Almost every major community on both sides of the U.S.-Mexico border suffers from poor air quality, according to a report due to be released shortly by U.S. and Mexican environmental agencies. The poor air is a byproduct of the North American Free Trade Agreement, which led to the construction of 84 assembly plants on the border in Mexico that are not answerable to strict emissions limits. On top of that, some plants on the border in the U.S. are exceeding pollution limits. The findings raise concerns about the possible health effects — including respiratory illness, heart problems, lead and carbon monoxide poisoning, and cancer — for the more than 10 million people who live along the 2,000-mile border.