Emerging and legacy organophosphate flame retardants in the tropical estuarine food web: Do they exhibit similar bioaccumulation patterns, trophic partitioning and dietary exposure?

Abstract

Emerging organophosphate flame retardants (E-OPFRs) are a new class of pollutants that have attracted increasing attention, but their bioaccumulation patterns and trophodynamic behaviors in aquatic food webs still need to be validated by comparison with legacy OPFRs (L-OPFRs). In this study, we simultaneously investigated the bioaccumulation, trophic transfer, and dietary exposure of 8 E-OPFRs and 10 L-OPFRs in a tropical estuarine food web from Hainan Island, China. Notably, the Σ₁₀L-OPFRs concentration (16.1–1.18 × 10⁵ lipid weight (lw)) was significantly greater than that of Σ₈E-OPFRs (nondetectable (nd) - 2.82 × 10³ ng/g lw) among the investigated organisms, and they both exhibited similar trends: fish<mollusk<crustacean. Significant biomagnification was found only for triphenyl phosphate (TPHP, an L-OPFR) with a trophic magnification factor (TMF) of 1.55, whereas other E- and L-OPFRs showed limited trophic transfer potential. Storage lipid was the dominant adsorption phase for most E-OPFRs and L-OPFRs on the basis of the fugacity approach. The water content controls the main trophic partitioning for the L-OPFRs of triethyl phosphate (TEP) and tris(2-chloroethyl) phosphate (TCEP) in the food web. Storage lipid and structure protein are equally important for 2,2-bis(chloromethyl)-propane-1,3-diyltetrakis(2-chloroethyl) biphosphate (V6, an emerging OPFR). The investigation of metabolites and the biotransformation rate (K_M) confirmed the role of biotransformation in offsetting trophic transfer for both legacy and emerging OPFRs. Furthermore, the hazard quotients (HQs) were found to be <1 for South China residents for both the E- and L-OPFRs, but the health risks of these two kinds of OPFRs should be given sustained attention.