As dozens of wildfires continue to burn across Canada, flames are sending far-reaching plumes of smoke into the sky and unhealthy air to distant places. Some of the more gigantic blazes have been delivering thick smoke that spread southward into the United States over recent days.

The U.S. Environmental Protection Agency warns that wildfire smoke contains dangerous pollutants in the form of fine particles known as PM 2.5 that can penetrate deep into the lungs and enter the bloodstream. Short-term exposure can lead to bronchitis, worsen asthma and create other health issues.