(Berkeley Lovelace Jr./ NBC News) — Air quality advisories were in effect for 110 million people in the United States on Wednesday morning, ranging from New Hampshire to South Carolina and covering the Northeast, including Boston, New York City and Philadelphia.
In the Northeast, the poor air quality is the result of wildfires raging in eastern Canada, sending smoke wafting into the U.S. In some areas, the smoke is so dense that people can smell it and the skies appear hazy. About 90 million people in the U.S. are impacted by the smoke.
Beyond the Northeast, high concentrations of ground-level ozone — also known as smog — are driving unhealthy air quality levels in a number of urban areas across the country.
Poor air quality can be caused by any airborne “irritant” — a particle or substance in the air that is harmful to a person to breathe in, according to Dr. Purvi Parikh, an allergist and immunologist at the Allergy & Asthma Network, an advocacy group for people with asthma, allergies and related conditions. (…)