Mixed “anti-androgenic” chemicals at low individual doses produce reproductive tract malformations in the male rat

• Published in: Toxicological sciences 2018-07, Vol.164 (1), p.166-178
• Main Authors: Conley, Justin M., Lambright, Christy S., Evans, Nicki, Cardon, Mary, Furr, Johnathan, Wilson, Vickie S., Gray, L. Earl
• Format: Article
• Language: English
• ISSN: 1096-6080; 1096-0929
• DOI: 10.1093/toxsci/kfy069

Biomonitoring efforts have clearly shown that all humans are exposed to chemical mixtures. Of concern is whether or not exposure to mixtures during pregnancy contributes to congenital abnormalities in children even when each chemical is at an individual dose that does not affect the fetus. Here, we hypothesized that in utero exposure to a mixture of chemicals covering multiple “anti-androgenic” mechanisms of action at doses that individually have no adverse effect would result in permanent reproductive tract alterations in the male rat after birth. Pregnant dams were exposed to a range of dilutions (100, 50, 25, 12.5, 6.25%, or vehicle control) of a mixture containing pesticides, phthalates and drugs (p,p’-DDE, linuron, prochloraz, procymidone, pyrifluquinazon, vinclozolin, finasteride, flutamide, simvastatin, and 9 phthalates (dipentyl, dicyclohexyl, di-2-ethylhexyl, dibutyl, benzyl butyl, diisobutyl, diisoheptyl, dihexyl, and diheptyl)). The top dose contained each chemical at 20% of its lowest observed adverse effect level (LOAEL) for the most sensitive male reproductive alteration following in utero exposure. We found that male rat offspring displayed a variety of neonatal, pubertal, and permanent adult effects across all dose levels. Even at the lowest dose (each chemical ~80-fold below LOAEL) there were permanent reductions in several reproductive tract tissue weights. In the top dose group, 100% of male offspring displayed permanent severe birth defects including genital malformations. Despite acting via 5 different molecular initiating events, a mixture of 18 chemicals can combine to produce additive effects even when each compound is at is at a relatively low dose.