Earlier this year, the tiny, pizza-loving town of San Vitaliano, Italy, made headlines when its mayor issued a three-month ban on the use of wood-fired ovens to curb local smog levels. Turns out, San Vitaliano isn’t the only town that’s struggling with the environmental consequences of cooking up the cheesy Italian staple. According to Vox, a new paper published in the journal Atmospheric Environment suggests that São Paulo, Brazil’s staggering air pollution levels are partly due to wood-burning ovens found in pizzerias and other restaurants.

Home to 21 million people, São Paulo is Brazil’s largest city, and the world’s fifth-largest metropolitan area. And where there are lots of people, there are lots of cars. In fact, the city’s streets and parking lots are filled with approximately 7 million road vehicles. These exhaust-belching vehicles are responsible for most of São Paulo’s air pollution. However, experts from seven international universities, including Dr. Prashant Kumar of the University of Surrey, noted that São Paulo's residents fill their vehicles with a mostly “clean” biofuel comprising sugarcane ethanol, gasohol (75 percent gasoline, 25 percent ethanol), and soya diesel.

"It became evident from our work that despite there not being the same high level of pollutants from vehicles in the city as other megacities, there had not been much consideration of some of the unaccounted sources of emissions,” Kumar, the study’s lead author, said in a release. “These include wood burning in thousands of pizza shops or domestic waste burning."

So Kumar and his colleagues took a closer look at Brazilians’ love affair with pizza, noting that São Paulo’s 8000 pizza parlors produce nearly one million pizzas a day. Many of these parlors still use old-fashioned, wood-burning stoves—which collectively burn 307,000 tons of wood each year. And that’s not even counting the unregulated emissions from steakhouses and other eateries.

The study’s researchers concluded that in São Paulo, oven emissions might actually be negating the positive effects of green biofuels—although another co-author, North Carolina State University's Dr. Yang Zhang, noted that most air quality studies in Brazil have focused on the impacts of vehicle emissions, and not on wood and coal burning and meat-cooking in pizzerias and restaurants. So far, the jury’s still out on how much enjoying smoke-charred foods actually contributes to São Paulo's environmental pollution. However, these kitchen staples, along with biomass burning from the neighboring Amazon rainforest, are potentially major factors.

Along with tweaking São Paulo’s transportation policy to reduce air pollution, restaurant owners can outfit their ovens with special filters or purifying systems to help curb the damage they’re doing to the environment. It might be a small step to take in response to a large problem, but when you keep in mind that 4655 people died as a result of air pollution in São Paulo in 2011, every little bit helps.

[h/t Vox]