By now, most of us have heard of PCBs. Polychlorinated biphenyls, or PCBs, are man made chemicals. The chemicals were widely used in industry for decades. In 1976, the federal government in the US banned the production of the chemicals.
However, there is still significant contamination of PCBs in the environment. This is largely due to contamination resulting from improper disposal of the chemicals. PCBs have been found in newborn babies and breastmilk, over thirty years after the chemicals were banned.
One of the problems with PCBs is they are not soluble in water. This results in a process known as bioaccumulation. They bind to sediment at the bottom of rivers and are eaten by small fish. These fish hold the chemicals in their tissues and are eaten by larger fish, birds and people. The accumulation up the food chain results in high levels in organisms higher on the food chain, including people.
The result can be high levels of PCBs in the bodies of pregnant women. When high levels of PCBs are present, problems such as reduced IQ and developmental disorders can occur in the babies. Over a lifetime, problems ranging from skin conditions to cancer are the result of repeated exposure.
Researchers have discovered another possible effect of exposure to PCBs, a higher rate of giving birth to female children. A study published in the Journal of Environmental Health studied women in the San Francisco Bay area who were exposed to high levels of PCBs in the 1950s and 1960s. These women were found to have a much greater chance of having female children.
The women in the study who were exposed to PCBs were found to be 33 percent less likely to have male children, compared to women not exposed to the chemicals. The higher the levels of PCBs in the blood, the greater the chance the woman had a female child.
Researchers aren’t sure why there appears to be a connection. There are several theories. One is that high levels of PCBs may increase fertilization rates for female sperm. Another theory is the presence of high levels of PCBs may result in a higher risk of loss of male embryos, resulting in more female live births. Further research is planned in this area.
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