While electric vehicles have become a cornerstone of the global energy transition, new research led 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 were to fully domesticize their supply chains for electric vehicles. The overwhelming majority of those SO­₂ emissions would come from refining and manufacturing nickel and cobalt — important minerals for today’s electric vehicle batteries.

“Many discussions about electric vehicles focus on minimizing emissions from the transport and power sectors,” said 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.”