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July 11, 2014
Science committee reviews ozone assessment

The Clean Air Act Scientific Advisory Committee (CASAC) has offered a lukewarm endorsement for EPA’s Second Draft Policy Assessment for the Review of the Ozone National Ambient Air Quality Standards, which the Agency issued in January 2014.

The CASAC says there is adequate scientific evidence to recommend the revision range of 60 parts per billion (ppb) to 70 ppb for the primary or human health-based standard, which the EPA says it considers appropriate in the draft policy.  But the CASAC adds that the upper bound “provides little margin of safety for the protection of public health, particularly for sensitive subpopulations.”

Second attempt

The draft policy assessment precedes EPA’s second attempt to revise the current 8-hour primary ozone NAAQS, which is set at 75 ppb.  The first attempt to lower the standard to the 60 ppb to 70 ppb range was contained in a 2010 proposal.  But the process was interrupted in September 2011 when President Obama told the Agency that any revision should await improved economic conditions.

The president said the EPA should undertake the revision in 2013, in line with the statutory time frame.  The EPA did not produce another proposal in 2013 and was brought to court by environmental groups.  A federal judge subsequently ordered the Agency to propose a revision of the existing standards by December 1, 2014, and take final action on that proposal by October 1, 2015.

Adverse effects at 70 ppb

According to the CASAC, the draft policy assessment is an “excellent summary of information needed to judge the adequacy of the current [NAAQS] for ozone and to consider alternative standards.”

The CASAC also approves of EPA’s recommendation to retain the existing 8-hour averaging time, which, says the CASAC, “provides programmatic stability by allowing for atypical meteorological conditions that can lead to abnormally high ambient ozone concentration while providing health protections.”

But while acknowledging that the choice of a level within the 60 ppb to 70 ppb range is a policy judgment, the CASAC states that at 70 ppb there is substantial scientific evidence of adverse effects, including decrease in lung function, increase in respiratory symptoms, and increase in airway inflammation.

“Although a level of 70 ppb is more protective of public health than the current standard, it may not meet the statutory requirement to protect public health with an adequate margin of safety,” says the CASAC.  “In this regard, the CASAC deliberated at length regarding advice on other levels that might be considered to be protective of public health with an adequate margin of safety.  For example, the recommended lower bound of 60 ppb would certainly offer more public health protection than levels of 70 ppb or 65 ppb and would provide an adequate margin of safety. Thus, our policy advice is to set the level of the standard lower than 70 ppb within a range down to 60 ppb.”

In 2010, the National Association of Manufacturers released a study that claimed that a 60 ppb primary ozone NAAQS would have an estimated annual attainment cost of $1.013 trillion between 2020 and 2030 (in 2010 dollars) and result in 7.3 million lost jobs by 2020.

Secondary standard

Regarding the secondary (welfare or environmental) ozone NAAQS, the CASAC recommends a separate standard in the range of 7 ppm-hrs to 15 ppm-hrs, noting that specific economically significant crops, such as soybeans, may not be protected at 15 ppm-hrs, but would be protected at 7 ppm-hrs.  The current secondary ozone NAAQS is identical to the primary NAAQS.

CASAC’s review of the draft policy assessment

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