by Electric vehicles are widely touted as a key means of curbing climate change through reduced emissions, but research into the dual benefits of reduced air pollution and improved health has been largely hypothetical.
A team of researchers from USC’s Keck School of Medicine has now begun documenting the real impact of EV adoption in the first study to use real-world data to link EVs, air pollution and health. Using publicly available datasets, the researchers analyzed a “natural experiment” that took place in California when the state’s residents rapidly transitioned to electric cars or light zero-emission vehicles (ZEVs). The results have just been published in the journal science of the whole environment.
The team compared data on overall registrations of ZEV, air pollution, and asthma-related emergency room visits across the state between 2013 and 2019. As ZEV adoption increased within a given zip code, local air pollution levels and emergency room visits declined.
“When we think about the actions related to climate change, it’s often on a global scale,” said Erika Garcia, PhD, MPH, assistant professor of population and public health sciences at the Keck School of Medicine and lead author of the study. “But the idea that making changes at the local level can improve the health of your own community could send a powerful message to the public and to policymakers.”
The researchers also found that while the total number of ZEVs increased over time, adoption was significantly slower in low-resource ZIP codes — what the researchers call the “adoption gap.” This inequality points to an opportunity to restore environmental justice in communities disproportionately affected by pollution and related health problems.
“It can be difficult to talk about the health impacts of climate change because they can feel very scary,” said Sandrah Eckel, PhD, associate professor of population and public health sciences at the Keck School of Medicine and senior author of the Study. “We’re excited to shift the conversation to climate change mitigation and adaptation, and these results suggest that the transition to ZEVs is a key element in doing so.”
Health and climate benefits
To study the impact of EV adoption, the research team analyzed and compared four different datasets. First, they obtained data on ZEVs (which includes battery-electric, plug-in hybrid, and hydrogen fuel cell vehicles) from the California Department of Motor Vehicles and tabulated the total number registered in each ZIP code for each year between 2013 and 2019.
They also received data from U.S. Environmental Protection Agency air monitoring agencies on nitrogen dioxide (NO2), a traffic-related air pollutant, and asthma-related emergency department visits at the zip code level. Asthma is one of the health problems that has long been associated with air pollutants such as NO2which can also cause and aggravate other respiratory diseases, as well as problems with the heart, brain and other organ systems.
Finally, the researchers calculated the percentage of adults in each zip code who had a bachelor’s degree. The level of education is often used as an indicator of the socio-economic status of a district.
At the ZIP code level, for every 20 additional ZEVs per 1,000 population, there was a 3.2% decrease in asthma-related emergency visits and a small reduction in NO2 levels. Averaging all ZIP codes in the state, ZEVs increased from 1.4 to 14.6 per 1,000 people between 2013 and 2019. ZEV acceptance was significantly lower in postcodes with lower levels of education. For example, a zip code containing 17% of the population with a bachelor’s degree had an average annual increase of 0.70 ZEVs per 1,000 people, compared to an annual increase of 3.6 ZEVs per 1,000 people for a zip code containing 47% of the population a bachelor’s degree.
Previous research has shown that underserved communities, such as low-income neighborhoods, tend to experience more pollution and associated respiratory problems than more affluent areas. If ZEVs replace gas-powered cars in these neighborhoods, they could benefit significantly.
“Should continued research support our findings, we want to make sure that communities overburdened with traffic-related air pollution really benefit from these mitigation efforts,” Garcia said.
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While climate change poses a massive public health threat, mitigating it presents a tremendous public health opportunity, Eckel said. As one of the first studies to quantify the real-world environmental and health benefits of ZEVs, the research can help demonstrate the effectiveness of this mitigation measure, including potentially reduced healthcare utilization and spending.
The results are promising, Garcia said, but many questions remain. Future studies should consider additional impacts of ZEVs, including emissions related to brake and tire wear, degradation of materials used in their manufacture, and disposal of old cars. Researchers also hope to study more pollutant types and other vehicle classes, in addition to a follow-up study on the impact of the ever-growing share of ZEVs in the country.
The transition to ZEVs is only part of the solution, Eckel said. Switching to public transport and being active, including walking and cycling, are other important ways to promote the environment and public health.
This work was supported by the University of Southern California Office of Research Strategic Directions for Research Award and the National Institute of Environmental Health Sciences [P30ES007048, P2CES033433].
