For those of you tracking the progress of EPA’s review of national air standards for smog (ozone), please note the EPA has posted its most recent staff analyses this morning (under “policy assessments” and “risk and exposure assessments” at http://www.epa.gov/ttn/naaqs/standards/ozone/s_o3_index.html
This “second draft” policy assessment – an effort by EPA’s career experts to distill a great mass of scientific information – confirms one big this: the current national standard for ozone is too weak and should be made tougher. (The current standard, set in 2008, is 75 parts per billion) EPA’s staff has also concluded that going down to a standard of 60 would provide the biggest health benefits – that is, reduce premature death and sickness from smog.
See the excerpt below:
It is appropriate to consider a standard level within the range of 70 ppb to 60 ppb, reflecting our judgment that a standard set within this range could provide an appropriate degree of public health protection and would result in important improvements in protecting the health of at-risk populations and lifestages. Standard levels within this range that were considered in staff analyses of air quality, exposure, and risk include 70, 65 and 60 ppb, representative of levels within the upper, middle, and lower parts of this range, respectively. Further, it would not be appropriate to consider increasing the level of the current standard, thereby decreasing public health protection.
In its “risk and exposure” assessment http://www.epa.gov/ttn/naaqs/standards/ozone/s_o3_2008_rea.html EPA’s staff scientists confirm that the biggest public health benefits would take place with a standard of 60. Here is from the executive summary:
In conclusion, we have estimated that exposures and risks remain after just meeting the existing standards and that that in many cases, just meeting potential alternative standard levels results in reductions in those exposures and risks. Meeting potential alternative standards has larger impacts on metrics that are not sensitive to changes in lower O3 concentrations. When meeting the 70, 65, and 60 ppb alternative standards, the percent of children experiencing exposures above the 60 ppb health benchmark falls to less than 20 percent, less than 10 percent, and less than 3 percent in the worst O3 year for all 15 case study urban areas, respectively. Lung function risk also drops considerably as lower standards are met. When meeting the 70, 65, and 60 ppb alternative standards, the percent of children with lung function decrements greater than or equal to 10 percent in the worst year falls to less than 21 percent, less than 18 percent, and less than 14 percent in the worst O3 year for all 15 case study urban areas, respectively. Mortality and respiratory hospitalization risks decrease by 5% or less for a level of 70 ppb, 10% or less for a level of 65 ppb, and 15% or less for a level of 60 ppb. These smaller changes in the mortality and morbidity risks, relative to the exposures and lung function risk reductions, reflect the impact of increasing O3 on low concentration days, and the non-threshold nature of the C-R function. Larger mortality and morbidity risk reductions are estimated on days with higher baseline O3 concentrations.