Something in the Air
by Sylvia Wright
The articles below, which feature several researchers of the School of Veterinary Medicine, originally appeared in UC Davis Magazine, Spring 2006.
Take a deep breath. Now entering your lungs, bloodstream and perhaps your brain—“air” bearing all the exhalations of modern life: tailpipe exhaust, fireplace smoke, flame-broiled animal fats, industrial chemicals and carpet fumes. If you are within 100 yards of a freeway, you also have inhaled tire shreds and partially burned diesel fuel. If downwind from a farm, then ammonia from animal wastes or soot from burning rice straw. At the coast, you’ll breathe in salt, of course, maybe trans-Pacific sand from eroding Chinese deserts and perhaps something unexpected: sulfuric acid from the smokestacks of unregulated cargo and cruise ships.
Every fifth-grader knows that we breathe carbon dioxide and oxygen. But no one knows exactly what else we breathe, how much, where it comes from or how it affects our health. Answering those questions now is particularly urgent: Some UC Davis researchers have found disturbing patterns that link air pollution with serious human health problems, including chronic asthma in children and early death in some adults, and others see novel roles for air pollution in climate change.
UC Davis has a tradition of expertise in many aspects of air pollution: shedding light on the contributions of agricultural activities, the origins of haze over national parks, the benefits of cleaner fuels and emission controls in automobiles. It’s a success strengthened by a delight in inventing new research tools when the need arises and a willingness to bridge the traditional divides between the biological and physical disciplines. Now, with 60 faculty and staff researchers focused on the issues and a record $50 million in directed funding, the campus has become a leader among the handful of institutions in the United States working intensively on problems related to air pollution.
A Winning Approach
How long has UC Davis been exploring the effects of air pollution on human health? Here’s one measure: The National Institutes of Health recently renewed a grant for ozone research at UC Davis School of Veterinary Medicine for the 32nd year. The project’s lead scientist, professor [emeritus] Charlie Plopper, jokes, “It has to be one of the few grants left with a three-digit ID number.” New grants now get numbers in the low five digits.
In fact, it was Plopper, along with Kent Pinkerton, Bill Adams and a handful of other now-senior faculty, who first put UC Davis on the air-and-health map in the 1980s and ’90s with groundbreaking findings about the unrecognized damage done to children’s lungs by ozone and secondhand tobacco smoke. Now they, and the young graduate students and assistant professors they have mentored, are managing the campus’s bulging portfolio of air quality and health studies.
Plopper credits the recent surge in activity to new interdisciplinary partnerships. “UC Davis has always had real strong expertise in the biological aspects of respiratory health—biochemists, cell biologists, pathologists, the full range, from the medical school, the vet school and the ag school—all working together,” he says. “But there was not a lot of mixture of physical scientists and biological scientists. Only recently has that occurred, which I think is just critical. Now is the time for it.”
Much of the credit for that development goes to engineering professor and modeling expert Tony Wexler, who came to Davis from the University of Delaware in 2000 with an interest in the health effects of very small airborne particles. Wexler revived an old mailing list of UC Davis researchers interested in air pollution and convened lunch discussions at the Silo. By 2002, at the urging of Vice Chancellor for Research Barry Klein, Wexler had organized a new research unit, the UC Davis Air Quality Research Center. By 2003, he and Pinkerton had set their sights on winning some of $40 million in grants that the U.S. Environmental Protection Agency would award in 2005 for air-quality research. The EPA specifically wanted to know much more about airborne particulate matter and its effects on human health. The answers, the agency emphasized, were to be discovered using “an integrated approach” and offering “the opportunity for investigators from different disciplines to work together.”
Pinkerton and Wexler proposed an ambitious research program that would experiment locally (in the notoriously polluted San Joaquin Valley) and produce results that would apply nationally. The genius of the UC Davis proposal lay in “the mixture” that Plopper describes. The physical scientists and engineers would not just collect and analyze airborne particles; the biologists would not just assess how living tissue responded when the pollutants were inhaled. Their expertise would overlap and magnify. For instance, if biologists identified a particularly toxic airborne particle, the physical side could manufacture a batch of those particles for further study. If physical scientists devised computer models of particle movement in the body’s transport systems (airways and bloodstream), the biologists could focus their attention on sites where particles were most likely to deposit and cause injury.
The UC Davis proposal was up against tough competition. In 2000, the first round of EPA particulate-matter (PM) center funding had gone to Harvard and New York universities, the universities of Rochester and Washington, and UCLA. Now all were running for renewal on their five-year records. But in the end, UC Davis’ innovative and collaborative approach carried the day. The grants to NYU and Washington were not renewed; UC Davis and Johns Hopkins University took their places.
One of the young UC Davis biologists whose work will be supported by the PM center grant is Michelle Fanucchi, who studies childhood lung development with Pinkerton and Plopper. Fanucchi was involved in the development of the PM center proposal and calls its collaborative spirit “amazing.”
“At the beginning, I told [associate professor of engineering] Mike Kleeman, ‘You have to talk to me like I’m a sixth-grader.’ They have 16 words for carbon!” Fanucchi says. “At the same time, the engineers have a lot to learn from the biologists. It’s been very challenging but very fun. And now we are uniquely set up to finally make advances in understanding how particulates affect health.”
A Toll on Human Health
UC Davis researchers have made major contributions to understanding how airborne environmental toxins (such as smoke, dust and vehicle emissions) affect human health, particularly children’s health. One of their most troubling findings: Contrary to common belief, very young children’s lungs are more susceptible than adults’ to injury by environmental toxins, and those injuries cause significant deformities in essential airways that may be permanent.
Charlie Plopper, an expert in lung health and development, says the human respiratory system is shaped like an inverted tree that admits air through its trunk and transports it through its branches. Cells of various types line the surfaces of these branchlike airways and act on the particles and gases carried on the flowing breath. Many cells are sentries that mechanically trap or enzymatically dismember intruders. Other cells, at the distant ends of the branches, conduct the remnants of the breath—mostly oxygen molecules with an unknown number of other compounds and particles that evaded capture—across the airway membrane into the bloodstream.
Having established that inhaled toxins are bad for children, UC Davis researchers now want to understand why that is and how long the damage persists. They also want to know how air pollution might be bad for adults; Kent Pinkerton, an expert in lung response to air pollution, has found structural deformities in the lungs of older Central Valley farm workers—changes that might have been provoked by long exposure to mineral dust, fertilizers and pesticides.
The investigators also hope to answer one of the most urgent questions in environmental studies: Which of the myriad features of airborne contaminants are the most damaging? Think of air pollutants as a flurry of teeny-weeny chocolate-coated raisins swirling into your lungs. What makes them dangerous—their sugary, fatty coating? Their size? Shape? Number? Or perhaps it is all those factors together, with the added variable of your individual vulnerabilities—exposure to tobacco smoke (directly or secondhand), an antioxidant-poor diet, diabetes, obesity.
Similarly, very little is known regarding where airborne particles come to rest internally and what they do there. UC Davis researchers are especially concerned about ultrafine particles—bits of stuff so tiny that a billion would fit on the period at the end of this sentence. Ultrafines are abundant in places like the Central Valley, where much of the pollution comes from burning fossil fuels in vehicle engines.
Pinkerton with his colleagues and graduate students have shown that when mice briefly inhaled ultrafine particles, their heart rates changed. Was it because the particles traveled through the animals’ bloodstreams directly to their hearts? Veterinary pathologist Dennis Wilson plans to find out. He will be hunting ultrafines throughout the body—in coronary vessels and heart tissue, as well as the liver and brain. Concurrently, Pinkerton will study whether the particles act on the heart indirectly, not by going through the bloodstream but rather by short-cutting through nasal tissues to the brain centers that control heart rate. “This has never been looked at,” Pinkerton says.
Go online to see the articles in their original context.