Democratic presidential candidate Elizabeth Warren visited Michigan’s most polluted ZIP code for the first time last week.

The Massachusetts senator toured a community center and a school in the 48217 ZIP code in southwestern Detroit, where playgrounds sit sandwiched between the Great Lake State’s only oil refinery and car manufacturing plants.

Rep. Rashida Tlaib (D-Mich.) guided the Sept. 29 visit, of which the campaign shared video with HuffPost.

“What’s that smell?” Warren says at the start of the video, turning to Tlaib in the backseat of an SUV.

“That’s what my people smell every day,” the congresswoman says. “I thought the smell was normal. I really did. I didn’t realize that it was killing us.”

Just as gobbling fatty snacks at the Iowa State Fair is a rite of passage for top-tier presidential hopefuls, a pilgrimage to the 48217 is now becoming a touchstone for any contender who wants to be taken seriously on the nation’s environment.