"Wildfires in Canada Trigger Code Red Air Quality Alerts Across Pennsylvania and West Virginia"

The air quality in Philadelphia has reached "unhealthy" levels due to smoke from wildfires in Canada. The entire state of Pennsylvania and Delaware are under a "code red" air quality alert, while New Jersey is under a "code orange" alert. The city has closed pools and moved summer camps indoors. Residents are advised to cancel outdoor events, close windows and doors, and wear high-quality masks if going outside. The poor air quality is expected to persist until Friday, with rain and thunderstorms helping to improve it. The air quality index (AQI) measures various pollutants, with PM2.5 being a chief component responsible for health effects.