UK chemists have gained new insight into the fate of pharmaceuticals released into river waters. Their strategy takes into account the effect of sunlight which is not currently part of environmental risk assessment, they say.   

Qin-Tao Liu at AstraZeneca in Devon and colleagues have found that -blockers, drugs used for treating heart conditions, degrade in sunlight through a process called phototransformation. These drugs are not removed from water by standard sewage treatment due to properties, such as water solubility, that allow them to interact with the human body, explains Liu. This has led to concerns about how long they persist in the environment.      

By comparing kinetic measurements of river water samples under simulated environmental conditions in the light and the dark, Liu found that -blockers were quickly removed from surface water by phototransformation in light conditions. This is in contrast to dark conditions like those of sewage treatment plants where the main routes for pollutant removal are biodegradation and sedimentation.   

The current EU environmental risk assessment regulations do not include phototransformation, explains Liu, which means the risk of some pharmaceutical drugs may be hugely overestimated. 'Our strategy addresses the need for a holistic way to understand the fate and behaviour of pharmaceuticals in surface waters,' she says.   

Linda Lawton, an expert in water quality monitoring at Robert Gordon University, Aberdeen, UK, highlights the importance of studies such as this looking at the many factors affecting compound degradation. 'It will be challenging to ultimately define the combination of factors that should be explored when determining the persistence of these trace contaminants, but the work goes a long way in addressing some of the key factors,' she says.   

Liu explains their approach could be developed in several ways in the future. This will include testing for different pharmaceuticals, understanding how different water parameters such as salinity and microbial populations affect degradation, and also investigating how the phototransformation products impact on the environment. 'This will help develop a framework for integrated fate testing of chemicals in the environment,' she says.   

Katherine Davies   

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