Occurrence, Bioaccumulation, and Potential Risks of Steroid Hormones in Freshwater Aquaculture Ponds in South China

Steroid hormones, recognized as emerging environmental contaminants, have garnered increasing attention in recent years. The present work studied the distribution characteristics in the environment, bioaccumulation in aquatic products, and the associated environmental and health risks of typical steroid hormones from commercial freshwater aquaculture farms operating under different aquaculture modes (monoculture and polyculture). Totals of 9 and 14 steroid hormones were detected in water and sediment samples, with concentrations ranging from 0.66 ± 0.17 ng/L to 40.5 ± 5.08 ng/L and from 0.36 ± 0.08 ng/g to 123 ± 19.9 ng/g, respectively. Hazard index (HI) calculations indicated that all sampling locations were identified as medium or high risk for both water and sediment matrices. Nineteen steroids were detected in at least one type of tissue, with the concentrations in the bile, plasma, muscle, liver, and gill ranging from <LOQ to 52.6 ± 4.82 ng/L, from <LOQ to 41.9 ± 4.80 ng/L, from 0.36 ± 0.07 ng/g to 321 ± 19.1 ng/g, from <LOQ to 1140 ± 107 ng/g, and from 0.36 ± 0.03 ng/g to 1450 ± 239 ng/g, respectively. Furthermore, four synthetic steroid hormones exhibited significant bioaccumulation across various tissues, such as MLA in bile and 5α-DHP in muscle, liver, and gill (BAF > 5000 L/kg). Notably, despite low estimated daily intakes (EDIs) (0.43–6.43 ng/day/person to 18.7 ng/day/person) and hazard quotients (HQs) (below 4.188 × 10⁻⁷), the high bioaccumulation factors (BAFs) underscore the necessity for stringent regulatory measures by local governments. Additionally, a comparison of EDI results across different aquaculture modes and fish species revealed that steroid hormone-related health risks to humans are influenced by both the fish species and the aquaculture mode. This study indicated that the consumption of poly-cultured fish (e.g., bighead carp) may pose a greater steroid-related health risk, compared to the consumption of mono-cultured fish.