National Toxicology Program

TR-136
Bioassay of Aldicarb for Possible Carcinogenicity (CAS No. 116-06-3)

The carbamate pesticide aldicarb is used for the control of insects, nematodes, and mites. It is now registered for use on cotton, sugar beets, sugar cane, potatoes, peanuts, and a variety of field- and nursery-grown ornamental plants.

A bioassay of aldicarb for possible carcinogenicity was conducted by administering the test chemical in feed to F344 rats and B6C3F₁ mice.

Groups of 50 rats and 50 mice of each sex were administered aldicarb at one of two doses, either 2 or 6 ppm, for 103 weeks and then observed for an additional 0 to 2 weeks. Matched controls consisted of 25 untreated rats and 25 untreated mice of each sex. All surviving animals were killed at weeks 103 to 105.

Mean body weights of the dosed male and female rats were essentially the same as those of the corresponding controls. Mean body weights of the dosed male and female mice also were essentially the same as those of corresponding controls. Hyperactivity was noted in the dosed groups of mice. Survival was not affected significantly in dosed groups of either the rats or the mice and was 72% or greater in all dosed or control groups at week 90. Sufficient numbers of animals were at risk for the development of late-appearing tumors.

No tumors occurred in either the rats or mice at incidences that could clearly be related to administration of the test chemical. In both rats and mice, however, there was no indication either through weight depression or early mortality that maximum tolerated dose levels were used. Therefore, the studies may not have been conducted using maximum sensitivity for the assessment of the possible carcinogenicity of aldicarb.

It is concluded that under the conditions of this bioassay, technical-grade aldicarb was not carcinogenic for F344 rats or B6C3F₁ mice of either sex.

Synonym: 2-methyl-2-(methylthio)propionaldehyde O-(methylcarbamoyl)oxime