When the Supreme Court decided West Virginia v. EPA last week, most of the response was focused on the ruling’s impact on the government’s regulatory power over carbon emissions. The decision limited the EPA from making certain broad regulatory decisions — such as implementing a cap-and-trade program — to control greenhouse emissions from power plants under the authority of the Clean Air Act. While the ruling didn’t get rid of the EPA’s authority to regulate greenhouse gas emissions, as many environmentalists feared the Court might, it still limits the agency’s overall policymaking power.

Climate action is the main victim, but fossil fuel power plants emit more than just CO2. They also emit air pollutants such as nitrogen oxides, sulfur oxides, and particulate matter. Conventional air pollution has damaging effects on health, life expectancy, cognition, productivity, and infant mortality. It’s a risk factor for heart disease, cancer, respiratory infections, and other major causes of death. Even small increases in air pollution lead to negative health consequences. And as bad as it is now, scientists are constantly learning that air pollution is even worse than we thought.

How bad? The WHO updated its guidelines in 2021 to take into account the most recent findings, and under these new, tighter suggested limits, most of the US is currently breathing unhealthy levels of pollution.

Since the new Supreme Court ruling curtails the EPA from implementing “generation shifting” measures that are proven to reduce both CO2 and air pollution, it has implications for health as well as the climate. Regulations and policies that accelerate the transition from coal and gas to renewable energy sources are doubly beneficial, and limiting the power of the EPA to do this — now and in future — will thus be doubly detrimental.

“There’s no greater current external threat to public health and well-being than air quality,” Michael Greenstone, director of the Energy Policy Institute at the University of Chicago (EPIC), told me.

Bad air is really, really bad for us

Recent research has underscored just how prevalent air pollution is in the US, and the toll it takes on Americans even today, as EPIC’s recent annual report on air pollution around the world demonstrates. The bottom line: Most of the world, including most of the US — especially California — breathes air the WHO says is not good enough.

Energy Policy Institute at the University of Chicago

The US has greatly improved its air quality since the implementation of the Clean Air Act in 1963, particularly in the East Coast, Midwest, and Texas. But no level of air pollution is entirely safe, and air pollution-related illnesses and premature deaths are still a major problem. According to 2019 research, fossil fuel-related air pollution caused almost 200,000 US deaths in 2015; another recent paper estimated that air pollution cost the US $790 billion, or 4.2 percent of its GDP, in 2014. Nineteen of the 20 most polluted US counties in 2020 were in California, due to the state’s huge population, mountainous terrain that traps pollution, warm climate, and persistent wildfires.

EPIC’s report focuses on levels of PM2.5 air pollution, or particulate matter that’s smaller than 2.5 microns — small, deadly particles that can enter the lungs and bloodstream and are a major contributor to respiratory and other diseases. PM2.5 particles are formed both by pollution directly emitted into the air (such as from fires and dust) and by chemical reactions from nitrogen oxides and sulfur oxides (such as from power plants and vehicles). PM2.5 particles are more dangerous than the larger PM10 particles because they can penetrate deeper into the lungs and bloodstream.

The concentration of PM2.5 globally has fallen over the past few decades, but most of this improvement has come from China, which has implemented strict policies that go after multiple pollution sources. The US, which began instituting anti-pollution policies decades before China, hasn’t seen as drastic or globally relevant a shift as China has over the past two decades, but air quality has still steadily improved. PM2.5 pollution in the US is down more than 40 percent from 1998, with the largest reductions concentrated in the South and Midwest.

How the Supreme Court affects air quality

While the EPA maintains the ability to regulate carbon pollution (and the particulate/nitrogen oxide/sulfur oxide pollution that power plants emit in parallel) under Massachusetts v. EPA, its ability to make broad regulations under the authority of the Clean Air Act has been curtailed by the Supreme Court.

The Clean Air Act, enacted in 1963 and amended many times since, put the US on a path to cleaner air and improved health. The 1990 amendments alone, which broadened federal authority to target urban air pollution, emissions, and ozone depletion, are estimated to have prevented over 230,000 premature deaths and millions of cases of disease. And the EPA estimates that the act’s benefits have exceeded its costs by 30 to 1, amounting to tens of trillions of dollars in savings. While most reductions in air pollution death rates across the world since 1990 have come from lessening indoor air pollution, in the US, reductions in air pollution-caused death estimates have been largely driven by reductions in outdoor air pollution — the sort the EPA can regulate.

The researchers I spoke to say the ruling, in isolation, is probably not going to make air pollution significantly worse. The EPA will still be able to regulate emissions from power plants, vehicles, and infrastructure. “My biggest worry was they were going to use this case to fundamentally challenge the authority of EPA to regulate greenhouse gases,” said Wei Peng, an air pollution researcher at Penn State, and that didn’t happen.

Electricity-related air pollution from fossil fuel sources still leads to 10,000 to 20,000 deaths per year, said Peng, even though almost all sulfur oxides and most nitrogen oxides have been eliminated through technologies like scrubbers and low nitrogen oxide burners. To get rid of the last pollutants in the electricity sector, she said, “we need to eliminate fossil fuel combustion from the electricity sector … the last mile problem is all about fuel switching.”

But this important move away from coal and gas wouldn’t have necessarily happened through the EPA. The increasingly cheap cost of renewable energy incentivizes companies to switch to wind and solar power even without regulation, and they can be further incentivized through clean energy tax credits. What was strange to Greenstone, at EPIC, is that the ruling took away the opportunity for the EPA to implement a cost-effective policy (cap and trade), while still allowing regulation, which he sees as effectively amounting to ruling “in favor of more expensive climate regulation.”

The Supreme Court, in West Virginia v. EPA, used the “major questions” doctrine to require impactful regulatory strategies to be explicitly approved by Congress, which sets a precedent that could prevent future environmental regulation by government agencies. So while the West Virginia ruling in itself probably won’t make air pollution significantly worse, there are further challenges to environmental laws that also have implications for pollution, and West Virginia v. EPA may make such challenges and limits on regulation more common. Movement away from coal, for example, is chiefly about greenhouse gases, said Peng, but coal is also a major source of conventional air pollution, so anything that curtails the ability of the EPA to drive that transition faster likely will have impacts on air pollution, too.

While federal and state legislators can still take action on climate change — Congress could even still authorize the EPA to do cap and trade — the hard reality is that Congress hasn’t been able to act to address climate change, and shows virtually no sign of being able to do so in the future, given polarization over the environment. That wasn’t always the case: The original Clean Air Act and its important amendments were passed by huge bipartisan majorities, and at least some — including the 1990 amendments — were passed under GOP presidents. Cap and trade itself is a market-based approach supported by Presidents Ronald Reagan, George H.W. Bush, and George W. Bush. But since climate action has now chiefly become a Democratic issue, any legislation around environmental concerns will struggle to pass.

The Clean Air Act drastically reduced conventional air pollution, saving hundreds of thousands of lives and trillions of dollars. But it’s also a relic of a time when caring about the environment — and its effects on human health — didn’t break down along party lines. As a conservative Supreme Court pares back the powers of the regulatory apparatus, hopes for future progress will fall back onto Congress — and that’s not much hope at all.