(Beyond Pesticides, July 28, 2009)
A new study by researchers at the National Food Institute, Technical University of Denmark shows that exposure to a mixture of pesticides and other chemicals has a synergistic effect on the development of male sex organs. Synergy occurs when the effect of multiple chemicals is greater than the sum of the individual effects. The study, “Synergistic Disruption of External Male Sex Organ Development by a Mixture of Four Antiandrogens,” was published July 15, 2009 in the online edition of Environmental Health Perspectives.
The researchers designed their study to determine the consequences of simultaneous exposure to multiple “antiandrogens.” An antiandrogen, or androgen antagonist, is any of a group of hormone receptor antagonist compounds that are capable of preventing or inhibiting the biologic effects of androgens, male sex hormones, on normally responsive tissues in the body. Disrupting the action of androgens during gestation, certain chemicals present in food, consumer products and the environment can induce irreversible malformations of sex organs among male offspring.
The team investigated the effects of mixtures of a widely used plasticizer, di(2-ethylhexyl) phthalate (DEHP), used in medical devices such as IV bags and tubing, beauty products, PVC toys, vinyl shower curtains, car seats, wallpaper and more; two fungicides present in food, vinclozolin and prochloraz; and, a pharmaceutical, finasteride, on landmarks of male sexual development in rats. These chemicals were chosen because they disrupt androgen action according to differing mechanisms of action.
According to the study results, combined exposure on malformations of external sex organs was synergistic, and the observed responses were greater than would be predicted from the toxicities of the individual chemicals. In relation to other hallmarks of disrupted male sexual development, including changes in anogenital distance, retained nipples, and sex organ weights, the combined effects were dose additive. When the four chemicals were combined at doses equal to no-observed-adverse effect levels estimated for nipple retention, significant reductions in anogenital distance were observed in male offspring.
The authors believe that current methods of chemical risk assessment “may lead to considerable underestimations of risks associated with exposures to chemicals that disrupt male sexual differentiation.”