Researchers and health advocates from Casa Familiar launched a website to provide real-time tracking of air quality in San Ysidro, where residents have long complained about emissions pollution from the steady stream of vehicles crossing the U.S.-Mexico border in that area.

Air monitoring at the San Ysidro Port of Entry, one of the busiest land crossings in the Western Hemisphere, has been inconsistent and inconclusive over the years.

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http://www.sandiegouniontribune.com/news/environment/sd-me-ysidro-air-monitoring-20170613-story.html