Polystyrene microplastics increase estrogenic effects of 17α-ethynylestradiol on male marine medaka (Oryzias melastigma)

Microplastics (MPs) and endocrine disrupting chemicals are ubiquitous pollutants in marine environments, but their combined ecological risk is unclear. This study exposed male marine medaka (Oryzias melastigma) to 10 ng/L 17α-ethynylestradiol (EE2) alone or EE2 plus 2, 20, and 200 μg/L polystyrene MPs for 28 days to investigate the impacts of MPs on the reproductive disruption of EE2. The results showed that 10 ng/L EE2 alone did not affect biometric parameters, while co-exposure to EE2 and 20, 200 μg/L MPs suppressed the growth and decreased gonadosomatic and hepatosomatic indices. Compared to EE2 alone, EE2 plus MPs exposure significantly increased plasma 17β-estradiol (E2) levels in a dose-dependent manner, and co-exposure to EE2 and 20, 200 μg/L MPs significantly increased the ratios of E2/testosterone (T). Moreover, EE2 plus MPs exposure elevated the transcription levels of estrogen biomarker genes vitellogenin and choriogenin, and estrogen receptor (ERα and ERβ). Morphological analysis also showed that co-exposure to EE2 and MPs induced more severe damage to the testes and livers, indicating that MPs increased the toxicity of EE2. The actual EE2 concentrations in the solution increased with the exposure concentrations of MPs, suggesting that MPs changed the fate and behavior of EE2 in the seawater. These findings demonstrate that MPs could increase the estrogenic effects of EE2 on marine fish, suggesting that the combined health risk of MPs and endocrine disrupting chemicals on marine organisms should be paid great attention.