A new study by researchers at the Keck School of Medicine of USC, published in the Science of the Total Environment journal, has found a link between the increased use of zero-emission vehicles (ZEVs) and improved air quality and public health in California. This is one of the first studies using real-world data to show that electric cars are associated with reductions in both air pollution and respiratory problems.
Gasoline-powered vehicles are major contributors to air pollution, including particulate matter and nitrogen oxides, which are associated with negative health outcomes such as respiratory symptoms, cardiovascular disease, and premature deaths. For example, car exhausts are responsible for 4 million new cases of childhood asthma every year. Electric vehicles with no exhaust and reduced use of brakes intuitively are capable of reducing such air pollution, but up to this point, little real-world data had been collected demonstrating this. Previous studies from Northwestern University and the American Lung Association have estimated that EVs can reduce premature deaths, and there is generally growing evidence about the importance of reducing air pollution with EVs to improve public health.
The study analyzed data on the number of zero-emissions vehicles (ZEVs), ambient NO2 pollution, asthma emergency department visits, and population characteristics in 1,238 California zip codes for the 2013-2019 time period. This represents a natural experiment — on average across zip codes in the state, ZEVs increased from 1.4 to 14.6 per 1,000 people between 2013 and 2019, allowing researchers to observe and quantify the impacts of rising EV adoption on NO2 and asthma-related ED visits. The results show that each increase of 20 ZEVs per 1,000 people within a zip code reduced NO2 by 0.41 parts per billion in the air, and reduced asthma-related emergency visits by 3.2%, indicating an early transition to ZEVs in California has resulted in positive outcomes for both the environment and public health. The study also controlled for confounding factors by using age-adjusted rates of asthma emergency visits. Today, EVs in California exceed 20 per 1,000 people, with the vast majority being Teslas, meaning that EVs led by Tesla have reduced asthma-related emergency room visits by several thousand just in California alone.
However, the study also highlights the ZEV adoption gap in neighborhoods with low educational attainment, a proxy for socioeconomic status. For instance, a zip code with only 17% of the population having a bachelor’s degree had, on average, an annual increase of 0.70 ZEVs per 1,000 people from 2013 to 2019 compared to an annual increase of 3.6 ZEVs per 1,000 people for a zip code with 47% of the population having a bachelor’s degree. Such a distribution of ZEV adoption produces socioeconomic disparities in cleaner air and improved public health.
The findings of the study are important for policymakers as they consider the future of transportation and the transition to an electrified transportation sector. The results provide crucial evidence for creating policies that will ensure a just and equitable transition to ZEVs, which will help mitigate the effects of climate change and provide environmental and health benefits for all. This is especially true on the state and local levels since the environmental air pollution and public health benefits of ZEVs are highly localized. “When we think about the actions related to climate change, often it’s on a global level,” said Erika Garcia, PhD, MPH, an assistant professor of population and public health sciences at the Keck School of Medicine and the study’s lead author. “But the idea that changes being made at the local level can improve the health of your own community could be a powerful message to the public and to policymakers.”
The authors of the study stress the need for future research to better understand the long-term effects of the transition to ZEVs on air quality and public health. Specifically, future research can consider more ambient air pollutants such as particulate matter as well as more health outcomes besides asthma-related emergency visits, while considering more vehicle classes and public transportation as well.
Overall, the study highlights the potential of ZEVs to positively impact the environment and public health, while also pointing to the need for continued research and policy development to ensure a just and equitable transition to an electrified transportation sector.