[Teratogenic effect of ethylurea and nitrite in rats]

Evaluation of the nitrate drinking water standard with reference to infant methemoglobinemia and potential reproductive toxicity

In view of published results of epidemiologic studies which suggested an association between nitrate in drinking water and human malformations, an assessment of the toxicology of nitrates and nitrites in relation to possible adverse effects on reproduction and development was performed. The current water standard for nitrate is based on protection from methemoglobinemia. A review of the animal data failed to provide evidence for teratogenic effects attributable to nitrate or nitrite ingestion. Adverse reproductive effects reported occurred at doses that were about one thousand times and higher than the estimated human intake. Neither nitrate nor nitrite in experimental animals concentrated in the mammary gland or milk. The present assessment concludes that the maximum contaminant level of 45 ppm nitrate ion, or 10 ppm nitrate-nitrogen, adequately protects the very young from nitrate-induced toxicity, both pre- and postnatally.

[ct-Mode of Action in the Teratogenic Experiment]

The doses of 10 and 20 mg/kg N-methyl-N-nitrosourea which were teratogenetically effective after a single dose were distributed over 12,24, 48, and 96 hrs during the embryonic developmental phase of the rat. It turned out that the effects were enormously increased when both doses were given in ten single doses during 12 hrs. The number of fetuses that had died down during gestation was increased considerably, the surviving fetuses bore, without exception, the marks of extreme malformations, as, for example, big haemorrhagic cysts instead of the mandible and the tongue. The distribution of the doses over 24 hrs showed, as far as quantity is concerned, comparable teratogenic effects, which, however, during the time of treatment varied in quality according to the variation of the critical sensitivity of the developmental phase. The distribution over even longer periods of time gradually weakened the effect. There were also some other symptoms that became manifest. So it can be said that N-methyl-N-nitrosourea is according to its teratogenic effects also a typical ct-poison (Druckrey) with the maximum of cumulation after distributing the dose over 12 hrs of the gestation.