Air quality in Pima County was good in the winter of 2009-'10, with no unhealthy days recorded by the county Department of Environmental Quality.

The department, which monitors six air pollutants, described the October-March season has ending "uneventfully" in a release.

That may change this summer, when the federal Environmental Protection Agency has proposed strengthening of its ozone standards.

"This summer's air pollution season may put our community into non-attainment of the EPA's health-based ozone standard for the first time in our air quality history," the release said. "EPA has proposed strengthening the ozone standard to better protect public health, and PDEQ's monitors will likely record an exceedance of that proposed lower standard."

Motor vehicles cause most of the air pollution in Pima County. "A special effort is being made to remind everyone to maintain their vehicles; check and properly inflate their tires monthly; avoid engine idling at locations such as schools and drive thru lanes; and carpool, bike, ride Sun Tran, or walk at least one day a week to give your car a rest and keep our air healthy to breathe," the release said.

For the ninth year in a row, carbon monoxide pollution levels were in the "good" range every day during the 182-day winter season. The region has not violated the federal standards for carbon monoxide in 22 years.

Levels of particulate matter 10 microns or less were in the "moderate" range nine days this winter, down from 12 days the previous year. EPA's health standard for those particulates have not been violated in Pima County since 1999. Elevated particulate levels are most often associated with high winds and dry conditions.

For up-to-the-hour air pollution information, visit or call (520) 882-4AIR.

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