Occurrence and exposure evaluation of perchlorate in outdoor dust and soil in mainland China

A total of 98 paired soil and outdoor dust samples were collected across mainland China for survey of perchlorate. Perchlorate was detected in all of the soil and outdoor dust samples. High levels of perchlorate were found in soil, ranging from 0.001 to 216 mg/kg in Northern China and from 0.001 to 25.8 mg/kg in Southern China. Even higher perchlorate concentrations were detected in dust samples, with concentrations ranging from 0.132 to 5,300 mg/kg in Northern China, and from 0.270 to 3,700 mg/kg in Southern China. This is the first known report of perchlorate in dust samples. The high perchlorate levels in soil and dust may raise concern on the potential risk for organisms and human. The daily perchlorate intakes were evaluated based on our measured perchlorate concentrations via inhalation, ingestion, and dermal contact of soil and dust for both children and adults, respectively. In general, the exposure from soil does not appear to lead to perchlorate intakes exceeding the US EPA reference for both children and adults. However, children can be at risk from exposure to perchlorate via dust, and it needs considerable concern for both children and adults at the sites with high dust perchlorate concentrations. After comparison with other possible exposure pathways, such as from drinking water, we suggested that dust may be an important potential source of perchlorate exposure in China, and further study is needed, especially for indoor dust.