The regulation of ozone pollution has had a complicated history in recent years, but today marks a potential turning point toward an ozone standard that protects public health.
Today the EPA is expected to release a draft rule on ambient ozone pollution proposing a standard of 65 to 70 parts per billion (ppb), as EPA Administrator Gina McCarthy announced in an opinion piece on CNN Money. This range falls within the upper half of the 60 to 70 ppb range recommended by EPA’s Clean Air Science Advisory Committee (CASAC), a group of external experts that advise the agency on air pollution standards. To understand why today’s proposal is big news, we need to briefly review the history.
While we’ve made great strides in air quality in recent years, ozone pollution continues to be at unsafe levels in cities across the country.
A history of interference
Few pollutants have been as big and prolonged of a political problem as ozone. Ozone forms in the atmosphere when sunlight interacts with precursor pollutants emitted from tailpipes, power plants, and natural sources (more on this here). This means that ozone is geographically disperse, with even rural counties downwind of major cities experiencing unsafe ozone levels (in fact, my own doctoral research showed this). Moreover, because many sources are involved in ozone production, its regulation can affect many sectors. So when the science began to show adverse health effects even at lower levels of ozone, control of ozone pollution became politically challenging.
Spoiler alert: Science didn’t win. Under both the George W. Bush and Obama Administrations, the ozone standard didn’t adhere to the advice of EPA’s science advisers (full details on this here and here). The current standard of 75 ppb has long been out of sync with CASAC, who first recommended the 60 to 70 ppb range way back in 2007.
In this backdrop, it’s worth recognizing the significance of today’s draft rule that finally proposes a standard within range believed to be protective of public health. This is in spite of political pressure to maintain the status quo, pressure from regulated industries, and pressure from members of Congress—all asking the administration to compromise the health of thousands of Americans by failing to tighten the standard.
I’m glad to see a proposed standard that would finally be more protective of Americans’ health.
State of the science on ozone
Interestingly, CASAC’s recommendation of 60 to 70 ppb includes some qualifying language. In its letter to the EPA administrator, the committee concluded that although 70 ppb was included in their recommended range, such a standard would not provide an “adequate margin of safety,” as the Clean Air Act mandates. The committee goes on to note that with a 70-ppb standard there is “substantial scientific evidence of adverse effects … including decrease in lung function, increase in respiratory symptoms, and increase in airway inflammation.”
Thus, if the administration chooses to go with a standard of 70 ppb, they are doing so with the knowledge that their scientific advisers do not feel that this protects public health with an adequate margin of safety, a decision that could prove difficult for the administration to make.
The challenge of a science policy decision
On the other hand, the administration faces pushback from some regulated industries, who claim high costs associated with tightening of the ozone standard. While there is reason to believe that such claims are greatly exaggerated, there is another reason they aren’t relevant here—the EPA cannot legally consider them. The Clean Air Act dictates that the standard must be set based solely on what level is protective of public health; economic considerations cannot be considered in setting the standard. This was reaffirmed in the 2001 Supreme Court case Whitman v. American Trucking Associations, Inc. This ruling has perhaps never been more meaningful than for this ozone standard update, when efforts are being made to pressure the administration to prioritize cost considerations over public health.
Ultimately, this is where science meets policy. Last spring, when the EPA science advisers were discussing the ozone standard they would recommend, they noted how far the science took them and where the decision then became a policy question. They noted health effects at 70 ppb and they agreed that 60 ppb would better protect public health, but they gave the administration discretion within this range. The administration has narrowed the proposal to 65 to 70 ppb but has said they will take comments on a rule down to 60 ppb.
Toward a science-based ozone standard
It may be unlikely that the administration would set a standard below 65 ppb at this juncture, but the hope is that the final rule will heed the advice of EPA’s science advisers and (at last) set a standard below 70 ppb. The EPA will no doubt get many comments offering diverse perspectives on what the rule should be and it is difficult to know what standard the administration will set in the final rule. But one thing is for sure, the science is there.