We think so. EPA’s latest round of rulemaking setting a National Ambient Air Quality Standard for ozone lowers the tolerance level from 75 to 70 parts per billion (ppb). Though the change in the numbers is small, it is expected to be very difficult to achieve, and, we argue, not “appropriate” as required by the Clean Air Act. This is particularly true in areas of the country that are already struggling to comply with the previous levels, and the new rule will subject additional regions to stricter emission controls or permit denials.
Today, in our first major legal brief challenging the rule in court, we detailed why EPA has actually exceeded its statutory authority to reduce the level. A key reason stems from background ozone levels. The new limits will simply be impossible to achieve if ozone naturally occurs at 70 ppb without any cars, trucks, power plants or manufacturers in this country.
EPA said it was prohibited from considering the effect of background levels of ozone when setting its standard. Unfortunately, background levels fluctuate. Spikes in ozone can occur from natural phenomena like wildfires, lightning storms, and weather conditions that transport ozone and the substances that create it from other countries, including those as far away as China. Even vegetation like pine trees produce gases that react to create ozone. Studies show that lightning can add as much as 25-30 ppb and wildfires can add more than 50 ppb. One modeling study estimates that Asian emissions contributed 8-15 ppb in certain areas of our country and that nearly half of springtime ozone readings above 70 ppb in the southwestern United States would not have occurred without migration of these pollutants from Asia.
A region fails to comply with the standard if it exceeds the ozone limits for an average of 4 days a year. Shouldn’t there be an exception when there are identifiable spikes from uncontrollable external sources? The law requires that standards be attained, but lowering the standard to this new level makes that much harder if not impossible in some areas. EPA must take appropriate account of the evidence that background ozone concentrations that cannot be controlled can reach levels that will prevent attainment. The Act requires such consideration and failure to do so is arbitrary.