Heat and extreme drought have worsened smog and air pollution in California over the last year, slowing down progress toward cleaner air and increasing health risks.
Pollution regulators have downplayed the recent uptick in smog as merely a blip in a decade-long trend of improved air quality. However, dry spells have brought more temperature inversions, which result in a layer of warmer air trapping cooler air below.
This leads to concentrating pollution near the ground. Rain or wind could clear the air, but high-pressure systems have caused less circulation and fewer storms. Conditions grew worse in part because higher temperatures accelerate the chemical reactions that form ozone, the lung-damaging ingredient in warm-weather smog. In a vicious circle, heat boosts demand for electricity, increasing smog-formation emissions from power plants.
Hot and dry conditions have also led to an increase in California wildfires, releasing more smoke. Dry farmland has also been adding more dust into the air.
The drought caused air pollution to increase across California last quarter as well. Fine particles jumped to their highest concentrations since 2001, over three times the federal standard. This fall, the valley and Southern California reported more bad air days from ozone.
Another unusual spell of high temperatures and a strong inversion layer hit the San Joaquin Valley last week, leading to fine-particle pollution to build up to dangerous levels. The region’s air quality officials have told residents to reduce driving and stop burning wood in hopes of counteracting the particle build up.
Though air pollution is a year-round problem, it becomes increasingly worse in two distinct seasons: winter and summer. In winter, fine particulate matter, or soot, becomes the main air problem. Tiny particles emitted by diesel engines, fires, and other combustion sources measure less than 1/30th of the width of human hair. Once inhaled deep into the lungs, they can damage the heart, blood vessels, and impair breathing. Chronic exposure to the fine particles is linked to heart attacks and cardiovascular disease.
The main problem in the summer comes from the ozone. It is not emitted directly but formed after cars, power plants, factories, and trucks release gases and unburned hydrocarbons. The pollutants cook in the heat and form ozone, a corrosive gas. Breathing ozone can harm lungs and trigger respiratory problems such as bronchitis and worsen heart and lung disease. On days with high ozone pollution, hospital visits for asthma increase.
Air pollution could go down as soon as this winter if enough storms blow in to stir up the air and sweep out the pollution. Forecasters say a weak El Niño, an abnormal warming of surface ocean waters in the eastern tropical Pacific, has a 58% chance of developing in the Pacific Ocean this winter and could bring more rain to California, cleaning the air.
Despite this, California is still far from meeting air quality standards. To meet a 2032 deadline and comply with current air standards, the South Coast Air Quality Management District will have to slash smog-forming gases, called nitrogen oxides, by over 75%. Reaching that level will require near-zero emissions across the economy.
Rising temperatures and drought are making it difficult for smog to be controlled. The resulting effects pose new challenges in the district which will impact residents from Los Angeles, Orange, San Bernardino, and Riverside counties.
“There’s a steady trend of air quality getting better, but layered on top of that is the meteorology, which is a crazy, up-and-down thing that is very hard to predict,” said Anthony Wexler, director of the Air Quality Research Center at UC Davis.