Winter air quality alerts in Phoenix have arrived on schedule as stagnant winter weather conditions and pollution from fireplaces settle over the Valley.
The state Department of Environmental Quality, with Maricopa County Air Quality, have issued high pollution advisories this week, and have declared “no burn day” restrictions as minuscule particular matter — PM2.5 and PM10 — spiked to unhealthy levels.
A PM2.5 high pollution advisory is in effect Friday and pollution watches continue through the weekend. No burn day rules are in effect Friday and Saturday.
The winter haze is often caused by an atmospheric phenomenon called an inversion, which can trap smoke, dust and other pollutants in stagnant air. During the winter, surface temperatures tend to cool and warm air rises, creating a lid in the atmosphere that holds pollutants below.
Even though temperatures have been above average this week, the surplus of smoke from fires and the relatively calm atmospheric conditions have created a window for pollution to accumulate in the desert skies.
Precipitation and wind can help clean the air, but windy days and showers can be less common during Phoenix winters.
On high pollution days, Maricopa Air Quality declares “no burn days,” during which residents are prohibited from lighting fire pits, fireplaces, fireworks and other unnecessary combustions to alleviate pollution.
Fine particulate pollution like PM2.5 and PM10 can endanger vulnerable populations like children, teens, older adults and those with asthma, COPD, heart or lung issues.
Health risks:For people with asthma and breathing problems, winter air pollution can feel deadly
These particles are small enough to reach deep into the lungs or enter the bloodstream, creating difficulty breathing, increasing the risk of heart attack or stroke and causing irregular heartbeats.
During high pollution advisories, all residents — especially those more vulnerable to pollution — are asked to minimize time and activity outdoors.
While county officials expect PM10 to drop down to moderate levels over the weekend, PM2.5 is forecast to remain elevated likely due to fireplace usage.
PM2.5 advisories and watches will continue through the weekend and likely into the holidays as residents continue wood burning despite restrictions.
Hayleigh Evans writes about extreme weather and related topics for The Arizona Republic and azcentral.com. Email her with story tips at hayleigh.evans@arizonarepublic.com.