Size fraction effect on phthalate esters accumulation, bioaccessibility and in vitro cytotoxicity of indoor/outdoor dust, and risk assessment of human exposure

Indoor and outdoor dusts from two urban centers in the Pearl River Delta, China, were analyzed and phthalate esters varied from 4.95 to 2220μgg^-1 in indoor dust, significantly higher than outdoor dust (1.70-869μgg^-1). Di-2-ethylhexyl phthalate (DEHP) was the dominant phthalate found and the highest distribution factor (DF) (1.56±0.41) was noted in the <63μm fraction (p<0.05). In vitro cytotoxicity of dust extract on human T cell lymphoblast leukemic cell line (CCRF-CEM) indicated by Lethal Concentration 50 (LC₅₀) decreased with particle size. The power model was found as a better fit for explaining the relationship between LC₅₀ and phthalates (R²=0.46, p<0.01). Bioaccessibility of phthalates in dust varied with different particle sizes, with the greatest bioaccessible fraction (2.49-38.6%) obtained in <63μm. Risk assessment indicated that indoor dust ingestion accounted for the major source for DEHP exposure (81.4-96.4% of non-dietary exposure and 36.5% of total exposure), especially for toddlers. The cancer risks associated with DEHP via home dust were high (10^-6-10^-4), with 10% of houses estimated with unacceptable risks (>10^-4). After corrected with the bioaccessibility of phthalates, the cancer risks of dust exposure were moderate (10^-7-10^-5).