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If you love wood-fired pizza or wood-smoked barbecue, then go outside right now and peel that “Go Green” bumper sticker off your Prius. Science says your favorite foods may be major causes of environment pollution.

A study conducted by 10 air pollution experts from seven universities has found that burning wood to cook your trendy kale-and-feta pie or your old-fashioned Texas brisket is polluting the air we breathe.

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A chef at Ráscal, a popular Italian restaurant chain in Brazil, tends to pizza in a wood-fired oven. There are over 8,000 pizza parlors that produce close to a million pizzas a day in São Paulo, Brazil. (Sasha Bogursky)

The collaborative study, whose findings have been published in the journal Atmospheric Environment, was conducted in the fifth largest metropolitan area in the world: Sao Paulo, Brazil, home to 21 million people, 7 million road vehicles and one very dangerous air pollution problem.

In an effort to address it, the city switched to biofuels like sugarcane ethanol, gasohol and soya diesel to run its vehicles. But when the pollution levels remained high, the scientists started searching for another culprit.

Who would have guessed it would be a calzone?

"It became evident from our work,” said Dr. Prashant Kumar, who led the study, “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. These include wood burning in thousands of pizza shops or domestic waste burning."

According to Phys.org, a web-based science, research and technology news service, “People of all ages line up for hours outside pizzerias every Sunday evening and the city is home to around 8,000 pizza parlors that produce close to a million pizzas a day and can seat up to around 600 people a time.

“In addition to the 800 pizzas a day being made using old-fashioned wood burning stoves, a further 1,000 a day are produced for home delivery, with Sunday being the busiest day of the week.”

That’s a lot of mozzarella … and a lot of wood.

"A total of over 307,000 tons of wood is burned each year in pizzerias," Kumar said.

"This is significant enough of a threat to be of real concern to the environment, negating the positive effect on the environment that compulsory green biofuel policy has on vehicles."

So saving the earth may mean giving up pizza-- or even barbecue.

In 2015, the Environmental Protection Agency funded a study on propane grill emissions and their effects on the environment. The researchers suggested pit masters use special trays to catch grease drippings and a "catalytic" filtration system to reduce air pollution.