There is evidence that DDT causes teratogenic effects in test animals as well. In mice, maternal doses of 26 mg/kg/day DDT from gestation through lactation resulted in impaired learning performance in maze tests. In a twogenerational study of rats, 10 mg/kg per day resulted in abnormal tail development. Epidemiological evidence regarding the occurance of teratogenic effects as a result of DDT exposure are unavailable. It seems unlikely that teratogenic effects will occur in humans due to DDT at likely exposure levels.
The evidence for mutagenicity and genotoxicity is contradictory. In only 1 out of 11 mutagenicity assays in various cell cultures and organisms did DDT show positive results. Results of in vitro and in vivo genotoxocity assays for chromosomal aberrations indicated that DDT was genotoxic in 8 out of 12 cases, and weakly genotoxic in 1 case. In humans, blood cell cultures of men occupationally exposed to DDT showed an increase in chromosomal damage. In a separate study, significant increases in chromosomal damage were reported in workers who had direct and indirect occupational exposure to DDT. Thus it appears that DDT may have the potential to cause genotoxic effects in humans, but does not appear to be strongly mutagenic. It is unclear whether these effects may occur at exposure levels likely to be encountered by most people.
The potential association between DDT (and DDT derivatives) and reproductive end points has been examined in numerous studies. The effects on reproduction in animals include decreased fertility and abortions, and stillbirths. In multigeneration studies in rodents, DDT decreased fertility and gonadal weights, decreased the number of implantations, decreased litter size, increased the length of the estrous cycle, increased the rate of embryo mortality, and increased the length of gestation. According to Laug et al., in a threegeneration study in rats, the mortality rate of offspring increased at all doses, the lowest of which corresponded to about 0.2 mg/kg body weight per day. Three other studies in rats and mice showed that at higher doses (16.5 mg/kg body weight per day) there were no effects on reproduction.
The effects on development observed pre or postnatally after DDT treatment that may be related to estrogenicity include embryolethality, decreased fetal growth and prematurity in rabbits and dogs fed diets providing a dose of 5 mg/kg body weight per day, and decreased ovarian weights, cystic ovaries, loss of corpora lutea, infertility, premature puberty, altered onset of vaginal opening, tail anomalies, and increased pup mortality rates in rodents. The lowest relevant NOAEL (No Observed Adverse Effect Level) for developmental effects was reported to be 1 mg/kg body weight per day in rats.