No one is going so far as to say the air makes it unsafe to live here. The potential for dying from particulates, although real – is small – compared to other health risks. If you want to significantly cut your chances of premature death, stop smoking, exercise, maintain an ideal weight and wear seat belts.

But one researcher at the University of California at Davis says that he "wouldn't be a happy camper" if he lived in Bakersfield, Kern County's largest city. "I don't like living in a place where it looks like I'm taking an unnecessary risk," says Thomas A. Cahill, a UC Davis professor emeritus of atmospheric science and physics.

Air pollution researchers say it may be no coincidence the San Joaquin Valley has heart attack mortality rates that defy demographics. Five of its eight counties rank among the top 15 in the state for deaths from heart disease.

Heart disease is the leading cause of death in Fresno County, with more than 1,500 people dying of cardiac problems each year.

A Fresno doctor describes the effect on the heart from particulates as equivalent to a 5-foot, 10-inch tall man carrying an extra 40 pounds; or a nonsmoker cohabiting with a pack-a-day smoker and breathing the secondhand smoke.

A 1998 study of heart attacks and particulate pollution in six California counties showed dusty Tulare and Kern counties had rates 23% higher than Sacramento and Yolo counties, where the air was cleaner. The two counties with the best air – Shasta and Butte – had 30% fewer cardiac deaths than any of the six counties studied.

Researchers say evidence continues to mount that more people die prematurely from heart attacks and other illnesses when particulate levels increase. Yet, it's the mention of cancer in the same breath with smog that raises the bar of public concern about air pollution.

DIRTY FILTERS: Samples of captured particulates, the main winter pollutant, show up black on high pollution days, lighter on days when pollution isn't as heavy. (Mark Crosse / The Fresno Bee)

Evidence is not clear-cut that particles cause cancer, but a 1999 California air-toxins study by the South Coast Air Quality Management District found breathing soot from cars and trucks increases the odds. Diesel exhaust particles account for 71% of the cancer risk from air pollution for people living in the Los Angeles area, say the researchers. Overall, motor vehicles are responsible for 90% of the cancer risk.

In September, the EPA added its cautionary voice to the cancer debate, saying chronic exposure to diesel exhaust may cause lung cancer and other respiratory diseases.

Between 300 and 400 people are diagnosed with lung cancer each year in Fresno County; and more than 300 die annually.

Fresno oncologist John Reinsch says a change in the pattern of lung cancers he sees in adults is worrisome. Lung cancers are almost always smoking-related, but in the past few years, Reinsch says, he is seeing more lung cancers in nonsmokers.

Air pollutants could be a possible reason for the shift, he says. But he adds, "we just don't know what's causing these cancers."

Soot can kill

Researchers have known for years that billowing smoke from factories and power plants can be dangerous to breathe. Episodes in history tell the grim story of what happens when grime hovers overhead.

In London, England, nearly 5,000 air pollution-related deaths were recorded in 1948, 1952 and 1956. People in Los Angeles experienced smog attacks in the summer of 1943 and 1944 that sent thousands inside their homes.

And in 1948, the specter of air pollution entered the nationwide consciousness when a killer fog engulfed Donora, Penn., a mill-working town tucked in a narrow river valley about an hour south of Pittsburgh.

At the end of that week in October 1948, 20 people were dead and another 7,000 – half Donora's population – were in hospitals or recuperating at home.

By the 1980s, dangers from soot clouds appeared to be a footnote in air pollution history. Pollution controls had reduced visible emissions, and huge black plumes mostly disappeared from the landscape.

Pollution researchers had long since shifted their focus to ozone; and it remained there until about 10 years ago when scientists began studying smaller particles.

How minute are these particles? A strand of human hair is 60 to 100 microns wide. Large airborne particles range from 2.5 to 10 microns wide. Fine particles are even smaller, less than 2.5 microns wide, and ultrafine are less than .1 of a micron wide.

It has only been in the past decade that sophisticated monitors were developed to capture fine and ultrafine particles for scientists to dissect.

"The reality is, we've worked on ozone for decades and decades. We know a lot about what's going on with it, both healthwise and atmospheric processing," says Anthony Wexler, who creates mathematical air pollution models at UC Davis. "With particles, there's just a lot less known. And the evidence that it causes health problems is a lot more recent."

Thus far, this is known about particles:

The observed changes are slight, but may be enough to damage an already weak heart and cause a heart attack. They also could explain why people with heart and lung disease are more prone to illness when particulate levels peak.

"No matter how low you go, you can still find some small health effect – even on mortality," says Dan Costa, chief of the pulmonary toxicology branch of the Environmental Protection Agency Research Triangle Park in North Carolina.

Valley air pollution regulators are struggling to reduce the public's exposure to particulates.

A 1997 cleanup plan for the Valley is being retooled to satisfy the federal government's health concerns about particles. The Valley air district must have a plan approved by February 2004 or the federal Environmental Protection Agency could step in and write its own.

RAT TRAP: In his lab at UC Davis, Kent Pinkerton studies the effects of particulate matter on rats. He hopes his research will explain how particles cause damage to lung cells. (Mark Crosse / The Fresno Bee)

One indication of how seriously the particulate problem is being taken: People living in the San Joaquin air basin will most likely be forbidden next winter from burning wood in fireplaces and wood stoves on several days each year. Only several Bay Area cities and one other region in California – Mammoth Lakes – have such a prohibition. The EPA required the burn ban in the Valley as part of a lawsuit settlement.

Fresno seniors studied

Fresno's exhaust-heavy skies drew EPA researcher John Creason to choose a retirement center in Fresno for a 1999 particulate study.

Initial results from blood and other tests of 60 seniors at the San Joaquin Gardens Retirement Community in north Fresno found an impact on the heart from ultrafine particles. The sources of these microscopic particles are primarily vehicle exhaust and residential wood burning.

The results from Fresno need more analysis, but may help explain why deaths from heart attacks increase when soot levels rise. Creason found an effect on the heart's capacity to adjust the length of time between beats. In the past few years, medical studies have linked sudden deaths in people with heart disease to a problem in the heart's ability to change intervals between beats.

Creason needed seniors who live in a place where particles are primarily nitrate-based and vehicle exhaust is a major source of emissions.

To do the study, he set up an outdoor air-monitoring station at San Joaquin Gardens on Fresno Street. The apartments are less than a mile east of Freeway 41, a heavy source of car and truck exhaust.

Dr. Betsy MacCracken, 88, a retired Los Angeles deputy public health officer, participated in the research.

Told that breathing Fresno's air changed her heart rate, MacCracken was not surprised. "It would affect the amount of oxygen you're consuming and therefore your heart rate would speed up."

She hesitated, then added, "That's just a guess."

Ag dust attacks lungs

Research is like opening Pandora's box; one discovery usually leads to a dozen more questions. Air pollution scientists look for one answer at a time.

A UC Davis pollution researcher is finding evidence that suggests agricultural dust may be a greater health concern than previously thought.

The study looked at the autopsies of lungs from 42 men who died in Fresno County between June 1994 and June 1995. About half the men were farmworkers, ranging in age from 18 to 73, with a median age of 33. All had died suddenly or unexpectedly – but none of respiratory diseases. Most of the deaths were from motor-vehicle accidents, heart disease, homicide or suicide. More than half the men had lived in Fresno County 10 years or more.

The study found mineral dust in small airways and in the area of the lungs where oxygen/carbon dioxide exchange occurs. Wall thickening and tissue scarring of the lungs also were found.

"What it shows is that the dust particles ... are not just a nuisance or inert," says the study's author, Marc Schenker, professor and chairman of the UC Davis Department of Epidemiology and Preventive Medicine.

Schenker says the study is small and should be assessed with caution, but there is increasing evidence that agricultural dust may be a health risk, particularly in dry-climate farming, such as in California's Central Valley.

Lung cells vulnerable

UC researcher Pinkerton hopes his research will explain exactly how particles of differing size cause damage to lung cells.

Pinkerton conducted experiments in both fall and winter in Fresno. Rats were exposed over three weeks to concentrated particulates for three days, four hours a day. Air from the roof of the science building at California State University, Fresno, was condensed to 20 times the amount of particles in the outdoor air.

The particle composition varied each week. But on the first week in October 2000, over half the particles were ammonium nitrates; about 5% to 7% ammonium sulfates; 15% organic carbons. Metals were another 5%.

The sources of these particles likely are from vehicle emissions and agricultural production, including ammonia from dairy farming.

From the research, it appears exposure to these particles damages lung cells, called macrophages, that are responsible for protecting the lungs. The macrophages had leaky membranes and were in the process of dying.

Protecting the defenseless

Atop the Fresno State science building, Pinkerton shades his eyes and notices a gauzy haze hanging in the September sky – an indication that particles are diffusing sunlight.

"You can't see the mountains." He pauses, maybe realizing the impact of his words.

Most healthy people have defenses that protect them against particles, he says in a calming voice. It's the elderly, people with heart and lung disease – and children – who are the most defenseless.

It's children who motivate his research, he says. The more researchers can learn about particles, the better chance of protecting those who are vulnerable.

"We're not spinning our wheels in any way," Pinkerton says. "We are learning things; we are moving forward."