Urinary concentrations of dichlorophenol pesticides and obesity among adult participants in the U.S. National Health and Nutrition Examination Survey (NHANES) 2005–2008

Accumulating evidence from recent studies has suggested a possible link between exposure to environmental pesticides and obesity. In this study, we assessed the potential associations between exposure to dichlorophenol pesticides and obesity in adults. Study participants aged 20–85 years were selected from the 2005 to 2006 and 2007 to 2008 U.S. National Health and Nutrition Examination Survey, and were categorized as obese and non-obese based on body mass index. Creatinine-corrected urinary concentrations of dichlorophenols were determined to assess level of exposure to environmental pesticides. Multivariate logistic regression was performed using SAS 9.3 to assess the association between 2,4-dichlorophenol (2,4-DCP) and 2,5-dichlorophenol (2,5-DCP) levels in urine and obesity with adjustment for potential confounders. Significantly higher geometric means of urinary concentrations of both 2,5-DCP (p < 0.0001) and 2,4-DCP (p = 0.0170) were seen in obese adults, compared to that in non-obese adults. A dose-dependent increase in the prevalence of obesity was observed in the study participants across increasing levels of urinary 2,5-DCP (p-trend < 0.0001). Urinary concentrations of 2,5-DCP were significantly associated with obesity among the second (AOR: 1.47, 95% CI: 1.12, 1.93), third (AOR: 1.41, 95% CI: 1.07, 1.87), and fourth (AOR: 1.62, 95% CI: 1.21, 2.17) inter-quartiles after adjustment for age, gender, race, education, total fat intake, and physical activity. A statistically significant association was not seen between urinary 2,4-DCP and obesity. Our findings suggest a potential relationship between exposure to the fumigant insecticide paradichlorobenzene, measured as urinary concentrations of 2,5-DCP, and obesity in adults. Because we cannot rule out the possibility of reverse causality in our study, prospective studies measuring exposure during etiologically relevant periods are warranted.