EU Science Hub

Chemical pollutant mixtures: how safe are they?

Jul 08 2014

The JRC recently published the results of a co-authored study on the risks posed by chemical pollutant mixtures in the environment. This work is part of the first EU-wide campaign to test the use of biological based assay (bioassays) for assessing water quality in Europe, following the recommendations of the communication of the European Commission on the effects of chemicals (COM(2012) 252), calling for a greater effort to understand and assess the risks associated with chemical mixtures.

Results of the study highlighted the need of precautionary actions even in cases where individual toxicants are present at seemingly harmless concentrations. Some of the observed effects of chemical pollutant mixtures included: changes in marine microbial composition, microalgae toxicity, fish embryo toxicity and increased presence of genes linked to stress response.


The effects of complex chemical mixtures on wildlife and humans have rarely been analysed under environmentally relevant scenarios. To address this issue, the study proposes an innovative approach bridging the gap between ecological and chemical monitoring. Two mixtures were tested, composed of 14 and 19 substances of concern, each present at its safety limit concentration as imposed by European legislation: pesticides, pharmaceuticals, heavy metals, polyaromatic hydrocarbons, surfactants and plasticisers. The effects of the mixtures were assessed in 35 bioassays, among them in vivo studies, based on eleven organisms all having a different position in the food chain.


Effects of this chemical mixture have been also investigated as gene expression changes in four different organisms. The objective is to identify biomarkers that could be used as early warnings of exposure, even before other adverse outcomes become visible.

Further work will be needed to evaluate the performances and harmonise the different bioassays currently available.


The JRC, within its work programme on water quality assessment, contributed to the study by testing the effects of mixtures on its in-house model organism - the marine diatom (algae) Thalassiosira pseudonana - and performed an assay to detect the estrogenic receptor-binding compounds.