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NEWS & COMMENT= Showdown Over Clean Air Science Industry and environmental researchers are squaring off over studies linking air pollution and illness in what some are calling the biggest environmental fight of the decade Nine years ago, epidemiologist Joel Schwartz stumbled across a disturbing pattern of death. Schwartz, then at the Environmental Protection Agency (EPA), noted that when soot levels in the air of Steubenville, Ohio, rose on any given day in the 1970s and 1980s, the number of fatalities among residents would jump the next day--even when air pollution levels were supposedly safe. Schwartz went on to document the same chilling pattern in four more cities that track soot: Philadel- phia; Detroit; St. Louis; and Kingston, Ten- nessee. Projecting these findings to the en- tire U.S. population, Schwartz estimated that 60,000 people c.ould be dying each year--more .than the annual number of car crash victimsufrom heart and lung diseases aggravated by tiny airborne par- ticles. At scientific meetings in 1991 and 1992, recalls Schwartz, now at Harvard, the studies got "a tremendous amount of attention." Today, the analysis is provoking a furor. Schwartz's findings and similar studies by other researchers lit the fuse of a political powder keg: a debate over whether industry should take costly steps to reduce the amount of soot and other pol- lutants released into the atmo- sphere. Heeding the results from Schwartz and others, on 16 July the EPA unveiled final rules de- signed to tighten ozone standards and clamp down on particles. The cost of implementing the rules-- which EPA estimates at $9.7 bil- lion per year for measures such as installing new equipment on power plants and diesel trucks--has sparked a fierce protest on Capitol Hill from industry groups and many state and local officials. So far, EPA has stood its ground. The agency has refused to scale back the standards, first proposed in November, and President Clinton has said he supports them. But now the bell has sounded for round two of what is shaping up to be the biggest environmental fight of the decade: Con- gress is about to consider legislation that would quash the standards. Opponents argue that the science fails to support the new regulations, which would lower maximum ozone levels by a third and, for the first time, set acceptable airborne levels of fine particles less than S ELECTED PARTICLE-POLLUTION STU DI ES 466 2063633901 2.5 micrometers in diameter, called PM2.s, which are generated mainly by burning fos- sil fuels. Although industry groups have sharply criticized the new ozone standards, arguing that the health benefits would be marginal compared to the costs, most of the scientific debate has centered on the limits on particulate matter. Critics charge that Schwartz's popula- tion studies and others like it do not link individual pollutants to human health ef- fects; instead, they argue, different factots-- such as other pollutants and lifestyle fac- tors--may be responsible for the increased death rate. Moreover, scientists have yet to propose a plausible explanation for how fine particles might harm the body (see sidebar health effects in scores of cities, says John Bachmann, associate director for science policy in EPA's Office of Air Quality Plan- ning and Standards. EPA acknowledges, however, that many questions remain about how fine particles cause harm. "All of us agree we need way more science," says Bachmann. However, he says, "We're not supposed to wait until people are dead in the streets." But many scientists say the problem is not the standard itself, but the levels EPA has chosen. "These studies can't readily lead to a specific number," says Johns Hopkins University epidemiologist Jona- than Samet. "It all makes sense to regulate PMz.5. The question is, do we have the quan- titative information to do it? That's where the debate begins." Study Design Kay Findings Utah Valley (Pope et aL, 1989) Philadelphia (Schwartz & Dockery, 1992) Hospital admissions & PMIo levels across period encompassing 13-month shutdown of steel mill Daily mortality and total PM levels Admissions for respiratory disease higher when mill operating Significant association, with greater risks for elderly and for death from chronic obstructive pulmonary disease Six Cities Interviewed 8111 26% higher death rate (Dockery people for lifestyle in most polluted vs. et aL, 1993) factors and tracked least polluted city deaths over 14 to 16 yrs.; used several PM measures American Used health infor- 17% higher death rate Cancer Society mation from in most polluted vs. 151 cities 552,138 ACS least polluted city (Pope et aL, volunteers, PM2.s 1995) for 50 cities on p. 469). Because of such shortcomings, the Air Quality Standards Coalition, rep- resenting 500 petroleum, automotive, and other industry and business groups, derides the science as "totally inadequate." Adds epidemiologist Suresh Moolgavkar of the Fred Hutchinson Cancer Research Center in Seattle, "EPA is espousing a certainty in its language that is simply not justified by the data." But EPA Administrator Carol Browner contends that there are plenty of data to support the rule, even the particularly con- tentious PMz.5 standard. The evidence comes from more than 60 published health studies that show a link between soot and adverse Fine particle distinctions Researchers have been well aware of the dangers of particles ever since several disastrous air pollution epi- sodes in Europe and the United States in the middle of this cen- tury, such as a deadly week in Lon- don in 1952 when choking soot and sulfur dioxide--at least 10 times today's average levels---killed thou- sands, mostly children and elderly people with heart or lung ailments. Such incidents spurred controls on pollutants. Since 1971, EPA has ordered limits on levels of par- ticles, which are composed of dust from soils, bits of carbon spewed by diesel vehicles and power plants, sulfates, and gases such as nitrogen oxides and volatile organics that condense onto seed particles. Ini- tially, hese rules covered particles up to 50 micrometers in diameter. But after studies showed that coarse particles tend to be safely expelled from the body's upper air- ways, the agency in 1987 restricted only finer particles, less than 10 micrometers in diameter (PM~0). By the early 1990s, however, $chwartz's study and dozens like it had convinced many experts that the PM~0 standard might not be protective enough, especially for the elderly, children, people with frail immune systems, and other vulnerable groups. In cities in the United States and other countries, death rates and hospital admissions for people suf- fering from cardiac problems and respiratory . SCIENCE • VOL. 277 • 25JULY 1997 • www.sciencema~.org

problems such as asthma seemed to rise and fall with daily particle levels. For example, a study led by biostatistician Richard Burnett of Health Canada found that in Ontario in the mid-1980s, for every 13 micrograms/ meted rise in daily levels ofsulfater~a surro- gate for overall PM2.5--hospital admissions for respiratory and cardiac events shot up 3.7% and 2.8%, respectively. Researchers also began to recognize that they needed to focus on finer particlesm PMz.5 or smaller--because animal studies using radioac- tively tagged particles and lung casts made from human cadavers had shown that such tiny particles are most likely to lodge deep in lungs. "The finer particles repre- sent a completely different class of materials than the coarser PMI0, and it is logical that they probably have dif- ferent activities and types of toxicity," says toxicologist Joseph Mauderly of the Love- lace Respiratory Research Institute in Al- buquerque, New Mexico. The PMm is mostly inert crustal dust, while the combustion- generated fine particles contain the nasty stuff--corrosive acids and metals--that can damage tissues. Many experts, however, were skeptical of these red flags. Their main beef was th~at the daily mortality studies were unable to discern whether air pollution levels were signifi- cantly shortening lives or perhaps hastening by hours or days the deaths of very sick people already on the verge of dying. "People believed the studies were picking up a real phenomenon, but the interpretation was unclear," says Columbia University epidemi- ologist Patrick Kinney. A more convincing set of findings came along in 1993, however, when a Harvard team headed by Douglas Dockery examined soot and other pollutant levels and 1429 deaths that occurred in 8111 adults the team followed for 14 to 16 years in six Eastern U.S. cities (known as the Six Cities study). The researchers interviewed subjects about weight, smoking, and other risk factors, correcting for these lifestyle differences, which had not been possible in earlier studies comparing city death rates. They found that the stron- gest association bet~veen any pollutant and death rates was with fine particles, and that the risk of death was 26% higher in the most polluted city--Steubenvitle--compared to the cleanest--Portage, Wisconsin. The re- sults supported the findings of the daily stud- ies and raised additional concerns by suggest- ing that the harmful effects of particles can build up over years. A second long-term study 2 years later strengthened the case against airborne par- tides. Tapping an American Cancer Soci- ety (ACS) database of smoking, age, occu- pation, diet, and other data on over 550,000 volunteers in 151 cities, along with sulfate data and PM2.~ readings for 50 cities, the Harvard group and environmental econo- mist Arden Pope of Brigham Young Univer- sity in Provo, Utah, found a 17% difference over 8 years in death rates between the cleanest and dirtiest cities. "We're not likely to see/t study of this quality and mag- "It is impossible to say one component is any more responsible than any other." mSuresh Moolgavkar nitude [again] in our lifetimes,"says Alan Krupnick, an economist with Resources for the Future, a W~shington, D.C., think tank. "I think that pushed a lot of people over the edge," adds Kinney. A Natural Resources Defense Council study extrapolated the results and came up with 64,000 annual deaths that were up to 2 years premature. Using this "body count" and its own analyses, EPA estimates that its regulations will prevent 15,000 premature deaths each year and 9000 hospital admis- sions, for a total estimated cost savings ors 19 billion to $104 billion a yearmabout two to 12 times the estimated cost of compliance. Industry chokes on rules After a 1993 lawsuit brought by the Ameri- can Lung Association forced EPA to stick to its mandated 5-year schedule for reviewing "This whole industry argument that it's all other pollutants is just not supported by the data." m Joel the latest evidence of particle health effects, critics of the science behind the new rules launched their assault. "We'd go to meetings and testify at hearings," says Dockery, "and they'd say, 'We get different results.'" Critics have saved most of their barrage for the mortality studies. Hutchinson's Mool- gavkar, for instance, reanalyzed Schwartz's Philadelphia data on behalf of the American Iron and Steel Institute. When Moolgavkar took into account other air pollutants-- ozone and nitrogen dioxide--and analyzed them all simultaneously, it was impossible to separate the health effects of particles from those of sulfur dioxide. "It is impossible to say one component is any more responsible than any other," says Mootgavkar. Others point out that the long-term ACS and Six Cities studies captured only a frac- tion of the total pollution the subjects were exposed to over their lives. "How does that relate to what people are exposed to across their lifetimes? We really don't know," says Samet of Johns Hopkins, who nonetheless says he believes the link between daily mor- tality and particles is real. Biostatistician Fred Lipfert, a consultant who has worked for the Electric Power Research Institute in Palo Alto, California, also argues that the Har- vard team "kind of just took a first cut at socioeconomic status," and that a more sed- entary lifestyle in, say, Steubenville com- pared to Portage might account for the differ- ences in mortality that the Six Cities study attributes to fine particles. Other concerns center on how EPA esti- mated the potency of these tiny particles. Because only a few excess deaths and hospi- talizations occur when the air contains low levels of particle pollution, the studies lack the statistical power to precisely estimate how dangerous particles are at these levels. So EPA assumed that the health threat in- creases in a linear fashion with dose, ignor- ing the possibility that the risk may taper off at lower levels. Adding to the uncertainty, few studies actually measured PM2.5--most used PMm or a surrogate such as sulfates. "There's very little information on the ra- tio" between PMt0 and PMz.5, says Yale epi- demiologist Jan Stolwijk. Moreover, without knowing what it is about particles that causes ill heakh effects, it's impossible to be sure that the regulations are targeting the right source, says toxicolo- gist Roger McClellan, presi- dent of the Chemical Industry Institute of Technolog~ in Re- search Triangle Park, North Carolina. For example, he says, a state might target diesel en- gines or clamp down on plow Sc[1wart::~ dust, when the problem is actu- ally sulfates from power plants. Says McClellan: "We run a real hazard here of putting in place a new standard that we don't know how effective it will be." A lot of hot air? EPA scientists disagree, saying they are con- fident that the science supports their regula- tions. "We think we've done a totally legiti- mate, rational analysis of the studies we had," says the agency's Bachmann. He points to

Puzzling Over a Potential Killer's Modus Operandi Experts may clash over the strength of the science behind the new clean air regulations (see main text), but they do agree on one thing: It's still a mystery how airborne particles could trigger a bout of asthma or cause someone to drop dead of a heart attack. A dozen labs are now racing to find a modus operandi. ~ This is not the first time that an unknown mechanism has bedeviled researchers trying to assess a potential environmen- tal hazard. But unlike some other alleged risks--such as elec- tromagnetic fields--it's apparent that the more particles one breathes, the greater the danger, says Keith Florig, a science policy expert at Carnegie Mellon University in Pittsburgh. "If you observe a strong enough dose response, that's pretty com- pelling," he says. PMm for 6 hours per day for three straight days, 37% of the bronchitic animals died; all the healthy rats survived. Godleski has also tightened balloons around the coronary arteries of dogs to simulate angina, or cardiac chest pain, theft exposed the dogs for 6 hours to PMz.5. At particle concentrations of about 116 tig/m3 and 175 gg/m3, levels often reached in heavily polluted cities, the dogs' hearts developed arrhythmias that are commonly observed in people nearing a fatal heart attack. God- leski says these animal studies could help explain the observation that when particle pollution soars, "a lot of people are dying outside of the hospital. These could very well be sudden deaths" from heart attacks, he says. Now that researchers have potential animal models for the The best way to unravel a pollutant's mechanism is to study how it triggers health effects in animals. Until recently, however, re- searchers had drawn a blank. "I've done lots of studies" exposing healthy mrs to diesel soot for nearly their entire lives at particle levels more than 10 times what people typically encounter, and "nothing happens," says toxicologist Joseph Mauderly of the Lovelace Res- piratory Research Institute in Albuquerque, New Mexico. But in a parallel to the epidemiological studies that first drew. attention to the hazards of airborne particles, toxicologists in the last year or two have begun to find that sickly animals exposed to fine particles get sicker and-sometimes die. For example, pulmo- nary biologist John Godleski of the Harvard School of Public Health in Boston found that rats with chronic bronchitis are especially vulnerable. '~¢;hen he exposed the animals to particles smaller than 2.5 micrometers (PMz.5) strained from Boston air, at levels equivalent toabout twice the current'EPA daily limit for health effects, they are trying to sort out whether a particle's chemical composition dictates how dangerous it is, and how it triggers health effects. "Nobody is sure what it is in, or on, or of khe particles" that causes health effects, notes toxicologist Judith Zelikoff of. New Ydrk University School of Medicine. Freshly created particles appear to be more toxic than aged particles, so the culprit may be some reactive chemical groupm such asan acid, a metal, an organic compound, or a peroxide-- attached to a particle'ssurface, says Morton Lippman, also at New york University School of Medicine. Others think that ultrafine particles, or those less than 0.1 micrometer in diam- eter, are the problem, because they are much more potent than larger particles at provoking immune responses in the lungs. "The problem is, none of these hypotheses really seems to be a solid explanation for all the effects," Mauderly says. "Probably they all contribute.'? , . .; ~-J .K. what he calls "overwhelming consistency"-- more than 60 of 86 population studies linked health effects to fluctuations in particulate matter levels and the coherence between deaths, hospitalization, and respiratory dis- ease. Others point to a study published this month in Environmental Health Perspectives by EPA researcher Tracey Woodruffand col- leagues at the Centers for Disease Control and Prevention in Atlanta. They found that infants in cities with high particle pollution levels are 25% more likely to die of sudden infant death syndrome than are those in cit- ies with relatively clean air. "It certainly adds support," says California EPA epidemiologist Bart Ostro. Schwartz also takes aim at the argument that pollutants other than particles may be blurring the picture. Cities with only one or two major airborne pollutants--such as Santa Clara, California, which has low air levels of sulfur dioxide and ozone in winter-- still show a link between particle levels and health problems, he says. "This whole in- dustry argument that it's all other pollut- ants is just not supported by the data," says Schwartz. New York University School of Medicine epidemiologist George Thurston says "it's a valid criticism" that some of the Harvard daily city studies underestimated the effects of other pollutants, but those con- tributions "just reduce" the estimated danger levels of particles. "It doesn't make [the ef- fects] go away." Finally, Bachmann says, even ff PM2.5 itself is not the bad guy--if sulfates alone are the problem, for example--- targeting it should also control whatever pol- lutant is taking lives. Most experts contacted by Science agreed that EPA was justified in setting a standard for PMz.s. "There's enough circumstantial evidence that it does make sense to begin to look at and regulate fine particles as a class," says Mauderly. At a minimum, Mau- derly and others add, setting a standard will force the states to collect data that could help pin down PM2.s health effects. But they split on just how stringent that standard should be. "We have a tremen- dous amount of uncertainty as to what the dose-effect relationship is--how dangerous particles might be and under what circum- stances," says Mauderly. "The scientific ba- sis for [EPA's planned levels] is totally lack- ing," Stolwijk says. "You have to make sev- eral leaps of faith." Yet while the studies "have their limita- tions," says environmental health scientist Arthur Upton of the Robert Wood Johnson Medical School in Piscataway, New Jersey, "I'm not aware that we can dismiss their find- ings'as unimportant or irrelevant." Deciding whether to set a stringent standard, Upton says, "becomds a value judgment. It's not a scientific question .... Do we dismiss the data? Or do we accept them as warning signs and act accordingly?" EPA's judgment won't be the final word. The House Commerce Committee is con- sidering a bill that would impose a 4-year moratorium on the standards while EPA does more monitoring and research. Con- gress may also try to kill the rules through a new law passed last year to shield small busi- nesses from overly burdensome regulations. And the White House announced last month that EPA will conduct another scientific review, starting this year, before it imple- ments the PMz.5 standard. Congress is ex- pected to set aside up to $35 million next year in EPA's budget for research on par- ticles. And Upton is heading a reanalysis of the Six Cities and ACS studies by the Health Effects Institute, an industry- and EPA- funded research organization in Cambridge, Massachusetts. "It's a vexing question, and I wish I were Solomon and knew exactly what the right answer was," Upton says. "But we'll work on it." -Jocelyn Kaiser www.sciencemag.org • SCIENCE • VOL. 277 ° 25 JULY 1997 469