Pollutants

Background: Human exposure to environmental endocrine-disrupting chemicals (EDCs) rarely occurs in isolation, yet most epidemiological research has assessed chemicals individually. PFASs, toxic metals, phthalates, and VOCs are ubiquitous contaminants with well-documented reproductive toxicity. Objective: The aim of this study was to investigate the joint and individual effects of 28 EDCs spanning four chemical classes on six reproductive hormone biomarkers in a nationally representative U.S. population—using an innovative approach that simultaneously characterizes nonlinear mixture effects and chemical interactions across multiple exposure domains. Methods: This cross-sectional study used NHANES 2017–2018 data (n = 9254). Multivariable linear regression and Bayesian Kernel Machine Regression (BKMR) characterized individual and mixture associations, respectively. Missing data were handled using multiple imputations by chained equations. Survey design weights were applied in linear regression models. Results: Linear regression revealed heterogeneous associations across chemical classes and hormones. PFOA was positively associated with SHBG (β = 12.35; 95% CI: 8.33, 16.38) and LH (β = 6.91; 95% CI: 1.44, 12.38), while mercury was inversely associated with estradiol (β = −3.38; 95% CI: −5.12, −1.65). BKMR analyses identified pronounced non-monotonic dose–response relationships and emergent mixture effects not predictable from single-chemical analyses for all six hormones. Posterior inclusion probabilities identified cadmium, PFOA, MEHP, and MBzP as the most influential predictors across hormone endpoints. Conclusions: Concurrent real-world exposure to PFASs, toxic metals, phthalates, and VOCs is associated with measurable, nonlinear alterations in reproductive hormone profiles. Chemical mixture effects cannot be reliably predicted from single-pollutant analyses, underscoring the necessity of mixture-based methodologies in environmental reproductive epidemiology. Prospective studies are needed to establish causal temporality and identify critical windows of susceptibility.

The gut microbiota of fish plays a crucial role in nutrition, metabolism and immune regulation, and is highly sensitive to environmental stressors such as pesticide exposure. This study investigated the effects of emamectin benzoate (EMB) exposure on Asian stinging catfish (Heteropneustes fossilis) gut microbiota using an integrated culture-dependent and culture-independent approach to assess functional and taxonomic dysbiosis. Gut smear samples from control and EMB-treated fish at two sublethal concentrations (0.5 µg/L and 5 µg/L) were analyzed for major functional bacterial groups, including heterotrophic, lipid-hydrolysing, starch-hydrolysing, spore-forming, and Gram-negative bacteria and Pseudomonas spp., using standard plate count techniques. In parallel, microbial community composition and diversity were examined through 16S rRNA (V3–V4 region) gene amplicon sequencing followed by bioinformatic analysis. Culture-based results showed a significant decline in total heterotrophic bacteria and key functional groups in EMB-treated fish, indicating suppression of microbial metabolic activity and functional imbalance. Lipid-hydrolysing and starch-hydrolysing bacteria showed pronounced sensitivity to pesticide exposure, while spore-forming bacteria exhibited a marked reduction, suggesting compromised microbial resilience. Although Gram-negative bacteria declined overall, Pseudomonas spp. displayed a non-linear response, with an initial decrease, followed by partial recovery under higher exposure. Culture-independent analysis demonstrated reduced alpha diversity, altered community structure, and taxonomic shifts in EMB-treated fish. Pseudomonadota exhibited a distinct pattern characterized by decline at 0.5 µg/L and partial recovery at 5 µg/L, reflecting adaptive tolerance rather than restoration of microbial homeostasis. Overall, the combined evidence indicates pronounced EMB-induced gut dysbiosis at both functional and compositional levels. This study highlights the fish gut microbiome as a sensitive biomarker of stress and underscores the ecological risks associated with EMB in aquatic environments.

Microplastics (MPs) adsorb hazardous substances and are ingested by a wide range of organisms; therefore, indicators for managing their environmental concentrations are needed. Ideally, threshold values should be based on health impacts. However, the diversity of MPs and the complexity of their environmental behavior make it difficult to establish unified environmental concentration standards. In this study, we propose a threshold for the presence of MPs on sandy beaches based on “visual cleanliness,” derived from the amount of MPs that people find psychologically unacceptable. Three types of MPs were used: white polypropylene (PP), blue PP, and white polystyrene (PS; expanded polystyrene). The survey was conducted in Japan, and the number of valid responses was 245. For defining a narrow-range cleanliness threshold, volume concentration was more appropriate than mass concentration. White particles were expected to be less noticeable because they tended to blend with white shell fragments, which are ubiquitous on beaches. In contrast, blue particles were expected to be less acceptable owing to their rarity. However, we found no difference in unacceptability between white PP and blue PP. The threshold, defined as the volume concentration at which half of the respondents find MPs psychologically unacceptable, ranged from 1 to 2 cm³-MPs/m²-sand. Gender, age, travel time to the beach, and frequency of beach visits did not influence unacceptability. Strong concern about marine plastic pollution and experience in cleaning public spaces were associated with a tendency toward low tolerance for MP contamination on beaches.