The EHP gives warning that environmental chemicals (EDCs) may have dangerous effects on reproduction for several generations

The scientific journal Environmental Health Perspectives (EHP) reports that chemicals, such as the endocrine disrupting chemicals (EDCs), have relevant reproductive effects that may persist for four generations. Transgenerational effects from the fourth generation onwards can be definitely linked to epigenetic changes (which are heritable changes marking the DNA, but not the DNA sequence itself). The EHP reports that such transgenerational effects have been found for a variety of EDCs.

In recent years there has been an explosion in studies showing transgenerational effects from exposure to a wide array of environmental stressors, as chemicals. First evidences were spotted at the Washington State University, where it has been discovered that a particular insecticide – called methoxuclor – affects sex determination in embryonical animals. This finding helped to reevaluate environmental health threats perception. 

Chemicals that are under indictment for transgenerational effects are: permethrin, DEET, bisphenol A, certain phthalates, dioxin, jet fuel mixtures, nicotine, and tributyltin, among others. Although these findings come from rodent studies, worries of possible negative effects on human reproduction arise immediately.

Despite the fact that the way in which environmental exposures causes transgenerational effects remain unclear, current hypothesis focuses on epigenetic inheritance patterns, which involve chemical modifications to the DNA rather than mutations of the DNA sequence itself.

Researchers have found that transgenerational effects can result from chemical dosing at precise windows in fetal development, especially around embryonic days 10.5–12.5 – which is the time for sexual determination.

Experiments and observation on rats show an impressive decrease in sperm production and motility caused by pesticides, and that prenatal exposure to nicotine may cause asthma-like symptoms. Suspicious examples like these are numerous. 

In humans the evidence for environmentally induced multigenerational effects began to emerge years ago from an isolated community in Northern Sweden. Researchers investigated whether an abundance of food in childhood had any influence on the risk of heart disease and diabetes among a child’s future descendants. An initial study published suggested the answer was a conditional yes.

Many other studies followed, letting emerge epigenetic evidences in humans. The growing evidence on environmental exposures might open new questions about where human evolution is headed, as humans are all combinations of what they inherit and what they are exposed to during their whole lives.