Updated EPA ‘Significant Impact Levels’ May Ease PM Rule Implementation

June 17, 2024
EPA has quietly updated its “significant impact levels” (SILs), which are screening tools for emissions considered too small to count in air permitting, a measure that could address state and industry concerns over how to attain EPA’s tougher national ambient air quality standards (NAAQS) for fine particulate matter (PM2.5). EPA’s decision earlier this year to tighten the annual health-based NAAQS for PM2.5 from 12 micrograms per cubic meter (ug/m3) down to 9 ug/m3 has prompted extensive criticism from states and...

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