The Pollution in Your Pizza

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A recent paper Atmospheric Environment says that wood burning stoves in pizza restaurants, and charcoal in steakhouses, are adding a lot of pollution.

But don't swear off Dominos just yet. This was a case study, and not a science study, and it was in Sao Paolo, which has a lot of confounding factors.

Though the pork and bean stew called feijoada is Brazil’s national dish, in Sao Paolo pizza is king. It is the Sunday dinner for most of the city’s residents and there are around 8,000 pizza parlors producing almost 1,000,000 pizzas. Some restaurants seat up to around 600 people a time.

But all those wood stoves may be causing a particulate matter problem.

“There are more than 7.5 hectares of Eucalyptus forest being burned every month by pizzerias and steakhouses. A total of over 307,000 tonnes of wood is burned each year in pizzerias. 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,” says Dr. Prashant Kumar from the University of Surrey.

What positive effect? Sao Paulo’s inhabitants fill their vehicles with a biofuel comprising of sugarcane ethanol, gasohol (75 percent gasoline and 25 percent ethanol) and soya diesel. All of that is actually worse for the total environment than regular gasoline.

The huge number of passenger vehicles and diesel trucks remain the dominant contributor to particle emissions, not to mention the seasonal burning of sugar cane. There are other confounders -- those natives in the Amazon rain forest love to burn it and that crosswind is a contributing factor in why the city’s air pollution is so toxic. And urban pizza still requires a lot of rural farming, and that adds pollution.

Once in the air, emitted pollutants can undergo complex physical and chemical processes to form secondary pollutants, such as ozone and secondary aerosol, so it's good to consider all sources. But vehicle emissions remain the biggest problem for air quality and human health, not emissions from wood or coal burning restaurants serving up meat and pizza.

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Citation: Kumar, P., Andrade, M.F., Ynoue, R.Y., Fornaro, A., de Freitas, E.D., Martins, Martins, J.L.D., Albuquerque, T., Zhang, Y., Morawska, L., New Directions: From biofuels to wood stoves: the modern and ancient air quality challenges in the megacity of São Paulo. Atmospheric Environment 140, 364-369, doi:10.1016/j.atmosenv.2016.05.059