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Marin and San Francisco counties were declared nearly smog-free by the American Lung Association.
Breathe in and savor the air. As long as you're in Marin or San Francisco, and not San Jose or Oakland, that is.
San Francisco and the North Bay enjoy some of the cleanest air in the region, according to a report released by the American Lung Association on Wednesday.
According to the Marin Independent Journal, the nonprofit group examined the levels of ozone, also known as smog, and fine particle pollution to determine who has good air -- and, to Alameda and Santa Clara counties' cases, bad.
Both Alameda and Santa Clara received "F" grades for their air, in contrast to the "A" grades given to San Francisco and Marin.
More than three smog days a year meant an "F" grade, the newspaper reported. No smog days earned an "A".
That said "winter wood smoke in Marin remains an issue," according to lung health watchdogs, who note that children and the elderly are most susceptible to bad air.
Out of roughly 252,000 residents, 15,773 adults in have asthma, as do 3,464 children, the newspaper reported. Another 9,179 people have chronic bronchitis and 4,449 have emphysema, the lung association reported.