BAKERSFIELD, Calif. — The San Joaquin Valley Air District analyzed air pollution around the Central Valley for the past few months and they say they've certainly seen a difference amid stay-at-home orders.

The district says one of the main ways they measure air pollution is by monitoring for nitrogen oxides, or NOx. NOx contributes to ozone and comes from mobile sources like cars, trucks, and trains. So the district measured NOx levels along the valley’s entire portion of the 99 freeway and compared it with the same data from the past five years.

“I would say April was probably the biggest decrease that we saw in the past five years to 2020," said Jessica Olsen, program manager for the district.

Olsen says in April, Bakersfield saw a 22% reduction in ozone, compared to the average of the previous five years. She says the air district’s data lines up with CalTrans data tracking how many vehicles were on the road during those same times. The data showed a potential spike in cars on the road in may this year.

“In April we saw a 45% percent decrease from last year to this year on that stretch of the 99, and in May it went back to just a 20% difference," she said.

And Olsen says that difference in May correlates with a difference in air quality. May had a 13% reduction in ozone, compared with April's 22.

“There’s confidence that the shelter-in-place orders definitely influenced that, but to what degree there’s definitely still room for taking a look at that," Olsen said.

The district says ozone has already been on the decline in recent years, due in part to cleaner energy initiatives by state and local agencies. But still, the data they collected sends a valuable message.

“We certainly saw that decrease, and it’s very encouraging so we want to continue to push for cleaner technologies to support what we’ve seen so far," Olsen said.