“It’s becoming increasingly clear that current regulations ... are not sufficient to ensure public health,” says UCI epidemiologist Dr. Ralph Delfino. Steve Zylius / University Communications

Driving research on traffic pollution

Dr. Ralph Delfino and his colleagues in UCI's School of Medicine are on the forefront of efforts to understand the role of vehicle exhaust in human illnesses.

In 2003, UC Irvine epidemiologist Dr. Ralph Delfino received a $3 million National Institutes of Health grant to lead one of the U.S.’s first major public health studies on ultrafine particles in urban air pollution and coronary disease in the elderly.

Results have shown that these particles – which are less than 100 nanometers in size, small enough to pass through the lungs and into blood cells – increase heart attack and stroke risk in people with existing cardiovascular conditions. This year, Delfino published research further linking the pollutants to higher blood pressure and more inflammatory cells in the bloodstream.

He and his colleagues in UCI’s School of Medicine are on the forefront of efforts to understand the role of vehicle exhaust in human illnesses. Their work is helping governmental agencies establish automotive emissions guidelines, and for his contributions, Delfino received a Clean Air Award from the South Coast Air Quality Management District in 2005.

Q: What is particularly noxious about vehicle exhaust pollution?
A: Precisely how these chemicals affect cardiovascular health is still being worked out, but some key mechanisms are beginning to emerge. These pollutants are enriched in chemicals that can cause oxidative stress, and the subsequent inflammation can be destructive to cells and tissues. Other chemicals can attack biomolecules and irreversibly damage critical proteins – such as antioxidant enzymes – and DNA, which leads to mutations. Finally, particles emitted near traffic sources are much smaller, coated with toxic chemicals, and capable of high rates of deposition and retention in the lungs. These effects promote adverse cardiovascular responses, including increased blood pressure and cardiac ischemia, which can result in heart attacks and strokes.

Q: The implication is that the closer you live to freeways and high-traffic-volume streets, the greater the risk. Is there a “danger zone”?
A: Certainly, the nearer you are to sources of traffic-related air pollutants, the higher your exposure and, therefore, your risk will be. However, the concentrations of potentially toxic chemicals and ultrafine particles in the air will vary considerably depending on such conditions as wind speed and direction. For example, you could live on the ocean side of a highway and be minimally exposed when there are offshore breezes. But there are periods during colder seasons when air stagnates and vehicular pollutants settle near the ground over wide areas on either side of the highway.

Q: What can local and state governments do to mitigate the problem?
A: It’s becoming increasingly clear that current regulations on “criteria” air pollutants are not sufficient to ensure public health. Regulation of greenhouse gases to reduce the environmental effects of global warming, though, is likely to also protect us from the health effects of traffic-related pollution, since it aims to decrease the amount of fossil fuel combustion.

Q: Southern California – with its reliance on cars and freeways – is a prime location for your research. But do the findings have national and global relevance?
A: Southern California is not unique; major urban centers around the world are heavily affected by traffic. And the health ramifications will probably deepen, given that fossil fuel use is projected to rise both in the U.S., according to the Department of Transportation, and worldwide, according to the U.S. Energy Information Administration.

Q: Those of us raised in Southern California can remember “smog days” and dirtier air decades ago. Hasn’t air quality here gotten better?
A: Improvements in air quality are laudable, but it’s important to understand that they’re based on controlling certain “criteria” pollutants. The health burden from overall tailpipe emissions may be worse. For example, we don’t know whether ultrafine particle concentrations have intensified recently because they’re not regulated. Continued increases in the number of vehicles and amount of fuel consumed are likely to be correlated with increases in ultrafine particles and associated toxic chemicals.

Q: Do people who drive a lot face significantly heightened health risks?
A: I suspect we’ve underestimated the effects of traffic-related air pollution, since nearly all epidemiological studies have relied on measurements or estimates from fixed sites, which at best include a person’s home and school or work address. However, commuters can be exposed to additional toxic pollutants and ultrafine particles from the exhaust of both other vehicles and their own. This is an active area of research by my group, especially as it concerns pregnant, working women who commute long distances, with potentially adverse effects on the fetus.