While the smoke may cloud your vision of the sky or ruin a day at the beach on this week's warmest days of the season so far, it is more than just a nuisance. All across the U.S., the smoke is causing poor air quality, which can cause health effects from mild symptoms in the healthy to dangerous risks for sensitive groups.

Smoke from Canadian wildfires began to worsen air quality in the eastern U.S. on Wednesday as several Midwestern states continued to battle conditions seemed unhealthy by the federal government