Estimating chemical footprint: Contamination with mercury and its compounds

Chemical pollution is a problem of global importance. However, there are currently no agreed approaches for integrated environmental impact assessment (EIA) of chemical effects at global scale. We present a new systems-based approach to EIA of chemicals. Our methodology considers propagation of chemical pollutants in the environment, in conjunction with the approach followed in the Russian regulatory system. To estimate chemical footprints related to environmental contamination by potentially toxic substances, measured environmental concentrations were combined with results from the UNEP-SETAC scientific consensus model USEtox, which is recommended for and widely applied in life cycle impact assessment. Our approach was tested using the example of mercury, which has been shown to be a hazardous pollutant at regional and global scales. Results show that the main contribution to the overall chemical footprint of mercury and its compounds is related to releases into aqueous bodies from human activities. Estimations of Maximum Available Concentration overrun show that calculated and experimental data agree to a good extent, particularly for mercury contamination in freshwater bodies. Discrepancies between calculated and actual data are mainly due to extrapolated data used for model validation, averaged data applied to entire Russian Federation districts, the omission of industrial soil as a separate model compartment, and not accounting for cumulative damage from emissions in previous years. These aspects will inform future efforts to refine the methodology. The results of this study were presented to the Ministry of the Natural Resources and Environment of the Russian Federation. It is planned to use these results as one basis for prioritizing action on sources of environmental mercury contamination and as a benchmark for minimizing such impacts.