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Last changed: 06 February 2017

Swedish municipal drinking water is considered safe to drink, but it can sometimes still contain chemical pollutants. In the project entitled SafeDrink, SLU researchers are developing methods to detect hazardous substances in drinking water at an early stage, methods which could be of international importance.

Professor Karin Wiberg is leading the project and says that the previous discovery of these hazardous organic pollutants has often been a matter of chance.

The drinking water in Tullinge outside Stockholm is one example. There, the discovery was made during a laboratory experiment being conducted by upper secondary school students, who were analysing drinking water they had brought from home.

"They detected high levels of perfluoralkylated substances in one sample. These substances were present in aqueous film-forming foam used for fire-fighting close to the drinking water well nearby," says Professor Wiberg.

Hard to look for unknown substances

One problem facing drinking water treatment plants is knowing exactly which substances to search for as part of their water quality controls. Another problem is knowing where the pollutants originate from. In addition to this is the risk of contamination of water wells as a result of the effects of climate change such as more frequent and intense flooding, leading to water finding new pathways.

Professor Wiberg says it is difficult to carry out tests blind. An analysis of drinking water using mass spectrometry can produce thousands of hits. Among these hits, most may be unknown chemical substances. So how can we identify them? And how can we find out whether they are toxic? An adult human consumes between 2 and 2.5 litres of water a day for drinks and cooking purposes, which means that even very low concentrations of pollutants can result in high intakes.

Early detection is essential

"We need to be able to detect the risks associated with hazardous pollutants in drinking water at an early stage, i.e. before people are significantly exposed to them and before health effects occur."

In the SafeDrink project, Professor Wiberg and her research group are working with SLU Professor Agneta Oskarsson and her toxicologists to develop a methodology for detecting hazardous organic chemicals in drinking water. The method integrates chemical and toxicological characterisation and starts by concentrating a water sample by a factor of around 10,000. The sample is then ready for toxicological bioassays and chemical analysis.

"My research group is carrying out both targeted and non-targeted chemical analyses with the aim of characterising the sample content as accurately as possible."

Exposing human cells to water

The toxicologists' bioassays are based on exposing cultivated human cells to the concentrated drinking water samples. These tests can show various effects, such as endocrine disruption, mutagenicity and oxidative stress. If it becomes apparent that the sample is affecting the cells, a very thorough chemical analysis is initiated.

The idea is to divide samples which have shown toxic responses into fractions and then test for toxicity again. The fractions that show toxic effects will be subjected to further chemical characterisation.

"By repeating this in loops, we can narrow down the problem and hopefully identify which substances are harmful."

Water issues are global

The aim of this integrated chemical-toxicological method is to search for pollutants which were previously unknown to drinking water producers. SafeDrink will thus draw attention to hazardous emergency pollutants and help the community to prioritise chemicals that should be included in routine monitoring at drinking water treatment plants. The project will also develop knowledge needed for optimising the removal of harmful substances in drinking water.

Water issues are also important internationally and Professor Wiberg believes that SafeDrink's results will prove to be important in many other countries.

"The risk of chemical pollution of drinking water has increased as we use more and more chemicals. Chemical legislation is also weak in some regards. We must therefore develop feasible control systems. Drinking water is after all the most important food in the world!