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Smog in Los Angeles, California.

Smog in Los Angeles, California

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New U.S. ozone standard won’t please greens or industry

After years of controversy, the U.S. Environmental Protection Agency (EPA) today tightened its national limits on ground-level ozone pollution, a main contributor to smog. But it has picked a level that the agency's own science advisers have said might not fully protect health and the environment.

EPA will lower the standard from the current 75 parts per billion (ppb) to 70 ppb, a move that agency officials say will deliver health benefits (in the form of avoided maladies such as asthma attacks, premature deaths, and sick days) that outstrip the costs by a factor of two to four. The move will disappoint industry groups that had waged an expensive and intense campaign to keep the standard at 75 ppb.

And it will also disappoint environmental advocates, who have argued that even EPA’s own technical advisers had said in 2014 that scientific evidence would support a tighter standard. "For a standard that’s supposed to protect health with an 'adequate safety margin,' we don’t think that’s been done here with that many lives sacrificed and that many asthma attacks allowed," John Walke, clean air director at the Natural Resources Defense Council, tells ScienceInsider.

Walke also suggests that the rule conflicts with recommendations from EPA's science advisers. Under the Clean Air Act, EPA must set national air limits on six "criteria pollutants"—one of which is ground-level ozone—based only on scientific data of its harms. The standards must be strong enough to protect public health and welfare "with an adequate margin of safety." States then can factor in the rule's costs in devising a plan to implement it.

EPA's Clean Air Scientific Advisory Committee (CASAC) suggested a standard between 60 and 70 ppb, but it attached a big caveat to 70 ppb—that it would provide "little margin of safety for the protection of public health, particularly for sensitive subpopulations." A 70-ppb standard thus "may not meet the statutory requirement to protect public health with an adequate margin of safety," CASAC said at the time.

That advice diverged from the assessment of EPA's policy staff, who wrote in a 2014 analysis that a standard within the 60 to 70 ppb range would improve on the current standard and "could reasonably be judged to provide an appropriate degree of public health protection, including for at-risk populations and lifestages."

EPA Administrator Gina McCarthy told reporters on a conference call today that 70 ppb reflected her best judgment of what the science says about what standard is needed to satisfy the Clean Air Act. Although her EPA predecessor, Lisa Jackson, had once proposed a standard below 70 ppb, McCarthy rebuffed a suggestion that regulatory costs might have influenced her decision to go with 70 ppb. She said new studies since that time suggest that 70 ppb is more appropriate from a scientific standpoint, with the evidence for harm below those levels far weaker. “My final decision … reflects my consideration of [CASAC’s] advice and my obligation to weigh the science, including the uncertainties that remain,” McCarthy said.

The letter of the law requires that EPA set a standard that “is no more or less stringent than necessary to protect at-risk groups,” McCarthy said in prepared remarks, adding that such a judgment can be difficult. Clinical data show that 72 ppb is the lowest exposure that causes health problems in healthy, exercising adults, McCarthy said. She cut that value down to 70 to protect the most vulnerable subpopulations like children.

Reacting to today’s news, the National Association of Manufacturers (NAM) said that EPA had displayed leniency with the 70-ppb decision. But the industry group still criticized EPA for tightening the standard at all, saying that it will impose major new costs on manufacturers. "It still feels like a punch in the gut,” said Tom Riordan, chair of NAM's small and medium manufacturers group, in a statement.

The American Petroleum Institute (API) went one step further, calling on Congress to block the rule because many areas still haven’t come into compliance with the 75-ppb standard. “The administration ignored science by changing the standards before allowing current standards to work,” API President Jack Gerard said in a statement. (Industrial sectors such as oil and gas production don’t emit ozone directly; rather, they emit compounds—such as nitrogen oxides and volatile organic compounds—that get converted to ozone in the atmosphere.)  Senator James Inhofe (R–OK), chairman of the Senate environment committee, agreed with Gerard and vowed in a statement that he would pursue legislation to block or weaken the rule.

But medical and health groups reject Gerard’s view of the science and wanted EPA to go further. Many, including the American Academy of Pediatrics and the American Medical Association, had pushed for a 60-ppb standard, the most stringent level CASAC had recommended. EPA health analyses found that a 60-ppb standard would prevent nearly 2 million child asthma attacks and missed school days each in 2025, versus more than 300,000 each at 70 ppb, the groups note. An upcoming report by the American Thoracic Society (ATS) will say that a 70-ppb standard would result in 3700 more premature deaths than a 60-ppb standard would. Vickie Patton, general counsel at the Environmental Defense Fund, cited the ATS findings in criticizing EPA's final ozone rule. “While the air quality standard announced today is an improvement, it falls short of what is necessary," Patton said in a statement.

McCarthy suggested that the scientific evidence isn’t strong enough to support lowering the standard to 60 ppb. “While some studies have shown effects in adults at levels as low as 60 ppb, these studies do not show that these effects are harmful,” McCarthy said. And even at a 70 ppb standard, some 98% of children will experience exposures below 60 ppb, she notes; that’s because the standard only allows few days where the level rises to 70 ppb itself, she says.

The move by EPA is just the latest in a long series of battles over ozone that have resulted in disappointments to environmental groups from a presidential administration that has otherwise mostly been an ally. Starting in 2010, EPA experienced a series of delays in issuing a proposal to tighten the 75-ppb ozone standard, which was set during George W. Bush’s presidency. The Obama administration had received immense public pressure from industry and Republicans over the rule, which they argued would trample an already weak economy. In 2011, President Barack Obama asked EPA to pull the plug on the rule until 2013.

Environmental and health groups were outraged, but finally scored a victory in 2014, when a court ordered that the Obama administration finalize a new ozone rule no later than today.

Now, even with today's news, it seems that the long-raging battle over ozone isn't over. “Not at all," Walke says. “It’s just begun.”

*Update, 1 October, 4:00 p.m.: This article has been updated with additional reactions and quotes.