Radiolytic degradation of levonorgestrel and gestodene: Performance and bioassays

This study reports the feasibility of ionizing sources (60Co source and electron beam radiation) to degrade the progestins hormones levonorgestrel (LNG) and gestodene (GES) in synthetic solutions and real pharmaceutical wastewater (RPW). Doses of 0.5–100 kGy and dose rates of 2.5 and 10 kGy h−1 were applied. LNG was shown to be more recalcitrant than GES, with 90% removals achieved at doses around 7.7 kGy (LNG) and 1.6 kGy (GES) in model systems, with LNG showing greater reactivity with reducing species in γ-radiolyis, unlike GES. Furthermore, LNG removal remained around 60% in RPW at low doses, while more than 60% GES removal was observed for all doses. LNG and GES toxicities to Daphnia similis were absorbed dose-dependent, with low doses resulting in toxicity reductions of around 32% (LNG) and 42% (GES); in turn, high doses promoted a fourfold increase in toxicity. γ-radiolysis reduced the cytotoxic character of LNG to NIH-3T3-L1 cells, while non-irradiated or irradiated GES solutions did not exhibit any cytotoxic effect. Finally, the estrogenic activity, evaluated by the YES assay, was dose-dependent for both progestins, which may be related to the evolution of transformation products formed by water radiolysis in each case, decreasing for high doses.