EmbryotoxicJty of ametryn in rats Technical grade ametryn, a herbicide, was embryotoxic when administered orally to pregnant rats at maternally toxic dose levels of 404 or 539 mg/kg body weight/day on days 6-15 Of pregnancy. Foetal body weight and length were significantly reduced and there was a slight increase in resorptions, but no foetal malformations were observed. At 202 mg/kg body weight/day, two of the 23 dams died but no other adverse effects were evident (maternal or foetal), while the lowest dose of 101 mg/kg body weight/day was without effect (Asongalem E.A. and Akintonwa A., Bulletin of Environmental Contamination and Toxicology 1997,
58, 184). Placenta no barrier to genotoxic cidial A study in pregnant mice, in which the widely used pesticide cidial (phenthoate) was administered orally at three dose levels, found increased chromosome damage in maternal and foetal cells. Although clearly dose related, and probably present even at the lowest dose of 54 mg/kg body weight, the data achieved statistical significance from the the mid-dose of 107 mg/kg body weight. Cidial gave clear evidence of cytotoxicity (inhibition of mitotic activity) at the lowest tested dose in foetal and at the mid-dose in maternal cells (El Nahas S.M. et aL, Environmental and Molecular Mutagenesis 1997, 29, 53).
Ethylene glycol monomethyl ether and sperm formation in rabbits This solvent given in drinking water for 12 weeks produced a dose-dependent depression in sperm production in adult rabbits. A clear effect occurred at 25 mg/kg body weight/day. The investigators noted that the rabbit was markedly more sensitive than are rats or mice to the testis toxicity of EGME (Berndtson W.E. and Foote R.H., Reproductive Toxicology 11, 29).
Subchronic inhalation toxicity of styrene in rats and mice "State-of-the-art subchronic and chronic inhalation studies in rats and mice in compliance with Good Laboratory Practice Regulations to provide an adequate basis for human health hazard assessment" have been commissioned by the Styrene Information and Research Center. The results of the 13-week studies have been reported. In rats
signs of local irritation were seen at all tested concentrations (200-1500 ppm, 6 hours/day, 5 days/week). Pathological changes in the nasal tissues occurred at 500 ppm, but not at 200 ppm. Effects on the nasal tract also occurred in mice even at the lowest tested concentration of 50 ppm. Liver and lung pathology were found in the mice of the higher dose groups. The chronic (2-year) studies are currently under way (Cruzan G. et al., Fundamental andAlyplied Toxicology 1997, 35, 152).
Indium phosphide and lung inflammation in rats This semiconductor material has been found to induce inflammation and cell damage in the respiratory airway of rats when it was instilled directly into the windpipe at a dose of 62 gg/kg body weight. Doses of 6 ~tg/kg body weight were without effect (Oda K., IndustrialHealth 1997, 35, 61).
Trifluoroiodomethane m subchronic toxicity and genotoxiclty in rats... This iodinated hydrocarbon, which has a low ozone-depleting potential, is being considered for a career in fire extinguishers. US Air Force investigators have been unable to establish a no-adverse-effect level in a 13-week inhalation study in rats. Even at the lowest exposure concentration (2%), there were effects on the thyroid (increased follicular colloid content, altered thyroid hormone levels) and on the testes (degeneration). This concentration also produced chromosome damage in the bone marrow. Exposure to 4% and 8% trifluoroiodomethane resulted in impaired growth and nasal inflammation (Dodd D.E. et aL, Fundamental and Applied Toxicology 1997, 35, 64).
... and genotoxicity in mice and bacteria One of the above US Air Force investigators, working with two other researchers, has further defined the genotoxic potential of trifluoroiodomethane. It induced a slight, dose-related increase in chromosome damage (micronuchi) in the blood of mice exposed for 3 days (6 hr/day) to atmospheric concentrations of 5 or 7.5%. Mutagenicity was seen in bacteria (in the Ames test), but not in mouse cells in culture, either with or without metabolic activation, when tested up to cytotoxic concentrations (Dodd D.E. et aL, Inhalation Toxicology 1997, 9, 111).