Association of serum concentrations of persistent organic pollutants with the prevalence of learning disability and attention deficit disorder.

OBJECTIVE: Even though persistent organic pollutants (POPs) are well-known neurotoxicants, there is no previous study, even cross-sectional, on the association between background exposure to POPs and clinically significant developmental disorders, such as learning disability (LD) or attention deficit disorder (ADD), among children from a general population.
DESIGN: Cross-sectional study.
SETTING: Study subjects were 278 children aged 12-15 years included in the National Health and Nutrition Examination Survey 1999-2000. The seven most commonly detected POPs (each detectable in >/=20% of children: 3,3',4,4',5-pentachlorobiphenyl; 1,2,3,4,6,7,8-heptachlorodibenzo-p-dioxin (HPCDD); 1,2,3,4,6,7,8,9-octachlorodibenzo-p-dioxin (OCDD); 1,2,3,4,6,7,8-heptachlorodibenzofuran (HPCDF); beta-hexachlorocyclohexane; p,p'-dichlorodiphenyltrichloroethane; and trans-nonachlor) were selected. MAIN
RESULTS: Compared with children with non-detectable levels of POPs, adjusted prevalence ORs (95% CIs) of LD among those with detectable levels of HPCDD, OCDD or HPCDF were 2.08 ( 1.17 to 3.68), 2.72 (1.24 to 5.99) and 2.18 (1.15 to 4.15), respectively. For ADD, the corresponding figures were 3.41 (1.08 to 10.8), 3.33 (0.94 to 11.8) and 2.31 (0.62 to 8.63), respectively.
CONCLUSIONS: Associations were observed between serum concentrations of POPs belonging to the categories of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans and the prevalence of two clinically significant development problems, LD and ADD. The nature of these associations needs to be clarified by prospective studies.