A new study shows that caffeine levels can indicate water contamination due to sewarage systems.

"E coli bacteria is commonly used to evaluate and regulate the levels of fecal pollution of our water from storm water discharge, but because storm sewers systems collect surface runoff, non-human sources can contribute significantly to the levels that are observed," said lead author and professor of the University of Montreal's Department of Chemistry, Sébastien Sauvé.

"Our study has determined that there is a strong correlation between the levels of caffeine in water and the level of bacteria, and that chemists can therefore use caffeine levels as an indicator of pollution due to sewerage systems."

Taking water samples from streams, brooks, and storm sewer outfall pipes, researchers analyzed them for caffeine, fecal coliforms, and carbamazepine, an anti-seizure drug which, also often used for psychiatric treatments.

Researches thought that carbamazepine would be a useful indicator because of its extremely slow degrading process, but unlike caffeine, a correlation between the two was not found.

To their surprise all of the samples contained various concentrations of these contaminants, which they explain that this would suggest that contamination is widespread in urban environments.

The presence of caffeine, the authors explained, is a sure indicator of human sewage contamination, as agriculture and industry do not tend to release caffeine into the environment.

Caffeine is widely consumed and degrades within a few weeks to 2-3 months in the environment.

The research team explained that the data suggest that Montreal's storm water collection system is widely contaminated by domestic sewers.

The researchers observed high levels of fecal coliforms but some of the samples contained little or no caffeine, which they attribute to urban wildlife.

"This data reveals that any water sample containing more than the equivalent of ten cups of coffee diluted in an Olympic-size swimming pool is definitely contaminated with fecal coliforms," Sauvé said.

"A caffeine sampling program would be relatively easy to implement and might provide a useful tool to identify sanitary contamination sources and help reduce surface water contamination within an urban watershed."