Combined toxic effects of polystyrene microplastics and 3,6-dibromocarbazole on zebrafish (Danio rerio) embryos.

Microplastics (MPs) and polyhalogenated carbazoles (PHCZs) are widely detected in the aquatic environment, and their ecological risks have become a research focus. Although there is an extensive co-distribution of MPs and PHCZs, their combined toxicity to aquatic organisms is still unclear. This study investigated the toxic effects of polystyrene microplastics (PS-MPs) and 3,6-dibromocarbazole (3,6-DBCZ) on zebrafish embryos by individual/combined exposure. This study showed that individual or combined exposure of PS-MPs (10 mg/L) and 3,6-DBCZ (0.5 mg/L) could significantly increase the rate of zebrafish embryo deformity, whereas no significant effect was observed on mortality and hatching rate. Furthermore, exposure to 3,6-DBCZ or PS-MPs increased reactive oxygen species (ROS) levels in zebrafish embryos, and the resulting oxidative stress induced apoptosis. Comparably, the levels of oxidative stress and apoptosis in zebrafish embryos were significantly reduced with the combined exposure of 3,6-DBCZ and PS-MPs. These observations suggest that the combined exposure of 3,6-DBCZ and PS-MPs has an antagonistic effect on oxidative stress and apoptosis. Fluorescence PS-MPs tracing and 3,6-DBCZ enrichment analysis showed that, with the protection of chorion, the entry of PS-MPs (5 and 50 µm) into the embryonic stage (55 hpf) of zebrafish was prevented. Moreover, after exposure for 96-144 hpf, PS-MPs served as a carrier to promote the 3,6-DBCZ accumulation and its dioxin-like toxicity in zebrafish larvae through ingestion. Compared with 5-µm PS-MPs, 50-µm PS-MPs promoted higher accumulation and dioxin-like toxicity of 3,6-DBCZ in zebrafish larvae. These findings provide that MPs can be used as an important carrier of PHCZs, influencing their toxicity and bioaccumulation in the organisms.

Protein-specific distribution patterns of perfluoroalkyl acids in egg yolk and albumen samples around a fluorochemical facility.

In this study, eggs from free-range and barn chickens in farms around a fluorochemical facility were collected to assess the distribution profiles of perfluoroalkyl acids (PFAAs), including isomers of perfluorooctane sulfonate (PFOS), perfluorooctanoic acid (PFOA), and perfluorohexane sulfonate (PFHxS), in egg yolk and albumen. The results revealed that the concentrations of PFAAs in yolks were significantly higher than those in albumen. All 17 PFAAs examined could be detected in yolks, showing decreasing concentrations with increasing distance from the fluorochemical facility. The three predominant compounds in yolks were perfluorobutanoic acid (PFBA, mean concentration 81.4 ng/g ww), PFOS (28.0 ng/g ww), and PFOA (4.83 ng/g ww), and this result is consistent with the product structure of the facility. Moreover, n-PFOA, n-PFOS, and n-PFHxS were the dominant contaminants in yolk, with mean concentrations of 4.75, 25.7, and 4.29 ng/g ww, respectively. In albumen, PFBA was still the predominant PFAA congener (mean concentration = 3.93 ng/g ww), followed by PFOA. Docking analysis indicated that the PFAAs presented higher binding abilities with the low density lipoprotein, high density lipoprotein, and vitellin proteins in yolk than that with ovalbumin albumen proteins, which might be the main factor influencing the possible difference in distributions of PFAAs in yolk and albumen.