reilla might get a sympathetic hearing if he visited the Tokyo District Court. This October, the court handed seven Tokyo asthmatics a victory in their lawsuit against the national government and the highway authority. Tailpipe pollution in the city, the judges said, had "caused and exacerbated" the plaintiffs' disease.
In Tokyo, as in the Bronx, the worst problem is diesel. A contributor to ozone and a source of unhealthy substances such as sulfur dioxide, diesel exhaust also carries soot in particles so tiny as to be invisible. Breathing fine soot is extremely dangerous. When diesel particulate levels in the air go up, so do death rates among the sick and elderly. And so do the number of asthmatics admitted to emergency rooms.
What about development of the disease? Andrew Saxon, chief of clinical immunology at the University of California at Los Angeles, exposed volunteers to an allergen they were never likely to encounter in the normal course of events, a mollusk protein called KLH. Initially, none of the volunteers showed any sensitivity at all to the protein. But when KLH was combined with diesel exhaust particles, people who had breathed it easily beforehand demonstrated a heightened allergic response. In another study, Saxon combined known allergens with diesel exhaust and exposed allergic volunteers to the combination. He saw a fivefold increase in total allergic protein levels and a fiftyfold increase in the allergic antibodies. In his experiments, the dosage of diesel exhaust particles was 0.3 milligrams -- comparable to what you'd breathe in two days in Los Angeles or one day in Tokyo.
"Something about diesel exhaust primes the immune system," explains Gina Solomon, a doctor and medical researcher at NRDC. "Even a mild dose of common allergen that you might not have noticed suddenly turns into a major reaction."
Along with researchers at the University of California at San Francisco, Solomon analyzed dozens of recent studies on diesel for an article in the peer-reviewed journal Environmental Health Perspectives . They found epidemiological studies showing, among other things, that children living near heavily traveled trucking routes are much more likely than others to develop wheezing and have trouble breathing.
But most interesting were the studies, that, like Saxon's, point to a physiological connection between diesel and allergies. Diesel soot steps up the body's production of many of the immune system cells and antibodies that drive allergies and asthma attacks. Among them is the antibody called Immunoglobulin E (IgE), which is a hallmark of allergies. Diesel also raises the body's levels of TH1 -- a kind of immune system cell implicated in atopic asthma. Moreover, says Solomon, production of TH1 actually suppresses the body's ability to make other cells that work to prevent allergies. "So once things start to go out of whack," she says, "they can go out of whack pretty badly."
Neither Saxon nor Solomon thinks diesel is the sole answer to the asthma riddle. But unquestionably, says Saxon, "diesel is a player."
o breathe is to live. But for us asthmatics, when the air is full of pollens and particulates, what we need most becomes our worst enemy. When I was young, asthma meant only my personal affliction and the chores it demanded: regulating my breath, paying attention to allergens, and medicating. But as an adult, I'm implicated. If air pollution causes asthma, what does that mean about the energy I use and the car I drive? What does it mean that 6 million children in the United States have trouble breathing? I know I'm supposed to stay calm. But the evidence and the reality of it make me want to hyperventilate.
Michael Lerner, of the health and environmental research organization Commonweal, says the new air pollution research has "enormous political salience." He adds, "Parents are agonizingly aware of the reality that their children can't breathe, and of the tremendous impact that has on a child's life -- on their ability to participate in sports and live childhood the way childhood is meant to be lived."
And then there's this: While the scientists continue their studies, the rest of us are left to control our breath. Air pollution is a hazard for many asthmatics, whether it caused our asthma or not. "We have enough data now on air pollution and asthma and mortality to say we need to be moving in the direction of more control [of pollution]," says Jonathan Samet of Johns Hopkins University. "Would another finding make a difference?"