Effects of pharmaceuticals on aquatic invertebrates. Part II: the antidepressant drug fluoxetine.

Fluoxetine, a selective serotonin reuptake inhibitor antidepressant and high-prescription-volume drug, is excreted unchanged or as a glucuronide from the human organism. Little is known about its fate in sewage treatment plants. Effects of fluoxetine on life-cycle parameters of the midge Chironomus riparius, especially development (mean emergence time), emergence, sex ratio, and fecundity, were assessed, as well as effects on reproduction of the oligochaete Lumbriculus variegatus and of the freshwater mudsnail Potamopyrgus antipodarum. Due to the moderate lipophilic properties of the compound with a log P (OW) of 4.05, C. riparius and L. variegatus were exposed to fluoxetine via spiked artificial sediment at a nominal concentration range between 0.15 and 5.86 mg/kg (dry weight). Additionally, a test was performed exposing P. antipodarum via water in a nominal concentration range between 0.64 and 400 mug/L. As endpoints, emergence rate and timing, sex ratio, clutch numbers and clutch size of the midges, the number of worms in the oligochaete test, as well as the number of embryos in the snail test were monitored. For C. riparius, no clear substance-related effects were observed; for L. variegatus, the results indicated a slight increase in reproduction, which was statistically significant at nominal fluoxetine concentrations of 0.94 and 2.34 mg/kg. In P. antipodarum, the antidepressant reduced reproduction significantly. No observed effect concentration (NOEC) and 10% effect concentration (EC(10)) were determined to be 0.47 and 0.81 mug/L, respectively, based on measured fluoxetine concentrations in water. These low values indicate that P. antipodarum and possibly other aquatic mollusks are sensitive to fluoxetine and that the drug might pose a risk to gastropod populations in the field.