Variability in the levels of 3-phenoxybenzoic acid by age, gender, and race/ethnicity for the period of 2001–2002 versus 2009–2010 and its association with thyroid function among general US population

Data from National Health and Nutrition Examination Survey for the years 2007–2008 were used to evaluate the impact of the observed levels of 3-phenoxybenzoic acid (3-PBA) in urine on the levels of thyroid hormones in serum for those aged ≥12 years. There was no evidence of any association between the levels of 3-PBA and thyroid function. As compared to their levels in 2001–2002, levels of 3-PBA rose (p ≤ 0.03) in 2009–2010 for children, adolescents, adults aged 20–64 years, males, females, non-Hispanic whites, non-Hispanic blacks, Mexican Americans, non-smokers, and smokers. Rise in the levels of 3-PBA among children aged 6–11 years was higher than the similar rise in all other demographic groups. Since the levels of 3-PBA are still on the rise, previously observed adverse health effects among children associated with the levels of 3-PBA require that additional preventive measures be put in place to protect them from exposure to pyrethroids.