Map of life expectancy at birth from Global Education Project.

Monday, February 27, 2006

The Romance of the Highway

I've been working with some colleagues on a proposal to study the exposure that people living along major highways experience to hazardous emissions from motor vehicles. The physico-chemistry and biology of this problem are not my department, but I've been getting an education. My mission, which I suppose I have chosen to accept, is to study people's knowledge, attitudes and behaviors about highway air pollution.

What I have learned from my environmental science and physician friends was a bit of an eye opener. Most of what we know about air pollution levels in the real world comes from a small number of monitoring stations, which are used to characterize pollution over wide areas -- no smaller than zip code size. But in fact, the pollution people are exposed to varies enormously over just a few tens of meters near highways. You might think that an urban avenue, with idling diesel buses and cars backed up in traffic is worse, but you'd be wrong. Traffic on the interstate puts out some bad stuff, particularly microscopic particles of soot. The natural defenses in our sinuses and lungs can't filter these out, and they go right into the alveoli and then get into the blood stream.

Believe it or not, while you are probably most worried about air pollution being a risk factor for respiratory diseases and lung cancer, these particles apparently cause inflammatory reactions which increase the risk of heart disease, and exposure to highway pollution has actually been linked directly to increased rates of heart attacks and death. This is not a huge factor -- the stuff you already know about, like smoking and diet and exercise and obesity -- are much more important. Nevertheless it's something that people can't control, except by living somewhere else, which makes it a special kind of concern from an ethical and public policy point of view. And, as you might expect, locations near highways are less desirable so that's where low-cost housing is likely to be and that's where low-income people are likely to live. Again, we're talking very small increments of distance - the pollution falls off rapidly within 100 meters or so.

What I have found out, in what is my department, is that people's perceptions of their risk from air pollution are not related to their actual exposure. People think of air pollution as coming from factories and power plants, but motor vehicles are just as important, in fact much more important, for people who live near highways. The problem is, they don't know it.

No comments: