A REVIEW OF THE TOXICOLOGY OF ORGANOTINS WITH REFERENCE TO DRINKING WATER
Report No FR0101
S Hunt and M Wilkinson
To review the information on the toxicity of the organotins with reference to drinking water in order to provide a basis for the derivation of guideline values for the WHO.
There is a need to provide water suppliers with sound guidance on the maximum levels of toxic substances that should be permitted in drinking water. The WHO is undertaking a review of its drinking water guidelines for a number of substances. This review is part of the UK water industry's contribution to that process of establishing new guidelines based on a sound scientific assessment of the latest available data.
A number of the dialkyltins have a marked selective effect on the immune system, especially on the t-lymphocytes, of rats. Dioctyltin and dibutyltin compounds in particular induce a dose-related decrease in the weights of thymus, spleen and lymph nodes. Immunotoxic and renal effects have also been described for some of the trialkyltins in rats. Thymus weight reduction was found in rats fed tributyltin and triphenyltin. Trimethyltin and triethyltin may also be immunotoxic but this is overshadowed by their potent neurotoxicity to rodents. These compounds also appear to be neurotoxic in man. Several of the organotins have been shown to be hepatotoxic in rodents, the bile duct being particularly affected. Changes in the liver occurred at or above dose levels that resulted in immunodeficiency. Genotoxicity and carcinogenicity data are only available for a small number of the organotins. Although the majority of tests have proved negative the overall picture is unclear as some individual compounds have given positive or equivocal results in one test or another. Reproductive toxicity is of concern for tributyltin oxide in that developmental abnormalities were observed after oral dosing in mice. Standard analytical methods are adequate for the monitoring of organotins in drinking water.
There is a need for more quantitative data on the occurrence of organotins in food and in treated water. There is also a need for data on monoalkyltins, data on the reproductive toxicity of dialkyltins and data on the chronic effects of triethyltin in order to determine a no effect level which would enable the calculation of a guideline level. There should be further studies on the reproductive toxicity of tributyltin oxide, particularly on its effects to species other than mice. There is no information on the possible additive effects of the different organotins, neither are there any taste and odour data on any of the organotins. Studies should be carried out in both of these areas.
V RESUME OF CONTENTS
The report reviews the environmental exposure, the analysis and the toxicology of the organotins. This information is utilised in the consideration of guideline values for these compounds in drinking water.
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