Many trees planted in urban areas — species that are often chosen for their quick growth and climate resilience — are worsening ozone emissions, suggests the study published in Science Advances today
Ozone forms when volatile organic compounds (VOCs) released by some vegetation, vehicles and chemical industries react with nitrogen oxides (NOx), which are emitted mostly by traffic and industry.
Specifically, they mentioned Poplars and Willows. Perhaps more, but I hit the paywall, couldn’t read the whole thing.