Sex- and size-dependent accumulation of Dechlorane Plus flame retardant in a wild frog-eating snake Amphiesma stolata.

Despite several studies having addressed the bioaccumulation of Dechlorane Plus (DP) flame retardant in wildlife, there is still a dearth of information for reptiles in general and for snakes in particular. Here, we report the residue levels and trophic transfer of syn-, anti-, and anti-Cl11-DP in a frog-eating snake-namely, the striped keelback snake Amphiesma stolata-from a DP hotspot in South China. The concentrations of syn-, anti-, and anti-Cl11-DP in A. stolata ranged from 1.06-21.2, 2.13-21.5, and 0.16-10.6 ng/g lipid weight, respectively, with significantly higher levels in males compared with females. Statistical analysis showed that the concentrations of these chemicals were negatively correlated with body sizes (length and mass) of the snake. The fractional abundance of anti-DP (fanti) did not significantly differ either between the sexes or between A. stolata and its diet (i.e., frogs). However, fanti showed positive correlations with the snake's body size and negative correlations with ∑DP concentrations (summed concentrations of syn- and anti-DP), indicating that body size and DP residue levels are important factors influencing DP isomeric profiles in these snakes. Biomagnification factors estimated based on the relationship between A. stolata and frogs were 0.49 ± 0.01 (mean ± SE), 0.44 ± 0.09, and 1.79 ± 0.54 for syn-, anti-, and anti-Cl11-DP, respectively, suggesting trophic dilution of syn- and anti-DP and a mild biomagnification of anti-Cl11-DP from frogs to snakes.

Bioaccumulation and maternal transfer of two understudied DDT metabolites in wild fish species.

While the secondary metabolites of DDT such as 2,2-bis(chlorophenyl)-1-chloroethylene (DDMU) and 2,2-bis(chlorophenyl)methane (DDM) have been detected in the environment for several decades, knowledge is extremely limited on their bioaccumulation characteristics. Here, we reported the bioaccumulation and maternal transfer of p,p'-DDMU and p,p'-DDM in two wild fishes, i.e., the northern snakehead (Channa argus) and crucian carp (Carassius auratus), from a DDT contaminated site in South China. The hepatic concentrations of p,p'-DDMU and p,p'-DDM in the fish were up to 549 and 893 ng/g lipid weight, contributing 5.3% and 3.2% in average to ΣDDXs (the sum concentrations of DDT and its 6 metabolites), respectively. The residues of p,p'-DDMU and p,p'-DDM in the fish exhibited interspecific and intraspecific variations, resulting from the differences in lipid content, sex, and body sizes (length and mass) between or within species. Both p,p'-DDMU and p,p'-DDM were consistently detected in the fish eggs, demonstrating their maternal transfer in female fish. The mean eggs to liver lipid-normalized concentration (E/L) ratios of p,p'-DDMU and p,p'-DDM were 0.98 and 1.77 in the northern snakehead, 0.35 and 0.01 in crucian carp, respectively; which were comparable to or even exceeded those of DDT and its major metabolites calculated in the same individual. Statistical analyses of the data showed that the E/L ratios were positively correlated with body sizes of the fish, but negatively correlated with the hepatic concentrations of p,p'-DDMU and p,p'-DDM in females; suggesting the influences of fish sizes and the mother body residues on their maternal transfer efficiencies.

Halogenated flame retardants in wild, prey-sized mud carp from an e-waste recycling site in South China, 2006-2016: Residue dynamics and ecological risk assessment.

The crude e-waste recycling has been regulated in China since the late 2000s; however, information on the recent levels and the ecological risks of e-waste derived contaminants such as halogenated flame retardants (HFRs) in the e-waste sites are limited. We therefore examined the concentrations of several HFRs in wild, prey-sized mud carps collected from a typical e-waste site in 2006, 2011 and 2016, to understand the exposure dynamics and ecological risk of these chemicals. Several ecological and biological parameters including δ15N, δ13C, body size and lipid content of the fish were also examined, to ensure an overall uniformity of the sample set among the sampling years. Among the HFRs measured, polybrominated diphenyl ethers (PBDEs) were detected at the highest concentrations (contributing >90% to ∑HFRs), followed by Dechlorane Plus (DPs), polybrominated biphenyls (PBBs), and alternative brominated flame retardants (ABFRs). The fish concentrations of ∑PBDEs, ∑PBBs and ∑DPs significantly dropped by 65%, 57% and 53% from 2006 to 2011, and 12%, 74% and 51% from 2011 to 2016, respectively; likely reflecting the positive impact of the environmental regulations on crude e-waste recycling. The ∑ABFRs concentrations were also decreased by 80% from 2006 to 2011, but increased by 127% from 2011 to 2016; suggesting possible fresh input of these novel HFRs in recent years. In addition to the changes in the HFR concentrations, contaminant profiles in the fish were also changed, possibly due to environmental degradation of the HFRs. Despite our conservative method of risk assessment, we found that PBDEs posed an important risk both for the mud carp and for piscivorous wildlife that inhabit the e-waste site.