Measurement and health risk assessment of PM2.5, flame retardants, carbonyls and black carbon in indoor and outdoor air in kindergartens in Hong Kong.

Indoor air pollution is closely related to children's health. Polybrominated diphenyl ethers (PBDEs) and dechlorane plus (DP) transmitted through indoor PM2.5 and dust, along with carbonyl compounds and black carbon (BC) aerosol were analysed in five Hong Kong kindergartens. The results showed that 60% of the median PM2.5 levels (1.3×101 to 2.9×101µg/m3 for indoor; 9.5 to 8.8×101µg/m3 for outdoor) in the five kindergartens were higher than the guidelines set by the World Health Organization (2.5×101µg/m3). Indoor PM2.5 mass concentrations were correlated with outdoor PM2.5 in four of the kindergartens. The PBDEs (0.10-0.64ng/m3 in PM2.5; 0.30-2.0×102ng/g in dust) and DP (0.05-0.10ng/m3 in PM2.5; 1.3-8.7ng/g in dust) were detected in 100% of the PM2.5 and dust samples. Fire retardant levels in the air were not correlated with the levels of dust in this study. The median BC concentrations varied by >7-fold from 8.8×102ng/m-3 to 6.7×103ng/m-3 and cooking events might have caused BC concentrations to rise both indoors and outdoors. The total concentrations of 16 carbonyls ranged from 4.7×101µg/m3 to 9.3×101µg/m3 indoors and from 1.9×101µg/m3 to 4.3×101µg/m3 outdoors, whilst formaldehyde was the most abundant air carbonyl. Indoor carbonyl concentrations were correlated with outdoor carbonyls in three kindergartens. The health risk assessment showed that hazard indexes (HIs) HIs of non-cancer risks from PBDEs and DPs were all lower than 0.08, whilst non-cancer HIs of carbonyl compounds ranged from 0.77 to 1.85 indoors and from 0.50 to 0.97 outdoors. The human intake of PBDEs and DP through inhalation of PM2.5 accounted for 78% to 92% of the total intake. The cancer hazard quotients (HQs) of formaldehyde ranged from 4.5E-05 to 2.1E-04 indoors and from 1.9E-05 to 6.2E-05 outdoors. In general, the indoor air pollution in the five Hong Kong kindergartens might present adverse effects to children, although different schools showed distinct pollution levels, so indoor air quality might be improved through artificial measures. The data will be useful to developing a feasible management protocol for indoor environments.