The dust on indoor and outdoor surfaces of the window glasses were collected using sterile cotton balls in 11 cities. Twenty-nine per uoroalkyl acids (PFAAs) were quanti ed to investigate concentration, composition and toddlers' exposure. The concentrations of ∑PFAA ranged from no detection (nd) to 43 ng/m 2 (mean 8.9 ± 10 ng/m 2 ). Per uorobutanoic acid (PFBA) was detected in 78% samples, and accounted for 55% ± 21% of ∑PFAA concentrations. 6:2 Fluorotelomer sulfonic acid (6:2 FTSA) and hexa uoropropylene oxide dimer acid (HFPO-DA) were detected in more than 50% samples indicating the use of alternatives. Fluorotelomer carboxylic acid (FTCA) and uorotelomer unsaturated acid (FTUCA) were found in the dust, implying the degradation of precursors. The highest concentration of ∑PFAA (43 ng/m 2 ) was found in outdoor dust from Xinzhou, Shanxi Province, which is famous for its coal resources. Higher ∑PFAA concentrations were found in indoor dust than outdoor in 6 paired samples (3 from Feb. 14 and 3 from Feb. 21). In Tianjin and Handan, the concentrations of ∑PFAA from outdoor surfaces were higher in sampling campaign I (SC I, Feb. 21) than in sampling campaign II (SC II, Feb. 14), implying intensive outdoor release. The exposure of 2 year-old toddlers to PFAA via hand-to-mouth ingestion and dermal absorption was estimated; the mean values of intake were 2.1 and 1.5 pg/kg body weight, respectively, assuming an exposure time of 1 hour.

The dust on indoor and outdoor surfaces of the window glasses were collected using sterile cotton balls in 11 cities. Twenty-nine perfluoroalkyl acids (PFAAs) were quantified to investigate concentration, composition and toddlers’ exposure. The concentrations of ∑PFAA ranged from no detection (nd) to 43 ng/m2 (mean 8.9 ± 10 ng/m2). Perfluorobutanoic acid (PFBA) was detected in 78% samples, and accounted for 55% ± 21% of ∑PFAA concentrations. 6:2 Fluorotelomer sulfonic acid (6:2 FTSA) and hexafluoropropylene oxide dimer acid (HFPO-DA) were detected in more than 50% samples indicating the use of alternatives. Fluorotelomer carboxylic acid (FTCA) and fluorotelomer unsaturated acid (FTUCA) were found in the dust, implying the degradation of precursors. The highest concentration of ∑PFAA (43 ng/m2) was found in outdoor dust from Xinzhou, Shanxi Province, which is famous for its coal resources. Higher ∑PFAA concentrations were found in indoor dust than outdoor in 6 paired samples (3 from Feb. 14 and 3 from Feb. 21). In Tianjin and Handan, the concentrations of ∑PFAA from outdoor surfaces were higher in sampling campaign I (SC I, Feb. 21) than in sampling campaign II (SC II, Feb. 14), implying intensive outdoor release. The exposure of 2 year-old toddlers to PFAA via hand-to-mouth ingestion and dermal absorption was estimated; the mean values of intake were 2.1 and 1.5 pg/kg body weight, respectively, assuming an exposure time of 1 hour.