A global review of PCBs and halogenated flame retardants in indoor Air: Implication for human exposure risks

Polychlorinated biphenyls (PCBs) and several halogenated flame retardants (HFRs) are chemicals of high environmental and human health concerns. Accidental indoor dust-ingestion and dietary intake currently account for the primary human exposure pathways. There is however increasing evidence of the importance of inhalation exposure to these chemicals. Fifty-four relevant documents, sourced from Scopus, Web of Science, PubMed® and Google Scholar core databases, were studied to: understand the current global levels of PCBs and HFRs in indoor air; deduce the present risk of inhalation exposure and examine the current emission factors. Concentrations are likely underestimated for few studies due to misapplication of passive sampling rates. High concentrations were reported in several locations globally with emerging flame retardant concentration reaching 42,000 pg/m³ in Turkiye. Specific concentration order cannot be pinned to microenvironments as concentrations vary with emission sources, indoor activities, building characteristics and air-exchange. The air profile is frequently dominated with PCB-28, PCB-52, BDE-209, BDE-47, BDE-99, DBE-DBCH, DBDPE, EH-TBB and DDC-CO with factors primarily related to dominant applications and volatilization properties. No major regional difference was observed in the air profile. In few instances, inhalation exposure compared well with that of dietary and accidental ingestion and needs to be routinely considered in the overall human exposure risk assessment, particularly from a large data set. In view of the increasing detection of more volatile compounds in indoor environment, specific global or regional inhalation reference dose will be required for robust human exposure risk assessment.