The epic rainfall that has pummeled Southern California this winter has lifted the area out of extreme drought – and it’s also been great for air quality.
Strong winds blow smoke, soot and particulates out of the L.A. basin, while rain rinses the air clean. This winter is the 7th wettest in Southern California since 1946, according to data through February 24.
Air pollution has exceeded federal standards for particulate matter on just 7 days since November 2016. Compare that to 35 days in the same period in 2014-2015, the worst winter of the drought.
“We can’t depend on the weather to improve air quality, of course, but that said, from one year to the next weather plays a very major factor in the air quality,” said Sam Atwood, a spokesman for the South Coast Air Quality Management District.
During the drought, pollutants built up in stagnant, dry air. Wintertime inversions worsened the situation by trapping cold, dirty air close to the ground.
“Clear, cold and calm would be probably the three words to describe the conditions most conducive to wintertime air pollution,” said Daniel Swain, a climate scientist at UCLA.
Winter and summertime air pollution differ. Summer in Southern California is smog or “ozone” season. Ozone requires sunlight to form and there is typically not enough sun during the winter to trigger that chemical reaction.
Winter, meanwhile, is particulate-matter season because of the added pollution from wood-burning stoves. Seasonal fog and cloud help particulates form in the air.
The SCAQMD issues burn bans throughout the winter when the agency thinks particulate matter is going to reach unhealthy levels. This winter, the agency has issued just eight burn bans, down from 14 last winter and 25 in the winter of 2014-2015.
Particulate matter lodges inside the lungs and can cause respiratory infections, asthma, and, over the long term, a higher risk of lung cancer as well as early death.