Back in 2008, the EPA went against the advice of its Clean Air Scientific Advisory Committee and set the limit for ground-level ozone at 75ppb. Today, the agency has announced it will set the primary standard at between 60 and 70 ppb measured over eight hours, which is what the CASAC had recommended. The Washington Post’s Juliet Eilperin reports:

The smog proposal, which must undergo 60 days of public comment before becoming final, would help determine the quality of the air Americans will breathe for at least a decade. Under the Clean Air Act, the federal government must reexamine every five years whether its ozone standards are adequate, but it traditionally takes more than 10 years to enact new rules.

The final target that the Obama administration adopts will have huge implications for the regulations state and local officials will have to set in the coming months to meet the new federal requirements. Power plants and motor vehicles are significant emitters of pollutants such as nitrogen oxides and other chemical compounds, which form ozone when exposed to sunlight, but sources as small as gas lawnmowers could face restrictions depending on what EPA chooses as its ultimate goal.

Depending on the level of the final standard, EPA estimates the proposal will cost between $19 billion and $90 billion to implement and will yield health benefits of between $13 billion and $100 billion. The proposal would translate into thousands of avoided premature deaths by 2020, though the exact number depends on what exact limit the agency adopts.

An editorial from the American Journal of Respiratory and Critical Care Medicine, published prior to the 2008 standard change, reminds us why strong ozone limits are so important (short version: think of the children!):

Increasing numbers of epidemiological studies suggest that ozone is detrimental to children’s respiratory health, including increased hospitalizations, emergency room visits, and decreased pulmonary function. Current ozone levels in Canada’s largest cities are associated with increased hospitalization for respiratory problems in neonates under 1 month of age. Ozone levels lower than current U.S. EPA standards have also been associated with difficulty breathing in infants (aged 3 mo to 1.5 yr), particularly in those with asthmatic mothers, and with increased use of rescue medication in children with asthma under 12 years of age using maintenance medication. The incidence of new diagnoses of asthma in children who exercise heavily is associated with average ozone levels of 55.8 to 69.0 ppb during the daytime (10 A.M. to 6 P.M.), levels below the current NAAQS. The effects of childhood exposure may be long-lasting. Decrements in small airways function have been reported in college freshmen who have grown up in polluted areas of California’s South Coast Air Basin.

Growing concern is emerging regarding the relative risks of increased morbidity and mortality among adults as well. A series of recently published meta-analyses and primary national-scale epidemiological studies have documented consistent associations between premature mortality and ozone exposures below the current 8-hour standard of 0.08 ppm. Controlled human exposure studies of healthy adults have demonstrated reduced lung function, increased respiratory symptoms, changes in airway responsiveness, and increased airway inflammation following 6.6-hour exposures to 0.08 ppm ozone. Recent studies demonstrate that some of the individuals tested experience these adverse effects at concentrations of 0.06 ppm and below.

The authors closed by urging EPA to adopt a standard of 60 ppb, so they may not be satisfied with the 60-70 ppb range the agency proposed today. Perhaps they’ll weigh in during the 60-day comment period, which is sure to bring in lots of complaints about the cost associated with the change, as well as applause for taking this important step toward healthier air.