"Particulate matter and ozone have both been found to be associated with admissions for pneumonia and chronic obstructive pulmonary disease." (Schwartz, Joel. (1994). Air Pollution and Hospital Admissions for the Elderly in Birmingham, Alabama. American Journal of Epidemiology, 139, 589-598.)

"The risks associated with ozone and other air pollutants are especially increased for children and adults with asthma, however, children with no underlying pulmonary diseases also are at risk for adverse health effects associated with these pollutants." (Morbidity and Mortality Weekly Report: Children at Risk from Ozone Air Pollution--United States, 1991-1993, April 28, 1995, Vol. 44(16), 309.)

"Studies in the U.S., along with similar research in locations ranging from Brazil to Germany, consistently link higher levels of particulates to increased risks of respiratory-, cardiovascular-, and cancer-related deaths, as well as pneumonia, lung function loss, hospital admissions, asthma, and other respiratory problems. Individuals with existing respiratory conditions appear to be most vulnerable, but the data also show significantly higher death rates for the general population in areas with high levels of particulate matter in the air." (Reichhardt, Tony. (1995). Weighing the Health Risks of Airborne Particulates. Environmental Science and Technology, 29(8), 360-364.)

Impact on Economy 

"Researchers also found that mixtures of PM_2.5 and ozone are more toxic than either pollutant is separately, suggesting that control of one pollutant alone may not be sufficient to protect human health. Data suggest that long-term exposure to these (ozone and particulates) may have a greater effect on human life expectancy than short-term exposure during peak episodes." (Environmental Science and Technology/News, 1996, Vol.30(9), 382.)

"Epidemiological studies have consistently shown an association between particulate air pollution and not only exacerbations of illness in people with respiratory disease but also rises in the number of deaths from cardiovascular and respiratory disease among older people." (Seaton, A., et al. (1995). Particulate Air Pollution and Acute Health Effects. Lancet, 345:176-178.)

"In any active individual, high ozone levels can cause restrictive lung dysfunction, and high carbon monoxide levels can impair oxygen delivery. Sulfur dioxide worsens nasal symptoms in people who have allergies and causes bronchospasms in those who have asthma. Airway irritation from fine particulates can lead to bronchospasm. SO₂, O₃, NO₂ and fine particulates are respiratory irritants that can cause bronchospasms; epithelial injury; or an increase in airway reactivity, mucous production, or the frequency or severity of respiratory illnesses." (Gong, H. and Krishnareddy, S. (1995). How Pollution and Airborne Allergens Affect Exercise, The Physician and Sports Medicine, 23(7), 35-42.)

The American Heart Association, an influential guide for physicians and the public on preventing heart disease, issued its first warning on June 2, 2004 that air pollution contributes to cardiovascular disease.

People with heart or lung disease should avoid exercising outdoors during episodes of polluted air, the association cautions.

Adding air pollution as a risk factor -- albeit a less potent risk factor than cigarette smoking or physical inactivity -- represents a shift for the association, which until now had remained unconvinced that bad air was linked to heart disease.

But a growing body of evidence over the past decade indicates that air pollution, particularly fine particles, can trigger strokes and heart attacks, according to a study published in the June 1 issue of the journal Circulation by the association's committee of researchers and clinicians.

"Although the relative risk of air pollution for any one individual is small when compared to the major traditional risk factors of high blood pressure, cholesterol and diabetes, there's clearly enough evidence to support the position that air pollution contributes to cardiovascular risk,'' said lead author Dr. Robert Brook, a vascular specialist in the University of Michigan's division of cardiovascular medicine.

"When the risk is applied to tens of millions of people who are exposed involuntarily throughout a lifetime, it becomes a serious problem,'' Brook said.

Air pollution was linked to a greater number of deaths from heart disease than from respiratory disease, according to the heart association's review of nearly 200 published studies.

The review also found that heart risks from air pollution may approach those of secondhand smoke, the single largest contributor to indoor air pollution. Secondhand smoke from one cigarette a day accelerates the progression of hardening of the arteries, studies have found.

Particulate pollution comes from vehicle emissions, tire fragments, road dust, power generation and industrial combustion, smelting and other metal processing, construction and demolition, wood burning, windblown soil, pollens, molds and forest fires.

The association is recommending that doctors advise sensitive patients about reducing the risk of exposure to air pollution.

It recommends that people check their local air quality through the U.S. Environmental Protection Agency's Air Quality Index. Daily information on particles and smog is available every day for 150 cities, including from the Bay Area air monitors, at www.epa.gov/airnow.

Here are two of the most important studies:

-- Earlier this year, Brigham Young University researcher Dr. C. Arden Pope III and others published a study in Circulation examining data from 500, 000 residents of 146 metropolitan areas over 16 years showing a 12 percent increase in cardiovascular deaths related to long-term exposure to fine particles.

They found an 18 percent increase in heart attack deaths for every additional 10 micrograms of 2.5 micron particles per cubic meter of air. (Three microns is less than one-thousandth thickness of the shaft of a paperclip.)

For comparison, a clean city such as Vancouver averages 5 micrograms of fine particles per cubic meter of air while a dirty city such as Mexico City averages 30 micrograms of fine particles per cubic meter of air.

-- Based on data from 90 of the largest U.S. cities, Johns Hopkins University researcher Jonathan Samet and others reported in the New England Journal of Medicine in 2000 that all deaths and deaths from heart or lung disease increased in the short term by 0.21 percent and 0.31 percent, respectively, for each 10 micrograms per cubic meter of air increase of 10- micron particles over 24 hours.

More research is needed on how pollutants can trigger heart problems, the study said. Scientists believe that air pollution may disrupt the body's functions at the cellular level.

"When you breathe air, little engines in your cells produce byproducts called 'reactive oxygen species,' which can induce inflammation and damage DNA, '' said Dr. Ira Tager, professor of epidemiology at the UC Berkeley School of Public Health and an author of the new report.

Normally, the body keeps these byproducts from causing too much damage. However, particulate pollution can produce these same substances, adding a burden that can overwhelm the natural defenses, said Tager. The increased amount of these substances may set off a series of biological responses associated with a higher cardiovascular death risk, including alteration in heart variability and allergic and nonallergic inflammation, which affects clotting.

The body's defenses, he said, can be further depleted by such factors as diet, genetic constitution and chronic diseases, he said. (Kay, Jane. (2004). Air pollution a risk in heart disease. San Francisco Chronicle, June 2, 2004. Page A-4.)

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