Neonicotinoid insecticides have attracted worldwide attention due to their ubiquitous occurrence and detrimental effects on aquatic organisms, yet their impacts on fish reproduction during long-term exposure remain unknown. Here, zebrafish (F0) were exposed to a neonicotinoid, acetamiprid, at 0.19–1637 μg/L for 154 d. Accumulation and biotransformation of acetamiprid were observed in adult fish, and the parent compound and its metabolite (acetamiprid-N-desmethyl) were transferred to their offspring. Acetamiprid caused slight survival reduction and significant feminization in F0 fish even at the lowest concentration. Hormone levels in F0 fish were remarkedly altered, that is, gonad 17β-estradiol (E2) significantly increased, while androstenedione decreased. The corresponding transcription of steroidogenic genes (ar, cyp19b, fshβ, gnrh2, gnrh3, and lhβ) were significantly upregulated in the brain and gonad of the females but downregulated in the males. The vtg1 gene expression in the liver of male fish was also upregulated. In addition to F0 fish, parental exposure to acetamiprid decreased hatchability and enhanced malformation of F1 embryos. Chronic exposure to acetamiprid at environmentally relevant concentrations altered hormone production and the related gene expression of the hypothalamic-pituitary-gonad (HPG) axis in a sex-dependent way, caused feminization and reproductive dysfunction in zebrafish, and impaired production and development of their offspring.

Per- and polyfluoroalkyl substances (PFASs) have attracted worldwide attention due to their ubiquitous occurrence, bioaccumulation, and toxicological effects, yet the fate of PFASs in a lotic ecosystem is largely unknown. To elucidate spatial distribution and multimedia partitioning of legacy and emerging PFASs in a lotic river flowing into an estuary, PFASs were synchronously analyzed in water, suspended particulate matter (SPM), sediment, and biota samples collected along Guangzhou reach of the Pearl River, South China. Geographically, the concentrations of PFASs in the water phase showed a decreasing trend from the upper and middle sections (urban area) to the down section (suburban area close to estuary) of the river. While perfluorooctanoic acid predominated in water and SPM, more diverse compositions were observed in sediment and biota with the increase in contributions of long-chain PFASs. Field-derived sediment–water partitioning coefficients (K d) and bioaccumulation factors (BAFs) of PFASs increased with the increase in perfluorinated carbons. Besides hydrophobicity, water pH and salinity significantly affected the multimedia partitioning of PFASs in a lotic ecosystem. In addition, 87 homologues (63 classes) were identified as emerging PFASs in four media using suspect analysis. Interestingly, K d and BAF of the emerging PFASs were often higher than legacy PFASs containing the same perfluorinated carbons, raising a special concern on the environmental risk of emerging PFASs.

Interspecies sensitivity to the same chemical can be several orders of magnitude different. Quantifying toxicologically internal levels and toxicokinetic (TK) parameters is critical in elucidating the interspecies sensitivity. Herein, a two-compartmental TK model was constructed to characterize the uptake, distribution, and elimination kinetics toward interspecies sensitivity to an insecticide, imidacloprid. Imidacloprid exhibited the highest lethality to the insect Chironomus dilutus, followed by Lumbriculus variegatus, Hyalella azteca, and Daphnia magna. Interspecies sensitivity of imidacloprid to these invertebrates varied by ∼1000 folds based on water concentrations (LC50). Remarkably, the sensitivity variation decreased to ∼50 folds based on the internal residues (LR50), highlighting the critical role of TK in interspecies sensitivity. A one-compartmental TK model failed to simulate the bioaccumulation of imidacloprid in these invertebrates except for D. magna. Instead, a two-compartmental model successfully simulated the slow elimination of imidacloprid in the remaining three species by internally distinguishing the highly dynamic (C 1 ) and toxicologically available (C 2 ) fractions. We further showed that the species sensitivity of the invertebrates to imidacloprid was significantly related to C 2 , demonstrating that C 2 was toxicologically available and responsible for the toxicity of imidacloprid. This mechanistic-based model bridged the internal distribution of organic contaminants in small invertebrates and the associated toxic potency.

To improve the accuracy of mixture risk assessment, researchers are employing suspect analysis with expanded lists of contaminants in addition to conventional target lists. However, there are some inherent challenges for these instrument-based analyses, including subjective selection of suspect contaminants, no information for chemical bioactivity, requirements for costly verification, and limited regional coverage. As a supplementary approach, we propose a data-driven suspect screening and risk assessment method informed by mining big data from high-throughput screening bioassay platforms and the refereed literature. The Pearl River Delta (PRD) with main event drivers of arylhydrocarbon receptor (AhR) and oxidative stress (ARE) response was examined. Bioactivity concentrations were collected from the CompTox Chemicals Dashboard, which contained more than 900 000 substances. In addition, exposure metadata from 24 986 literature entries for the environmental occurrence and distribution of contaminants in the PRD over the past three decades were mined. Collectively, a regional distribution map of aquatic hazards induced by AhR- and ARE-active compounds was generated, indicating gradients of low to moderate risks. This study specifically reports a novel big data approach for addressing the increasingly common challenge of objectively selecting analytes during suspect screening, which was recently identified as an urgent research question to advance more sustainable environmental quality.

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