Mixtures of "harmless" pollutant concentrations are actually toxic – EU regulation needs to be adjusted
The risk posed by complex chemical mixtures in the environment to wildlife and humans is increasingly debated by scientists and politicians alike. To address this issue, the Ecotox Centre participated in a ring test where two mixtures of pesticides, drugs, heavy metals and other substances were investigated for their toxic effects. In both mixtures all individual substances were present in concentrations that are considered as safe under the current legislation of the European Union.
The scientists conducted 35 different bioassays with 11 organisms representing different trophic levels. The substance mixtures caused toxic effects in bacteria, nematodes, crustaceans, amphibia and fish. These results question the methods that are currently used to assess the risk of chemicals on the environment. The currently used environmental quality standards are based on the toxicity of individual substances and, according to the results of this study, do not offer enough protection when multiple chemicals are present at the same time. However, in nature this is almost always the case. So it can be expected that chemical mixtures may also be harmful if the individual pollutants occur in seemingly harmless concentrations.
Carvalho, R.N. et al. (2014) Mixtures of chemical pollutants at European Safety concentrations: how safe are they? Toxicological Sciences doi: 10.1093/toxsci/kfu118