Effect of triclosan and triclocarban biocides on biodegradation of estrogens in soils

We have investigated the effect of antimicrobials triclosan (TCS) and triclocarban (TCC) on biodegradation of 17β-Estradiol (E2) and 17α-Ethynylestradiol (EE2) in a sandy soil from South Australia. Two separate batch studies were conducted. In the first, the rates of loss of E2 and EE2 were determined at time intervals of 0, 3, 7, 14, 21, 28 and 56 d after initial spiking of soil with each estrogen at 1 mg kg−1 and the antimicrobials at 10 and 100 mg kg−1. Little loss of E2 and EE2 (<15%) under sterile conditions was noted compared to rapid loss in non-sterile soil (>60% in 24 h). There were no measurable effects on estrogen degradation by the two antimicrobials at spiked concentrations up to 100 mg kg−1. The experiments were repeated to study degradation rates of the estrogens within the first 24 h (0, 3, 8, 24 h), 3 d and then weekly to 56 d. Again, E2 and EE2 degradation was not significantly affected by the presence of TCS up to 100 mg kg−1 (p > 0.05). However TCS did significantly affect biodegradation of the estrogens when the soils were spiked with 1000 mg kg−1 of TCS (p < 0.0005). In contrast, presence of TCC in soil showed no significant effect on biodegradation of the two compounds up to 1000 mg kg−1 (p > 0.05). Considering environmental concentrations of the antimicrobials reported in the literature, it is highly unlikely these biocides would have any adverse impact on biodegradation of E2 or EE2 in soils.