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October 30, 2012
Committee advises EPA on ozone standard

In a review of EPA’s August 2012 policy assessment (PA) of the national ambient air quality standards (NAAQS) for ozone, the Clean Air Scientific Advisory Committee (CASAC) notes that the Agency provides a strong rationale for lowering the current ozone primary and secondary NAAQS of 75 parts per billion (ppb) to a level in the 60 to 70 ppb range, which conforms to previous CASAC recommendations.  In addition, the CASAC notes that the PA also provides adequate justification for the EPA to consider revising the standard to the 50 to 60 ppb range. 

Apart from the positive feedback on justification for lowering the standard, the CASAC found little to like in the PA.  Both EPA’s PA and CASAC’s review are draft documents.  The EPA is scheduled to issue a decision on revising the ozone NAAQS in 2013. 

Policy assessments

As part of EPA’s statutorily required review of the ozone NAAQS, staff in the Agency’s Office of Air Quality Planning and Standards prepare a PA, which is intended to provide the EPA administrator with the staff’s conclusions about the broadest range of policy options that could be supported by the currently available scientific evidence and technical information.
Crop work needed

While acknowledging the “first draft” status of the PA, the CASAC still faulted
EPA’s effort on many points.  According to the CASAC, the PA:

  • Fails to provide a clear description and definition of historical ozone background, which will be a factor as possible revisions of the ozone NAAQS are considered.
  • Is inconsistent in its interpretation of evidence for a causal relationship between long-term exposure and respiratory effects.
  • Provides an unbalanced consideration of welfare (secondary) impacts, particularly regarding the impact of ozone on crops.  The CASAC would like to see greater emphasis on analyzing yield losses for a number of crops planted widely across the United States, especially soybeans and others known to be sensitive to ozone.

Will EPA go lower?

Regarding setting a NAAQS below the 60 to 70 ppb level, the CASAC states:  “The draft policy assessment also provides an underlying empirical basis for considering short-term levels lower than 60 ppm, such as 50 ppb or 55 ppb.”  And later:  “The abundant evidence of important health effects below the current standard reviewed in the various documents suggests that a range of alternative standards certainly as low as 60 ppb (and even 50 or 55 ppb for comparison purposes) should be explored.” 

The CASAC emphasizes that the Clean Air Act requires that the NAAQS be set at a level that protects public health with “an adequate margin of safety,” but the most vulnerable sub-groups (e.g., asthmatic children) can be affected by ozone concentrations below the 60 to 70 ppb range.  The EPA may consider this view as it proceeds with the anticipated revision of the ozone NAAQS and so should states and industries that would be most affected by new ozone attainment and compliance obligations.

Click here for EPA’s draft Policy Assessment for the Review of the Ozone National Ambient Air Quality Standards.

Click here for  CASAC’s October 2012 draft review of the PA.

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