Sources and Pathways of Human Exposure to Perchlorate in the United States: A Comparison of Environmental Monitoring and Biomonitoring Approaches

Abstract

Perchlorate is an ubiquitous environmental pollutant and a known thyroid hormone disruptor. Little is known about the sources and pathways of human exposure to perchlorate. We measured perchlorate in drinking water, foodstuffs, indoor dust and urine collected from various locations in the United States, with a vast majority of them collected in New York State. The highest concentration of perchlorate was found in indoor dust, at a geometric mean (GM) concentration of 280 ng/g, followed by foodstuffs including beverages (1.77 ng/g) and drinking water (0.09 ng/mL). Among nine categories of foodstuffs analyzed, notable perchlorate concentrations as high as 839 ng/g were found in vegetables. The estimated average perchlorate exposure dose for adults from various sources was 141 ng/kg body weight (BW)/day. Previously reported perchlorate concentrations in breast milk from the United States in 2007 were used for the estimation of exposure doses in infants, and were 1580, 1230, and 1010 ng/kg BW/day for 0–3, 3–6, and 6–12 months of age, all of which exceeded the United States Environmental Protection Agency’s (EPA) chronic reference dose (700 ng/kg BW/day). Breastfeeding was the dominant exposure pathway accounting for >90% of perchlorate exposure among infants <1 year, whereas dairy products including milk, vegetables, and beverages were the dominant sources (73–83%) for age groups >1 year. Perchlorate was detected in all human urine collected from Albany, New York (N=31) at a GM concentration of 2.30 ng/mL. The GM perchlorate exposure doses calculated from urinary concentrations through a reverse dosimetry approach were 46.1 and 37.8 ng/kg BW/day for age groups 16–21 and >21 years, respectively, which were similar to those calculated from external sources of exposure.

Note:
Funding declaration: The research reported here was supported, in part, by the US National Institute of Environmental Health Sciences (NIEHS) under award number U2CES026542 (KK).

Conflict of Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Ethics Approval Statement: The protocol for the analysis of human urine specimens was approved by the institutional review board of New York State Department of Health

Keywords: Perchlorate, Foodstuff, Indoor dust, Drinking water, Urine, Exposure assessment