The drugs we release into the environment are likely to have a significant impact on plant growth, according to scientists working in the UK.

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The results of research by scientists at the University of Exeter's Medical School and Plymouth University suggest that the residues of certain anti-inflammatory drugs could be affecting the growth of edible crops, even at the very low concentrations found in the environment.

Looking at lettuce and radish plants, the researchers tested the effects of several commonly prescribed drugs, including diclofenac and ibuprofen. The potential for the chemical residues of these drugs to influence plants is becoming ever more relevant, as waste management systems can't remove many of the compounds from sewage.

This means that worldwide, drugs prescribed for human use are making their way into soil through a number of routes, including the use of sewage sludge as fertiliser and waste water for irrigation.

There are mounting concerns about the presence of pharmaceuticals in the environment, evidence is emerging that pharmaceutical compounds can affect the development of animals, and potentially contribute to antibiotic resistance in bacteria. Even so, the researchers said the possible effects on plant growth remain poorly understood.

The changes examined by the researchers included water content of plants, root and shoot length, overall size and how effectively the plants photosynthesised. Each of the drugs tested appeared to have a specific effect on plants. The effects even differed between drugs that are closely related. For example, drugs from the fenamic acid class affected the growth of radish roots, whilst ibuprofen had a significant influence on the early root development of lettuce plants.

Commenting on the research, Dr Clare Redshaw, who led the project, said, "The huge amounts of pharmaceuticals we use ultimately end up in the environment, yet we know very little about their effects on flora and fauna. As populations age and generic medicines become readily available, pharmaceutical use will rise dramatically and it's essential we take steps towards limiting environmental contamination. We haven't considered the impact on human health in this study, but we need to improve our understanding quickly so that appropriate testing and controls can be put in place."