Occurrence of liquid crystal monomers in indoor and outdoor air particle matters (PM): Implications for human exposure indoors.

Liquid crystal monomers (LCMs) are potentially persistent, bioaccumulating, and toxic substances. However, limited data are available on the occurrence of LCMs in indoor and outdoor air particle matter (PM) in residential areas. Herein, residential areas near an e-waste dismantling center (Guiyu Town, Shantou City), as well as areas away from the e-waste site (Jiedong District, Jieyang City) were selected as the sampling areas. PM was collected from the indoor environments of Guiyu (IGY) and Jieyang (IJY), as well as those from the outdoor environments (OGY and OJY) using the high-volume air samplers (TH-10000C). The levels of 57 LCMs in PM were analyzed, and the highest concentrations of LCMs were found in IGY (0.970-1080 pg/m), followed by IJY (2.853-455 pg/m), OGY (0.544-116 pg/m) and OJY (0.258-35.8 pg/m). No significant difference was observed for LCM levels in indoor PM between the two areas (p > 0.05), which were significantly higher than those in outdoors (p < 0.05), indicating that the release of electronic products in general indoor environments is a source of LCMs that cannot be ignored. The compositions of LCMs in outdoors were not consistent with those of indoors. The correlation analysis of individual LCMs suggested potential different sources to the LCMs in indoor and outdoor environments. The median daily intake values of ΣLCMs via inhalation were estimated as 0.440, 1.46 × 10, 0.170 and 1.19 × 10 ng/kg BW/day for adults, and as 2.27, 2.60 × 10, 0.880 and 2.10 × 10 ng/kg BW/day for toddlers, respectively, indicating much higher exposure doses of LCMs indoors compared with the outdoors, and much higher doses for toddlers compared with adults (p < 0.05). These results reveal the potentially adverse effects of LCMs on vulnerable populations, such as toddlers, in indoor environments.