What happens when the Environmental Protection Agency issues an air pollution regulation?

First, whoever is regulated – power plants for example – must take action to comply with new requirements. The company incurs the costs of controls, perhaps installing a scrubber to remove pollutants or switching to a less polluting fuel. These actions reduce pollutant emissions so the air we breathe is cleaner, enabling us to live longer and healthier lives. Before it issues a regulation, EPA typically compares the value we place on these health improvements to the costs of controls – to determine whether the benefits justify the costs.

But this month, reversing decades of practice, EPA announced that it will no longer trace the impacts of changes in emissions on health.

Controlling pollutants, such as fine particulate matter (PM_2.5), reduces premature deaths; the value of these averted deaths accounts for a substantial share of the benefits of many air pollution regulations. Such controls also decrease the risks of numerous other health conditions, ranging from asthma to heart attacks, both now and in the longer term. Without information on these health impacts, it will be unclear whether incurring the costs of pollution controls is worthwhile.

EPA provided the rationale for its decision in a January regulatory analysis, citing uncertainties in the estimates. Ignoring uncertain impacts is contrary to longstanding White House and agency guidance, which emphasizes the need to quantify these effects. Quantification allows government officials and the general public to appropriately weigh the effects of uncertainty in the decision-making process. For example, understanding that estimated benefits may cover a wide range – e.g., from $500 million to $1 billion – is more useful than having no information on the possible magnitude. The decision to instead ignore these benefits feeds directly into President Trump’s deregulatory agenda.

Many of the news reports on EPA’s decision focus on the metric used to estimate the value of mortality risk reductions – the value per statistical life (VSL). This often-misunderstood metric reflects what people are willing to pay for small reductions in their own risk of dying, based on decades of research. The EPA decision has implications far beyond the metrics used for valuation, however. The agency will now simply ignore health benefits from cleaner air altogether, a move that makes it much harder to advocate for pollution controls.

What is the role of benefit-cost analysis?

Benefit-cost analysis has been a key component of the regulatory development process for over 40 years. In 1981, President Reagan required federal agencies to estimate the costs and benefits of their major regulations; in 1993, President Clinton revised these requirements; and in 2025, President Trump expanded the requirements to cover additional agencies.

Comparing benefits to costs has remained a priority across Republican and Democratic administrations in part because it identifies the policy option likely to deliver the greatest net benefits. More importantly, it promotes systematic exploration of both positive and negative impacts, including impacts that might otherwise be hidden. In combination with legal authority, political goals, budgetary feasibility, and other factors, the results help shape the decision by synthesizing information and testing how uncertainty affects the conclusions.

What is the rationale for EPA’s decision?

In its regulatory analysis, EPA states that it is “no longer monetizing benefits from PM_2.5 and ozone but will continue to quantify the emissions until the Agency is confident enough in the modeling to properly monetize those impacts.”

Quantifying emissions alone tells us almost nothing about health impacts: Changes in emissions must be linked to changes in individuals’ exposure to the pollutants, and the relationship of these exposures to health risks must also be estimated. Without estimates of health impacts, monetary valuation is not possible, and related benefits cannot be compared to costs.

EPA says prior analyses were over-reliant on a single estimate, failing to appropriately characterize uncertainty. It is especially critical of benefit-per-ton estimates, which have been used when detailed modeling is infeasible. While improving approaches to estimating benefits and incorporating uncertainty is a laudable goal and consistent with existing guidance, excluding these values in the interim promotes a false sense that they are zero. Deep cuts in EPA staffing and budget also suggest that such improvements are unlikely to materialize anytime soon. Thus, what is described as an interim approach will likely persist.

Uncertainty does not equal zero

These analytic decisions have real world impacts, affecting health and environmental outcomes in the U.S. and beyond.

Treating uncertain impacts as zero deprives decisionmakers of critical information. For example, the National Ambient Air Quality Standards (NAAQS) for particulate matter is one of EPA’s largest recent regulations. In 2032 alone, EPA expects the regulation to avert 2,000 or more deaths nationally and a substantially larger number of hospital visits and nonfatal effects. In that year, EPA’s central estimate of regulatory costs is about $590 million, with counterbalancing benefits of over $22 billion. Its estimates are accompanied by both qualitative and quantitative discussions of uncertainty, suggesting that it is highly unlikely, perhaps impossible, that benefits would be zero.

In the absence of information on health benefits, it will be difficult to advocate for appropriate regulation of these and other threats to our health and longevity, balancing costs against human suffering.

All perspectives expressed in the Harvard Climate Blog are those of the authors and not of Harvard University or the Salata Institute for Climate and Sustainability. Any errors are the authors’ own. The Harvard Climate Blog is edited by an interdisciplinary team of Harvard faculty.