Mexico City declared an air pollution alert for the second straight day Wednesday, urging people to stay indoors, canceling school and moving the semi-finals of the first-division football league to ...

Federal regulators ruled Monday that pollution from Mexico , not local sources, is why Phoenix fails air quality standards.

Add Yahoo as a preferred source to see more of our stories on Google. Officials in the Rio Grande Valley are urging residents, especially those with breathing issues, to consider donning N95 masks ...