The Epigenetic Consequences of Paternal Exposure to Environmental Contaminants and Reproductive Toxicants

Human populations are exposed to a wide spectrum of environmental contaminants, some of which are considered reproductive toxins. The influence of such toxins on the male reproductive system has been investigated extensively in animal models, while epidemiological studies seek to understand the effect of human exposures. The basic tenant of epidemiological studies in male human reproduction is to infer how one or more substances alter the hormonal profile, seminal characteristics, or both. Determining if a substance alters semen quality may not always provide the underlying mechanism. The mechanisms by which toxins may alter human sperm and semen quality are typically examined as a function of hormonal changes and cellular damage. The possibility that more subtle epigenetic alterations underlie some of the reproductive changes has, until recently, received little attention. In this review, we discuss the roles of epigenetics in human spermatogenesis, while considering the impact of reproductive toxicants on the epigenome.