FRESNO, Calif. (AP) — California's San Joaquin Valley is suffering through the longest period of air pollution in a dozen years. Since the beginning of December dirty air has exceeded federal health standards nearly every day.
The pollution is the unhealthiest kind — microscopic, chemical-laden particles that can get into lungs and absorbed into the bloodstream to create health risks in everyone, not just the young and infirm.
The San Joaquin Valley, in the state's agricultural heartland, traditionally records the highest level of particulate pollution in the United States.
The valley is surrounded on three sides by mountains and the state's two major north-south highways cut through its interior. Cold temperatures and a lack of rain have trapped diesel exhaust and fireplace emissions.
Air officials are warning the public to limit outdoor activities.