The Statewide Mobile Monitoring Initiative (SMMI) has been at work for about two years, with active air quality monitoring since mid-2025.
The project is set to conclude next month and served as a first-of-its-kind study to deliver community air pollution data across the state, funded by a $27 million legislative appropriation in the Budget Act of 2022, said David Ridley, chief of the Air Monitoring Support Branch at the California Air Resources Board (CARB).
“The data is intended to serve a screening function, identifying areas of concern to help prioritize locations for potential further assessment,” Ridley said in an email. “In many cases, SMMI will provide the first measurements of key pollutants in these communities. We anticipate that the data will be used to inform future air monitoring, prioritize inspections, bolster Community Air Grant applications, and support local community emission reduction plans.”
Some 62 communities in the state have been identified as areas with consistently problematic air. The technology, provided by Aclima, involves a network of “mini mobile labs” complete with air quality monitoring technology to measure about 10 different pollutants at high resolutions, Aja Ellis, Aclima SMMI project manager, said. Vehicles travel the streets of the neighborhoods collecting data every second.
The data is intended to give officials a detailed understanding of “where air pollution is, where air pollution isn’t, where it goes, and what areas are really impacted by it,” Ellis said.
The state of New York has also worked with Aclima on a similar “hyperlocal” air quality and greenhouse gas monitoring project in disadvantaged communities. The $3 million project in 2022 selected 10 communities for monitoring.
The traditional approach to air quality monitoring has been what Ellis described as the “regulatory approach,” which involves a stationary monitor, generally administered and operated by local government.
“They’re expensive to operate. But they provide really good data, really important data sets that show general trends in communities. They show when pollution is going down, like over a decade time period,” Ellis said. “But what they don’t necessarily show is that really high granularity, like what’s going on, from one block to another in a community.”
Mobile air monitoring is seen as a “screening tool,” Ridley said, noting it helps to identify where pollution levels may be elevated, leading to additional testing and analysis.
“The data collected will be used by government agencies, scientists, and the public for multiple purposes,” Ridley said. “It can help understand the variability of air pollution within and across communities and identify areas where air pollution was higher than average during the study period."
Some results from the mobile monitoring have given insights into specific locations. In one city, where a street was not intended as a truck route, the data showed that it was heavily used by trucks, Ellis said, due to high concentrations of black carbon, carbon monoxide, and other particulate matter near a school.
Aclima uses mostly electric or hybrid vehicles to collect the data, and algorithms in its monitoring technology remove data that could be impacted by the vehicle’s exhaust — what’s known as “self sampling.”
The technology “can really identify to a very precise location potential sources that might be impacting a community, on a smaller spatial scale,” Ellis said.
Data gleaned from the project, Ridley said, “is intended to serve a screening function, identifying areas of concern to help prioritize locations for potential further assessment.”
In a number of cases SMMI is turning up some of the first measurements of key pollutants in communities, which officials said will be used to inform future air monitoring and inspections, and contribute to emission reduction plans in those areas.
