Reproductive and Developmental Toxicity of N,N-Diethyl-m-toluamide in Rats

N,N-Diethyl-m-toluamide (mDET, DEET) is widely used as a topicalinsect repellent. It is the active ingredient in many consumerformulations, which usually contain 10–25% mDET in analcohol base. More concentrated consumer products are also available,including some that are pure technical grade mDET. Persons livingor employed in mosquito-infested areas may have very high seasonalexposures to mDET. Because contradictory reports had been publishedon the reproductive and developmental toxicity of mDET, a seriesof studies was conducted in male and female Sprague-Dawley rats.All treatments were administered by daily subcutaneous injectionsof undiluted mDET. A dose finding study was done using 12 time-matedfemales per group treated on Gestational Days (GD) 6–15with 0.50, 0.62, 0.78, 0.92, or 1.2 ml mDET /kg/day. No femalessurvived 10 days of mDET dosing with 1.2 ml/kg/day. Deaths occurredin all other groups except the low dose (0.50 ml/kg/ day). Pregnantfemales treated on GD 6–15 with 0 or 0.30 ml/ kg/day wereused for the teratology study. Half of each group was euthanizedon GD 20: the second half was singly housed in nesting boxesand allowed to deliver litters. Live pups were counted and weighedsoon after birth on Postnatal Day (PD) 0 and again on PD 3,9, and 14. Proven fertile males were treated 5 days/week for9 weeks with 0, 0.30, 0.73, 1.15, or 1.80 ml mDET /kg/day fora male dose-finding study. Each group consisted of 20 males.No males survived the 1.80 ml/kg/day. Deaths occurred in allremaining dose groups except the 0.30 ml/kg/ day and controlgroup. Immediately following the final treatment of the maledose study, 11 males were randomly selected from the 0.30 and0.73 ml/kg/day groups. They were cohabited for 7 days with 4females per male during post-treatment Weeks 1 and 2. Half ofthe females were euthanized 12–14 days after the lastday of cohabitation for a dominant lethal study; the remainingfemales were singly housed in nesting boxes and allowed to deliverlitters. Live pups were counted and weighed on PD 0 and 3. Therewas no evidence of reproductive or developmental toxicity inany of these assays, but there were signs of neuro-toxicityin treated adult male and female rats, which may relate to reportsof neurotoxicity in humans heavily exposed to mDET -containinginsect repellents, o 1992 society of Toxicology.