Clean Air SGV Community Air Monitoring Study Page

Community-Led Air Monitoring in Alhambra and Monterey Park

Background

Alhambra and Monterey Park are two diverse, working-class cities in the western San Gabriel Valley that are significantly affected by air pollution. These communities are bordered by multiple freeways, adjacent to commercial and industrial zones, and experience high volumes of diesel truck and vehicle traffic. Despite these burdens, many areas have historically lacked local air quality data and state monitoring infrastructure.

The Clean Air SGV project was launched in direct response to:

The 2021 UCI report, Spatial and Temporal PM2.5 Trends in Alhambra and Monterey Park: Application of Purple Air Sensor Network for Asian Pacific Islander Forward Movement (APIFM), which revealed significant data gaps in PM2.5 monitoring. The report highlighted that many SB 535-designated census tracts lacked any sensors and recommended future deployments in those areas, especially near schools and sensitive receptors.
Ongoing input from residents, particularly youth, who expressed concerns about pollution near schools, freeways, and high-traffic corridors.
California legislation, including SB 535 and AB 617, which prioritize investments in communities disproportionately burdened by environmental hazards.

This research builds on APIFM’s earlier work and directly responds to the UCI report’s call for expanded sensor coverage and stronger community engagement in pollution-burdened neighborhoods. The current studies expand upon those findings by also evaluating the effectiveness of low-cost indoor air filtration strategies to reduce PM2.5 exposure.

Project Goals

Clean Air SGV is a community-based air monitoring project led by APIFM in partnership with the USC EJRL and 15 local residents. The goals of the project were to:

Expand the air sensor network in neighborhoods lacking adequate coverage
Document local PM2.5 pollution trends in high-priority areas
Evaluate low-cost solutions that help residents reduce indoor air pollution
Equip residents with data, tools, and experience to advocate for environmental justice
Generate findings that can inform local policy and support broader AB 617 and SB 535 implementation

About the Community

Alhambra and Monterey Park are home to large Asian American and Latinx populations. These cities are intersected by major transportation routes, including I-10, SR-60, SR-710, and SR-19, which expose residents to elevated levels of fine particulate matter. According to CalEnviroScreen 4.0, several census tracts in these cities rank in the top 25 percent of pollution burden statewide. Many are designated as historically disadvantaged communities under SB 535. Residents in these communities face elevated health risks, including asthma, heart disease, and respiratory illness, due to persistent environmental stressors and a lack of access to clean air infrastructure.

Mark Keppel High School, a site featured in our study, is located less than 100 feet from the I-10 freeway. Fremont Elementary and East Los Angeles College, two other featured locations, are also near heavy traffic or industrial activity. These communities face a combination of poor environmental conditions and limited infrastructure for monitoring and responding to air pollution threats.

Project Presentation

Watch a short presentation to learn about the project, how the studies were designed, and what we discovered here.

Study Summaries and Infographics

Study 1: Outdoor PM2.5 Monitoring at Community Hotspots

Purpose: Fill data gaps by measuring outdoor PM2.5 levels at four community-nominated hotspot locations.

Approach:

Sensors installed at two locations in Alhambra and two in Monterey Park

Hotspots identified through community mapping activities and feedback
Monitored hourly PM2.5 levels from October 2023 to September 2024

Key Findings

Average PM2.5 levels exceeded annual EPA and state thresholds at all sites
Highest pollution levels occurred during weekday rush hours and on weekends
Major pollution sources included freeway traffic, school zones, and nearby industrial operations
July 5th recorded the highest PM2.5 levels, likely due to fireworks

Study 1 Community Reports:

Study 2: Indoor Air Quality and Filter Effectiveness

Purpose: Assess the ability of different air filters to reduce indoor PM2.5 in homes located in SB 535 communities.

Approach:

Ten homes were selected in pollution-burdened areas
Each home was assigned one of three conditions: commercial HEPA filter, DIY box fan filter, or no filter
Sensors collected indoor and outdoor PM2.5 levels over nine months

Study 2 Key Findings

Homes with filters had indoor PM2.5 levels that were 5 to 6 micrograms per cubic meter lower than outdoor levels
DIY filters performed slightly better than commercial filters
Homes with no filters showed minimal improvement and sometimes had worse air quality indoors
Filters were especially helpful during wildfire events, such as the Eaton Fire

Study 2 Community Reports:

Full Technical Report

To learn more about the research methods, statistical analyses, and policy implications, download the complete technical report.

Read testimonials and see photos from study participants below:

I’m glad I got to participate in the air quality study. I’m a mother of a child who was exposed to a lot of second-hand smoke during my pregnancy, and as my son has gotten older he’s had some respiratory issues come up. So I was very interested in what the air quality in my community was and how it affects us all, especially after things we’ve experienced lately like the Covid-19 pandemic and wildfires in our area. The things that I noticed the most were that our indoor air quality sensors went up when we used our gas stove to cook, as well as any time our neighbors set off any fireworks (go Dodgers). I was also surprised that even though we live pretty close to a major freeway, our air quality doesn’t seem to be that bad. I think air sensors would be great for any family to have, just to have an idea of what the air quality is around them and get a sense of any sort of factors that might affect it. I would hope that at some point in the future, there would be a stricter ban/enforcement on fireworks in my community, since that seems to be the biggest contributor to bad air quality around me.

I was thrilled to be offered this study several months ago, particularly because I’ve been concerned about air quality since my emphysema diagnosis five years ago—a condition I developed despite never smoking. My work for a decade in a garage just ten feet from the San Bernardino freeway likely contributed to my health issues, as prevailing winds carry pollutants northward, affecting those living nearby continuously. Since my work circumstances changed, I no longer needed to be in the garage, yet my concerns about air quality persisted. I actively monitored it by frequently checking online resources and changing my air conditioning filters monthly. I invested in indoor air quality sensors from Amazon and Govee but found outdoor air quality sensors to be financially out of reach. Having the PurpleAir sensors has been great. They provided me with real-time access to outdoor air quality and temperature data! I discovered that the temperature readings reported by news outlets and various apps were often understated by 5 to 10 degrees, which my additional outdoor temperature readings corroborated.

I have been personally impacted by air pollution. I have asthma and I’m affected when the pollution levels are too high. Having the PurpleAir sensor has taught me that pollution is much worse than I thought. It has also taught me that having an air purifier in my home makes a big difference in the air quality. I was often surprised at the air quality in my area. It was often very high. My reaction (to the data) was mostly shock. Then after it helped confirm bad air days. I would recommend air sensors. Especially if you are sensitive to the environment. I live on main street and the pollution from all the cars is very apparent. I would love to see some solutions to pollution in high traffic areas, carbon capture, etc. The air filter, while a bit noisy, was a fixture for the past few months. I was able to identify the cause of indoor reading spikes pretty much every time. It was often incense, smoke, spray deodorant, or opening a window.

I think the best I got out of this experience is the informational presentation I attended hosted by Ms. Su'a. We learned detailed elements about the air quality and made more aware of our environment. Also, the purpose of us participating was to offer more data for the area that did not have a sensor around, so there was a lack of data in this area. I hope by having a sensor in our yard, we can help continue to collect data required. However, just knowing what it is is not enough; I wish, at some point, the problem is accompanied by solutions. We know how bad the air is, but what are the solutions?