Those in the highest tertiary of urinary 2,5-dichlorophenol concentration had a significantly higher probability of taking a prescription medication for asthma-related wheezing (P=0.02) than those in the second or lowest tertiaries, Elina Jerschow, MD, of Albert Einstein College of Medicine in Bronx, N.Y., and colleagues reported at the American Academy of Allergy, Asthma, and Immunology annual meeting in San Antonio.
Furthermore, patients in all but the lowest tertiary of 2,4-dichlorophenol concentrations were also significantly more likely to miss work days due to wheezing (P<0.001).
Although the association between atopy and phenols — which are used in bactericidal agents, herbicides, insecticides and pesticides worldwide — is known, the relationship between these chemicals and asthma is not.
So Jerschow and colleagues analyzed phenol concentrations, asthma medication use and serum immunoglobulin E (IgE) levels in 159 atopic individuals aged 6 years and older who participated in the National Health and Nutrition Examination Survey (NHANES) in 2005-2006 and 114 control participants who were not atopic.
Patients were then grouped by on low, medium or high urinary phenol concentrations and assessed for outcomes including self-reported asthma, wheezing in the past year, prescriptions for wheezing medications, missed work or school days due to wheezing, and wheezing during exercise.
After multivariable adjustments, total IgE levels were positively associated with urine 2,5-dichlorophenol and 2,4-dichlorophenol levels (P values=0.02 and 0.04, respectively) but not with ortho-phenylphenol, 2,4,5-trichlorophenol, or 2,4,6-trichlorophenol.
Atopic participants with the highest concentrations of urinary 2,5-dichlorophenol had greater than two-fold odds of taking prescription drugs for wheezing (OR=2.25; 95% CI: 1.07-4.73, P=0.02) and were more than 10 times more likely to miss work or school due to wheezing (OR=10.13; 95% CI: 3.98-25.80, P<0.001) than those who were not atopic.
“Excessive use of chlorophenols may contribute to atopy and an increase in asthma medications,” the researchers concluded.
They acknowledged these associations between phenols and asthma do not establish causation, and added that further studies are needed to confirm the finding.