Add Yahoo as a preferred source to see more of our stories on Google. Wildfires in Canada are sending heavy smoke across the northern U.S., and New Jersey is experiencing some unhealthy air pollution.

As winter sets in, a thick layer of smog enveloped the national capital Delhi on Wednesday morning. The city's air quality remains in the 'Very Poor' category, with an AQI of 376 at 7 am, according to ...