reproduced in this document.
NH NH2
3. ANALYTICAL METHODS
For measurement of phenylhydrazine in water, reduction of Cu(II) to Cu(I) by phenylhydrazine has been used as the basis for spectrometric analytical methods measuring coloured complexes (Besada, 1988; Hasan, 1988). The methods are not specific and react to other reducing substances. A detection limit of 10 :g/litre is given for one method (Hasan, 1988).
In a method published by NIOSH (1994) for mea- surement of phenylhydrazine in workplace air, the air is sampled into a midget bubbler containing hydrochloric acid. Phosphomolybdic acid is added to the resulting solution, and the reaction with phenylhydrazine causes the formation of a bluish-green complex that can be measured at 730 nm with a spectrophotometer. This method has a detection limit of about 5 mg/m3 (about 1 ppm), based on a 100-litre sample. Potential interfer- ences are listed as other hydrazine derivatives, alde- hydes, and ketones.
Both the MIRAN 1B and the Bruel and Kjaer 1302 Multigas Monitor may be used to measure phenylhydra- zine in air, with a detection limit of around 13.5 mg/m3 (3 ppm) (Brooke et al., 1997). Any other substance having similar infrared absorbances can be expected to interfere with the measurement.
There are no published biological monitoring methods available for phenylhydrazine.
4. SOURCES OF HUMAN AND ENVIRONMENTAL EXPOSURE
There are a few reports of the natural occurrence of phenylhydrazine in plants (BUA, 1995). Phenylhydrazine is produced commercially by the diazotization of aniline followed by reduction of the azo compound.
Production figures for 1990–1992 in Germany were about 3000–4000 t/year; use figures for Western Europe in 1988 totalled 6650 t (BUA, 1995). Use patterns for Western Europe in 1988 and for Germany in 1990–1992 are shown in Table 1.
Table 1: Phenylhydrazine use patterns in Western Europe and Germany.
Phenylhydrazine use (%) Industry
Western Europe, 1988
Germany, 1990–1992
Pharmaceuticals 37.6 70.2
Agrochemicals 42.9 7.2
Dyes 15 21.8
Others 4.5 0.8
From production and processing of phenylhydra- zine in Germany during 1990–1992, an estimated 50 kg and <13 t were emitted to the atmosphere and the hydro- sphere, respectively, each year. Less than 50 t of phenyl- hydrazinium chloride were released to water each year in the same period (BUA, 1995).
There are now no manufacturers of phenylhydra- zine or the phenylhydrazine hydrochloride salt in the United Kingdom (Brooke et al., 1997). Two firms are known to import phenylhydrazine into the United King- dom, one from its manufacturing site in Germany and the other from Japan. The total market for phenylhydrazine in the United Kingdom is thought to be about 20 t/year, whereas the market for phenylhydrazine hydrochloride is not known. The market for phenylhydrazine has been static for several years.
Phenylhydrazine is used worldwide mainly as a chemical intermediate in the pharmaceutical, agrochemi- cal, and chemical industries. The United Kingdom’s pattern of use appears representative. One company uses phenylhydrazine to produce a chemical intermediate for use in the photographic industry.
Another manufacturer uses the chemical in the synthesis of organic chemicals. Phenylhydrazine is also used as a chemical intermediate in the pharmaceutical and agrochemical industries in the United Kingdom. In addition, there is some laboratory-scale use of this chemical.
There are no known consumer uses of phenylhy- drazine or its hydrochloride salt in the United Kingdom or Germany. No information is available regarding the potential for consumer exposure in other countries.
5. ENVIRONMENTAL TRANSPORT, DISTRIBUTION, AND TRANSFORMATION
Most emissions of phenylhydrazine into the environment are into the hydrosphere. At acidic pH, phenylhydrazine occurs as the salt (BUA, 1995).
In the atmosphere, phenylhydrazine would exist solely in the vapour phase (HSDB, 1998). Calculated half-lives of 3.1 h (BUA, 1995) and 9 h (Meylan &
Howard, 1993) have been reported for phenylhydrazine following reaction with hydroxyl radicals in the atmosphere.
Phenylhydrazine strongly absorbs ultraviolet light in the environmentally significant range, suggesting that it may photolyse in sunlight (HSDB, 1998); slow photo- decomposition in diffuse daylight in the absence of oxygen is deduced in BUA (1995). In the presence of oxygen, phenylhydrazine is subject to autoxidation, the reaction being accelerated by light and heat; the sub- stance becomes reddish brown on exposure to air as a result of this autoxidation (Ullmann, 1977).
No hydrolysis is expected to occur (BUA, 1995).
The Henry’s law constant for phenylhydrazine has been calculated at 9.69 × 10–3 Pa@m3/mol (BUA, 1995).
This is equivalent to a dimensionless Henry’s law constant (air/water partition coefficient) of 3.92 × 10–6. These values indicate that phenylhydrazine is
essentially non-volatile from water surfaces.
Reported log octanol/water partition coefficients (log Kow) range from 1.25 to 1.90 (BUA, 1995); an estimated bioconcentration factor of 5 was based on the lower value (HSDB, 1998), indicating a low capacity for bioaccumulation. However, sorption based on chemical binding is possible, which could lead to some bioaccu- mulation (BUA, 1995). The sorption coefficient (Koc) can be calculated to range between 7.3 (Organisation for Economic Co-operation and Development [OECD]
Technical Guidance Manual) and 11 (Karickhoff et al., 1979), indicating little sorption to particulates and a capacity for mobility in soil. However, the regression equations on which these estimates are based derive from hydrophobic compounds and may not adequately reflect the likely sorption of the hydrophilic phenylhy- drazine.
In a modified OECD ready biodegradability screen- ing test (OECD 301E), phenylhydrazine was “readily biodegradable”; elimination was 77% after 10 days and 97% after 28 days using non-adapted inoculum.
Elimination through abiotic processes in controls was 11% after both 10 and 28 days (BASF, 1993). In the Zahn-Wellens test for inherent biodegradability (OECD 302B), 20–30% elimination occurred over 3 h (sorption), with 80% chemical oxygen demand achieved over 15 days using non-acclimatized industrial activated sludge.
Using acclimatized activated sludge, 85% elimination was seen after 10 days (Hoechst, 1980, 1992). A similar value of 85% elimination in 9–13 days was reported in the same test by Wellens (1990).
6. ENVIRONMENTAL LEVELS AND HUMAN EXPOSURE
6.1 Environmental levels
Phenylhydrazine was not detected (detection limit 0.002 :g/ml with high-performance liquid chromatog- raphy) in 30 samples of surface water in the 1986 monitoring of the general environment by the Japan Environment Agency (1987). It was also not detected in 30 samples of sediment (detection limit 0.2 :g/kg with high-performance liquid chromatography).
Monitoring of wastewater at the Hoechst produc- tion plant in Germany failed to detect the compound in either inflow or outflow wastewater (detection limit 500 :g/litre) (BUA, 1995).
6.2 Human exposure
The number of persons potentially exposed to phe- nylhydrazine or its hydrochloride salt is not known, but it is expected to be small (Brooke et al., 1997). Industry in the United Kingdom has not been able to provide any personal exposure data, although it has been indicated that exposure to airborne phenylhydrazine between 1993 and 1994 was controlled by process enclosure, the provi- sion of local exhaust ventilation, and personal protective equipment.
As there are no measured data available, the sections below describe the use of computer-modelled exposure data from the EASE model. This is a general- purpose predictive model for workplace exposure assessments, which is used when measured exposure data are limited or not available. In its present form, the model is in widespread use across the European Union for the occupational exposure assessment of new and existing substances.
Following descriptions of precautions taken during use, the most appropriate parameters for the use of the EASE model are non-dispersive use with local exhaust ventilation in place. Exposure between 25 and 40 °C with these assumptions is predicted to be within the range 2.3–13.5 mg/m3 (0.5–3 ppm) (8-h time-weighted average).
Further, as only small quantities are involved, and as extensive containment is provided by the combination of a vessel open only at the bung hole and transfer being achieved by vacuum transfer, exposure will be at the low end of this range (i.e., 2.3 mg/m3 [0.5 ppm] 8-h time- weighted average). In practice, the 8-h time-weighted average exposure will be less than this figure, as the activities involving exposure to phenylhydrazine will take place for only part of the shift.
These predicted exposures would be even lower for work carried out in fume cupboards and would be extensively mitigated at the operator by use of respira- tory protective equipment; air-fed suits would effectively reduce exposures of these magnitudes to zero.
For direct handling and non-dispersive use with a contact level assumed to be incidental from the process descriptions, EASE predicts dermal exposures to range from 0 to 0.1 mg/cm2 per day. If direct handling is eliminated, dermal exposure is very low. Again, these exposures would effectively be reduced to zero by adoption of high-quality personal protective equipment and distancing procedures described in this assessment.
7. COMPARATIVE KINETICS AND METABOLISM IN LABORATORY ANIMALS
AND HUMANS
Phenylhydrazine reacts readily with the carbonyl group, –C=O, which is common among biological molecules. It is therefore expected that direct binding to biological molecules would occur.
There is only limited information available on the toxicokinetics of phenylhydrazine. Evidence from toxi- cokinetic and toxicity studies and from human experience indicates that phenylhydrazine is well absorbed by the inhalation, oral, and dermal routes in animals and humans.
Once absorbed, some phenylhydrazine appears to be rapidly taken up by red blood cells, where destructive intracellular reactions may occur.
Evidence from a number of studies in vitro and in vivo suggests that phenylhydrazine interacts with haemoglobin and cytochrome P-450 in an oxidation reac-
tion, resulting in the generation of destructive free radicals, which are responsible for subsequent haemol- ysis (e.g., Itano et al., 1975; Valenzuela et al., 1977, 1981;
Goldberg et al., 1979; Jain & Hochstein, 1979; Jonen et al., 1982; Hill, 1985; Marks, 1985; Di Cola et al., 1988, 1989; Maples et al., 1988).
There is little information available on tissue distribution.
There is only one study available that investigates the metabolism and excretion of phenylhydrazine, following oral dosing in rabbits (McIsaac et al., 1958).
This study shows that phenylhydrazine is extensively metabolized following oral administration, although the complete metabolic pathway has not been characterized.
The main reactions identified in this study were hydrox- ylation of the aromatic ring to p-hydroxyphenylhydra- zine, followed by conjugation, probably with glucuronic acid, and production of phenylhydrazones, by reaction with natural keto acids.
This study also indicated that the major route of excretion is via the urine. A significant proportion of a single dose was excreted relatively slowly; 50% of the dose was excreted within 4 days of dosing. There are insufficient data to determine whether there is any accumulation of phenylhydrazine in body tissues on repeated exposure.
8. EFFECTS ON LABORATORY MAMMALS AND IN VITRO TEST SYSTEMS
Many of the studies reported for phenylhydrazine have been conducted using phenylhydrazine hydro- chloride. This salt is a weak, complex-forming compound, and either the salt or the free base will form depending on the physiological medium, regardless of the form in which the phenylhydrazine is administered (NIOSH, 1978). The toxicological properties of the salt can therefore be considered to be at least equivalent to those of free phenylhydrazine. Differences in toxicity may arise when properties such as pH or solubility contribute to the expression of toxicity. All dose values quoted throughout this document refer to free phenylhydrazine.
8.1 Single exposure
In relation to inhalation exposure, there is only one very poorly reported study, which reports LC50 values for an unstated exposure period of 2745 mg/m3 (610 ppm) in the rat and 2093 mg/m3 (465 ppm) in the mouse (Pham, 1979). However, it is expected that the marked toxicity seen following oral and dermal exposure
8 would also be expressed following inhalation. Phenylhy-
drazine is toxic by oral administration, and oral LD50 values in the range 80–188 mg/kg body weight have been reported for the rat, mouse, guinea-pig, and rabbit (Ekshtat, 1965; Pham, 1979). Clinical signs reported were motor excitation and tonic/clonic spasms. In rabbits, dermal exposure to 380 mg phenylhydrazine/kg body weight for 24 h resulted in 20–30% mortality, although no deaths occurred in rats at this dose (Derelanko et al., 1987). The toxic effects are characterized by destruction of red blood cells, causing a reduction in erythrocyte count, increased reticulocyte count, methaemoglobin formation, and the formation of Heinz bodies, and a cyanotic external appearance may develop. Enlargement and dark coloration of the spleen are also reported, effects that are considered to be secondary to the erythrocyte damage.
8.2 Irritation and sensitization
In the single-dose dermal toxicity study in rabbits and rats reported in the previous section, phenylhydra- zine hydrochloride was applied to the skin as a solid moistened with distilled water, under either an occlusive or semi-occlusive dressing, for 24 h (Derelanko et al., 1987). Skin irritation was seen in all rabbits, with some necrosis at the treated site at 24 h post-application and sloughing of the skin reported in some animals. Skin irritation, which appeared within 24 h and persisted for up to 7 days post-exposure, was seen in a high propor- tion of rats. Necrosis developed in a small number of rats.
The quality of skin irritation data from other studies is limited; overall, however, the results support the conclusion reached by Derelanko et al. (1987) — that phenylhydrazine should be considered a skin irritant (Jadassohn, 1930; von Oettingen & Deichmann-Gruebler, 1936; Roudabush et al., 1965; Schuckmann, 1969;
Derelanko et al., 1987). Further details of these studies can be obtained in the source document (Brooke et al., 1997).
The only available information on the eye irritation potential of phenylhydrazine in animals comes from a poorly described study in which application of a 50%
solution of phenylhydrazine to the eyes of rabbits was reported to cause severe suppurative conjunctivitis (Pham, 1979).
There are no good-quality studies available in animals that investigate the skin sensitization potential of phenylhydrazine. Only one poorly described study in guinea-pigs is available (Jadassohn, 1930). When a 10%
solution of phenylhydrazine in alcohol was painted on a skin site that had been pretreated 2–3 weeks previously with undiluted phenylhydrazine, very intense erythema and swelling, followed by scaling and encrustation, were
consistently seen. This response to 10% phenylhydra- zine was more severe than that described in animals that had not been pretreated.
No information is available in relation to respira- tory tract sensitization.
8.3 Short-term exposure
There are only very limited, poor-quality data available in relation to short-term repeated-dose toxicity.
The effects seen are similar to those seen following single exposure — in particular, destruction of circu- lating red blood cells. Toxicity to the spleen, liver, and kidney has also been observed in animal studies, possi- bly secondary to haemolysis.
Kelly et al. (1969) administered phenylhydrazine hydrochloride to 21 mice by oral gavage once weekly for 8 weeks, at an estimated dose of 85 mg/kg body weight per week. There were 10 saline-treated controls. The study report described only tumour-related findings.
There was 30% mortality in treated mice compared with none in controls.
Haematological changes were reported in four dogs administered 60 mg phenylhydrazine/kg body weight, either as a single dose or as 2, 3, or 10 equal doses on consecutive days (Giffin & Allen, 1928). There was a marked reduction in erythrocyte count that was comparable in magnitude in all dogs at the end of 10 days, but that occurred at a faster rate after a single high dose compared with repeated lower doses.
In another dog study, 60 mg phenylhydrazine/kg body weight was administered daily to three dogs for 5 days (Allen & Giffin, 1928). One animal was moribund at sacrifice on the fifth day and one animal died on the fifth day, although it is not specified that death was treatment related. Full necropsy was performed on only one animal, in which it was found that the blood was brown and did not coagulate readily. Several organs, including the liver and kidneys, were darkly coloured, and several organs contained capillaries engorged with blood. Blood pigment and partially destroyed erythro- cytes were found in the spleen. Hepatic cell atrophy was noted, and there was an increase in the iron content of the liver. Similar liver effects were seen in the two other dogs.
Bolton (1935) briefly reported the effect of repeated oral administration of 14 mg phenylhydrazine hydro- chloride/kg body weight to one dog on 4 consecutive days. There was a reduction in erythrocyte count and haemoglobin concentration, whereas white cell count gradually increased. These parameters had returned towards pretreatment values 12 days after the last dose.
Pathological findings were reported to be non- conclusive, but no details were given.
Overall, the frequency, duration, and level of exposure often varied throughout the studies reported above, so that interpretation of results is very difficult.
In all studies, phenylhydrazine as phenylhydrazine hydrochloride was administered either by stomach tube or by subcutaneous injection. The authors report that similar findings were obtained regardless of route. There were no control animals. None of the treated animals showed clinical signs of toxicity, and there was no excessive weight loss or gain reported.
There have been a number of studies that investi- gate the effect of short-term repeated parenteral admin- istration of phenylhydrazine (Bodansky, 1923; von Oettingen & Deichmann-Gruebler, 1936; Säterborg, 1974;
Ades & Cascarano, 1979; Jain & Hochstein, 1979;
Goldstein et al., 1980; Nishida et al., 1982; Dornfest et al., 1986). These studies confirm the ability of phenylhydra- zine to damage red blood cells but otherwise do not provide any other information in relation to the toxicity of phenylhydrazine administered by occupationally relevant routes of exposure.
8.4 Long-term exposure 8.4.1 Subchronic exposure
In a very poorly reported study from which limited conclusions can be drawn, rats, mice, guinea-pigs, and rabbits were exposed to phenylhydrazine vapour at 0, 0.1, 15.8, 22.5, or 225 mg/m3 (0, 0.03, 3.5, 5, or 50 ppm) (Pham, 1979). Group sizes, duration of exposure, and exposure regime were not given, although it can be inferred that some animals were exposed for at least 6 months. Deaths were reported to occur in animals exposed to 225 mg phenylhydrazine/m3 (species not specified). Severe weight loss and unspecified haemato- logical changes and changes in central nervous system function were reported to precede death, and there was evidence of haemolysis and dystrophic changes in the liver, spleen, and cerebrum. Animals exposed to 15.8 and 22.5 mg/m3 were reported to have a reduction in erythrocyte count and haemoglobin concentration, an increase in reticulocytes, and methaemoglobinaemia;
these changes were reversible at 15.8 mg/m3. Haemolysis and dystrophic changes in the liver and other unspeci- fied organs were also reported for animals exposed to 22.5 mg/m3. No further information is available on pathological changes at 0.1 mg/m3. It is not clear if there were lung effects at any of the exposure concentrations.
It is not possible to draw firm conclusions from a poorly reported study in three dogs in which the effect of phenylhydrazine administration on renal and hepatic function and on erythropoiesis was investigated (Allen
& Giffin, 1928). Three dogs were administered phenylhy- drazine in 146 daily doses over a period of 8 months, to give a total dose of 950 mg/kg body weight; the dosing regimen included a period of about 60 days of
uninterrupted administration of a single dose level or of two dose levels (6–12 mg/kg body weight per day).
Again, the route of administration was unclear. Kidney function and hepatic function were unaffected by treat- ment. Erythrocyte count was reduced by treatment but recovered after cessation of treatment, at a rate that was unrelated to the duration of exposure, thus indicating that the administered dose had no effect on erythropoi- etic function. Pathological examination was conducted on two of these dogs at 12 or 13 months. There was evidence of spleen toxicity, liver congestion, and kidney damage.
In a very briefly reported study, phenylhydrazine was administered to 25 female Swiss mice by oral gavage, 5 days/week for 40 weeks, at an estimated daily dose of 17–33 mg/kg body weight (Roe et al., 1967).
There were 85 untreated controls. Marked anaemia necessitated a reduction in the dose during the sixth week of treatment. No other toxic effects were observed.
8.4.2 Chronic exposure and carcinogenicity Phenylhydrazine hydrochloride was administered daily by stomach tube for 42 weeks to 30 BALB/c mice, at an estimated dose level of 25 mg phenylhydrazine/kg body weight (Clayson et al., 1966). Thirty control animals were included in the study, but a control animal was killed whenever a treated animal died, to match survival rates. There was a statistically significant increase in the incidence of animals with lung tumours in the treated group (53%) compared with controls (13%). There was also a slight increase in the average number of tumours per mouse, and the majority of treated mice had multiple pulmonary tumours. Adenomas accounted for 83% of pulmonary tumours in the treated group, half of which were judged to be becoming malignant, and 17% of tumours were carcinomas.
Phenylhydrazine hydrochloride was administered in drinking-water to 100 Swiss mice for their lifetime, at an estimated daily dose of 22 mg/kg body weight (Toth
& Shimizu, 1976). There were 200 control mice. Complete necropsy was performed on all animals. All organs were examined macroscopically, and histological analysis was performed on a wide range of tissues as well as on any organ showing gross pathology. Phenylhydrazine was reported to decrease survival in comparison with controls, and many of the treated decedents showed splenomegaly, although numbers were not given. There was a statistically significant increased incidence of blood vessel tumours (mainly angiosarcomas and angiomas) in the liver of treated animals (21%) compared with controls (0%).
10 8.5 Genotoxicity and related end-points
Phenylhydrazine and phenylhydrazine hydro- chloride have been investigated in a number of Ames tests, in a variety of strains, and in the presence and absence of exogenous metabolic activation using up to 1000 :g phenylhydrazine or phenylhydrazine hydro- chloride per plate (Shimizu et al., 1978; Tosk et al., 1979;
De Flora, 1981; Parodi et al., 1981; Levin et al., 1982;
Malca-Mor & Stark, 1982; Rogan et al., 1982; De Flora et al., 1984a,b; Wilcox et al., 1990; Muller et al., 1993). The quality of these studies is generally high, and the studies were apparently conducted according to standard methodology, although detailed reporting of the results is not always available.
There is some variability in the findings, although positive results have been obtained in Salmonella typhimurium strains TA97, TA100, TA102, TA1537, and TA1538 in the absence of exogenous metabolic
activation. In addition, positive results were obtained in the presence of metabolic activation in TA98 and TA1535. Some investigators have reported that the mutagenic action is slightly decreased by the presence of exogenous metabolic activation (Parodi et al., 1981;
Malca-Mor & Stark, 1982; De Flora et al., 1984a,b).
However, one study reports an increase in mutagenic activity in the presence of metabolic activation (Rogan et al., 1982).
Phenylhydrazine has also given positive results in a number of other, less well validated bacterial assays (using S. typhimurium strains such as TA2638, TP138, BA9, and BA13), in the presence and absence of exogenous metabolic activation (De Flora et al., 1984b;
Ulitzur et al., 1984; Ruiz-Rubio et al., 1985; Levi et al., 1986; Muller et al., 1993).
Phenylhydrazine has not been tested in an in vitro chromosomal aberration assay. In a brief abstract of a mammalian cell gene mutation assay in V79 cells, with and without metabolic activation, a positive result was reported for phenylhydrazine (Kuszynski et al., 1981).
However, no firm conclusions can be drawn from this report because of deficiencies in the reporting.
In an unscheduled DNA synthesis assay in rat and mouse primary hepatocytes, concentrations of 0.0144–
144 mg phenylhydrazine hydrochloride/litre were assessed (Mori et al., 1988). Although toxicity was measured, no details were given, and quantitative data were not reported. A positive result was obtained in both cell types, although the effect was small.
Phenylhydrazine was tested in a micronucleus assay in vitro using primary mouse bone marrow cells (Suzuki, 1985). Bone marrow cells from the femur were exposed to 1–50 :g phenylhydrazine/ml for 30 min, in
the presence and absence of metabolic activation. A total of 1500 polychromatic erythrocytes (PCEs) per concentration was scored for the presence of micronuclei. There was no measure of cytotoxicity.
The percentage of micronucleated PCEs was statistically significantly increased, in the presence of S9 only, at phenylhydrazine concentrations of 5 :g/ml and greater in a concentration-related manner.
BALB/c mice were administered a single intra- peritoneal injection of phenylhydrazine, and the inci- dence of micronucleated PCEs in the bone marrow was measured at 24 and 48 h (Suzuki, 1985). Phenylhydrazine was reported to be positive in this test, but no details of the results or of the test were given. In view of the poor reporting, no firm conclusions can be drawn from this study.
Groups of 11–12 female BALB/c mice were given a single intraperitoneal injection of 50 mg phenylhydra- zine/kg body weight in saline (Steinheider et al., 1985).
Blood smears of tail vein blood were prepared at 24-h intervals for 7 or 11 days, and reticulocytes and micro- nuclei in normochromatic erythrocytes (NCEs) and PCEs were counted. It is not stated how many cells were counted per mouse. There was no reporting of toxicity.
Phenylhydrazine caused a statistically significant increase in the reticulocyte count on days 2–4 post- injection and in PCEs on day 3. There was a statistically significant increase in the incidence of micronucleated PCEs at 24 h post-injection (from 1 to 4.7 per 1000) and in micronucleated NCEs at 48 h post-injection (from 0.7 to 2.3 per 1000).
However, similar increases in micronucleated NCEs were also seen following bleeding of the animals and splenectomy. The authors suggest that the increase in micronuclei seen following phenylhydrazine treatment was due at least partly to stimulation of erythropoiesis because of the haemolysis induced by phenylhydrazine, thus leading to more errors of nuclear expulsion; hence, the results do not necessarily indicate a direct genotoxic action of phenylhydrazine.
Groups of 7–12 mice were given a single intraperi- toneal injection of either 85 or 170 mg phenylhydrazine/
kg body weight and killed 1 and 6 h, respectively, after treatment (Parodi et al., 1981). In addition, six mice were given a series of five daily intraperitoneal injections of 7.6 mg phenylhydrazine/kg body weight and sacrificed 6 h after the last injection. Control animals were injected with saline only. DNA damage was assessed by measurement of the alkaline elution rate of single-strand DNA from liver and lung tissue extracts.
A statistically significant change in the elution rate of liver and lung DNA was seen in all groups of treated animals compared with controls, except in the case of lung tissue DNA from mice given a single dose of 85 mg phenylhydrazine/kg body weight. Phenylhydrazine is considered to give a positive result in this assay for DNA damage.
. The formation of DNA adducts (N7-methylguanine and a trace of O6-methylguanine) in the liver was demon- strated in rats receiving 65 mg phenylhydrazine/kg body weight by oral gavage (Mathison et al., 1994). Other tissues were not examined.
8.6 Reproductive and developmental toxicity
Each of three dogs (one dog per dose group) received 20, 30, or 40 mg phenylhydrazine/kg body weight in saline by subcutaneous injection on 2 consecutive days (Witchett, 1975). Two control animals were not injected. At necropsy, performed on all three animals within a few days of dosing, a “striking”
reduction in spermatogenesis was reported, with an absence of sperm in the epididymis. The validity of this result is not clear, given the apparent extreme rapidity of the effect.
Groups of 8–12 pregnant Wistar rats were given an intraperitoneal injection of 7.5 mg phenylhydrazine/kg body weight as phenylhydrazine hydrochloride on days 17, 18, and 19 of gestation; or 15 mg phenylhydrazine/kg body weight as phenylhydrazine hydrochloride on days 18 and 19 of gestation (Tamaki et al., 1974). Control animals were not treated. There was no reporting of maternal toxicity or of the effect of treatment on gestation or pup viability. Toxicity of the pups was reported only insofar as there was incidence of jaundice and/or anaemia among the offspring of treated animals.
Twelve male offspring with severe jaundice and anaemia, selected from treated dams, and nine males from control dams were assessed at 9–22 weeks of age for functional and behavioural status.
Although the authors reported that experimental animals showed statistically significant differences from controls in some tests, these findings are not considered to be reliable because of the small numbers of animals used and the exclusion of a control animal from the analysis. In addition, it is noted that only a brief part of the gestation period was covered by the treatment regime (days 17–19); no explanation is available for this choice of dosing regime.
Yamamura et al. (1973) reported in a brief abstract that intraperitoneal injection of pregnant rats with 15 mg phenylhydrazine/kg body weight as phenylhydrazine hydrochloride on days 18 and 19 of gestation produced
hyperbilirubinaemia (resulting from haemolysis) in fetuses and newborns.
8.7 Immunological and neurological effects
No studies are available that specifically investi- gate the immunological and neurological end-points, and there is no relevant information from toxicity studies in animals.
9. EFFECTS ON HUMANS
In humans, no information is available in relation to single exposure via the inhalation or oral routes,
although effects similar to those seen following dermal exposure would be expected to occur. Systemic toxicity developed in humans after dermal exposure to liquid phenylhydrazine, despite immediate attempts to reduce exposure by removal of contaminated clothing and washing of skin (Schuckmann, 1969). Toxicity was manifest by damage to red blood cells, in one case resulting in haemolytic jaundice. No such systemic effects were reported in two cases of skin contamination with solid phenylhydrazine hydrochloride.
In relation to skin irritation, information is available from worker exposure data. There was no reporting of irritancy effects in workers exposed to liquid phenylhy- drazine following accidental exposure, although systemic effects were seen (Schuckmann, 1969). Skin irritation following contact with phenylhydrazine hydrochloride powder was reported in two workers following accidental exposure. Local irritation, superficial erythema, and partly bullous-papular changes were noted in one case following spillage of powder on arms; multiple burn marks and small blisters at the site of contact were reported in the second case in which phenylhydrazine hydrochloride had spilled into the worker’s gloves and shoes. The author also refers to medical records at the works that describe a number of cases of skin irritation of differing severity due to phenylhydrazine hydro- chloride, but no details are given.
There are no data available on the eye irritation potential of phenylhydrazine in humans.
There are a number of case reports of skin hyper- sensitivity reactions to phenylhydrazine and its hydro- chloride salt in humans. Solomons (1946) conducted a patch test in one subject with a phenylhydrazine crystal placed on the forearm under a dressing for an unstated exposure period. Marked erythema and some oedema developed on the exposure site after 18 h, with the
12 formation of vesicles after 30 h and crusting after a
further 24 h.
Similar hypersensitive skin reactions were reported following individual exposures to solid or aqueous solutions of phenylhydrazine or phenylhydrazine salts (Wright & Joyner, 1930; Frost & Hjorth, 1959; Pevny &
Peter, 1983).
There is also evidence that cross-sensitization can occur between hydrazine compounds, so that subjects already sensitized to hydrazine, a known skin sensitizer, are also sensitized to hydrazine derivatives, including phenylhydrazine (Malten, 1962; Van Ketel, 1964;
Hovding, 1967; Rothe, 1988).
No data are available on the potential of phenyl- hydrazine to cause respiratory tract sensitization.
Earlier this century, phenylhydrazine and phenyl- hydrazine hydrochloride were administered orally (usually around 100–200 mg/day) for the treatment of blood disorders (e.g., Giffin & Allen, 1933). In some cases, treatment was effective; in others, however, the outcome was fatal (e.g., Giffin & Conner, 1929). The effects seen (beneficial or otherwise) may have been related to the disease process and cannot be attributed entirely to phenylhydrazine.
10. EFFECTS ON OTHER ORGANISMS IN THE LABORATORY AND FIELD
10.1 Aquatic environment
Results of acute toxicity tests on aquatic organisms are summarized in Table 2. All concentrations are nominal.
In the early life stage test summarized in Table 2 (Xiu et al., 1992), newly fertilized eggs of the zebra fish were exposed to concentrations of phenylhydrazine through hatch and into the larval stage (total exposure time was 16 days). A NOEC (survival) was established for eggs at 5 days post-fertilization at 0.0039 mg/litre, with a lowest-observed-effect concentration (LOEC) at 0.0078 mg/litre. At the end of the test (16 days), the NOEC for larvae was 0.000 49 mg/litre, and the LOEC was 0.000 98 mg/litre. The study was conducted according to a Swedish standard protocol (ss 028193).
In a study on the goldfish (Carassius auratus), 40% of fish died when exposed to phenylhydrazine at a nominal concentration of 1 mg/litre for 48 h. Signs of toxicity included erratic swimming, sinking to the bottom
of the test tank, and slowed and erratic respiration. No gross lesions were found following dissection, although all viscera showed focal haemorrhaging (Houston et al., 1988).
Effects on blood cells and the haematopoietic system, comparable to those found in mammals, were seen in fish injected with phenylhydrazine. Chinook salmon (Oncorhynchus tshawytscha) juveniles were injected with 12.5 mg phenylhydrazine/kg body weight.
Red cell count, haemoglobin, and haematocrit fell to 1–5% of their normal values within 10 days of treatment;
a slight improvement was reported 15 days following injection, and values had returned to normal 95 days after treatment (Smith et al., 1971).
10.2 Terrestrial environment
Phenylhydrazine at 21.6 mg/litre in a nutrient culture medium had no effect on the growth of various soil fungi (Zsolnai, 1975).
A phenylhydrazine concentration of 50 mg/litre in a hydroponic culture solution inhibited germination of Hordeum seeds for at least 6 days, whereas growth was stimulated in Lepidium. At 100 mg/litre, seedling growth was stimulated in Hordeum but not in Lepidium. At 500 mg/litre, phenylhydrazine inhibited growth in seedlings of both species, although the seedlings were still apparently “healthy” (Bokorny, 1933).
Exposure of soil nematodes Caenorhabditis briggsae in culture to phenylhydrazine at 50 mg/litre of medium resulted in reduced growth of all four larval stages (the effect was most marked on the last larval instar) and therefore delayed development to adults.
However, the adults formed were capable of reproduc- tion, although the number of progeny was reduced. A concentration of 15 mg/litre also delayed development, although to a lesser degree compared with the higher concentration (Kampfe et al., 1986a,b). A 6-day EC50 of 12 mg/litre was reported for production of progeny in culture for the same nematode (Kreil, 1982).
No dietary or oral toxicity studies have been performed on birds. However, injection studies have shown haemolytic anaemia and reduced white cell counts in birds. In contrast to mammals, cell division in erythropoietic tissue is unaffected by phenylhydrazine (Williams, 1972; Clark et al., 1988; Datta et al., 1989, 1990).
Table 2: Acute toxicity of phenylhydrazine to aquatic organisms.
Organism End-point Concentration (mg/litre) Reference
Bacteria
Photobacterium phosphoreum 30-min EC50 (luminescence) 66.9 Kaiser et al. (1987) Facultative anaerobes
(mixed culture)
24-h toxic threshold 60 Hoechst (1980)
Escherichia coli minimum inhibitory concentration 109.3 Romero & Canada (1991) Escherichia coli, Micrococcus
luteus, Bacillus licheniformis
minimum inhibitory concentration >3000 Zemek et al. (1978)
Invertebrates water flea (Daphnia magna)
LC50 (immobilization) 2–5 Hoechst (1980)
Fish zebra fish
(Brachydanio rerio)
96-h LC50
96-h NOEC
0.16–0.25 0.1
Hoechst (1982) zebra fish
(Brachydanio rerio)
5-day NOEC (eggs) 16-day NOEC (larvae)
0.0039 0.000 49
Xiu et al. (1992) Japanese killifish
(Oryzias latipes)
48-h LC50 15.7 Tonogai et al. (1982)
common carp (Cyprinus carpio)
24-h LC100
96-h NOEC
1.0 0.1
Menzie (1979)a bluegill
(Lepomis macrochirus)
48-h LC50
96-h NOEC
0.1 0.01
Menzie (1979)a
a Menzie C (1979) Value taken from the DIMDI/ECDIN database. Test performed by the United States Fish and Wildlife Service, Bureau of Sports, Fisheries and Wildlife, Department of the Interior, Washington, DC [cited in BUA, 1995].
11. EFFECTS EVALUATION
11.1 Evaluation of health effects
11.1.1 Hazard identification and dose–response assessment
Phenylhydrazine is toxic by single exposure via the oral route (LD50 80–188 mg/kg body weight) and is expected to be toxic by the inhalation and dermal routes (data from these routes of exposure are less clear). Phe- nylhydrazine solution was severely irritating to rabbit eyes; hence, it is reasonable to predict that it would have significant eye irritation potential in humans.
Phenylhydrazine also has skin irritation potential, and there is evidence from human case reports that it has skin sensitizing properties. Exposure to phenylhydrazine may cause damage to red blood cells, potentially result- ing in anaemia and consequential secondary involve- ment of other tissues, such as the spleen and liver. The dose (exposure)–response characteristics for the induc- tion of damage to the red blood cells are poorly defined, and a no-effect level has not been identified. Where phe- nylhydrazine has been used therapeutically in humans, via the oral route, for the treatment of blood disorders,
daily doses of the order of 1.5–4 mg/kg body weight per day have caused a reduction in the numbers of red blood cells; given the health status of the individuals con- cerned, however, these data are of limited use. Phenylhy- drazine is mutagenic in vitro, and, although not
conclusive, there is some evidence to indicate that it may express genotoxic activity in vivo. The substance is clearly carcinogenic in mice following oral dosing, inducing tumours of the vascular system. The mecha- nism for tumour formation is unclear, and, given the genotoxic profile of phenylhydrazine, a genotoxic component cannot be excluded. Carcinogenic potential in humans cannot be excluded given the profile of genotoxicity and animal carcinogenicity, particularly as other expressions of phenylhydrazine toxicity are common to a number of species, including humans.
No conclusions can be drawn from the available information on fertility or development.
11.1.2 Criteria for setting guidance values for phenylhydrazine
There are no adequate data available regarding reproductive or developmental effects; hence, it is not possible to evaluate the risk to human health for these end-points.
14 The use pattern and physical/chemical characteris-
tics of the compound suggest that exposure of the gen- eral population would be negligible.
Using United Kingdom workplace conditions as an example (section 6.2), exposure to phenylhydrazine vapour during most occupational processes would result in a body burden of up to 0.33 mg/kg body weight per day, assuming a 70-kg worker breathes 10 m3 of air in a working day and that 100% phenylhydrazine is absorbed. There are no data available from which to estimate the contribution to body burden from dermal uptake, although this is expected to be negligible. A threshold for the induction of red blood cell damage probably exists but has not been identified, although daily oral doses calculated at about 1.5 mg/kg body weight per day and above are associated with such effects. Overall, at these levels of predicted inhalation exposure, the risk of developing damage to the red blood cells is considered to be low; if the levels were exceeded (e.g., of the order of a few ppm, approximately 15–20 mg/m3), however, then this would be cause for some concern.
On the basis that the carcinogenicity of phenylhy- drazine may involve a genotoxic mechanism, it is not possible to reliably identify a threshold below which occupational exposure to phenylhydrazine would not result in some risk to human health.
11.1.3 Sample risk characterization
The scenario chosen as an example is occupational exposure in the United Kingdom.
The main health concerns associated with expo- sure to phenylhydrazine are damage to the red blood cells, deleterious effects on genetic material, and the development of cancer.
It is recognized that there are a number of different approaches to assessing the risks to human health for genotoxic and carcinogenic substances and in the subsequent risk management steps that may be taken. In addition, although not used in the United Kingdom, there are models for characterizing potency that may be of some benefit in priority-setting schemes. In the United Kingdom occupational setting, a Maximum Exposure Limit or MEL (which is not a health-based standard) has been proposed at 0.9 mg/m3 (0.2 ppm), 8-h time-weighted average. The numerical value for the MEL was based on a level of control that was deemed (by tripartite agreement) to be reasonably practicable under United Kingdom workplace conditions, and in the United Kingdom there is a continuing requirement to reduce exposure levels as far as reasonably practicable with the technology that is currently available.
Phenylhydrazine also possesses skin and eye irritant properties and possibly skin sensitizing potential.
The information available indicates that local exposure of these tissues is unlikely; if it did occur, however, then there would be risk of irritation to the eyes and the development of irritant and/or allergic dermatitis.
11.2 Evaluation of environmental effects No atmospheric effects are expected given the release of phenylhydrazine predominantly to water, its extremely low volatilization from water to the atmos- phere, and its rapid calculated atmospheric half-life following reaction with hydroxyl radicals.
Few toxicity studies are available for terrestrial organisms, and little emission to land is expected; on this basis, no quantitative risk assessment can be attempted for the terrestrial environment.
Phenylhydrazine is degraded photochemically and autoxidizes in water. It is readily biodegradable, and this is expected to be the major route of breakdown in the environment. There is minimal sorption to particulates.
Phenylhydrazine is toxic to aquatic organisms, with the lowest reported NOEC in acute fish tests at
0.01 mg/litre; fish are generally more sensitive than either daphnids or bacteria. A NOEC for embryo-larval stages following 16 days of exposure from fertilization has been reported at 0.000 49 mg/litre for the zebra fish.
There are no reported measurements of phenylhy- drazine in environmental media. Monitoring studies of both inflow and outflow to the wastewater treatment plant of the Hoechst Hochst production plant in Ger- many showed no detectable phenylhydrazine (detection limit 500 :g/litre) in weekly samples. Maximum emission to wastewater was estimated at 13 t/year, and this will be used as a worst-case example.
Based on this emission rate, and using mainly default values from the OECD Technical Guidance Manual, the initial predicted environmental concentra- tion of phenylhydrazine in river water (PEClocal (water), in g/litre) would be as follows:
PEClocal (water) = Ceffluent (1 + Kp(susp) × Csusp) × D where:
# Ceffluent is the concentration of phenylhydrazine in the wastewater treatment plant effluent (g/litre), calculated as Ceffluent = W × (100 ! P)/(100 × Q), where:
W = emission rate (35.6 kg/day)
P = percent removal in the wastewater treatment plant (based on the “ready biodegradability” of the compound, 91%)
Q = volume of wastewater in m3/day (default 200 litre/day per capita for a population of 10 000 inhabitants;
wastewater volume for the production plant is unknown)
# Kp(susp) is the suspended matter/water adsorption coefficient, calculated as Kp(susp) = Koc × foc(susp), where:
Koc = organic carbon/water partition coefficient (7.3)
foc(susp) = fraction of organic carbon in suspended matter (default 0.1)
# Csusp is the concentration of suspended matter in the river water (in kg/litre; default 15 mg/litre)
# D is the dilution factor for river flow (flow rate for the River Main averages 188 m3/s compared with the estimated flow rate of the wastewater at 0.02 m3/s; dilution factor approximately 10 000) Under these very conservative conditions, PEClocal (water)
= 0.16 :g/litre.
Of the reported acute toxicity test results for organisms in the environment, those for the majority of fish tested are substantially lower than those for other organisms tested. The predicted no-effect concentration (PNEC) will therefore be based on the fish results.
No long-term test results are available. Applying an uncertainty factor of 1000 to the lowest reported standard acute LC50 value of 0.1 mg/litre for the bluegill (Lepomis macrochirus) would give a PNEC of
0.1 :g/litre. This is a factor of 100 lower than the lowest reported NOEC for the same species. Alternatively, applying an uncertainty factor of 10 to the NOEC for the early life stage test on the zebra fish larvae gives a PNEC of 0.049 :g/litre. The more conservative value will be used in estimating risk.
The low PEC of 0.16 :g/litre would not have been detected in the monitoring at the site. Assuming that this value is the worst case, a PEC/PNEC ratio of 3.2 is generated. This indicates that the risk to aquatic organ- isms is low, based on very conservative assumptions.
The distribution of reported toxicity test results against the worst-case PEC is plotted in Figure 1, illustrating the safety margin.
12. PREVIOUS EVALUATIONS BY INTERNATIONAL BODIES
Previous evaluations by other international bodies were not identified. Information on international hazard classification and labelling is included in the Interna- tional Chemical Safety Card (ICSC 0938) reproduced in this document.
13. HUMAN HEALTH PROTECTION AND EMERGENCY ACTION
Human health hazards, together with preventive and protective measures and first aid recommendations, are presented in the International Chemical Safety Card (ICSC 0938) reproduced in this document.
13.1 Human health hazards
Phenylhydrazine induces damage to red blood cells. Repeated or prolonged contact with the substance causes skin sensitization, and there is cause for concern for carcinogenicity.
13.2 Advice to physicians
Phenylhydrazine is a haemolytic agent. There is no specific antidote, but treatment should be supportive.
13.3 Health surveillance advice
Periodic medical examination of the area of the skin exposed to phenylhydrazine and annual blood count should be included in the health surveillance programme.
16 14. CURRENT REGULATIONS,
GUIDELINES, AND STANDARDS
Information on national regulations, guidelines, and standards may be obtained from UNEP Chemicals (IRPTC), Geneva.
The reader should be aware that regulatory deci- sions about chemicals taken in a certain country can be fully understood only in the framework of the legislation of that country. The regulations and guidelines of all countries are subject to change and should always be verified with appropriate regulatory authorities before application.
