Drinking water guideline for ethylene thiourea, a metabolite of ethylene bisdithiocarbamate fungicides.
The ethylene bisdithiocarbamate fungicides are the most heavily used pesticides in Maine. Ethylene thiourea (ETU) is a metabolite and environmental decomposition product of these compounds, is highly water soluble, and has been detected in groundwater in the state. ETU is a recognized animal carcinogen and teratogen. When administered in the diet, ETU produced a significant increase in thyroid carcinomas in rats in two studies. Two strains of mice fed ETU in the diet developed an increased incidence of hepatomas and a slight increase in lymphomas. Application of the linearized multistage model resulted in virtually safe doses (10(-5) lifetime cancer risk) of 0.25 to 1.6 micrograms/kg/day. The major teratologic effect has been the development of hydrocephalus and other CNS defects postnatally, resulting in a high mortality rate among the offspring. The NOEL for this effect was 5 mg/kg in a single oral dose. Retarded parietal ossification was observed at 5 mg/kg/day. Serious nononcogenic thyroid effects, such as goiter, decreased 131I uptake, and reduced thyroxine production, have been observed. Thyroid hyperplasia was produced at doses as low as 0.3 mg/kg/day ETU ingested in the diet. Based on protection against thyroid and/or liver tumors and alteration in thyroid function, the recommended Drinking Water Guideline for ETU is determined to be 3 ppb. This will also provide protection against developmental effects, since these occur at doses that are one to two orders of magnitude higher.
D000818:Animals; D002274:Carcinogens, Environmental; D005028:Ethylenebis(dithiocarbamates) / Q000378:metabolism; D005031:Ethylenethiourea / Q000592:standards* / Q000633:toxicity; D005659:Fungicides, Industrial / Q000378:metabolism; D007093:Imidazoles / Q000592:standards*; D008452:Maximum Allowable Concentration; D013723:Teratogens; D013959:Thyroid Diseases / Q000139:chemically induced; D014873:Water Pollutants / Q000633:toxicity; D014874:Water Pollutants, Chemical / Q000633:toxicity
D002274:Carcinogens, Environmental; D005028:Ethylenebis(dithiocarbamates); D005659:Fungicides, Industrial; D007093:Imidazoles; D013723:Teratogens; D014873:Water Pollutants; D014874:Water Pollutants, Chemical; D005031:Ethylenethiourea