La Paz, Bolivia is both literally and figuratively breathtaking. The city begins at the edge of a cliff and spills down a nearly vertical canyonside, two and a half miles above sea level. To descend into the frenetic city center on a hazy morning is to descend through the clouds—a dizzying journey to take outside of an airplane’s pressurized cabin.

When professor Mike Bergin and his team of Duke engineering students step off their plane in the neighboring city of El Alto, they are immediately plagued by altitude sickness. Neon signs direct lowland foreigners to the airport’s stores of emergency oxygen—the only relief from the thin mountain air. At an altitude of 14,000 feet, El Alto (which translates roughly to “The Heights”) is the highest major metropolis in the world. Just a few thousand feet higher, human habitation ceases to exist.

“I think it’s amazing that people live here,” says Heidi Vreeland, an environmental engineering PhD student and one of the teaching assistants for Bergin’s class. Her research, like Bergin’s, focuses on air pollution and its effects on human health and the environment. “It seems so unnatural. There are planes that don’t fly as high as we are right now.”

At this altitude, the air contains 30% less oxygen than at sea level, making it a challenging but rewarding field site for Bergin’s civil and environmental engineering class to measure air quality.

“There’s really a recipe for bad air quality in La Paz,” Bergin says. “It’s highly populated, it’s really high altitude, and it’s a relatively poor country. What I’ve seen in my research is that when you put all those things together, you’re looking at bad air quality pretty much across the board.”

Andean Adaptation

As the team begins the winding drive into the lower city districts of La Paz, Bergin points out fleets of vehicles 15 to 20 years old, emitting clouds of exhaust that make the air feel even thinner. Vreeland will spend much of the week holding sensors to this black carbon fog, helping students measure particle pollution on the streets of La Paz and El Alto.

In the United States, she explains, particle pollution from traffic rarely exceeds a regulated annual average of 12 micrograms per cubic meter (µg/m³). Here, where most vehicles are older and poorly maintained, and where combustion is influenced by low air pressure, levels can easily exceed five times the U.S. standard, sometimes reaching up to 300 µg/m³.

These numbers are particularly troubling in light of recent studies showing just how significantly clean air reduces lung stress in children, particularly in those prone to asthma.

“We’re curious as to whether locals are under inflammatory stress disproportionally to the way we are as visitors,” Bergin says. “For people like us who visit for a short time, I’m sure the altitude exacerbates any potential problems we have with the air pollution because our bodies haven’t developed those physiological responses to help us adapt.”

Vreeland and her students have prepared to test this hypothesis by measuring lung inflammation—both their own and that of local collaborators at the Universidad Mayor de San Andrés—with a device that measures exhaled nitrous oxide (eNO). At this elevation, however, the machine only produces an “error” message, itself a hint at the wide-ranging effects of altitude.

The team and their Bolivian partners descend to 10,000 feet—about twice the height of Denver, Colorado—before the machine will return a measurement. When it does, the Duke team sees that their lungs are experiencing up to twice the stress they experienced on Duke’s campus in Durham, where the elevation is only several hundred feet. The machine returns lower numbers on average for their three Bolivian peers, indicating better lung health.

The limited information they are able to collect does not produce a scientifically robust data set, but the team’s curiosities are temporarily satisfied, and they return to La Paz to refocus their research on particle pollution, visibly suspended in the city streets.

Rising Above Air Pollution Challenges

To travel quickly to and from their test sites, the team hops on the Teleférico, the largest and highest urban cable car system in the world, which connects La Paz and El Alto.

The system opened in 2014 to provide alternate transportation to the cities’ thousands of commuters, and to decrease the number of vehicles on the chaotic streets below.

In past work with local collaborators, Vreeland and Bergin have observed the Teleférico’s effects on passengers’ pollution exposure. “The really cool thing is that you can go from one part of town to the other during rush hour on the Teleférico,” Bergin said, “and what we showed, unsurprisingly, was that the Teleférico is removed from this intense pollution level almost all the time.”

In addition to decreasing air pollution exposure levels tenfold, the cable cars whisk locals and visitors upward for sweeping views of the city and of the surrounding mountains, which themselves are not immune to the effects of pollution.

From the window of the cable car, one of the team’s Bolivian peers from the Universidad Mayor de San Andrés points toward the cliffs surrounding the city, many of them lush with vegetation.

“I have lived in Bolivia my whole life,” he says. “Ten years ago, those mountains were not green.”

A Deserted Mountain

With nearly a week of acclimatization under their belt, Bergin, Vreeland and the students climb higher, to the peak of the once snowcapped Mount Chacaltaya. The name is well known by climatologists, for whom this mountain is an alarming example of glacial retreat.

Here, at approximately 18,000 feet, a single step feels like ten. The mountain is home to the Mount Chacaltaya Laboratory, one of the highest atmospheric labs in the world, and even its regular visitors and local researchers feel the effects of hypoxia: fatigue, light-headedness, numbness of the limbs. “Memory is fragile [on the mountain],” the lab’s safety manual warns. “Cognitive functions slow down at high altitudes. Never lose calm... Never walk alone to the summit.”

For Vreeland, who has a tattoo of the Antarctic ozone hole between her shoulder blades, the retreat of tropical glaciers is not news. But to stand this far above sea level with mountain rock under your feet and no snow in sight is discontenting, even for those who don’t study climate change.

Not many years ago, Chacaltaya was, in fact, a year-round destination for skiers from across the globe, home to the highest altitude ski lift in the world. By 2009, however, the mountain’s nearly 20,000-year-old glacier had melted completely, more than five years before scientists’ estimation.

“In Laz Paz we know that we’re breathing in pollution from the cars next to us, but indirect air pollution affects all aspects of people’s lives,” Vreeland says.

The World Bank, which reported on the Chacaltaya ski lodge’s closing in 2013, has forecasted powerful effects of glacial melt on the Andes region’s vital water supply. In La Paz, where glaciers provide almost 30% of potable water during the dry season, the eventual shortages will affect everything from the hydropower industry to the availability of drinking water.

Looking Toward the Future of Environmental Problem-Solving

It’s challenging work, Bergin and Vreeland agree, identifying the most dangerous pollutants and implementing appropriate mitigation strategies for the health of the planet and its inhabitants.

“With time, this field is only going to become more and more important,” Bergin says, aware that the students he mentors today will hold this responsibility in their hands in the years to come. “If even one person in this class is interested in this subject and it enriches their lives and they have a career related to the environment, that’s worth my work for my entire academic career.”

But Bergin and Vreeland know that the work is never done, even as their final night in La Paz comes to a close. For their students, this fieldwork experience might be the very beginning.

“[This trip] has been a good test of resilience for everyone,” Vreeland says. “It’s entirely true to the real world of engineering. I think experiences like this”—not unlike the often daunting tasks environmentalists face on a global scale—“are so important and beneficial to everyone, as long as you’re up for the challenge.”

Read the students’ blog and watch more about their trip: