Millions of Americans are under air quality alerts as a combination of ground-level ozone and wildfire smoke sweeps across the nation.
Officials in Arizona, California, Colorado, Indiana and Michigan have issued advisories warning that the air could become unhealthy, particularly for sensitive groups.
The alerts are being driven primarily by ground-level ozone in Arizona, California, Indiana and Michigan, while Colorado is facing the dual threat of wildfire smoke and elevated ozone pollution.
Ground-level ozone inflames the airways, making it harder to breathe and increasing the risk of asthma attacks, while microscopic particles in wildfire smoke can travel deep into the lungs and even enter the bloodstream, where they can damage the heart and other organs.
Wildfire smoke, a toxic mix of gases and microscopic fine particles, can penetrate deep into the lungs and bloodstream. It causes symptoms like stinging eyes, a scratchy throat, coughing, and chest pain.
Health officials are urging people to limit strenuous outdoor activity, remain indoors if smoke becomes thick and reduce physical exertion if they experience breathing problems.
The advisories range from daytime alerts on Tuesday in Arizona and California to longer warnings lasting from Tuesday morning through Wednesday morning in Colorado and from midnight Tuesday night through midnight Wednesday night in parts of Indiana and Michigan.
Children, older adults and people with asthma, heart disease or other respiratory conditions are considered especially vulnerable. In several states, residents are also being encouraged to reduce driving and avoid using gasoline-powered equipment to help curb pollution levels.
Officials in Arizona, California, Colorado, Indiana and Michigan have issued advisories warning that the air could become unhealthy, particularly for sensitive groups (stock)
The Arizona Department of Environmental Quality has issued an Ozone High Pollution Advisory for Maricopa County, including the Phoenix metropolitan area, warning that weather conditions are expected to produce ozone concentrations that pose a health risk.
In California, an Air Quality Alert has been issued for the Imperial Valley, where harmful ozone pollution is expected throughout Tuesday.
Residents are encouraged to stay indoors when air quality deteriorates, keep windows and doors closed and avoid activities that generate additional pollution, such as using gasoline-powered lawn equipment or delaying trips to the gas station until the evening.
Colorado faces the most widespread air quality concerns, with health advisories covering much of the state due to moderate to heavy wildfire smoke drifting from fires burning in Colorado and Utah.
The Colorado Department of Public Health and Environment warned that smoke could aggravate heart and lung disease and increase respiratory symptoms, particularly among children, older adults and people with existing medical conditions.
Residents are advised to reduce prolonged or heavy outdoor exertion until conditions improve.
At the same time, Colorado's Front Range Urban Corridor, including the Denver metropolitan area, remains under an Ozone Action Day Alert.
An Ozone Action Day Alert is a warning that the air near the ground has reached unhealthy levels of pollution
Colorado (pictured) faces the most widespread air quality concerns, with health advisories covering much of the state due to moderate to heavy wildfire smoke drifting from fires burning in Colorado and Utah
Officials said hot, smoky conditions are expected to push ozone into the Unhealthy for Sensitive Groups category, while wildfire smoke is also elevating particle pollution across the region.
In Indiana, an Air Quality Action Day has been declared for northwest portions of the state, including LaPorte County and communities near Lake Michigan.
Ozone levels are forecast to reach unhealthy levels for sensitive groups, prompting officials to advise active children, adults and people with asthma or other respiratory illnesses to limit prolonged outdoor exposure.
Residents are also encouraged to carpool, avoid idling vehicles and postpone using gasoline-powered lawn equipment until the evening.
Meanwhile, southwest Michigan is under an Air Quality Alert after the Michigan Department of Environment, Great Lakes, and Energy forecast elevated ozone levels caused by warm temperatures, abundant sunshine and southwest winds.
Officials warned residents to avoid strenuous outdoor activities where possible and to watch for symptoms including wheezing, coughing, chest tightness, dizziness and burning of the nose, throat and eyes.
They also urged residents to reduce activities that contribute to ozone formation, such as topping off fuel tanks and using charcoal lighter fluid.
