Improving Air Quality in San Joaquin Valley: Part 2 - Stockton’s Crosstown Freeway, Air Quality Trends, and Indoor Air Quality

In Spring 2025, engineering students from UC Berkeley worked with community organizations within the Stockton AB 617 area, as well as Stanislaus County, to identify local air pollution sources and design mitigation strategies. This is part 2 of a 3-part blog series that highlights the student projects and resources to share with the community. Please see this page for more information.

Alternatives for the Crosstown Freeway:

The city of Stockton has been divided by the Crosstown Freeway since its construction in the 1970s. The freeway physically divided the city and destroyed the historic Filipino community known as Little Manila. Moreover, the freeway has continuously polluted those living around it through air pollution from traffic. In Spring 2025, UC Berkeley students analyzed the feasibility of different options to reduce exposure to traffic emissions. These options included adding a toll for trucks to use the freeway, undergrounding the freeway, and replacing the freeway with a truck-free boulevard. These scenarios were modeled using traffic flow software to examine the impacts of potentially rerouting trucks on the surrounding community. The students created a website that expands on these solutions, along with temporary solutions such as tolling to try to create immediate pollution reductions for residents impacted by the freeway.

More information on this project: Website | Report | Slides | One Pager

Air Quality Trends and Patterns:

Poor air quality driven by surrounding industries, highway traffic, and weak regulations is one of the largest contributors to Stockton having some of the highest asthma rates in California. The city faces significant levels of PM_2.5, which is linked to health issues from asthma to heart disease. UC Berkeley students analyzed 3 years' worth of air quality data from PurpleAir sensors across Stockton in collaboration with SJVAir from Central California Asthma Collaborative. The group identified patterns in the data showing increased pollution levels from November to February, when wintertime atmospheric inversions trap pollution near the ground. The data also show that residents in South Stockton are exposed to higher concentrations of PM_2.5 than Stockton overall. This analysis aims to empower Stockton residents with transparent data, to advocate for stronger policies and an expanded citywide air monitoring network.

More information on this project: StoryMap | Report | Slides | One Pager

Indoor Air Quality:

Most people spend about 90% of their time indoors, and indoor air quality can be 2 to 5 times worse than outdoor air quality, often due to a lack of ventilation, outdoor pollution influence, and indoor sources of pollution. The UC Berkeley student group focused on outreach to public housing units and daycares for documentation of air filtration systems. They found that daycares would benefit from additional air filtration units. Similarly, public housing residents would benefit from MERV-13 air filtration in home HVAC systems, to efficiently remove indoor air pollutants. Students also helped build and distribute 120 DIY air purifiers to Stockton families during the 2nd annual Stockton Unified School District Earth Day celebration in April 2025. 

More information on this project: Storymap | Report | Slides | One Pager