PHOTOLYSIS OF TESTOSTERONE, PROGESTERONE AND 17β-ESTRADIOL BY UVA LIGHT

ABSTRACT: Wastewater treatment facilities and agricultural production are potential sources of steroid hormones in the environment. The fate of steroid hormones in the environment has not been extensively studied. Important degradation pathways must be identified to predict the long-term impact of steroid hormones and their metabolites. Chemical oxidation, biodegradation, and photodegradation have been identified as potential mechanisms for the transformation of these compounds. While some studies have investigated the photodegradation of steroid hormones under conditions relevant for engineered systems, few studies have examined the importance of photolysis on the transformation of steroid hormones under environmentally relevant conditions. Consequently, the objectives of this study were to determine the potential for direct and indirect (i.e., by humic acid and nitrate) photolysis of 17β-estradiol, testosterone and progesterone by light in the UVA range (305 to 410 nm) in a phosphate buffered media at pH 5.5. Photolysis of 17β-estradiol, testosterone, and progesterone was observed. The photolysis was modeled using pseudo first-order reaction kinetics and half-lives were found to be in the range from 3 to 6 hours, depending on the type of hormone and solution composition. Both testosterone and progesterone were directly photolyzed. In the presence of humic acid (HA), testosterone was photolyzed at increased rates, while HA did not influence the photolysis of progesterone. 17β-estradiol was only photolyzed (indirectly) in the presence of HA. This study indicates that photolysis of hormones might be an important removal mechanism in natural systems and tha