Pesticides, Chlorinated Water May Lead to Food Allergies

Larry Hand

December 06, 2012

Widely used pesticides and chlorinated water may be contributing to an increasing incidence of food allergies in the United States, according to a study published in the December issue of the Annals of Allergy, Asthma, and Immunology.

Elina Jerschow, MD, from the Albert Einstein College of Medicine/Montefiore Medical Center, Bronx, New York, and colleagues analyzed the records of a subset of participants aged 6 years old and older who had urinary metabolites of chlorinated phenols and allergen-specific immunoglobulin E levels measured as part of the National Health and Nutrition Examination Survey (NHANES) 2005-2006.

In addition to the measurements, participants filled out a questionnaire about the use of pesticides during the previous 7 days. Specifically, the researchers sought to determine whether dichlorophenols (2.4-dichlorophenol and 2.5-dichlorophenol), used as common pesticides and in water chlorination, are associated with allergy sensitizations.

Of 10,348 NHANES participants, 2548 had both dichlorophenol urine testing and serum antigen-specific IgE testing. Of those, the researchers excluded 337 participants whose records were missing data, leaving a study population of 2211 (representing 232,512,264 US persons) for this analysis. The researchers found that 2182 participants had levels of 2.5-dichlorophenol above the detection limit (0.14 μg/L) and 2020 participants had levels of 2.4-dichlorophenol above the detection limit.

In unadjusted analysis, the researchers found that the presence of 1 or more dichlorophenol metabolites in urine "was significantly associated with sensitization to food and environmental allergens. Food but not environmental allergen sensitivity was positively associated with the use of home pesticides and urban living."

In multivariate analysis, after adjusting for age, sex, race, vitamin D levels, hay fever, asthma, urban or rural residence, and insecticide use, the researchers found a significant association between high levels of both dichlorophenol metabolites in urine and sensitization to food allergens (odds ratio [OR], 1.8; 95% confidence interval [CI], 1.2 - 2.5; P = .003). However, they found no significant associations between dichlorophenol exposure and environmental allergens or between the place of residence and sensitization to food or environmental allergens.

Further analysis showed associations between food allergen sensitization and male sex, low vitamin D levels, self-reported allergies, home use of insecticide, and non-Hispanic black ethnicity.

In a subanalysis of 1500 participants with likely inherited allergies, 358 of whom had both food and environmental allergies, the researchers found that high urine levels of both dichlorophenols were significantly associated with both food and environmental allergies (OR, 1.61; 95% CI, 1.2 - 2.2; P = .005).

"To our knowledge, this is the first study demonstrating an association between high dichlorophenol levels and allergic sensitization," the researchers write.

Limitations of the study include the inability to establish a causal relationship and the lack of inclusion of children younger than 6 years. Median age of participants was 37.2 years.

"Our research shows that high levels of dichlorophenol-containing pesticides can possibly weaken food tolerance in some people, causing food allergy," Dr. Jerschow said in a news release. "This chemical is commonly found in pesticides used by farmers and consumer insect and weed control products, as well as tap water."

She concluded, "Previous studies have shown that both food allergies and environmental pollution are increasing in the United States. The results of our study suggest these two trends might be linked, and that increased use of pesticides and other chemicals is associated with a higher prevalence of food allergies."

This research was supported in part by the National Center for Research Resources and the National Center for Advancing Translational Sciences. The authors have disclosed no relevant financial relationships.

Ann Allergy Asthma Immunol. 2012:109;420-425. Abstract