Exploring the San Joaquin Valley’s Air Quality and Vehicle Emission Challenges
The San Joaquin Valley in California is grappling with significant air pollution issues, ranking among the top in the state for pollution burden. Despite this, the region lags in the adoption of zero-emission vehicles (ZEVs).
According to the state’s Office of Environmental Health Hazard Assessment, all eight counties in the Valley are within the top 10 for pollution burden scores in California. Coincidentally, the region has a lower percentage of ZEVs compared to the state average, with more than 97% of vehicles running on fossil fuels, which contribute to the pollution problem.
Jaime Holt from the San Joaquin Valley Air Pollution Control District clarifies that the link between poor air quality and low ZEV adoption is coincidental. The district, alongside the California Air Resources Board and U.S. Environmental Protection Agency, manages air quality efforts in the area.
Jon Klassen, the Valley air district’s director of air quality science, emphasizes that while mobile sources dominate air pollution, it is primarily heavy-duty vehicles, not passenger cars, that contribute significantly to the region’s pollution. These include trucks, buses, and construction equipment.
The Valley’s air pollution varies across counties, affecting residents’ health. Kern, Tulare, Fresno, Kings, and Madera counties are particularly burdened by ozone, while Merced, Stanislaus, and San Joaquin counties also rank high. Fine particulate matter, often produced by vehicles and industries, is another concern, with most counties ranking in the top 10 for this pollutant.
Heavy-duty vehicles are responsible for about 70% of nitrogen oxides (NOx) emissions, which contribute to ozone formation. With approximately 150,000 such vehicles registered in the Valley and more passing through, they significantly impact air quality. Passenger vehicles, although more numerous, account for only about 10% of NOx emissions.
Efforts to Reduce Emissions from Vehicles
The air district can regulate stationary pollution sources but lacks authority over mobile sources. However, it offers incentives for adopting cleaner vehicles, including ZEVs and newer models, to help reduce emissions. The focus is not solely on ZEVs, as the district also aims to replace older vehicles with cleaner-burning ones, given the socioeconomic challenges in the Valley.
Sales of ZEVs have been increasing, with new registrations rising from 3.5% in 2020 to 15.3% in 2025. San Joaquin County leads in ZEV adoption, while Kings County has seen a rapid increase in the percentage of ZEVs among new vehicles sold.
Federal tax credits that supported electric vehicle purchases expired recently, and high demand led to the suspension of a local rebate program. The district continues to promote cleaner vehicles through various programs, addressing both emission reductions and affordability.
Challenges in Charging Infrastructure
While ZEV numbers grow, charging infrastructure remains a challenge, particularly in rural areas. Homeowners often install chargers, but larger installations in apartment complexes face utility limitations. The Valley’s electrical grid struggles to support the needed infrastructure, affecting both passenger and heavy-duty vehicle charging capabilities.
Efforts are underway to develop charging sites along major highways to support commercial traffic, but grid capacity issues persist.
Impact of Heavy-Duty Vehicles
Heavy-duty vehicles, like big rigs, pose challenges due to their significant emissions. Cities like Fresno face community concerns when large distribution centers are proposed, leading to legal actions and measures to mitigate pollution impacts.
Despite being outnumbered by passenger vehicles, heavy-duty vehicles generate most of the Valley’s NOx emissions. Efforts to introduce zero-emission trucks are progressing, with projects demonstrating successful deployment of electric trucks in commercial operations. However, infrastructure and vehicle range remain limiting factors for broader adoption.
Original Story at themercedfocus.org