Occurrence and potential risk of steroid hormones in selected surface water and wastewater treatment plants in western Kenya.

Steroid hormones are significant contributors to endocrine disruption, affecting the hormonal functions of both humans and aquatic organisms. However, data on their occurrence and risks in fresh water systems particularly in low- and middle-income countries, is scarce. In this regard, a comprehensive investigation of 58 steroid hormones in rivers and wastewater treatment plants (WWTPs) was conducted in western Kenya. Grab water samples were extracted by solid phase extraction, and analysed using liquid chromatography tandem mass spectrometry (LC-MS/MS) and liquid chromatography high-resolution mass spectrometry (LC-HRMS). Forty-three steroids were identified with 24 of them being found in both rivers and WWTPs. The median concentrations of detected steroids ranged from 0.06 ng/L to 9 ng/L in rivers, 1.9 ng/L to 670 ng/L in the influents and 0.61 ng/L to 270 ng/L at the effluents. The most frequently detected compound in the rivers was 17β-estradiol occurring in 64% of the samples. Although 23 compounds were reduced to undetectable levels in WWTPs, 90% of the effluents exceeded tentative risk thresholds for estrogenicity. In rivers, concentrations of estrogenic and glucocorticoid effects were in the range of risk thresholds, while androgenic and progestagenic concentrations were below risk thresholds. This study contributes to the occurrence of steroid hormones and an understanding of their potential impacts on freshwater ecosystem and human health. The data generated from the study provides crucial information for the formulation of environmental policies in Kenya.