Mercury emissions from human activity have decreased, despite global data suggesting otherwise

Mercury pollution from human activities is on the decline, with a 10% drop in emissions, MIT scientists say

According to a new study published in PNAS by researchers from the Massachusetts Institute of Technology, mercury emissions due to human activities have fallen by 10% between 2005 and 2020.

These figures, however, seem to contrast with reality.

“It does seem mercury emissions are going in the right direction and may continue to do so, and that’s great to see,” says co-author Noelle Selin, MIT professor at the Institute for Data, Systems, and Society (IDSS) and the Department of Earth, Atmospheric, and Planetary Sciences (EAPS). “But that was the best we could do for mercury. We definitely need to continue to measure and move the science ahead.”

The study

For the new study, the researchers analyzed data from 51 monitoring stations across the Northern Hemisphere and found that the decline was indeed significant between 2005 and 2020. To ascertain the probable reason for the trend, they used two modeling approaches; both techniques suggested a decrease in mercury emissions through human activities as the most likely cause.

On the other hand, global studies report the opposite, estimating emissions using models that embed average emission rates of polluting activities and the global extension of these activities.

The divergence between the models and real data

Global inventories are based on models calculating the emissions considering the average pollution rates from human activities and their global scale. But, as now obvious, the real data collected from the monitoring stations told a different story.

For MIT’s former postdoctoral researcher Ari Feinberg, now lead author of the study, “We really need real data to improve models and emission estimates that do a better job of predicting mercury pollution trends”.

Nevertheless, the study finds that scientists still cannot explain such a wide disparity between inventory and actual data. They say this might be missing information from some nations or undetected changes in sectors such as small-scale mining for gold or disposing of products containing mercury.