Millions of Americans in three US states have been urged to stay indoors on Monday, as toxic smog blankets the region.
The National Weather Service (NWS) warned residents in parts of Arizona, Texas and California to limit outdoor activity and take precautions as dangerous ozone pollution spreads across heavily populated regions.
Ground-level ozone is a powerful oxidant that acts as a respiratory irritant, causing immediate breathing difficulties like coughing, throat irritation and chest pain.
It can damage the lungs, worsen asthma and other breathing conditions and increase the risk of long-term heart and lung problems.
Air quality alerts have been issued for the Phoenix metro area and Tucson region in Arizona.
The Arizona Department of Environmental Quality warned that weather conditions combined with existing pollution levels were expected to create dangerous ozone concentrations in both areas.
In Texas, the Texas Commission on Environmental Quality issued an Ozone Action Day for El Paso, including Downtown El Paso, Socorro, Fort Bliss and surrounding communities.
California officials also extended an air quality alert for the Imperial Valley, warning residents that ozone pollution levels would likely peak during the afternoon and early evening hours.
The National Weather Service (NWS) warned residents in parts of Arizona, Texas and California to limit outdoor activity and take precautions as dangerous ozone pollution spreads across heavily populated regions (stock)
Ground-level ozone is a harmful air pollutant that forms when emissions from cars, power plants and industrial facilities react with heat and sunlight, creating dangerous smog on hot days.
The largest alert was issued for the Phoenix metro area in Maricopa County, where the Arizona Department of Environmental Quality (ADEQ) warned that weather conditions combined with existing pollution levels were expected to create dangerous ozone concentrations through Tuesday.
Officials specifically advised residents to carpool, use public transportation and avoid using gasoline-powered lawn equipment during the hottest parts of the day.
A similar warning was issued for the Tucson metro area, including Green Valley, Marana and Vail, where ozone levels were forecast to reach concentrations considered hazardous to sensitive groups.
ADEQ warned that adverse health effects increase as air quality deteriorates and encouraged people to reduce physical activity outdoors.
The Texas Commission on Environmental Quality issued an Ozone Action Day for the El Paso area from 10am to 9pm Tuesday.
The advisory included Downtown El Paso, the Upper Valley, Socorro and Fort Bliss, where officials said atmospheric conditions would be favorable for producing high levels of ozone pollution.
Residents have been urged to share rides, conserve energy and keep vehicles properly tuned to help limit emissions.
California officials also extended an air quality alert for the Imperial Valley due to harmful levels of ozone pollution.
The advisory warned that ozone levels could vary throughout the day depending on pollution transport and weather patterns, with the highest concentrations expected during the afternoon and early evening hours.
The California warning included detailed health guidance for residents depending on Air Quality Index levels.
Officials said that when conditions reach the ‘Unhealthy for Sensitive Groups’ category, people with lung disease, children and older adults should limit extended outdoor activity. If conditions worsen to ‘Unhealthy’ or ‘Very Unhealthy,’ residents were advised to avoid prolonged time outside altogether.
Health experts have long warned that ground-level ozone differs from the protective ozone layer high in Earth’s atmosphere.
