Journey to the Coronary Valley

The Green Heart Project

When Dr. Aruni Bhatnagar, MD, of University of Louisville Medical Center first started talking about a study to test trees as a medical intervention, even his fellow researchers thought the idea sounded crazy.

Led by Dr. Bhatnagar, these scientists basically created the field of environmental cardiology. They’re presently working on a study of “forest bathing” – how trees can chemically affect human stress levels. They’re accustomed to thinking outside of the box.

The project has recruited 700 neighborhood residents to participate in several rounds of medical tests, tracking the residual evidence of air pollution in their blood and urine. Dozens of different chemical signals will be monitored, including the presence of cortisol and adrenaline that are produced when the body is under stress. Participants’ physiological reactions to air pollution will be studied over five years, because some compounds appear within hours of exposure while others take months or years to emerge.

“This is where we transform urine into data,” says Yeager with a smile, during a tour of his lab. “We’re essentially relying on people to volunteer as human environmental monitors.”

The end result will be a bank of medical data that tells the story of neighborhood residents’ heath, both before and after trees are planted, as well as data from those who live in nearby areas that will not receive trees.

Our Friends and Family Breathe This Air

A nitrogen flare atop a factory stack glows against the bright summer sky, hovering over a large American flag. A freight train rumbles by as if on cue, tankers and boxcars delivering the flotsam and jetsam of industry. The air feels heavy, with a scorched smell that’s hard to place.

This is Rubbertown, a neighborhood in West Louisville where 11 large chemical plants account for more than 40% of emissions in Jefferson County. Still an active industrial center, this part of Louisville made its name on chemical production, rubber manufacturing and the overwhelming amount of shipping that kept these engines of commerce firing. Today, it all seems a bit shabby —ghosts of an industrial past. Shiny pickup trucks from Detroit are still clustered behind the barbed-wire fence, but there are a lot fewer trucks than there used to be.

Just a few blocks away, two little girls are jumping on a trampoline in their front yard, laughing and taking deep breaths as they play. Even here, a stone’s throw from some of the city’s most significant pollution sources, the problem is largely invisible. There’s no smog like the dark clouds that envelop Beijing or the haze that hovers over Los Angeles — just a clear blue autumn sky.

“It’s continuous. It’s pervasive. We don’t have a choice. Our friends and family all breathe this air,” says Chris Chandler, urban conservation director for The Nature Conservancy in Louisville.

You might travel several blocks of boarded-up buildings with no trees on anyone’s front lawn, just cracked asphalt baking in the sun; then come upon an enclave of snug little brick houses with flowers by the porch and big old ash trees shading the front walk.

“You can’t see any smokestacks from here. It’s out of sight, out of mind. There’s a beautiful blue sky … how could anything be wrong?” explains Eboni Cochran. Cochran leads a local community organization called REACT: Rubbertown Emergency ACTion. The grassroots group was the first to address the city’s air pollution issues, working primarily in the West Louisville neighborhoods that border the industrial zone.

You might travel several blocks of boarded-up buildings with no trees on anyone’s front lawn, just cracked asphalt baking in the sun; then come upon an enclave of snug little brick houses with flowers by the porch and big old ash trees shading the front walk.

“You can’t see any smokestacks from here. It’s out of sight, out of mind. There’s a beautiful blue sky … how could anything be wrong?” explains Eboni Cochran. Cochran leads a local community organization called REACT: Rubbertown Emergency ACTion. The grassroots group was the first to address the city’s air pollution issues, working primarily in the West Louisville neighborhoods that border the industrial zone.

Like so many American cities, Louisville faces unequal health impacts from pollution. The life expectancy in the city’s leafy suburbs is as much as 13 years longer than that of neighborhoods in the city’s south and west with lower average incomes and less access to nature — zip code is a reliable predictor of health here. Income disparity, diet, smoking rates and a web of countless other interrelated factors affect life expectancy. But adding more nature to a city can address some aspects of this inequity.

Too often, Cochran’s neighborhood —and many others in this city —are portrayed as simply “dangerous” in news reports, she says. It’s true that crime is a challenge, just as unemployment and addiction are top-of-mind for people who care about their city.

But in this city where historic racial segregation still shapes neighborhood identity, fidelity to your own little corner of Louisville is a core value. There are people who live their whole lives on the city’s East Side, never traveling to the West, and vice versa. It’s a city of distinct neighborhoods, each with its own deep cultural identity and people who love it.

Tree Loss is a Public Health Crisis

Chris Chandler stands under a leafy branch in Wyandotte Park — the very heart of the Green Heart Project area, and points to large ash trees that were planted when the park was built 80 years ago. These are some of the biggest trees in the neighborhood, and they’re all at risk.

The city’s air quality problems are exacerbated by a loss of urban trees. Nationally, cities are facing reduced budgets for trees. In Louisville, the tree planting budget has been zeroed out for several years, while maintenance funding was halved. Meanwhile, new invasive insects, such as the emerald ash borer, are claiming many of the big old trees. Recently, Green Heart was able to treat some of the biggest trees, offering protection against disease, and saving these critical community resources, but the challenge remains.

“We’re losing 150 trees per day in this city,” Chandler says. “It’s ecologically alarming, but this is also a public health crisis.”

Trees address air quality in several ways. Yes, trees take up carbon dioxide and release oxygen when they photosynthesize, just as you learned in grade school science. But they do much more than that. The fine hairs on trees leaves can actually trap fine particulate matter pollution — a component of both automobile exhaust and power plant emissions — reducing pollution levels near a tree by as much as a third.

And fine particle pollution is a particular concern for public health, as the particles are so small that they can actually pass into the bloodstream, causing heart disease and strokes.

Trees also form physical barriers to block pollution. In fact, one key element of Green Heart is the addition of trees and shrubs along highways — a strategy that a small previous study at a Louisville school suggests can reduce pollution levels in adjacent areas by as much as 60 percent.