Photodegradation of steroid hormones is likely to be an important loss mechanism in surface waters since many of the steroid hormones feature aromatic rings of functional groups that can either absorb solar radiation or react with photogenerated transient species in natural waters (e.g. reactive oxygen species or photoexcited natural organic matter).

Accordingly, this presentation will discuss the influence of direct photolysis and indirect photochemical processes on the fate of 17β-estradiol, testosterone, and progesterone.  Experiments were conducted in quartz reactor tubes at 25 °C containing aqueous solutions of steroid hormones (100 μM) in the absence and presence of potential photosensitizers such as nitrate, humic acid, ferric oxalate, and manure as a function of concentration and pH. All experiments were conducted in a Rayonet RPR-200 photochemical reaction chamber which provides UV light in the range 300 to 400 nm and steroids were analyzed by HPLC-DAD/MS.

Our data shows significant differences in the photolysis rate constants between the compounds and with different treatments. For instance, 17β-estradiol is more resistant to photodegradation than testosterone and progesterone. Our studies indicate that steroid hormones can be photodegraded and that the photolysis half-lives will depend on the given environmental conditions.