What is the mechanism by which exposure to environmental toxins causes lifelong disabilities in children?
Much of the research so far has focused on exposure in utero, and via breast milk (or bottle milk), periods known for hypersensitivity to environmental exposures. There is increasing evidence, however, that toxin exposure also influences sperm quality.
A new study reported on in Science News (not linked since subscription only) shows that "exposure to dioxin as a child or teenager can permanently alter the reproductive system." A history of environmental toxin exposure may likewise be one important factor in the link between advanced paternal age and a variety of congenital conditions (e.g. autism).
Also, notable is the existence of "the decline of sperm quality recently seen in Western nations" reported to exist by a researcher connected with the dioxin study.
Another class of chemicals besides dioxins linked to poor sperm quality are phthalates, according to multiple articles in the May 2003 edition of the Journal Epidemiology.