New Primary Standard Set for Fine Particulate Matter

Ambient concentrations of fine particulate matter (PM 2.5) have dropped in recent years as a result of regulations set by the U.S. Environ­ mental Protection Agency (EPA), and the agency anticipates this trend will continue. But hundreds of studies con ducted since the regulations were last reviewed indicate that stricter rules still might be warranted to ade­ quately protect the U.S. population against adverse cardio vascular, respiratory, and pos­ sibly other health effects associated with PM 2.5. 2 In December 2012 the EPA reduced the annual primary National Ambient Air Quality Standard (NAAQS) for PM 2.5 to a level it anticipates will protect public health with an adequate margin of safety when com­ bined with the existing 24­hour standard. 3 The new primary annual standard of 12 µg/m 3 , down from the previous 15 µg/m 3 , falls at the low end of the 12­ to 13­µg/m 3 range the EPA proposed in June 2012. 4 With the new standard, more than 44 million U.S. residents live in counties that would violate the standard if it were fully in effect today, based on 2009–2011 monitoring data. However, by 2020—the deadline for implementation—only seven monitored counties are expected to be in violation as a result of ongoing implementation of other regulations already in place, such as those targeting diesel engines, other onroad and offroad vehicles, waste incinerators, and coal­fired power plants. It's plausible that ambient concentrations of PM will be generally lower nationwide in 2020 than they are today, says Lorraine Gershman, director of environment, regula­ tory, and technical affairs with the American Chemistry Council (ACC), which represents some of the industries affected by the regula­ tion. That, along with inconsistencies in findings on the health effects of particulate pollution, is why the ACC opposed lowering the standard. 7 Primary standards are set to protect human health against acute and chronic effects, whereas secondary standards are intended to address a range of environmental impacts, such as climate effects, damage to materials, and visibility impairment. The previous annual primary PM 2.5 standard of 15 µg/m 3 was set in 1997. EPA and directed the agency to explain how it would protect public health with an adequate margin of safety as required under the Clean Air Act. 9 The EPA attempted to address the court­identified short­ comings with this new 2012 regulation. The 24­hour pri­ mary standard remains unchanged from the Bush …