Meeting Abstract
Pharmaceutical compounds have been detected in natural waterways, due largely to ineffective wastewater treatment procedures. When exposed to ultraviolet radiation, many pharmaceuticals are converted into related compounds. These compounds are often more polar and are therefore predicted to be more toxic than the parent pharmaceutical. For many pharmaceuticals, continual input results in pseudo-persistence, whereby enough new material is added that levels remain elevated in spite of degradation. Although pharmaceutical degradants are expected to co-occur with the parent molecule, particularly for pseudo-persistent compounds, the toxicity of combinations of drugs and degradants has not previously been tested. We investigated the effects of UV degradation and pseudo-persistence on the toxicity of naproxen, a common nonsteroidal anti-inflammatory frequently found in natural waters. Southern toad (Anaxyrus terrestris) tadpoles were exposed to naproxen, its two photodegradants, and combinations of the three compounds in proportions corresponding to laboratory observations of naproxen photodegradation. Daily observations of tadpole mortality, activity, and behavioral changes were used to assess toxicity. Naproxen’s two photodegradants were significantly more toxic than naproxen itself, and combinations of naproxen and its photodegradants were particularly toxic. Thus, photodegradation of naproxen in the environment is predicted to result in increased risk for freshwater organisms. More generally, our data suggest that the ecological effects of pharmaceutical pollutants may be underestimated and that assessing toxicity of relevant combinations of pharmaceuticals and their degradants is important for evaluating the impact of pharmaceutical pollution.
