Toxicity: effect-directed water-quality measurement

What is the problem?

The Netherlands does not currently meet the (chemical) objectives of the Water Framework Directive. The reason is partly that there are too many toxic compounds present in our surface water. This concerns a large number of different compounds, including pesticides, pharmaceuticals for humans and animals, and compounds originating from the (chemical) industry.

It is a complicated matter to determine what compounds are present in the water and what their effects are on humans and the environment. One of the reasons for the difficulty is that combinations of different compounds can have effects that the separate compounds do not have (so-called ‘combination toxicity’).  The EU’s SOLUTIONS and MARS projects recently showed that exposure to such mixtures is ecologically significant: approximately 30 percent of ecological variation is explained by the exposure to mixtures.

Moreover, new compounds are constantly being developed, compounds whose effects are still not clear. This means that the number of compounds that are present in the water is actually greater than the number of those being assessed.

Water managers require more handles for an effective approach to toxic compounds. They need to be able to better determine the presence and the effects of the compounds. They also need a clearer idea on appropriate measures to mitigate ecotoxicological effects and improve water quality.

What are we going to do?

Since 2016, water managers have used Ecological Key Factor ‘Toxicity’ to determine the presence of compounds in water. This instrument calculates the effect of many compounds and of their mixtures on flora and fauna. This is known as the toxic pressure. This metric reveals whether any – and if so, how many – species would disappear because of the toxicity.

The Key Factor instrument needs to be further developed to make it more effective. First and foremost, this involves providing help in the interpretation of the toxic pressure, that is: What does it mean for the ecological status? We will also be making the instrument’s application more practical.

Determining and interpreting the toxic pressure is step one. Just as important is the derivation of (cost) effective measures against toxic pressure. We will therefore extend the tool with a ‘measure database’. This will allow water managers to choose from a wide range of options. They won’t have to reinvent the wheel themselves.

We will also help water managers improve their monitoring of toxic compounds. We will provide them with practical handles to mitigate the negative consequences of compounds.

The KWR researchers working on this project will focus especially on sample preparation techniques, the selection of relevant and effective bioassay sets, and the interpretation of bioassay results.

What are the deliverables?

The project will deliver a renewed and improved Ecological Key Factor ‘Toxicity’ instrument. To achieve this improvement we will draw on knowledge from the European SOLUTIONS and MARS projects. We will develop decision trees, infographics, tools and manuals which provide the user with staged assistance in applying the renewed Key Factor and interpreting the results, with a special emphasis on the derivation of effective measures. We will consult the users about the products, to ensure that they are truly applicable in practice.