Black carbon is linked to cardiac and respiratory problems. It contributes to climate change. And a primary source in Louisville and other cities is traffic exhaust.

This week, WFPL took an in-depth look at black carbon—where it’s found and how it affects Louisville and beyond. In a project that took months of preparation, environment reporter Erica Peterson relied on air monitors and interviews with experts and community members.

In part one, What Louisville Neighborhoods are Affected by Traffic Exhaust? All of Them, Erica placed air monitors in 17 Louisville area homes.

The quick summary of the data wasn’t much of a surprise. The lowest average black carbon concentration was in Prospect, several miles from the interstate. The highest average concentration was about nine times that, at the Glaab’s house in Portland.

“It’s just the price you pay for living here, I guess,” Geoff Glaab said, once I showed him the data. He’s not surprised that his home had the highest black carbon levels.

The data from the 17 homes can be found on this interactive map, assembled by Mark Schaver from WFPL’s cohorts at the Kentucky Center for Investigative Reporting.

In part two, Erica describes her long walks through the city while carrying air monitors. Like the first story, the results revealed some surprises.

According to the monitor, I was exposed to 75 percent more black carbon during the bucolic Cherokee Park walk than the walk near the highway.

This could be a fluke, or it could be because I got held up at a busy intersection, where I was in close proximity to idling cars. Both of the walks showed black carbon levels within the average background range for major American cities (which is 1-3 micrograms per cubic meter).

The data is also laid out in interactive charts for each walk. Here’s What Walks Through Louisville Reveal About Black Carbon Exposure.

In part three, Erica explores the ties between black carbon and climate change—and how that affects people. And polar bears, including Qannik at the Louisville Zoo.

It “makes the snow darker, so it absorbs more sunlight,” Sarah Doherty said. She’s a senior researcher at the University of Washington, and the co-author of a recent landmark assessment of black carbon’s effect on climate change.

When black carbon falls on snow and it absorbs more sunlight, it melts sooner, Doherty said.

“And if it melts sooner, the snow and ice itself is fairly white, but when it melts it exposes the underlying surface, which is either ocean or land, and that’s quite a bit darker than the snowpack,” she said. “So that absorbs more sunlight. So there’s sort of a feedback cycle where if you make the snow melt earlier, you get even more warming so it melts even more quickly.”

Funding for the series was made possible through a grant from the Society of Environmental Journalists.