California has some of the most aggressive climate laws in the country, including its Clean Vehicle Rebate Project, which incentivizes the purchase of electric vehicles (EVs), plug-in hybrids, and fuel cell vehicles. The state has issued more than half a million clean vehicle rebates since 2010. A new study shows that the program is having a mixed effect on air quality.
“I want to emphasize that the California Clean Vehicle Rebate Project has been very successful,” said environmental sociologist Jaye Mejía-Duwan, a doctoral candidate at the University of California, Berkeley. The program supports the decarbonization of transportation, a sector that emits nearly 40% of the state’s carbon dioxide emissions. Individuals who purchase one of the vehicles on the program’s approved list receive a check for between $1,000 and $7,500, depending on their income.
Air quality has improved in affluent communities as more clean cars hit the pavement between 2010 and 2021. But in inner-city neighborhoods? Not so much. These communities saw less reductions in nitrous oxide, sulfur dioxide, and soot-like particles called PM.2.5 of automobile exhaust fumes than wealthy neighborhoods.
The study is the first to compare pollution in more granular census tracts than in broader swaths of the entire county, a more accurate way to uncover differences in air quality between neighborhoods. The researchers considered air pollution between 2010 and 2021 based on public lists of rebates and emission models.
picking up the pieces
“One of the great things about California is that it reports high-quality, publicly available data,” Mejía-Duwan said. The Clean Vehicle Rebate Project publishes the make and model, vehicle type, and census tract of each rebate awarded.
Plug-in vehicles are “only as clean as the underlying power grid from which their electricity is drawn.”
Mejía-Duwan and her colleagues determined the change in local vehicle emissions using the State’s Emission Factor Model (EMFAC), which estimates how many air pollutants different types of vehicles emit. They applied those emission rates to the vehicles counted by the rebate project in each census tract. The researchers accounted for car movement by adjusting for emissions from surrounding census tracts within a 15-kilometer radius (the typical length of a California subway trip).
In the second half of the analysis, the researchers used the EPA’s AVERT (Averted Generation and Emissions Tool) electricity dispatch model to calculate the change in power plant emissions due to EV charging.
Plug-in vehicles are “only as clean as the underlying power grid from which you draw your electricity,” Mejía-Duwan said.
The researchers calculated the change in annual pollutants at each of the state’s 231 electric generating units as more plug-ins were connected. They assumed that people living within 5 to 20 kilometers (3 to 12 miles) of power plants were exposed to the emissions.
The study showed that emissions of carbon dioxide, nitrous oxide and sulfur dioxide fell across the state between 2010 and 2021. But the drop was uneven.
Annual nitrous oxide and sulfur dioxide emissions in underserved communities were reduced by a third of what affluent communities experienced. Surprisingly Primary PM Statewide2.5 emissions rose even as more cars went electric. (Heavier electric vehicles causing more tire and road wear contribute to PM2.5.) Still, wealthy neighborhoods were more likely to see declines or stagnation of PM2.5 instead of raises.
Sociologist Manuel Pastor of the University of Southern California in Los Angeles, who was not involved in the research, called the work “well done.” He praised the mix of modeling and varied power sources.
“The authors make the important contribution of considering air pollutant emissions from power plants that generate the electricity to drive electric vehicles,” said Lara Cushing of the University of California, Los Angeles, who was not involved in the study.
The sources of inequalities
Addressing historical inequities and ensuring a fair transition to low-emission technologies has been a “key priority” for California, said Dave Clegern of the California Air Resources Board, the state agency funding the rebate program. Clegern said the rebate program’s focus has evolved from pushing an emerging technology in 2010 to a program that actively addresses technology accessibility.
Disadvantaged communities “receive substantially less reimbursement than their disadvantaged counterparts.”
Although California seeks to help disadvantaged communities in the state, rather than leave them behind, “so far, the incentive program hasn’t done that,” said sustainable transportation researcher Dana Rowangould of the University of Vermont, who was not involved in the study. study.
Mejía-Duwan pointed to the structural challenges that prevent marginalized communities from benefiting from electric vehicles. The ability to purchase electric vehicles is highly dependent on income, and underserved communities “receive substantially fewer rebates than their disadvantaged counterparts,” she said. Although some models, like the compact Nissan Leaf, cost around $30,000, the average price of an electric car was $61,000 in 2023, according to Kelly Blue Book.
In addition, electric vehicles increase the burden on power plants, which are disproportionately located in underserved communities.
Environmental injustice, the disproportionate exposure of racial and ethnic minorities and low-income groups to pollutants, hazardous waste and other environmental hazards, is a “serious problem in both the state of California and the nation,” Pastor said. “These results will certainly make the state look further and make sure that it is addressing climate and equity goals in the most effective way.”
Starting in 2016, the state has adjusted the rebate program to shift resources toward low- and moderate-income groups, Clegern said. The state offers higher rebates to people with incomes less than or equal to 400% of the federal poverty level and now excludes high-income residents from receiving rebates. Clegern pointed to a new rebate benefit coming in July for $2,000 to support charging in disadvantaged neighborhoods.
The data showed that earlier adjustments to the payment structure improved the uneven distribution of refunds, “but not substantially in some ways,” Mejía-Duwan said. Before the changes, 5.9% of refunds went to disadvantaged communities, compared to 8.25% after.
“Vehicle electrification is useful in some important ways,” Mejía-Duwan said. “It is not a silver bullet, a magical technological fix for all our environmental inequalities.”
—Jenessa Duncombe (@jrdscience), staff writer
