Global Reductions in Mercury Emissions Should Lead to Billions in Economic Benefits for U.S.

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Determining how regulatory policies will ultimately lead to health and economic benefits is a complex and convoluted problem. To trace the pathway from policy to impacts, Selin and co-author Amanda Giang, a graduate student in MIT’s Institute for Data, Systems, and Society, began with estimates of mercury reductions set by both the Minamata Convention and MATS.

The team then used an atmospheric transport model to trace where emissions would settle over time, based on the reductions proposed by each policy scenario. From regional depositions of mercury, they then estimated the resulting mercury concentrations in fish and mapped these concentrations to seafood sources throughout the world.

Next, the team correlated seafood sources to fish consumption in the U.S., and calculated changes in human exposure to mercury through time. They used epidemiological models to estimate how changes in mercury exposure affect incidence of health impacts, such as heart attacks and IQ deficits. From there, Selin and Giang used economic valuation methods to translate heath impacts into economic benefits — namely, lifetime and economy-wide benefits to the U.S.

Understanding the drivers

While the researchers were able to come up with benefits in the billions for both the global and domestic policies, they acknowledge that these numbers come with a significant amount of uncertainty, which they also explored.

“We’re trying to understand different drivers in the variability of these numbers,” Giang says. “There’s a lot of uncertainty in this system, and we want to understand what shifts these numbers up and down.”

For example, scientists are unsure how far different forms of mercury will travel through the atmosphere, as well as how long it will take for mercury to accumulate in fish. In their analysis, Giang found that, even taking into account most of these uncertainties, the economic benefits from the global treaty outweighed those from the domestic policy, except when it came to one key uncertainty: where people’s seafood originates.

“We do find that in our scenario where everyone is eating local fish, the benefits of domestic policy are going to be larger than the Minamata convention,” Giang says. “Our study points to the importance of domestic policy in terms of protecting vulnerable populations such as subsistence fishers or other communities that do rely on U.S. freshwater fish.”

“There are a ton of uncertainties here, but we know that mercury is a dangerous pollutant,” Selin adds. “When you put in a policy, how do you think about its ultimate environmental and human effects? We think this method is really a way to try and move that forward.”

This research was funded, in part, by the National Science Foundation.