Breathing hazards: Perspective on the adverse health effects of organophosphate flame retardants.

Since the 1970s, flame retardants have been applied to consumer and industrial products to prevent combustion and the spread of fires, with polybrominated diphenyl ethers (PBDEs) being the most prevalent. However, due to environmental and human health concerns, the use of PBDEs was phased out and nearly eliminated by the early 2000s. As a safer alternative to PBDEs, organophosphate flame retardants (OPFRs) were proposed as they were believed to have a shorter half-life and increased degradation rate compared to PBDEs. OPFRs are widely used in consumer products, including electronics, textiles, and car interiors. The dusts produced from product usage results in OPFR exposure through inhalation, ingestion, and dermal absorption. Despite dusts being a major exposure source, the effects of inhalation and subsequent effects on lung health remain understudied. A few studies have demonstrated lung inflammation and airway hyperresponsiveness as consequences of OPFR inhalation exposure and these findings are supported by studies. However, significant gaps remain in our understanding of OPFR exposure and the implications for public health. Conducting additional epidemiological studies, alongside studies and the development of PBPK/TK models, can significantly enhance the power of hazard assessment for inhalation exposure in humans. This review article discusses the sources and routes of exposure to OPFRs and their adverse health effects, emphasizing inhalation toxicology. Furthermore, we identify critical gaps in current knowledge regarding the health risks posed by OPFRs and propose future research directions to explore their adverse environmental and human health consequences.