An assessment of the risks posed by human pharmaceuticals in the environment to wild birds

When a pharmaceutical is ingested, a proportion of it is excreted unchanged, ending up in sewage. Birds foraging at sewage treatment works can take up these pharmaceuticals by ingesting invertebrates living in the sewage. There is concern that low concentrations of human pharmaceuticals can alter behaviour and physiology in wildlife species because of the evolutionary conservation of drug targets. In this thesis I focus on a heavily prescribed and environmentally persistent antidepressant, fluoxetine, which is used by humans to treat anxiety, but also causes side effects e.g. changes in appetite, libido and activity. To assess the risks posed by fluoxetine in contaminated invertebrates to foraging birds, wild-caught starlings (12 fluoxetine-treated and 12 controls) were fed with an environmentally relevant dose (928 ng/day) over winter and into the breeding season. After 22 weeks of treatment, liquid chromatography coupled with a triple quadrupole mass spectrometer revealed that fluoxetine accumulation in the starling brain (3.1 ng/g) was approximately 30 times lower than in humans (corrected for differences in dose and body mass) and elimination from starling tissues was 2.2 to 31 times faster than is found in human plasma. After 16-weeks of fluoxetine treatment, relative to controls, the fluoxetine-treated birds fed 24% less, and at times of nutritional stress, they fed 41% less. In mate choice experiments, fluoxetine-treated females showed less interest in males, spending 49% more time in the ‘no-choice’ zone than the control females did. However, no effects on anxiety related behaviour or activity levels were found. In a separate in-vitro experiment, the bioaccessibility of fluoxetine in invertebrate prey only varied by 13% between humans and birds and so could not explain all the inter-species variability in tissue accumulation. The observed changes to behaviour and physiology in starlings may have been caused by neuro-adaptations occurring over time, as are observed in humans possibly due to greater receptor sensitivity than humans. It is now important to assess how the effects of fluoxetine on captive individuals could translate to free living individuals; how these impacts interact with other stressors and whether there could be consequences for population dynamics and ecosystem functioning.