The environmental fate of fluoxetine and diazepam in water, sewage-treated soils and crops

摘要

The environmental fate and effects of Pharmaceuticals have been the subject of numerous studies over the last few years. Many pharmaceuticals are rapidly removed by water treatment or sewage treatment; others survive such processes and occur in the environment where their subsequent fate is then of interest. A comprehensive investigation of the available literature, involving research into over a hundred pharmaceuticals detected in the environment was undertaken to establish the most suitable candidates for our studies. The following selection criteria were devised and applied to each pharmaceutical: 1. Toxicity data (availability and concentration) 2. Usage (UK Figures) 3. Previously conducted biodegradation studies 4. Previously conducted photodegradation studies 5. Metabolites (whether known and active) 6. Environmental occurrence (where and at what concentration) 7. Extent of removal in sewage treatment works (STW) 8. Other possible sources of the compounds 9. Additional relevant information On this basis a list of thirty-one pharmaceuticals was produced. Following further investigation, including refinement through presentations and consultations with sponsors, the anti-anxiety drug, diazepam (Valium~?), along with its human metabolites desmethyldiazepam (also known as nordiazepam), temazepam and oxazepam and the anti-depressant, fluoxetine hydrochloride (Prozac~?), which are all drugs which are now produced by numerous companies, were deemed suitable for further study. In particular we wished to examine the effects of phototransformation and biotransformation on the chemicals. However, early into the study, an account was published which comprehensively investigated the photochemical kinetics and phototransformation of fluoxetine hydrochloride in aqueous solutions. Whilst this study provided additional justification for our original selection of fluoxetine hydrochloride, it was felt that continued investigation of the photodegradation behaviour within the present study was unwarranted and the photodegradation study was restricted to diazepam and its related metabolites. Conversely, again once our studies were underway, reports of the biodegradability of diazepam emerged; thus our studies of diazepam biodegradation were curtailed. The final experiments reported here thus involved examination of the photodegradation of diazepam and derivatives in water with and without humic substances and the biodegradation of fluoxetine in water and soil. Finally, since biodegradation of fluoxetine in soil was slow and the possibility of accumulation in soils treated with sewage theoretically possible, we examined the uptake of fluoxetine by cauliflowers. The latter crop may be legally grown of sewage-treated soils in the UK.