To determine the effects of dichlorvos vapour on the tumour incidence in rats, 5 week old Carworth Farm E strain rats weighing between 94 and 150 g were exposed to 0, 0.05, 0.5 and 5.0 mg/m3 in a 2-year inhalation study. The growth rate of all treated rats was depressed, particularly in the males. There was increased survival of the rats exposed to 5 mg/m3. There were no consistent differences in food intakes, organ weights, haematological or blood chemistry estimations, except in cholinesterase activites, amongst the various groups of rats. No compound-related differences were seen in acetylcholine and choline estimations carried out on a small number of female rats' brain tissues after two years' exposure. There were no gross or microscopical compound-related changes in the rats' tissues. Ultrastructural examination of the respiratory tissues of the rats from the control and 5 mg/m3 group showed no changes attributable to dichlorvos. The results of a relative risk analysis of the tumour data showed that no dose-related increase in tumour risk was established for rats of either sex. These data confirm the results of earlier st.udies supporting the safety of insecticidal uses of dichlorvos.
Two mentally retarded adults with nonketotic hyperglycinemia had biochemical findings similar to those of the infantile form of the disease. Our patients differ from other adult patients and may represent the survival to adulthood of individuals with a mild form of infantile nonketotic hyperglycinemia.
Summary Twelve mineral oils, originating from naphthenic and paraffinic stocks and variously refined, were evaluated for their potential to induce cutaneous neoplasia in female CF1 mice. The oils were applied to the shorn dorsal skin for up to 78 weeks, using several different treatment regimes.The sole acid/earth refined naphthenic spindle oil was a moderately potent cutaneous carcinogen. By comparison, the 11 oils, processed by other refining routes, were less carcinogenic or non-carcinogenic to murine skin. Two of the 11 oils were weak cutaneous carcinogens viz, a naphthenic spindle oil refined only by mild hydrotreatment and a paraffinic spindle oil refined by mild solvent extraction and 'Ferrofining'. All 9 remaining oils had been solvent-extracted as part of the secondary refining process; none induced malignant tumours, although solitary benign tumours of the treated site were recorded after exposure to 3 oils.The cutaneous carcinogenic potential of the test oils did not correlate well with their potential to induce epidermal hyperplasia at the treated site. Consequently, hyperplasia caused after short term exposure is of little value for distinguishing between carcinogenic and non-carcinogenic oils.
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