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The biggest source of mercury in the U.S. continues to be coal power plants. booleansplit/flickr, CC BY-NC

Are tighter EPA controls on mercury pollution worth it?

Over 300,000 babies every year are born in the United States with levels of mercury that put them at risk of neurological and developmental problems. How much would you be willing to spend to reduce this number?

This might seem like an abstract question, but the judgments regulators make on this question can determine whether or not a proposed regulation survives challenges in court.

Regulation is an issue on the presidential campaign trail as well, with a number of candidates arguing that tighter environmental rules will strangle the economy and deliver few benefits.

One regulation at stake is an Environmental Protection Agency (EPA) proposal to control mercury emissions from power plants under the Clean Air Act, through the Mercury and Air Toxics Standards (MATS) issued in 2013, which remains in effect after a Supreme Court ruling last year challenged aspects of the decision to regulate.

We’ve done research to quantify the economic impacts from better public health of proposed mercury rules and found the benefits are substantial – on the order of billions of dollars per year, with significant improvements for at-risk populations.

Supreme Court versus EPA

Mercury is a global environmental pollutant. In its most toxic form, methylmercury, it bioaccumulates in fish, posing risks of health effects such as cognitive and behavioral impacts and cardiovascular damage in people who consume fish.

Mercury that contaminates fish comes from ongoing as well as historical human activities – primarily, burning coal in power plants as well as mining.

Mercury can travel long distances through the air before it deposits in aquatic ecosystems, so mercury emitted anywhere in the world can reach the U.S. This means that U.S. fish consumers are affected by both domestic mercury emissions, which contaminate nearby waterways, and global sources, which can travel across borders to affect oceans and watersheds worldwide.

In calculating the health benefits of mercury controls, at-risk groups of people, such as subsistence fishers, benefit to far greater degree than the whole U.S. population. mugley/flickr, CC BY-SA

In the United States, many sources of mercury emissions have already been regulated, and domestic emissions have decreased substantially in the past few decades. The largest remaining domestic source is emission from coal-fired power generation. Worldwide, mercury is the subject of a recent global environmental treaty, named the Minamata Convention after a city in Japan where methylmercury poisoning was first identified decades ago.

Regulating emissions, however, costs money. In the case of power plants, many would need new pollution control technology to meet the more stringent mercury controls of the EPA’s Mercury and Air Toxics Standards (MATS), which may become cost-prohibitive. A lot of discussion of the proposed regulation, therefore, centers on whether the benefits of mercury reductions – reduced risks to humans and the environment – warrant the costs of control.

This was a key question addressed when MATS was reviewed by the Supreme Court. In a 5-4 vote in June 2015, the Supreme Court held that the EPA should have considered costs when deciding to regulate mercury.

In his majority opinion, Justice Scalia drew attention to an apparent discrepancy between the costs and benefits of this regulation, saying:

One would not say that it is even rational, never mind ‘appropriate,’ to impose billions of dollars in economic costs in return for a few dollars in health or environmental benefits.

National cost of mercury pollution

To support development of the mercury standards, EPA conducted an assessment of the benefits of the rule. The EPA’s analysis included both specific benefits to selected communities affected by mercury, such as recreational fishers, subsistence fishers, and Native Americans, as well as so-called cobenefits – reductions in other pollutants, specifically atmospheric fine particulate matter (PM2.5).

While the EPA judged that the total benefits of the rule exceeded costs, the vast majority of the benefits were actually from the rule’s cobenefits. In fact, the EPA did not attempt to quantify the benefits of proposed mercury reductions to the general U.S. public, only quantifying IQ effects on a subset of the sensitive populations mentioned above.

This raises the question: is it possible to assess the benefits to the entire U.S. population?

In a recent paper published in the Proceedings of the National Academy of Sciences, we did just that. We linked a series of models and data to trace the complex, uncertain connections between emissions and their impacts as a way to estimate the health and economic benefits to the U.S. as a whole of proposed policy actions on mercury.

Specifically, we linked multiple models that track emissions of mercury, its global transport through the atmosphere, and its transformation into toxic methylmercury in aquatic ecosystems. We also linked models that figure how the consumption of contaminated fish affects human IQ and cardiovascular health, and their economic implications. In this way, we came up with a comprehensive analysis of the economic benefits of mercury controls for the United States.

Our model showed that the monetary benefits from improved health of mercury controls in the U.S. are substantial.

For example, we were able to project the lifetime health benefits from reduced exposure to mercury. Those include a person’s willingness to pay for lowering the risk of a fatal heart attack, cost savings from avoided medical care, and increased earnings from better health and reduced mercury IQ damages. Using this method, cumulative benefits from MATS reached US$147 billion by 2050.

We also estimated cumulative economy-wide benefits. The associated productivity gains of a national labor force with improved IQ and fewer heart attacks as a result of reduced exposure to mercury totals $43 billion in our model.

More than 90 percent of estimated benefits in our analysis are due to cardiovascular effects. Cardiovascular benefits, however, were not quantified by EPA’s analysis, as more scientific information on the association between mercury and cardiovascular impacts has emerged since the EPA’s analysis, which was finalized in 2011. While the cardiovascular effects of mercury exposure are considered more uncertain than IQ impacts, they can lead to potentially large social and economic burdens.

In addition to cardiovascular effects, there are several potential health benefits from reducing mercury emissions that we cannot quantify, including neurobehavioral effects, such as language skills and memory, and impacts on the immune system, such as risks for autoimmune disease.

At-risk populations

Our model allows us to quantify the economic impact of mercury rules from improved health, but our analysis also led to another conclusion: simple comparison of costs and benefits is likely inadequate for assessing whether and how to regulate mercury.

In particular, we found that mercury controls can have substantial benefits for communities consuming mostly locally caught freshwater fish from U.S. waters.

Communities that rely on fish intake for subsistence, recreational, or cultural reasons can be particularly vulnerable, including social and cultural impacts that can be difficult to quantify. One example is Native Americans, for whom fishing may be important for culture as well as nutrition.

Though these communities may represent only a small share of the U.S. population, traditional cost-benefit analyses don’t directly address issues of equity and environmental justice, which are a specific goal of hazardous air pollution policy.

Our research suggests that including a larger set of health effects – namely, both IQ and heart attacks – and the impact on specific populations could lead to mercury-related benefits estimates that are orders of magnitude larger than those reported by the EPA.

Regardless of the approach used to weigh advantages and disadvantages of policy, the research is now clear: the benefits of MATS are substantial.

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