Chemical Pollution in Freshwater Sources is Far Stronger Than Originally Thought

It turns out that chemical pollution may be far more widespread than once thought. Researchers have found that toxic chemicals, which were once thought to be more of a local problem affecting only a few bodies of water, are actually more of a large scale ecological risk that affect several thousands of European aquatic systems.

In order to see how chemicals might be impacting waterways, the researchers investigated the by how much risk thresholds  were exceeded in the river basin of major stream networks, such as the Danube and the Rhine River, at a pan-European level. More specifically, they estimated the extent for which risk thresholds were exceeded for fish, invertebrates and primary producers, such as algae.

So what did they find? It turns out that sampling varied considerably in terms of spatial coverage as well as timing, which means that direct comparisons between different countries was difficult. That said, it did show the widespread risk of contamination.

"Generally speaking we probably underestimated rather than overestimated the risks in our analyses," said Ralf Schafer, one of the researchers, in a news release. "The actual state and condition of European freshwater ecosystems is probably even worse."

So what did the researchers find? It turns out that chemical contamination is probably being mostly caused by discharge from agricultural activities, urban areas and municipal sewage treatment plants. The major toxicants of the freshwater systems were pesticides, though the researchers also found organotin compounds, brominated flame retardants and combustion-derived polycyclic aromatic hydrocarbons at critical levels of concentration.

"Fortunately the use of many of these priority substances is no longer permitted and therefore, their concentration levels are steadily decreasing in many parts of the European streams," said Werner Brack, one of the researchers, in a news release. "The real problem, however, is that a large number of chemicals which are currently in use are not taken into account at all in the context of water quality monitoring."

The findings reveal the importance of continuing environmental monitoring, especially when it comes to freshwater sources. Not only that, but the study highlights the fact that more steps need to be taken to purify water sources if certain environmental goals are to be met, including the targets of the Water Framework Directive.

The findings are published in the journal Proceedings of the National Academy of Sciences.