Electric vehicles (EVs) are the cornerstone of the global energy transition. However, the conversation about electric vehicles focuses on minimizing emissions from the transport and power sectors, new research spotlights the impact of electric vehicles through the supply chain.

Research by Princeton University has demonstrated that refining the critical minerals needed for electric vehicle batteries could create pollution hotspots near manufacturing hubs. Focusing on China and India, the researchers found that national sulfur dioxide (SO₂) emissions could increase by up to 20% over current levels if the countries fully domesticize their supply chains for electric vehicles.

“Many discussions about electric vehicles focus on minimizing emissions from the transport and power sectors,” says corresponding author Wei Peng, an assistant professor of public and international affairs and the Andlinger Center for Energy and the Environment. “But we show here that the impacts of electric vehicles don’t end with vehicle tail-pipe emissions or electricity. It’s also about your entire supply chain.“

China’s electric vehicles (EVs) industry is the largest globally, accounting for approximately 58% of worldwide EV production. In 2024, the market is projected to generate revenue of around USD 376.4 billion, with an anticipated annual growth rate of 2.17% from 2024 to 2029, reaching an estimated USD 419.0 billion by 2029.

As the manufacture of EVs grows, so does the associated impact due to sulfur dioxide emissions. Most of those emissions would come from refining and manufacturing nickel and cobalt, important minerals for today’s electric vehicle batteries.

Both China and India have good reasons to avoid SO₂ emissions: the compound is a precursor to fine particulate matter, contributing to a host of cardiovascular and respiratory problems. The two countries already suffer from high levels of air pollution. In 2019 alone, around 1.4 million premature deaths in China and around 1.7 million premature deaths in India were attributable to fine particulate matter exposure.

Sulfur dioxide poses significant environmental and health risks. When it combines with water and air, it forms sulfuric acid, a primary component of acid rain, which can cause deforestation, harm aquatic life by acidifying waterways, and corrode building materials. On human health, sulfur dioxide irritates the respiratory system, increasing the risk of infections, aggravating conditions like asthma and chronic bronchitis, and causing coughing, mucus secretion, and eye irritation.

“People generally assume the transition to a greener technology is always going to be a win-win, there will be climate and air quality benefits,” says Anjali Sharma, an assistant professor in the Centre for Climate Studies and Ashank Desai Centre for Policy Studies at the Indian Institute of Technology, Bombay.

Sharma further says that, without considering manufacturing, you might lower carbon and nitrogen oxide emissions but increase the air pollution burden for communities near manufacturing centers.

While the analysis focused on China and India, the researchers argued that if left unaddressed, pollution from battery manufacturing will become an increasingly global challenge as electric vehicle adoption rates rise.

The researchers recommend the adoption of stringent policies for proactive air pollution standards. For China, which already has stringent emissions controls for the power sector, the focus needs to shift to mitigating SO₂ emissions from the battery manufacturing process, which the researchers said is less familiar.

The researchers also examined how changing the battery chemistry in EVs could avoid unwanted sulfur dioxide emissions at a more global scale. Most electric vehicle batteries today rely on cobalt and nickel. Despite the battery’s high energy density (which means they can store more energy in a smaller and lighter package), mining and refining cobalt and nickel have adverse effects on the environment and labor concerns.

The rise of alternative chemistries that use iron and phosphate (lithium iron phosphate batteries) could circumvent some concerns. LFP batteries are highly durable, offering a long cycle life that typically exceeds 2,000 cycles, making them ideal for a wide range of applications. Although their energy density is lower than that of NMC batteries, which can result in a bulkier design for the same energy capacity, they excel in performance under extreme temperatures. This makes LFP batteries particularly well-suited for use in harsh environments. The iron and phosphate components are readily available and easily recyclable.

The researchers found that scenarios with high penetration of lithium phosphate batteries resulted in far fewer SO₂ emissions from manufacturing.

Peng said the findings serve as a reminder to keep people at the top of mind when designing decarbonization plans, as even the most promising technologies could come with unwanted and unintended consequences.