Smoke From Canadian Wildfires Blackens Skies, Prompts Air Quality Alerts in Much of U.S.

The smoke was so thick on Tuesday that New York City's skyline could not be seen clearly and air quality alerts were issued to residents from parts of the Northeast to the southern Mid-Atlantic region. "Exposure can cause short-term health effects such as irritation to the eyes, nose and throat, coughing, sneezing, runny nose, and shortness of breath," the alert warned. "Exposure to elevated levels of fine particulate matter [PM 2.5] can also worsen medical conditions such as asthma and heart disease. People with heart or breathing problems, and children...