The Idaho Department of Environmental Quality is asking the Environmental Protection Agency to exclude two days in 2011 from its calculations on Ada County’s compliance with air quality regulations.
DEQ officials say a dust storm Feb. 15 and 16, 2011 caused levels of particulates, known as pm10, to rise about level limits.
Exclusion of the high readings for those two days is critical to obtaining EPA approval of the Northern Ada County PM10 State Implementation Plan. The plan shows the steps the county takes to maintain air quality within the limits by such measures as keeping dust down at construction sites and testing automobiles.
Nationally EPA doesn’t regulate pm10, instead regulation even smaller particles, pm2.5, which are 2.5 micrograms and lodge deeper in the lungs. But the settlement of a lawsuit more than a decade ago required Ada County to continue its pm10 maintenance plan.
EPA allows states to flag air quality data as exceptional and exclude it when pollutant levels are due to events that are not reasonably controllable or preventable.