Occurrence and seasonal variations of organophosphate flame retardants in air and dust from college microenvironments at Qingdao, China: Implications for student's exposure and risk assessment

Organophosphorus flame retardants (OPFRs) are widely used as alternatives to brominated flame retardants in a variety of consumer products and their consumption has continuously increased in recent years. However, their concentration and human exposure in indoor microenvironments, particularly in a college environment, have received limited attention. In this study, the concentration and seasonal variation of 15 OPFRs were assessed in microenvironments typical of college students, including dormitories, offices, public microenvironments (PMEs: classroom, dining hall, gymnasium and library), and laboratories in two universities on the northern coast of China. Analysis of the OPFRs in both air and dust samples indicated widespread distribution on college campuses. The concentration of OPFRs in the winter (12,774.4 ng/g and 5.3 ng/m3 for dust and air, respectively) was higher than in the summer (2460.4 g/g and 4.6 ng/m3 for dust and air, respectively). The dust and air samples collected from PMEs and laboratories exhibited higher concentrations of OPFRs, followed by offices and dormitories. An equilibrium was reached between dust and air in all collected microenvironments. TBOEP, TDCP, and TPHP were more likely to partition in dust, while TEP, TIPP, TCEP, and TCPP were more likely to be in the air. The daily intakes of OPFRs were significantly lower than the reference dose. Dust ingestion was the primary intake pathway in the winter, while inhalation and dust ingestion were the main intake pathways in the summer. The non-carcinogenic hazard quotients fell within the range of 10−7–10−3 in both the summer and winter, which are below the theoretical risk threshold. For the carcinogenic risk, the LCR values ranged from 10−10 to 10−8, indicating no elevated carcinogenic risk due to TnBP, TCEP, and TDCP in indoor dust and air.