People fishing along the banks of the White River in Indianapolis often encounter warning signs about consuming the fish they catch. One danger is mercury poisoning, as mercury is a neurotoxic metal particularly damaging to children’s brain development, potentially causing reduced IQ, decreased earning potential, and increased health costs. A 2005 calculation estimated mercury-related productivity losses at nearly $9 billion annually. Mercury can enter river fish when emissions from coal-burning power plants are released into the air. The Environmental Protection Agency (EPA) implemented a rule in 2012 to limit mercury emissions from coal-fired power plants, but enforcement ceased under the Trump administration, citing industry costs as outweighing health benefits. The Biden administration is now working to reinstate this rule.
As a biogeochemist at Indiana University-Purdue University Indianapolis, I study mercury and its origins. Before the EPA’s mercury rule, my students and I began investigating how power plants around Indianapolis contributed to mercury levels in the environment. The threat of eating fish from rivers near these plants varies depending on the fish species and the consumer’s age and health. Mercury is bioaccumulative, meaning it builds up in organisms through the food chain. Emissions of mercury from coal plants fall to the ground, wash into water bodies, and bacteria convert it into the toxic form, methylmercury. This process leads to its accumulation in the food chain, with top predator fish like smallmouth bass and lake trout containing the highest mercury levels, making consumption potentially harmful, especially for pregnant women and children.
Our research sought to determine if local coal plants affected the environment significantly. Though mercury can be considered a global pollutant, we discovered that most contamination came from a visible coal-powered plant in the city, now switched to natural gas. Mercury tended to combine with atmospheric elements and rain, contaminating the landscape. Studies show elevated mercury levels in areas near power plants. When we analyzed soils and river sediments in Indianapolis, we identified a “plume” of mercury with high concentrations near the plant, diminishing further away. The White River, flowing against the city’s wind patterns, showed rising mercury levels as it coursed through Indianapolis, exposing rural anglers to high-mercury fish.
The EPA introduced the Mercury and Air Toxic Standards (MATS) rule in 2011 to address these health threats, requiring coal plants to reduce mercury emissions or transition to different energy sources like natural gas, which, though less risky for mercury, still poses health and climate issues. The Trump administration attempted to weaken this rule in 2020, but the Biden administration reinstated it in early 2022. The estimated cost of the MATS rule for the U.S. electricity sector is around $9.6 billion annually, matching past estimates of mercury-related productivity losses.