^aDivision of Laboratory Sciences, National Center for Environmental Health, Centers for Disease Control and Prevention, Atlanta, GA, USA

Correspondence: Dr Benjamin C. Blount, Division of Laboratory Sciences, National Center for Environmental Health, CDC, 4770 Buford Highway, NE, Mail Stop F47, Atlanta, GA 30341, USA. Tel.: +1 770 488 7894. Fax: +1 770 488 0181. E-mail: bkb3@cdc.gov

¹The findings and conclusions in this report are those of the authors and do not necessarily represent the views of the Centers for Disease Control and Prevention

Received 10 July 2006; Accepted 18 September 2006; Published online 18 October 2006.

Abstract

Perchlorate is commonly found in the environment and can impair thyroid function at pharmacological doses. As a result of the potential for widespread human exposure to this biologically active chemical, we assessed perchlorate exposure in a nationally representative population of 2820 US residents, ages 6 years and older, during 2001 and 2002 as part of the National Health and Nutrition Examination Survey (NHANES). We found detectable levels of perchlorate (>0.05 g/l) in all 2820 urine samples tested, indicating widespread human exposure to perchlorate. Urinary perchlorate levels were distributed in a log normal fashion with a median of 3.6 g/l (3.38 g/g creatinine) and a 95th percentile of 14 g/l (12.7 g/g creatinine). When geometric means of urinary perchlorate levels were adjusted for age, fasting, sex and race-ethnicity, we found significantly higher levels of urinary perchlorate in children compared with adolescents and adults. We estimated total daily perchlorate dose for each adult (ages 20 years and older), based on urinary perchlorate, urinary creatinine concentration and physiological parameters predictive of creatinine excretion rate. The 95th percentile of the distribution of estimated daily perchlorate doses in the adult population was 0.234 g/kg-day [CI 0.202–0.268 g/kg-day] and is below the EPA reference dose (0.7 g/kg-day), a dose estimated to be without appreciable risk of adverse effects during a lifetime of exposure. These data provide the first population-based assessment of the magnitude and prevalence of perchlorate exposure in the US.