Relationship between urine dichlorophenol levels and asthma morbidity

Background Chlorinated phenols are associated with atopic conditions, but it is not known whether they are associated with wheeze or asthma and whether atopy is involved in these associations. Objectives To test the association between urine levels of 2 dichlorophenols (2,4- and 2,5-dichlorophenols) and asthma morbidity in atopic and nonatopic wheezers and between total serum immunoglobulin E (IgE) levels. Methods Data from a sample of 2,125 participants at least 6 years old from the US National Health and Nutrition Examination Survey 2005 to 2006 were analyzed. Asthma morbidity data were available for those participants who reported wheezing in the past year ("wheezers"; n = 250). This subsample was categorized as atopic or nonatopic. Results Atopic wheezers with higher 2,5-dichlorophenol levels were more frequently diagnosed with asthma by a physician (odds ratio [OR] 4.7 for highest vs lowest tertile, P <.001), required more prescriptions for asthma medications (OR 2.2, P =.046), and reported more exercise-induced wheezing (OR 5.8, P =.045) than atopic wheezers with low dichlorophenol levels. Atopic wheezers with higher 2,5- or 2,4-dichloropheonol levels also were more likely to miss work or school because of wheezing (OR 10.0, P <.001; OR 11.4, P <.01, respectively). In contrast, in nonatopic wheezers, there were no significant associations between dichlorophenol levels and asthma morbidity measurements. The 2 dichlorophenol metabolites were positively associated with increased serum IgE levels in the larger study sample. Conclusion These findings indicate that in patients with atopy and a history of wheezing, asthma morbidity is associated with high urinary dichlorophenol levels. Increased urine dichlorophenol levels are associated with higher total serum IgE.