Synthetic estrogens from human pharmaceuticals and agriculture are contaminating waterways and causing intersex conditions and reproductive disruption in fish populations.
Endocrine disruption in fish represents a diffuse but pervasive welfare harm. While intersex fish may not experience the acute suffering of injury or illness, reproductive dysfunction and the physiological disruption of hormone systems almost certainly affect wellbeing. Fish in heavily polluted waterways may experience chronic physiological stress from endocrine disruption superimposed on all the other stressors of degraded aquatic environments. The welfare concern is compounded by population-level impacts - reduced reproductive success threatens the survival of wild fish populations, with cascading effects on the ecosystems that depend on them. Addressing estrogen pollution requires both improved wastewater treatment and reduced pharmaceutical and agricultural hormone use.