Seasonal differences of organophosphate flame retardants (OPEs) in dust from plastic sports courts in Beijing, China, and implications for human exposure

Organophosphate flame retardants (OPEs) are a kind of artificial chemicals widely added to plastic materials, and are mainly used as flame retardant and plasticizer used in a variety of consumer products, such as plastics, electronic products, foams, building materials, and textiles. Generally, the plastic tracks and artificial lawns in plastic sports courts are made in part from synthetic rubber which contain OPEs. Given that OPEs are incorporated into materials through physical addition rather than chemical bonding, thus OPEs can be easily released into the environment through volatilization, abrasion, and leaching, which then posed continuously exposure to human being and might lead to potential health risks. As such, it is urgently needed to understand the pollution characteristics, sources and health risk of human exposure to OPEs in plastic sports courts. Unfortunately, to date, no report is available on the exposure profiles and human exposure assessment of OPEs in plastic sports courts. In the present study, the residue concentrations of 14 OPEs were investigated in 97 dust samples from indoor and outdoor plastic playgrounds in Beijing, China, using high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). Distribution profiles of OPEs in different types of plastic sports courts (plastic track, plastic basketball court, plastic tennis court, artificial turf, and plastic badminton court) were also explored. Furthermore, the health risk of OPEs is estimated using the risk assessment method recommended by Environmental Protection Agency. The main objective of this study was to determine the occurrence and distribution patterns of OPEs in dust from plastic sports courts, to investigate the important factors involved in the distribution profiles of OPEs, and to provide a comparative analysis of human exposure to OPEs among different population groups. The results show that the Sigma 14OPEs in indoor dust are higher than that in outdoors, moreover, the Sigma 14OPEs in summer are higher than that in winter. The Sigma 14OPEs ranged from 12900-47200 ng/g and 283-38800 ng/g in indoor and outdoor plastic sports courts, respectively. TEHP is the most abundant OPEs in indoor plastic sports courts, while TCEP and TCPP are the most abundant monomers in outdoor plastic sports courts. Furthermore, the distribution of different OPEs monomers in dust samples showed obvious seasonal variation, suggesting that the occurrence characteristics of OPEs were closely related to the ambient temperature and their physical and chemical properties including the vapor pressure. Importantly, skin absorption is considered as the main pathway for young people to intake OPEs, while inhalation is estimated as the main exposure pathway of OPEs for children. The estimated daily intakes (EDI) of OPEs via inhalation and skin absorption for the youth and children were evaluated under two exposure scenarios: Average and high-end exposure. Correspondingly, the high-end exposure to OPEs in outdoor plastic sports courts showed a similar exposure mode as that of the average exposure. The estimated high-end exposure to OPEs was as high as 4010 and 3365 pg/(kg bw d) for youth and children, respectively. While, the average exposure to OPEs was 2505 and 1130 pg/(kg bw d) for youth and children, respectively. The estimated high-end exposure to OPEs in indoor plastic sports courts was up to 12239 and 10500 pg/(kg bw d) for youth and children, and the average exposure to OPEs was 7550 and 3510 pg/(kg bw d) for youth and children, respectively. However, the calculated EDIs of OPEs in all the population groups are lower than the proposed reference dose (RfD), indicating that the current dust exposure to OPEs in indoor and outdoor plastic sports courts would not cause any human health risks.