Statistical Modeling Suggests that Antiandrogens in Effluents from Wastewater Treatment Works Contribute to Widespread Sexual Disruption in Fish Living in English Rivers

Background: The occurrence of feminised male fish downstream of some wastewater treatment works has led to substantial interest from ecologists and public health professionals. This concern stems from the view that the effects observed have a parallel in humans, and that both phenomena are caused by exposure to mixtures of contaminants that interfere with reproductive development. The evidence for a “wildlife human connection” is, however, weak: Testicular dysgenesis syndrome, seen in human males, is most easily reproduced in rodent models by exposure to mixtures of anti-androgenic chemicals. In contrast, the accepted explanation for feminisation of wild male fish is that it results mainly from exposure to steroid estrogens originatingprimarily from human excretion. Objectives: We sought to further explore the hypothesis that endocrine disruption in fish is multi-causal, resulting from exposure to mixtures of chemicals with both estrogenic and anti-androgenic properties. Methods: Hierarchical generalized linear and generalized additive statistical modeling were used to explore the associations between modeled concentrations and activities of estrogenic and anti-androgenic chemicals in 51 UK rivers and feminised responses seen in wild fish living in these rivers. Results: In addition to the estrogenic substances, anti-androgenic activity was prevalent in almost all treated sewage effluents tested. Further, the results of the modelling demonstrated that feminizing effects in wild fish could be best modelled as a function of their predicted exposure to both anti-androgens and estrogens or to antiandrogens alone. Conclusion: The results provide a strong argument for a multi-causal aetiology of widespread feminisation of wild fish in UK Rivers involving contributions from both steroidal estrogens and xenoestrogens and from other (as yet unknown) contaminants with anti-androgenic properties. They may add further credence to the hypothesis that endocrine disrupting effects seen in wild fish and in humans are caused by similar combinations of endocrine disrupting chemical cocktails.