A Toll on Human Health

Kent Pinkerton

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. They hope to have some answers this spring.

Related stories:

From Labs to Law Books
Discoveries by university researchers don’t die after they are described in doctoral theses and published in science journals. They live on in public service, by informing the actions of policymakers and legislators. The laws that govern automobile owners, electricity providers, tomato processors, oil refineries, construction-site managers and even dry cleaners rely on scientific facts supplied by air-quality experts at UC Davis and elsewhere. [more]

Climate-Altering Effects
UC Davis scientists are looking for players in global climate change in unusual places: seashores, dead plankton and pine trees. [more]

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 for the 32nd year. The project’s lead scientist, professor 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. [more]

Air Profiles: The researchers, the questions their asking and the answers they're finding. [more]

Back to introduction

Links to more information:

Air Quality Research Center

John Muir Institute of the Environment

Institute of Transportation Studies

UC Davis–Caltrans Air Quality Project

Atmospheric Aerosols & Health program for graduate students

Stories and photos by Sylvia Wright, who writes about the environmental sciences for UC Davis.