Trends of Organophosphate Ester Flame Retardant Metabolites in Age- and Sex-Stratified Pooled Australian Urine Samples from the Past Decade (2012–2023)

Organophosphate ester flame retardants (OPFRs) are extensively used as flame retardants and plasticizers in plastic products. Their ubiquitous presence in the environment has raised concerns regarding possible exposure and adverse health effects. Thirteen OPFR biomarkers were measured in pooled, de-identified surplus pathology urine samples collected cross-sectionally between 2012 and 2023 from an Australian population (18,700 individuals represented by 187 pools). We assessed age, sex, and temporal trends of OPFR metabolites detected in >60% of pools. Concentrations in both sexes significantly decreased with age for bis(1,3-dichloro-2-propyl) phosphate (BDCIPP) and only in females for 2-ethylhexyl phenyl phosphate (EHPHP) and 2-ethyl-5-hydroxyhexyl diphenyl phosphate (5-HO-EHDPHP). The opposite was observed in males for 1-hydroxy-2-propyl bis(1-chloro-2-propyl) phosphate (BCIPHIPP) and EHPHP. Levels of BDCIPP, BCIPHIPP, and 5-HO-EHDPHP were significantly higher in males than in females in pools from 2020-2021 and all sampling years combined. A temporal increase in concentrations was observed for BCIPHIPP (males) and EHPHP (females). Risk characterization ratios (RCRs) showed mean exposures below derived no-effect levels (DNELs). Our observed age and sex trends, as well as mean concentrations, were comparable to previously reported trends and levels from Australia and other geographical locations. This study highlights age, sex, and temporal trends of OPFR exposure in Australia.