Every day, wastewater treatment plants, livestock farms and manure-fertilized fields release steroid hormones into rivers, lakes and coastal seas. The amounts are tiny — often measured in nanograms per liter — but for fish and other aquatic species, tiny is enough. Decades of research have linked these compounds to shifted sex ratios, impaired reproduction and population decline in fish. A new review in The Innovation Water argues that the usual way of tracking them — measuring a handful of parent compounds before and after treatment — understates both exposure and risk.
The review, led by Hang Yang and Yi Zhang of the Institute of Hydrobiology, Chinese Academy of Sciences, with Lei Wang of Shenzhen Polytechnic University, walks through the full life cycle of environmental steroid hormones: where they come from, where they go, what they do, and what can be done about them.
One central finding concerns what standard monitoring misses. Steroid hormones rarely travel as free, parent compounds alone. Conjugated forms excreted in urine can be deconjugated by microbes in the environment, regenerating active hormones; transformation products can retain or even gain biological activity. In some secondary wastewater effluents, the review notes, conjugated and halogenated estrogens together can account for 60–70% of the total molar load of steroid estrogens — fractions invisible to targeted assays focused on parent compounds.
Real waters also carry mixtures: natural hormones, synthetic analogues, transformation products and other co-contaminants such as microplastics and antibiotics. Mixture effects may be additive, synergistic or antagonistic, yet risk assessment frequently evaluates compounds one at a time. Evidence of harm is strongest for aquatic life — vitellogenin induction, skewed sex ratios, reduced fecundity — while direct epidemiological evidence linking environmental exposure to human health outcomes remains limited, a boundary the authors state explicitly.
On the treatment side, the review's message is equally cautious. Conventional processes lower parent-compound concentrations but vary with compound, process conditions and season. Sorption and membrane separation may simply relocate pollutants to sludge or concentrate streams; advanced oxidation can destroy parent structures without achieving full mineralization, leaving active transformation products. The authors argue that removal rates for parent compounds should not be compared across technologies without context, and that treatment should be judged by whether transformation products, residual endocrine activity and overall toxicity decline together.
Their proposed path forward is organized under a One Health framework: expand monitoring to wastewater, manure, agricultural runoff, receiving waters, sediments and indicator organisms; bring mixture effects into risk assessment; control sources from pharmaceutical use and disposal to livestock operations; and combine engineered treatment with nature-based solutions such as constructed wetlands and microalgae systems. Whether any of it works, the review concludes, should be verified by measurable, simultaneous declines in exposure, residual endocrine activity and toxicity — not by parent-compound removal rates alone.
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Yang H., Feng Q., Tang Y., et al. (2026). Environmental steroid hormones in aquatic systems: Biogeochemical dynamics, mixture risks, and sustainable mitigation. The Innovation Water 1:100015. https://doi.org/10.59717/j.tiw.2026.100015
Systematic review
Not applicable
Environmental steroid hormones in aquatic systems: Biogeochemical dynamics, mixture risks, and sustainable mitigation
20-Jul-2026
The authors declare no competing interests.