【正文】 s, jointly or separately, to achieve the sound management of chemicals in relation to human health and the environment. WHO Library CataloguinginPublication Data Chloral hydrate. (Concise international chemical assessment document 。 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 healthbased tolerable intakes and guidance values. 1 International Programme on Chemical Safety (1994) Assessing human health risks of chemicals: deriviation of guidance values for healthbased exposure limits. Geneva, World Health Organization (Environmental Health Criteria 170). 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 bees 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 highquality 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 piled by IPCS through remendations 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 reviewers39。g/litre. Since chloral hydrate is a metabolite of trichloroethylene and tetrachloroethylene, people will be exposed to chloral hydrate if they are exposed to these chemicals. The public will be exposed to the metabolites of chloral hydrate, trichloroacetic acid and dichloroacetic acid, as these chemicals are also formed when drinkingwater is disinfected with chlorine. In its use as a sedative for people, the usual clinical dose is 250 mg, 3 times a day (equivalent to mg/kg body weight per day). The metabolite trichloroethanol is responsible for the pharmacological effect. No quantitative information is available from occupational exposure. Chloral hydrate is irritating to the skin and mucous membranes and often causes gastric distress, nausea, and vomiting at the remended clinical dose. An acute overdose produces (in order of progression) ataxia, lethargy, deep a, respiratory depression, hypotension, and cardiac arrhythmia. There is some evidence of hepatic injury in people surviving nearlethal, acute overdoses, but no convincing evidence that hepatic injury results from the remended clinical dose. Several studies of the clinical use of chloral hydrate show a low incidence of minor sideeffects. Despite its long use in human medicine, there is no published information on toxicity in controlled studies in humans following extended exposure. Chloral hydrate is pletely absorbed and rapidly metabolized following oral administration. The major metabolites are trichloroethanol and its glucuronide and trichloroacetic acid. Some data suggest that a small amount of dichloroacetic acid may be formed. In humans, the halflife of trichloroethanol and its glucuronide is about 8 h。g/ml for trichloroethanol and trichloroethanol glucuronide and 181。C, the halftime for breakdown was 16 min. 6. ENVIRONMENTAL LEVELS AND HUMAN EXPOSURE Environmental levels No information is available. Human exposure The major route of exposure to chloral hydrate is from chlorinated drinkingwater. A typical concentration of chloral hydrate in a public water supply in the USA is 5 181。 no information is available on dermal absorption. Qualitatively similar metabolism occurs in mice, rats, dogs, Japanese medaka (Oryzias latipes), and humans (Marshall amp。 Hobara et al., 1986, 1987a,b, 1988a,b。 Fisher, 19