Dioxins linked with behavioral disorders
Two clinically significant behavioral disorders, namely learning disabilities and attention deficit disorder, have been linked with low or average blood serum concentrations of two dioxins and one furan. Researchers say these are the first indicators of a connection between such levels of persistent organic pollutants and diagnosed behavioral problems in children in the general population. Previous work has shown a correlation between these chemicals and reductions in cognitive function indicators. The findings, by Duk-Hee Lee with Kyungpook National University School of Medicine (South Korea) and colleagues from Spain and the U.S., were published in the Journal of Epidemiology and Community Health (2007, 61, 591–596).
The team discovered the link after reviewing 1999–2000 data for seven polychlorinated compounds as well as lead and cadmium from the U.S. Centers for Disease Control and Prevention's (CDC's) National Health and Nutrition Examination Survey. In 278 children aged 12–15, those who had detectable concentrations of three of the polychlorinated compounds were about 2–3 times as likely as those without detectable concentrations to report that they had been diagnosed with a learning disability. The researchers also found that exposure to two of those three compounds was linked with reports of a diagnosis of attention deficit disorder. The affected children tended to be white and to have mothers who were younger and smoked during pregnancy.
The tested concentrations of the three implicated compounds—1,2,3,4,6,7,8-heptachlorodibenzo-p-dioxin (HPCDD); 1,2,3,4,6,7,8,9-octachlorodibenzo-p-dioxin(OCDD); and 1,2,3,4,6,7,8-heptachlorodibenzofuran (HPCDF)—were in the middle or lower end of the concentration ranges in the CDC's Third National Report on Human Exposure to Environmental Chemicals.
These compounds usually are generated by certain chlorination, manufacturing, or incineration processes. Human exposures largely occur via breast milk or contaminated meat, milk, eggs, or fish.
The researchers acknowledge that limitations of the study preclude firm conclusions about the cause–effect relationships of these substances and behavioral disorders. However, they say that their research—including the discovery that these results would not have been predicted by using accepted toxic equivalency factors—adds to the growing knowledge and uncertainties about the neurotoxic effects of dioxins and furans.
