Experts Split Over Peril of Particulates

When tiny particles of pollution descend on a city, everything--skyscrapers, mountains, the horizon--drowns in a sea of soot that can persist for days and stretch for miles.

But something more ominous happens too. Death counts rise. People who might have survived a heart attack or bout of pneumonia or other illness are more likely to die.

Scientists consider the link between airborne particles and premature deaths about as compelling and well-documented as any finding can be. But even they are debating the merits of a Clinton administration plan to force a nationwide cleanup--staggering in scope and cost--when fundamental questions remain about why the microscopic particles seem to be killing people.

Although severe pollution has long been known to be harmful and even lethal, only in the last few years have researchers made the surprising discovery that deaths seem to be tied to the moderate particle pollution found in many cities today. But how can a fairly small dose hasten a person’s death? How can pieces of pollution made up of chemicals that are vastly different from city to city all be dangerous? And is it wise to mount a massive national effort to tackle the threat while such scientific mysteries linger?

Dilemmas Lead to Judgment Call

The move by the U.S. Environmental Protection Agency to tackle one of the nation’s most pervasive urban pollutants raises profound dilemmas for public health policy, focusing on how much danger is acceptable, how much proof of harm is needed, and how far health officials should go in an effort to protect lives. The answer winds up a judgment call, even for medical experts.

“You have to be willing to err on the side of being very careful, because the penalty for being wrong is that you’ve done nothing about a problem responsible for thousands of deaths per year,” said Dr. Philip Bromberg, director of University of North Carolina’s Center for Environmental Medicine and Lung Biology. “When you deal with public health, you accept less certainty for a basis for action.”

But University of Rochester toxicologist Gunther Oberdorster, who does research exposing lab animals to fine particles, disagrees. He said that setting new limits “is the wrong thing to do at this time” and should be postponed until scientists can nail down what makes tiny specks of pollution dangerous and which are the most potent types that warrant cleanup.

In November, the EPA proposed a new health standard that, for the first time, would limit the volume of ultra-fine particulates allowable in the air. One of the most far-reaching environmental proposals to emerge in a decade, it has triggered a bruising battle and fervent opposition from the oil and auto industries and others, as well as from many members of Congress, governors and mayors in both political parties. A court order requires the EPA to set final standards by July 19.

An estimated 167 counties nationwide--including nearly all of Southern California--would violate the agency’s proposed limit. Once standards are set, those areas have up to 15 years to cut pollution, most likely from trucks, cars, power plants, factories and wood smoke.

The EPA estimates the national cost at $6 billion a year, starting in 2007, while industry groups predict it will soar as much as 10 times higher.

The Los Angeles Basin, often veiled with gray-brown soot, faces the biggest burden. Even EPA Administrator Carol Browner acknowledges that California will probably need to find replacements for diesel fuel, which powers everything from generators to trucks, trains and ships. Midwestern states reliant on coal-fired power plants also would be hit hard.

The focus of the debate is an amorphous, complex blend of chemicals such as sulfates, carbon, nitrates and minerals. They have one thing in common: They measure less than 2.5 microns in diameter, much finer than a human hair or grain of sand. The EPA currently restricts only coarser particles, less than 10 microns, which come mostly from dust.

Virtually everywhere epidemiologists have looked, deaths and hospitalizations from heart and respiratory ailments increase on days when particle pollution rises. Such consistency in epidemiology is so rare it’s striking. Among the cities studied are Los Angeles, New York City, Philadelphia, Detroit, Chicago, Santa Clara, Seattle, Denver and Provo, Utah.

Based on those studies, an estimated 64,000 Americans are believed to be dying every year because of particulates. EPA officials say their proposed standard would save 15,000 of those lives and prevent several hundred thousand asthma attacks and bronchitis cases yearly.

Speaking at a medical conference in San Francisco last month, Terry Gordon, an associate professor of environmental medicine at New York University’s School of Medicine, said these “silent extra deaths” make particles as deadly as if an airliner crashed each time pollution rises.

Danger Exists, Health Experts Agree

Some scientists say the danger is so clear and the evidence so persuasive that the public deserves protection as soon as possible. Twenty-seven scientists--including some of the most prominent researchers in environmental medicine--sent a missive to President Clinton in January urging stringent standards.

But other scientists are skeptical about whether particulates are really the culprit for premature deaths, since no one knows why relatively modest doses could be lethal. They cannot at this point identify what may make fine particles capable of killing, especially when their chemical composition varies greatly, depending on whether they are emitted by cars, trucks, factories or fires. For instance, fine particles on the East Coast are largely sulfur, while California’s are mostly nitrates and carbon from gasoline and diesel.

“I am very well convinced that we are showing links between day-to-day numbers of deaths and air pollution. And the weight of the evidence indicates . . . particles seem to be responsible,” said Jonathan Samet, chairman of epidemiology at Johns Hopkins University’s School of Hygiene and Public Health. “But,” he said, “particles are a mixture. Do we know enough about the characteristics that may be causing the health damage so that we know what to regulate? These are some of the difficult issues we face.”

Some toxicologists contend that the EPA standards carry such a high cost that they should wait until these riddles are solved--a breakthrough, probably at least five years away, that could help pinpoint a solution with less severe economic consequences. Compared to the cost of regulation, the cost of additional science would be trivial, they say.

“It’s very important to first find out why particles are toxic,” said Robert Phalen, director of UC Irvine’s Air Pollution Health Effects Laboratory.

For any individual venturing outside on a polluted day, the risk is small. But because millions of people breathe the minute particles, the overall death and illness count can grow substantially.

Numerous studies have found that deaths rise 1% to 5% among the general population on days when particulates increase by a moderate amount. That amounts to 10 deaths per day in an area the size of Los Angeles County or New York City, or 300 people along the entire East Coast during a three-day episode.

In eastern Los Angeles County alone, the EPA calculates that 800 people died prematurely in 1995 from cardiopulmonary ailments aggravated by pollution. Riverside residents face the highest risk because particles are more voluminous there than in any other urban area in the country.

During severe sieges, there is no doubt particulates can kill.

In London in 1952, about 5,000 people died during a weeklong fog of coal smoke that soared to concentrations 40 times worse than anything measured today. Deadly particle fogs also struck a Pennsylvania valley in 1948 and Belgium in 1930.

But it wasn’t until the early 1990s that scientists linked deaths to the much lower pollution levels found in modern cities.

In more than 20 separate studies, researchers, dominated by a Harvard University team, examined tens of thousands of hospital records and death certificates in various cities and compared them with pollution conditions. Consistently, deaths were higher in the most polluted cities and on days when volume of particles increased.

“We’re convinced this is more than some oddball statistical nicety,” said John Bachmann, the EPA’s associate director of science policy. “It’s not as strong as cigarette data [showing a high cancer rate]. But we have three or four lines of evidence to suggest [death from particulates] isn’t just a statistical fluke.”

Still, some medical researchers and toxicologists remain suspicious because, over a lifetime, a minuscule volume of particles are deposited in a person’s body--probably less than a gram.

Questions Linger for Scientists

Toxicologists began trying to answer these questions just in the last few years. So far, they have been unable to figure out how particles damage the heart and lungs or how to replicate the deaths in healthy lab animals exposed to different compounds.

The danger is partially because of the particles’ size--the tiniest ones may irritate nerve endings that affect the heart and penetrate deep in the lungs. But some suspect that the real danger comes from acids that cling to some particles, while others believe it is metals such as iron, lead and zinc.

Medical experts also cannot pinpoint whether people with illnesses are having their lives shortened by days, weeks or years and what happens to people exposed over a lifetime.

Determining how particles can kill is of critical concern to those outside the laboratory as well. As states and cities across the nation frame multibillion-dollar strategies to clean the air over the next decade, they would prefer to know which sources to target to get the biggest bang for their bucks.

Phalen of UC Irvine said the economic and social impacts are so great it is premature for the EPA to limit particles based on mass when the real danger could be some hidden compound that attaches itself to a select group of them.

But EPA and many other health officials say too many lives are at stake to wait. Browner, the EPA’s administrator, compared it to the cigarette industry saying health warnings shouldn’t have been issued until scientists knew exactly how smoking causes cancer.

“If we had done something like that with leaded gasoline or tobacco smoke, years would have gone by,” she said.

The Clean Air Act requires the EPA to set standards providing “an adequate margin of safety” for all Americans, based on current science. But what if scientists are at odds? Of 21 scientists convened by EPA, 19 recommended that the agency limit ultra-fine particles. The 19, however, disagreed or wouldn’t give opinions on how stringent it should be, leaving Browner to reach her own conclusions.

The EPA’s proposal is “defensible but also attackable” on scientific grounds, said Bromberg of the University of North Carolina. Still, he believes a strong call for action is merited when the recent mortality findings are combined with lessons from the past, especially during the London fog.

Because particles are already declining in most cities thanks to smog-fighting efforts, some scientists, including Oberdorster of the University of Rochester, say new standards can wait.

The EPA standards, however, are designed with the more distant future in mind. After they are set in July, states and cities will have until 2002 to craft cleanup strategies, then eight to 10 years to implement them. By then, Browner said, scientists will have uncovered new clues to unravel the mysteries.

“To be honest with you, I don’t think the challenge [of cleaning up particulates] is small,” she said. “But we should not in this country walk away because we don’t know the answers.”

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Particle Pollution

Linked to premature deaths from heart and lung ailments, particulates are a noxious stew of various compounds. Their composition varies greatly from city to city, depending on its mix of vehicles, industry and farming, which means each area needs to come up with its own solutions.

SOURCES OF ULTRA-FINE PARTICLES (less than 2.5 microns)

Nitrates: Mostly car and truck exhaust. Also factories.

Sulfates: Coal-fired power plants, factories, boilers

Carbon: Diesel vehicles and equipment, fires, woodburning

Soil/minerals: Paved roads, construction, erosion, farm tilling

Ammonium: Fertilizer, manure, sewage plants

****

Los Angeles

Ammonium: 13%

Nitrates: 30%

Carbon: 43%

Sulfates: 13%

*

Anaheim

Ammonium: 12%

Nitrates: 32%

Carbon: 36%

Sulfates: 16%

Soil/Minerals: 4%

*

Riverside

Ammonium: 17%

Nitrates: 39%

Carbon: 27%

Sulfates: 10%

Soil/Minerals: 7%

*

San Joaquin Valley

Unknown: 12%

Nitrates: 34%

Carbon: 36%

Sulfates: 11%

Soil/Minerals: 7%

*

Phoenix

Nitrates: 13%

Carbon: 57%

Sulfates: 14%

Soil/Minerals: 16%

*

Washington, D.C.

Nitrates: 13%

Carbon: 35%

Sulfates: 47%

Soil/Minerals: 5%

****

HOT SPOTS

California has 14 counties that would violate the EPA’s proposed limit for fine particles. The Riverside, Visalia and San Bernardino areas have the nation’s worst concentrations.

Fresno

Imperial

Inyo

Kern

Kings

Los Angeles

Madera

Merced

Orange

Riverside

San Bernardino

San Diego

San Joaquin

Tulare

Source: U.S. Environmental Protection Agency and South Coast Air Quality Management District