Affects of Cause and Effect

24 April 2009

by Emily Russell and Laura Williams

It has long been known that polychlorinated biphenyls (PCBs) have the potential to affect developing children in adverse ways, and especially their brain development. PCBs have been banned in the United States since 1979. They were used in transformers, pesticides, and fire retardants, among other things. They are persistent in the environment because they do not dissolve in water, and they accumulate in the fatty tissues of animals. Human exposure occurs through groundwater contamination and through eating fish exposed to PCBs.

Now, in a series of just-released studies conducted by University of California-Davis researchers, solid evidence exists for the mechanism in which PCBs contribute to neurodevelopmental and behavioral disorders in children. Pamela Lein, an associate professor in the Department of Molecular Biosciences at the UC Davis School of Veterinary Medicine, said “The problem is that it has been difficult to establish a cause-and-effect relationship from the human epidemiological literature without a known mechanism.”

But wait, even without knowing the exact mechanism of action, the effects of PCBs have been known for decades. Even the EPA states in a Hazard Summary of PCBs back in 1992: “Epidemiological studies indicate an association between dietary PCB exposures and developmental effects.” Shortly thereafter, published in The New England Journal of Medicine in 1996, a study conducted by Wayne State University psychologists tracked the impact of mothers’ exposure to PCBs on their children. Mothers who ate salmon and lake trout from Lake Michigan a few times a month for six years prior to giving birth had children with lower IQs, poorer reading comprehension, and greater memory problems.

These recent studies have shown that small, chronic doses of PCBs were more detrimental to overall human health than large, acute doses of PCBs, which the body can recognize as harmful and thus, will excrete. For this reason, the US government needs to take a more active, precautionary approach to cleaning up languishing toxic waste sites. These sites persistently release chemicals like PCBs that contaminate the natural resources that we depend on for our everyday survival. The UC-Davis studies merely contribute to medical understanding of PCBs and how to treat PCB exposure; governmental understanding of the consequences of toxic exposures is the greater issue at hand. Is it sensible for the government to wait on hard scientific data to formulate our environmental policies before it decides that a contamination issue is worth addressing? Environmentalists have long asked this question. How soon before we act on effects and not causes?