When 2 Become 1

In the new Department of Environmental Health and Engineering, expect deep collaboration and smart solutions.

By David Glenn • Photos by Howard Korn

This summer, students and postdocs from the Bloomberg School will fan out to locations across Baltimore City to install more than 100 air-quality sensors. These highly sensitive devices—small, black metal boxes that look a bit like DVRs—will be placed on street corners and utility poles to measure fine particulate matter, carbon dioxide, methane and several other greenhouse gases. 

In concert, the Baltimore sensors will help scientists understand how air pollution from diverse sources—vehicle emissions, industrial activity, backup diesel generators—is spatially distributed across the city.

The stakes for public health are high: A 2013 study by MIT researchers found that Baltimore has a higher rate of emissions-related premature deaths than any other American city.

For Marsha Wills-Karp, one of the country’s foremost asthma experts, the Baltimore City air project is a perfect example of how environmental health scholars and environmental engineers can amplify each other’s work.

“Engineers and public health folks don’t necessarily speak the same language,” says Wills-Karp. “But when they work together on concrete problems, they can have a huge impact on areas of the environment that we’re all concerned with: air, water, soil.” 

Wills-Karp is in a good position to make that union flourish. Last summer, she was named chair of the newly configured Department of Environmental Health and Engineering. The department encompasses the Whiting School of Engineering’s Department of Geography and Environmental Engineering and the Bloomberg School’s Department of Environmental Health Sciences. 

It is the only program in the country that brings together a full range of environmental engineering and public health scholars within a single department.

The new department has deep historical roots. One of the most storied figures in Johns Hopkins history, Abel Wolman, pioneered modern methods of water purification and sanitary engineering. Wolman simultaneously headed the departments of sanitary engineering in the School of Engineering and in what was then known as the School of Hygiene and Public Health.

Photo of Abel Wolman at his desk
Crossing the Aisle: Abel Wolman, one of the most storied personalities in Hopkins history, frequently collaborated with researchers in other departments.

Wills-Karp and her colleagues seek to extend the Wolman tradition of marrying engineering and public health. The fledgling department has a strong wellspring to start with: Two Whiting School alumni, Yu Wu and Chaomei Chen, have donated $1 million to support collaborative research between the department’s engineering wing and its public health wing.

“The stipulation is that you have to have at least one partner from each of the two schools,” Wills-Karp says. “We had more than 120 people at our research retreat in January, and there was a huge amount of interest.”

The first seven pilot projects were announced in March. They include studies of antibiotic-resistant organisms in the Chesapeake Bay; contaminated sediments and Parkinson’s disease; and toxic groundwater leachates in streams. There will also be a pair of air-pollution studies led by two of the researchers involved in this summer’s air-quality-sensor project: Benjamin F. Hobbs, PhD, an Environmental Engineering professor, and Kirsten Koehler, PhD, MS, an assistant professor at the Bloomberg School.

“A lot of my work involves air-quality sensors, but I’m not an engineer by training,” says Koehler. “So it’s excellent to have this collaboration with Ben Hobbs, and to be able to draw on expertise from the Homewood campus to help solve some of the problems that we’re facing in our research.”  

“We really expect that this kind of collaboration will give our environmental engineering students an edge,” Wills-Karp says. “Most engineering students never have this kind of deep contact with public health scholarship, and the reverse is also true.” 



The path that led Marsha Wills-Karp to Johns Hopkins was strewn with poison ivy. 

As an undergraduate in the late 1970s at what was then known as Southwest Texas State University, she fell in love with science through a botany class. But there was a hitch: “I had the misfortune of being tragically allergic to poison ivy,” she says. “And this course involved gathering hundreds and hundreds of different plant specimens. I just kept getting exposed. Steroids weren’t helping. Finally the college physician just said, ‘You’ve got to get out of this. You need to change careers.’” (It may be fitting, then, that Wills-Karp has wound up studying the perversities of the human immune system.)

After abandoning plant life, Wills-Karp completed a major in human physiology. She stayed at Southwest Texas State for her master’s degree, studying in a lab that used novel techniques to isolate individual cardiac-muscle cells. 

“She had all the skills that people look for in a graduate student,” says her thesis adviser, Joseph Koke, PhD, who is now a distinguished professor emeritus at Texas State University in San Marcos. “She was patient and persistent in the lab. You’d tell her what needed to be done, and she’d find a way to do it.” 

For her doctoral studies, Wills-Karp entered the University of California at Santa Barbara’s Institute of Environmental Stress, an interdisciplinary center that sought to understand how human cells respond to pollution, aging and other stressors. “We had a huge metal chamber that looked like something out of the military,” she says. “Inside the chamber we had triathletes riding exercise bikes—these California athletes in tip-top shape. This was where I first became interested in the effects of the environment on respiratory function.” After completing her degree, she won a postdoctoral research position at Yale University.

At the urging of a colleague, she switched her studies from the smooth muscle of the heart to the smooth muscle of the lungs. She began to focus on asthma. And a mutual friend casually introduced her to Christopher Karp, who was beginning his medical residency at Brown University. They married less than five months later.

In 1987, Wills-Karp took a second postdoctoral position at Johns Hopkins while her husband began a fellowship at Georgetown. Her plan was to study in the lab of Harold Menkes, the head of the physiology program. Tragically, Menkes and his wife died in a car crash less than a month after she arrived. “It was a shock,” she says. “He was a great scholar. I was suddenly sort of left to my own devices.”

Wills-Karp successfully applied for an NIH early-career grant, and she continued to dig for the molecular mechanisms involved in airway hyper-responsiveness in asthma. At the time, scholars tended to believe that asthma attacks were triggered by a classic allergic response, with eosinophils and immunoglobulin-E as the primary mediators. But Wills-Karp came to realize that the picture was not so simple.

Through conversations with her husband and his immunologist colleagues, Wills-Karp eventually decided to pursue a radical hypothesis. She had begun to suspect that asthma was driven in part by the behavior of T cells—in other words, the branch of the immune system associated with infection, not allergies. Sure enough, after painstaking trials, she found that interleukin-13, a protein promoted by T cells, was fundamental to asthma. The discovery was published in Science in 1998.

“That finding about interleukin-13 has been reproduced hundreds and hundreds of times in both humans and mice,” says Stephane Lajoie, PhD, an assistant scientist at the Bloomberg School who has collaborated with Wills-Karp for nearly a decade. “It’s become one of the tenets of asthma research.” 

Two years after that breakthrough paper, Wills-Karp and her husband were hired by the University of Cincinnati to build a new immunology program—a project they pursued for a dozen years. They left Cincinnati in 2012, with Wills-Karp returning to the Bloomberg School as chair of Environmental Health Sciences and her husband taking a senior position at the Bill and Melinda Gates Foundation. “For the last four years, we’ve been a long-distance relationship,” she says. “He’s based in Seattle, but he also travels all over the world looking at infectious disease. We’ve both accumulated a lot of air miles.”

photos of the JHSPH building and Homewood campus
A Tale of Two Icons: EHE links the public health and Homewood campuses.


This academic year, Wills-Karp has had little time for research. Most of her energy is being spent on establishing Environmental Health and Engineering. “There’s been a huge amount of interest among prospective students,” she says. “When applicants to the environmental engineering program toured the Whiting School in March, they also wanted a full tour of our resources at the Bloomberg School.”

One young scientist who is excited about the new structure is Gaida Mahgoub, who earned a bachelor’s degree in 2014 with a minor in Engineering for Sustainable Development and then a master’s degree in 2015 from EHS at the Bloomberg School. “This kind of program is very much needed,” she says. “In both my undergraduate and master’s programs, I was always striving to combine engineering and environmental science, to find ways to address public health needs with practical and hands-on solutions.” Mahgoub, who has just started a fellowship at the EPA, intends to apply to the new department’s doctoral degree program.

“The simplest way to put it,” says Wills-Karp, “is that public health scientists can identify problems, and engineers are the solution arm. If water contamination is a problem, then engineers can find a way to mitigate that.” But she adds that her real hope is that the department can help young researchers collaborate in much deeper ways. Engineers and public health scientists, she believes, can work together to assess environmental challenges and to evaluate the effects of their interventions.

One of the first major examples of that interplay is this summer’s Baltimore air-quality-sensor project, part of a larger EPA-financed study that will weigh the effects of various potential “energy transitions.” For example, if the U.S. invests heavily in low-emission vehicles by 2045, how might that affect national rates of asthma and other respiratory illnesses? Hobbs’ lab at the Whiting School will model the emissions potentially produced by various emerging technologies, and other teams will analyze how those potential emissions patterns might shape human health—informed in part by the data collected by Koehler’s Baltimore sensors this summer. The project’s various collaborators include researchers from the Bloomberg School, the Whiting School, Yale University and several other institutions.

In addition to the sensors that will be installed outdoors in Baltimore, Koehler and her colleagues will outfit 100 volunteers with backpack-style personal air-quality monitors, which they will wear for four days each. On two of the four days, the volunteers will be asked not to use their cars. “We want to see how energy choices can affect personal exposures to pollutants,” Koehler says. “And the most obvious energy choice is how we commute to work.”

Another potential area of collaboration involves Wills-Karp’s own subject: asthma. In recent years she has worked with Thomas Sussan, PhD, an assistant scientist at the Bloomberg School, on studies of household cooking and pulmonary illness in India. In certain rural areas of India, most families use biomass materials—generally wood or cow dung—to fuel their stoves. Sussan has collected air samples from such households and instilled them into the lungs of mice in his lab in Baltimore. He found that chronic, low-level exposure to such smoke can cause a variety of infectious and asthmatic reactions, with the reactions predictably varying according to the type of fuel and the intensity of exposure. In the short term, cow dung-based fuel causes more severe inflammatory responses than wood-based fuel; but over an eight-week period, smoke from wood-based fuel was more likely to cause emphysema-like changes in the lung tissue. 

Could better-engineered stoves prevent those illnesses? “Biomass fuel stoves are an engineering challenge for sure,” Sussan says. “But it’s a very tricky issue. You need to design something that people will actually use, and something that they can use with minimal training. And you have to remember that these are some of the poorest people in the world, so these stoves can’t cost much.” The best way to approach the problem, he suggests, would be for small teams of engineers and public health scientists to work together. They should do their work on the ground, in close consultation with the people who use the stoves, bringing together engineering science, medical science, and social science at the point where they matter most.

It may take some time, Wills-Karp says, for faculty members from the engineering and public health traditions to become comfortable working together. “But what I’ve seen,” she says, “is that the faculty from both the Whiting School and the Bloomberg School are all highly committed to and engaged with environmental issues. That’s what has brought us together.”