In 2023, Harshit Gujral was one of 13 University of Toronto graduate students to receive a scholarship of $15,000 from Climate Positive Energy to further his research. Titled “Examining the public health impact of ZEV mandates in the US,” Harshit’s research project, supervised by Professor Steve Easterbrook, aims to quantify how adopting greener technologies can improve public health. Using a combination of statistical and explainable machine learning approaches to examine data, Harshit is able to measure the health co-benefits of sustainable infrastructure and policies, such as zero-emissions vehicle mandates. Now working towards completing his thesis, Harshit, who is also a teaching assistant at the university, shared insights with CPE on his research models and what he’s learned throughout his career.
Harshit is a multidisciplinary researcher cross-appointed in both the Department of Computer Science and the School of the Environment. With a background in computer science, Harshit was working in a corporate environment when he connected with Professor Steve Easterbrook. “I wanted to make research my job,” explains Harshit. “I read an article that was published in the Los Angeles Times in 2017, and that inspired my entire journey.”
The article referenced plans by the US government to roll back parts of California’s Clean Air Act, which aims to regulate greenhouse gas (GHG) emissions through restrictions on small particulate matter that make up smog.
“When I read it, I thought, now is not the time we remove the stringent climate laws. In fact, we probably need stricter laws.” Harshit began to wonder how he could demonstrate that these laws weren’t just beneficial for the environment, but also beneficial to human health.
“Health, and to be healthy, is something that everyone in the world wants.” Harshit started thinking about how his computer science background could help present evidence that would convince policymakers, industry leaders, and consumers to support climate policies and standards from a public health perspective – as opposed to one that just focused on the environment. “There was already years and years of research and data on the environment and climate out there.”
Harshit began to focus on existing data about Zero-Emission Vehicle (ZEV) programs and mandates across the US. Both the US Department of Energy and the Government of Canada classify a ZEV as a vehicle that either produces no tailpipe emissions or has the potential to produce no emissions. By this definition, all electric vehicles (EVs) are also ZEVs.
According to the International Council on Clean Transportation, California has been the pioneer state and first established a ZEV mandate in 1990. Nine other states have adopted California’s program. Collectively, these 10 states are referred to as the “ZEV states,” and account for more than a third of the total American ZEV market.
In a newly-published paper, Harshit and Professor Easterbrook, along with U of T Professor Meredith Franklin, analyze data to show how increasing sales of ZEVs is linked to lower childhood asthma rates. The data also shows that non-ZEV vehicle sales contribute to new cases of childhood asthma developing. The paper is the first to prove the measurable effect of ZEVs on health across the US. The research suggests that switching to ZEVs helps reduce health risks associated with air pollution.
“By looking at these and all other states, we are seeing that when we replace fossil-fuel based vehicles with ZEVs, we can prevent new cases of asthma,” explains Harshit.
To isolate the incidents of asthma due to fossil-fuel based air pollution, the research team looked at data on nitrogen dioxide, along with particulate matter, a byproduct of burning fuel that is emitted from vehicle tailpipes. Previous studies show that 18%–42% of all childhood asthma cases are caused by traffic-related air pollution.
The analyses indicate one asthma case is prevented for every 264 new EVs on the road. What surprised Harshit the most was that just an increase in ZEV market share – as opposed to replacing all non-ZEV vehicles – was associated with a potential reduction in childhood asthma cases. “What we are seeing is that we don’t even need every car to be an electric vehicle to see positive health outcomes. We are seeing that just a [ZEV] market share of around 50% is associated with a considerable reduction in asthma attributed to nitrogen dioxide.” This market share can range from 36% to 77% based on population density and geography of the neighborhood.
The research team studied observational data from US CDC and EPA monitors using a combination of statistical and explainable machine learning approaches. Harshit explains, “Statistical models always have some limitations. There are several factors that might be changing with the sales of ZEVs that also change cases of asthma. In our model, we considered variables such as geography and population density, to help us understand that the outcomes we were seeing were actually between ZEVs and asthma, and not some other variable.”
The researchers also note that while ZEV mandates have led to a greater fraction of EVs on the road, their benefits to improving public health are lesser known. Previous research has highlighted that while EVs effectively reduce tailpipe emissions, they may not significantly mitigate non-tailpipe emissions from brake wear, tire wear, and road dust that accumulates in the air. The study conducted by the U of T research team, however, shows that ZEV adoption has a significant impact on public health. Quantifying this effect will help build a strong evidence base for wider adoption of ZEV mandates – highlighting the importance of framing ZEV policies as not just an environmental issue, but a public health issue.
“ZEVs are a nice first step, but they are not a silver bullet,” explains Harshit. “We are seeing in our research that ZEVs decrease asthma, and we recommend developing targeted programs to replace diesel trucks and subsidies to encourage lower-income households to switch from older, fossil-fuel-based vehicles to EVs. Ultimately, we have to build a society that is heavily reliant on public transport or on biking, using cars only when necessary.”
Looking ahead to the future of his CPE-funded research, Harshit says, “this project has become my thesis proposal and part of the Ph.D. that I’m pursuing.” While working towards his Ph.D., Harshit is a Teaching Assistant for the course Confronting the Climate Crisis. “I’m seeing all of these students being serious and hopeful about climate change, and it is giving me hope as well. When we listen to some conversations about climate change, it can all seem a bit hopeless, like it’s not being taken seriously. But with the next generation, they’re serious about it, and their seriousness gives all of us hope, that it’s something we might be able to solve soon.”
Read the free research paper: https://pubmed.ncbi.nlm.nih.gov/39884530/
View Harshit’s Academic Profile: https://www.cs.toronto.edu/~harshit/
View Harshit’s Google Scholar: https://scholar.google.co.in/citations?user=MeEmmxgAAAAJ&hl=en
Connect with Harshit on LinkedIn: https://ca.linkedin.com/in/harshitgujral