Map Shows Where Millions Urged to Avoid Driving

A high pollution advisory for millions of residents in the Phoenix metropolitan area has been issued for Friday.

The National Weather Service (NWS) said in an announcement that the alert has been released for Maricopa County, the most populated county in Arizona, which includes the cities of Phoenix, Mesa, Chandler and Scottsdale. High pollution advisories are issued when forecast “weather conditions combined with existing ozone levels are expected to result in local maximum 8-hour ozone concentrations that pose a health risk,” read the announcement.

During the advisory, residents are “urged to car pool, telecommute or use mass transit.” The NWS added that the “use of gasoline-powered equipment should be reduced or done late in the day.”

According to the Arizona Department of Environmental Quality (ADEQ), ozone is a colorless gas that, when at ground level in the Earth’s atmosphere, can “harm human health” and cause health problems such as coughing, breathing difficulties or lung damage. Exposure to ozone can also make people more susceptible to a lung infection, aggravated lung diseases or an increased frequency of asthma attacks.

“Prolonged exposure to ground-level ozone concentrations is as harmful to human health as exposure to higher levels for shorter durations,” read a handout from the ADEQ.

Those who have lung disease, such as asthma, are at greater risk of experiencing harmful symptoms from breathing in ozone. Children and teenagers whose lungs are still developing are also at a higher risk, as are older adults or people who are active outdoors for prolonged periods.

The ADEQ suggests that during a high pollution advisory, residents should reduce their exposure to ozone by choosing “a less-strenuous activity,” taking frequent breaks from being outdoors and rescheduling activities to the morning, since ozone levels are generally at their highest in the afternoon.

To help reduce ozone, the ADEQ also suggests that residents ensure their vehicles’ engines do not idle and to refuel vehicles in the evening or at night, when ozone levels have dropped.

Friday’s air quality index for Phoenix is forecast to reach moderate levels of ozone by 11 a.m. MST. By 1 p.m., the index is expected to rise and push the ozone levels to unhealthy marks for sensitive groups, according to the ADEQ.

Maricopa County is also under a high pollution watch from Saturday to Monday.