Smog gets bad quickly in the San Joaquin Valley. Images taken just days apart show the dramatic shift
Sacramento’s air quality district says Tuesday will be the first official “Spare the Air” day of 2019 for the region, as air quality is expected to reach unhealthy levels for sensitive groups on a 103-degree day.
The forecast in Sacramento shows an ozone Air Quality Index reading of 126 expected Tuesday, according to the Sacramento Metropolitan Air Quality Management District. Any ozone AQI forecast of 126 or higher automatically triggers a Spare the Air alert.
The air quality district encourages those in the Sacramento region to limit driving in an effort to reduce air pollution.
“Share a ride, take transit or simply bring your lunch to work to avoid an afternoon car trip,” says a message on the Spare the Air website, which is run by the Sacramento, El Dorado, Feather River, Placer and Yolo-Solano air districts.
Ozone, commonly referred to as smog when it reaches ground level, is mainly created by heat and sunlight, creating higher risks of air pollution on hot summer days. Large wildfires with heavy smoke can also fuel ozone, and potentially trap it near ground level.
There is still wildfire activity in the region as crews work to contain the 2,220-acre Sand Fire in Yolo County. But wildfire smoke contributes more directly to a type of air pollution known as particulate matter (PM2.5), which registers on a separate air quality index.
PM2.5 readings spiked to a “moderate” air pollution level in the Yolo-Solano area Saturday, the day the Sand Fire started, but have remained at healthy levels each day since then, as had achieved 50 percent containment of the fire in Capay Valley as of Monday evening. This suggests that any significant air quality effects from the Sand Fire are fading.
Spare the Air days are tracked May through October in the Sacramento region. Last year had 20, between June 13 and Sept. 27, which was the most in the region since there were 22 in 2002. 2016 and 2017 each saw 17 Spare the Air days.