SYNERGY - Determination of site-specific biological effects of exposure to complex mixtures

Environmental exposure to complex chemical mixtures is feared to increase the toxic potential due to additive or synergistic effects and is of great concern to both the public and the regulatory authorities. As chemicals are regulated on basis of their individual effects there is a concern that exposure to multiple chemicals at low (safe) levels may result in a larger effect then predicted by the individual exposures. However, as most studies to date have been performed on laboratory defined mixtures, rather than natural mixtures, there is limited information on how individual chemicals in a mixed exposure behave in the environment. In the environment the mixtures are far more complex than those that are used in laboratory settings, including not only the tested chemicals but also the variability of other parameters of the natural waters. These complex natural exposures may not always results in additive or synergistic effects of the chemicals. It is possible that the individual chemicals in a mixture may block or neutralize the effects of other chemicals and thereby lower the deleterious biological effects. In line with this, results from our DOSE project of a closed mine and its recipient (Lake Hornträsket) indicates that the mixed exposure at this mining site results in a reduction or neutralization of the effects expected from the individual metals. In light of this it is therefore important to identity which chemicals that act synergistically as well as those combinations that reduce or neutralize the individual effects, and through which mechanisms this occur, in order to improve risk assessment.

In the present project we will therefore study the effects of chemical mixtures, primarily metal mixtures released from different mining operations. The goal is to collect biological data that can be used to improve risk assessment.