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.