Race cars and downtown air quality

Growling engines and squealing brakes are an integral part of the allure of auto racing.

In less than a week, Chicago will host its first NASCAR street race where elite stock cars that average around 5 mpg in a typical race will be hitting speeds over 100 mph downtown.

As race cars turn and brake, as tires screech, fine particulate matter is released into the air. And unlike commuter vehicles, race cars aren’t required to have pollution control devices that filter exhaust gases.

Among the 25 most polluted cities in the country, Chicago has plenty of its own air quality problems. In addition to factory and local vehicle emissions, pollutants from Canadian wildfires have regularly obscured the skyline over the past month. On July Fourth, the city will let loose with fireworks that can introduce, on a national average, 42% more pollutants into the air than are found on a normal day.

But many residents are also worried about the NASCAR race, complaining about pollution concerns, as well as traffic, safety and noise.

Evanston resident and retired mechanical engineer Fred Wittenberg said he is apprehensive about how race cars will contribute to air pollution in the city, especially if temperatures are hot and the air is stagnant — conditions that the city has been experiencing over the past month and ones that contribute to ozone and particle pollution.

“It can be very, very warm and humid, typical for July,” Wittenberg said. “And I can only imagine what’s going to happen with crowds down there and these cars racing around on Saturday and Sunday. That is my concern.”

[ NASCAR street race touts economic benefits for Chicago, but pushback grows over street closures, traffic, access and safety concerns ]

Experts, researchers and engineers, however, say the environmental consequences of a two-day NASCAR race are more nuanced.

“On one hand, it’s like a drop in the bucket, right?” said Greg Shaver, a mechanical engineering professor at Purdue University, referring to how emissions from vehicles that normally would be on downtown roads are cumulatively much higher than what will be produced by the race cars over two days.

But in the corner of Chicago where the race is occurring, there will be some effects, he said.

”Are we having more environmental impact during the race with these cars than we were with conventional cars? The answer is absolutely yes,” Shaver said. “They’re going faster and they’re gonna be using more fuel in that period of time because they’re being driven more aggressively than you and I would legally be allowed to drive.”

Since 2011, NASCAR has used fuel made of gasoline blended with 15% American-made, corn-based ethanol, called Sunoco Green E15. NASCAR said it has since reduced greenhouse gas emissions by 20% across its three national series.

“They are now…