Men who are exposed to higher levels of polluting chemicals known as PCBs (Polychlorinated Biphenyls) are slightly more likely to father boys.
PCBs are endocrine disruptor chemicals that act like hormones. They and related to chemicals known as dioxins are reported to have caused deformities of sexual organs in fish and alligators. PCBs can come from many different industrial sources including hydraulic fluids and oils, electrical capacitors and transformers. In humans, both dioxins and PCBs can cause cancer, infertility and, perhaps, other sexual changes. It can cause a variety of illnesses, including cancer and birth defects, in their children.
The research that was carried out at the Michigan State University showed that human beings could be affected sexually by the chemicals, which cause sex-related defects in animals. The researchers used information from studies of men and women who were exposed to a wide range of pollutants and chemicals. They were recruited by the Michigan Department of Community Health. Their blood levels of PCBs and other chemicals were measured. The 101 families that were studied had children born after 1963, and both the parents had detectable PCBs in their blood. There were a total of 208 children. Of these, 57 percent were boys, which is slightly higher than the normal trend of about 51 percent. Usually, 105 boys are born for every 100 girls. However, they did not detect that the PCB levels of mothers affected the sex ratio.
A change in the proportion of boys to girls, however, indicates that environmental contaminants may play a role in human reproduction. Thus, paternal exposure was linked to a higher proportion of male offspring. However, they stressed that they worked with too few people and more work was required in this field.
Journal of Occupational and Environmental Medicine January 2002, Vol. 44 (1)