Americans across five states are being urged to stay indoors as toxins fill the air.
The National Weather Service (NWS) on Thursday issued air quality alerts for parts of Arizona, California, Oregon, Washington and Idaho.
Wildfire smoke is expected to push pollution to unhealthy levels across large areas of the Pacific Northwest. Farther south, harmful concentrations of ground-level ozone are threatening communities around Phoenix, Tucson and Southern California.
Smoke alerts across Oregon, Washington and Idaho will remain in effect through Friday, with some areas facing potentially hazardous conditions.
Arizona’s high-pollution advisories cover the Phoenix and Tucson metropolitan areas through Friday evening. Southern California’s ozone alert will last until 8pm Monday, with pollution expected to peak during the afternoon and early evening.
Officials are urging residents to limit outdoor activity, keep children inside when smoke is present and close windows and doors as conditions deteriorate.
Both wildfire smoke and smog contain fine particle matter, or PM.25, which are microscopic soot particles that penetrate deep into the lungs and bloodstream, worsening respiratory and cardiovascular conditions
Breathing polluted air can cause immediate symptoms including burning eyes, a runny nose and difficulty breathing, according to the alerts.
The National Weather Service (NWS) on Thursday issued air quality alerts for parts of Arizona, California, Oregon (pictured), Washington and Idaho
Wildfire smoke can also aggravate heart and lung diseases and worsen other serious health conditions. Infants, young children, older adults, pregnant women and people with asthma or existing heart and lung conditions face the greatest risks.
Ozone pollution can trigger asthma attacks, cause breathing problems and damage the lungs.
While vulnerable groups are most likely to experience serious effects, officials warned that everyone can be affected when air quality reaches unhealthy levels.
In California, the South Coast Air Quality Management District issued an alert for harmful ozone pollution across the South Coast Air Basin and Coachella Valley.
The warning covers communities throughout the Inland Empire, San Bernardino and Riverside County valleys, the San Bernardino County Mountains, Orange County and the San Gorgonio Pass.
Affected cities include Riverside, San Bernardino, Ontario, Fontana, Rancho Cucamonga, Corona, Palm Springs, Palm Desert, Santa Ana, Anaheim, Irvine and Mission Viejo.
A separate alert includes the eastern and western San Fernando Valley, the San Gabriel Valley, Santa Clarita Valley, Santa Susana Mountains and portions of the San Gabriel Mountains.
Burbank, Glendale, Pasadena, Pomona, Santa Clarita, Woodland Hills and Northridge are among the cities facing harmful smog levels.
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In California, the South Coast Air Quality Management District issued an alert for harmful ozone pollution across the South Coast Air Basin and Coachella Valley (stock)
When the Air Quality Index reaches the orange ‘Unhealthy for Sensitive Groups’ category, vulnerable residents should reduce prolonged or intense outdoor activity.
At red, or ‘Unhealthy,’ levels, sensitive people should avoid spending extended periods outside because everyone may begin experiencing health effects.
If conditions reach purple, or ‘Very Unhealthy,’ vulnerable people should avoid all outdoor exercise, while everyone else should stay away from prolonged or strenuous activity.
At the maroon ‘Hazardous’ level, officials said everyone should avoid all outdoor physical activity.
Californians were advised to keep windows and doors closed and run air conditioners or air purifiers to protect the air inside their homes.
Officials also warned against using whole-house fans or swamp coolers that pull polluted outside air indoors. Residents should avoid creating additional indoor pollution by burning candles or incense, using fireplaces or grilling.
In Arizona, the Department of Environmental Quality issued an Ozone High Pollution Advisory for the Tucson metropolitan area from Friday morning through Friday evening.
The alert includes Tucson, Green Valley, Marana and Vail.
An existing advisory for Maricopa County, including the Phoenix metropolitan area, was also extended through Friday.
Weather conditions combined with existing pollution are expected to produce eight-hour ozone concentrations that pose a health risk.
Officials urged people to decrease physical activity and reduce the use of gasoline-powered equipment or delay using it until later in the day.
Residents were also encouraged to telecommute, carpool or use public transportation to help prevent pollution levels from climbing further.
Meanwhile, smoke from regional wildfires is degrading air quality across parts of Oregon.
An advisory covering Crook, Deschutes, Grant, Jefferson, Morrow, Umatilla, Union, Wallowa and Wheeler counties will remain in effect until noon Friday.
Another warning covers Baker, Harney and Malheur counties until 1pm Friday.
Cities under the advisories include Bend, Redmond, Pendleton, Hermiston, La Grande, Prineville, Madras, Baker City and communities across eastern Oregon.
Officials warned that smoke levels could change rapidly depending on weather conditions. Residents were told to remain inside if possible, shut windows and doors, avoid strenuous exercise and use high-efficiency particulate air filters or portable air purifiers.
In Idaho, unhealthy air is forecast across Ada, Canyon, Gem, Payette and Washington counties until 2pm Friday.
Everyone in the affected area was advised to limit prolonged or strenuous outdoor activity, while people sensitive to smoke were urged to avoid it altogether.
Open burning is also prohibited under air quality rules.
Washington’s warnings cover wide sections of the eastern part of the state, including Spokane, Pullman, Wenatchee, Omak, Moses Lake, Colville and Walla Walla.
Pollution is forecast to range from ‘Unhealthy for Sensitive Groups’ to ‘Unhealthy’ across much of the region.
The most dangerous conditions are expected in eastern Okanogan County near active wildfires, where air quality could deteriorate to ‘Very Unhealthy’ or even ‘Hazardous.’
Officials warned everyone in affected communities to reduce their exposure, limit time outdoors and avoid strenuous activity until the smoke begins to clear.
