The EPA asked its independent science advisers (yet again) to review the evidence. You will recall the Bush administration ignored the scientists’ advice and set a standard weaker than that justified by the evidence. EPA technically and legally is reconsidering that bad decision.
The science advisers officially responded to EPA in a March 30 letter that can be seen here:
And there is a very interesting wrinkle. Even though the science advisers reiterated their unanimous support for a new standard within the range of 60-70 parts per billion (compared to the Bush standard of 75), they also included language which seems designed to point the EPA towards the lower end of that range.
Note, for example, on page 2 of the letter, the scientists say
Given the results of EPA’s exposure and risk assessments, setting a new NAAQS in the range of 60 to 70 ppb is appropriate, but would provide little margin of safety at its upper end.[Emphasis added]
Similarly, on page 14 of the letter, the scientists note that even some healthy people could be adversely affected even at the low end of the range:
there is a great degree of variability of response magnitude among the healthy individuals studied, with some having clinically relevant responses, even at 60 ppb.
A separate recent EPA analysis of the ozone issue appears to confirm the need for a very tough standard. It found that adverse health effects have been documented at levels of 60 ppb and below. See table 2-3 on pp 2-36 - 2-38 [Chapter 2 under “downloads”] of the EPA “integrated science assessment” at http://cfpub.epa.gov/ncea/isa/recordisplay.cfm?deid=217463#Download
What does all this mean? We hope that EPA doesn’t wimp out and set the weakest possible standard within the recommended range. Public health groups have urged EPA to set a standard no weaker than 60.