As crews continue battling more than 100 wildfires in across the western United States, including the largest wildfire in California this year, air quality alerts have been issued for millions of people -- leading many to wonder when it is and isn't safe to be outside.
Wildfire smoke is made up mostly of fine particulate matter (PM2.5), or soot. Particles in the PM2.5 size range are able to penetrate deeply into the respiratory tract, reaching the lungs and bloodstream, according to IQAir, which reports real-time air quality conditions around the globe.
Particle pollution can cause serious health problems, including asthma attacks, heart attacks, strokes and early death. Exposure to fine particles can cause short-term health effects such as eye, nose, throat and skin irritation, coughing, sneezing, runny nose and shortness of breath. Studies have shown even short periods of exposure to elevated levels of PM2.5 can trigger asthma attacks requiring emergency medical treatment.
The best way to protect yourself when wildfire smoke is affecting air quality is to stay indoors with air conditioning, reduce strenuous activities and limit outdoor activities.
You can know when it is and isn't safe to be outside by checking the Environmental Protection Agency's Air Quality Index, or AQI. It's a color-coded way to see what the levels of some types of air pollution are in your area.
The higher the AQI, the higher the concentration of pollutants in the air and the more cause for concern. AQI values at or below 100 are generally thought of as satisfactory. When AQI values are above 100, air quality is unhealthy: at first for certain sensitive groups of people, then for everyone as AQI values get higher.
AQI Basics for Particle Pollution
Green: Good -- AQI 0-50
• Air quality is satisfactory and air pollution poses little or no risk.
• It's a great day to be active outside.
Yellow: Moderate -- AQI 51-100
• Air quality is acceptable. People who are unusually sensitive to air pollution should consider reducing prolonged or heavy exertion.
• Consider making outdoor activities shorter and less intense. Watch for symptoms such as coughing or shortness of breath. These are signs to take it easier
Orange: Unhealthy for Sensitive Groups -- AQI 101-150
• Members of sensitive groups (like people with heart or lung disease, older adults and children) may experience health effects and should reduce prolonged or heavy exertion. The general public is less likely to be affected.
• Make outdoor activities shorter and less intense. It's OK to be active outdoors, but take more breaks. Watch for symptoms such as coughing,
shortness of breath or unusual fatigue.
Red: Unhealthy -- AQI 151-200
• Members of sensitive groups should avoid long or intense outdoor activities. Everyone else should reduce prolonged or heavy exertion.
• Consider rescheduling or moving activities indoors. Take more breaks during outdoor activities.
Purple: Very unhealthy air quality -- AQI 201-300
• Health alert: the risk of health effects is increased for everyone. Members of sensitive groups should avoid all physical activity outdoors. Everyone else should avoid prolonged or heavy exertion.
• Reschedule activities to a time when air quality is better or move indoors.
Maroon: hazardous air quality -- AQI 300 and higher
• Health warning of emergency conditions. Everyone should avoid all outdoor exertion.
• Remain indoors and keep activity levels low.
When particle levels are high outdoors, they can be high indoors too. Keep particles lower indoors:
• Reduce your use of fireplaces and wood stoves. And don't use candles or smoke indoors.
• Use HEPA air filters in your HVAC system.
• Buy or make your own portable air cleaner designed to reduce particles indoors.
If you don't have an air conditioner, staying inside with the windows closed may be dangerous in extremely hot weather. If you are hot, go someplace with air conditioning or check with your local government to find out if cooling centers are available in your community.