From: E&E News
“In the past, EPA has used a “screening threshold” of 1 percent of the standard, which in this case equates to 0.7 ppb, Peter Tsirigotis, head of EPA’s Office of Air Quality Planning and Standards, wrote in the memo. But in examining other options, the agency found little difference if 1 ppb is instead used as the cutoff, Tsirigotis wrote. “Because the amount of upwind collective contribution captured with the 1 percent and 1 ppb thresholds is generally comparable, overall, we believe it may be reasonable and appropriate for states to use a 1 ppb contribution threshold, as an alternative,” he added. But in a news release this afternoon, Public Employees for Environmental Responsibility noted there’s a roughly 40 percent gap between the two thresholds. The guidance would make it harder for states with ozone compliance problems to trigger “good neighbor” safeguards intended to address upwind emissions elsewhere, the group said.