Roger Worthington, a Los Angeles attorney, makes his living suing manufacturers and building owners on behalf of people with a rare, asbestos-caused cancer called mesothelioma.
He's heard opponents argue the disease came not from their products, but from radiation, or from a polio vaccine, or from unknown causes.
He has never once heard anyone suggest in court that it sprang from asbestos fibers kicked up from the native soil around homes, schools or parks.
"Defense lawyers are very crafty in trying to pin the blame on somebody else," Worthington said.
"I believe if there truly was an argument about naturally occurring asbestos floating in the air that posed a significant public health risk, their experts, who get paid to defend asbestos companies, probably would have made this argument."
The lawyer is among many who are wondering aloud about how great a danger could be faced by those living amid rocks that contain asbestos, once construction slices through veins of the fibrous minerals and stirs up clouds of dust. Such speculation, born in El Dorado County, where a flurry of construction has cut through asbestos veins near homes and schools, is drawing growing attention nationwide.
On its surface, the question seems a simple one: If this is dangerous, where are the sick people? Where are the bodies?
The simplest answer is that no one knows for certain.
One possibility, bolstered by a new study, is that the dead have been piling up all along, but are too few in number for easy detection in a complex, mobile society with so many other factors that cause disease.
Another possibility is that there are no deaths, that although asbestos clearly kills in the workplace and around processing plants or mines, it may not do so through more sporadic exposures.
"I'd guess we're dealing with a situation between no risk and very, very low risk, and our capacity to detect the distinction ... is not very good," said Dr. Jack Siemiatycki, a professor of epidemiology at the University of Montreal.
It could be years before definitive answers emerge, as knowledge about naturally occurring asbestos builds, one laborious study at a time.
One of the most provocative came out online last month, by a team of UC Davis and Harvard researchers who examined about 3,000 California cases of mesothelioma.
They found a statistical link between the disease and living near the type of rock that frequently contains asbestos. The link was far weaker than the tie between mesothelioma and jobs that tend to involve asbestos, but it seemed unlikely to be coincidence, researchers said.
Left unspecified for now, though, is exactly how many illnesses were found nearer the rock and how many farther away. Researchers hope to provide more details on their peer-reviewed study soon.
Nationwide, many doctors and researchers say, there is no community documented today where simply living around disrupted asbestos veins has caused a detectable increase in disease.
They stress that that, too, is not conclusive.
For one thing, no one has looked in a rigorous way. No one has fully mapped where belts of the most dangerous types of asbestos lie or noted the spots where they intersect with large populations.
Just this month, the U.S. Geological Survey released the first in a series of databases that compile what's known about asbestos deposits in the United States.
The mapping effort has been closely followed by officials at the federal Agency for Toxic Substances and Disease Registry, which wants to know more about where people's homes and lives may cross paths with bands of asbestos.
"That's somewhere where we want to go," said John Wheeler, a senior toxicologist with the agency. "We've just started looking at where populations have grown around those areas."
Not only does no one today fully understand just where asbestos lies, there's also enormous ambiguity about the health impacts of all its permutations.
Asbestos is a generic label slapped on a half-dozen or more different minerals in their fibrous form. The single word obscures the fact that one very common type, chrysotile, is considered less dangerous than the straighter, amphibole fibers. Among the amphiboles, differences in fiber length and width affect how carcinogenic each fiber is. At least one animal study identifies a type of tremolite asbestos in California as more deadly than other tremolites.
So to look for disease near asbestos veins, it's crucial to know what kind of asbestos lies where, as well as whether those veins have been disrupted or are trapped in rock, unable to release dangerous fibers into the air.
That knowledge, just starting to be built at the federal level, is largely lacking at the state level. While the USGS databases try to note asbestos types, the California Geological Survey maps instead show locations of "ultramafic" rock, where asbestos veins tend to be found. That rock, while scattered among many counties, covers only about 1.4 percent of California's surface territory.
Health experts have begun wondering about neighborhood asbestos risks because it is well-documented that asbestos can kill.
Workers who have been heavily exposed risk a lung-scarring disease called asbestosis, as well as lung cancer and mesothelioma. Disease also has been found among workers' relatives, who presumably were exposed to fibers tracked home, and to those in communities around mines and processing plants. Fatal illnesses have turned up in rural villages around the globe where people built homes or used stoves or whitewashes made from rock rich in asbestos.
The question is whether the more sporadic raising of asbestos-laced dust, from jogging, bicycling, playing sports or living near heavy construction, also could be taking a toll on people's lives. Those are the kinds of elevated exposures that have been measured in El Dorado County by the U.S. Environmental Protection Agency.
The search for answers about those exposures tends to bypass lung cancer, because it has too many other origins. Instead, the focus is on mesothelioma.
That poses its own problems.
Mesothelioma is so rare, the time lag between exposure and disease so long, and Americans so mobile, that natural asbestos deposits may have been a quiet killer around the country for years, without anyone being able to trace or prove a link.
Mesothelioma is diagnosed in an estimated 3,000 to 3,500 people nationwide annually, and 80 percent of those cases are believed to be caused by working around asbestos or living with someone who does, said Dr. Vikas Kapil of the Agency for Toxic Substances and Disease Registry.
That would leave between 600 and 700 people a year, in a nation of close to 300 million, to be possible victims of naturally occurring asbestos - if there are no other causes for the cancer at all.
The estimate is enormously rough. Some say up to 90 percent of all mesothelioma cases are the result of workplace exposures, and others argue as few as 40 percent.
But it offers a crude, shorthand way to appreciate something about the scope of the disease and the possible impact of still-undocumented causes.
It also helps to know that roughly one mesothelioma case is diagnosed annually for every 100,000 Americans.
In scattered areas, "you could increase the rate two-or threefold and people would never notice," said Dr. Victor Roggli, a professor of pathology at Duke University.
What passes untracked in the large picture, of course, would be horribly noticeable at home, for any person stricken with a preventable cancer.
That is the dilemma faced by those who live near veins of asbestos that could be churned up by digging or weathering, as well as by those who regulate land use and air quality.
For some, the complexity of the issue raises another, starker question: Given the number of deaths that could be involved, how vigorously should prevention be pursued?
"Of course you want to prevent any environmental hazards that you can prevent, but at a certain point you've got to make a kind of cost-benefit analysis," said epidemiology professor Siemiatycki.
"How far do you want to go to figure out how to prevent one or two cases of cancer in a large population when there are so many other big social problems to deal with, with our limited resources?"
At the local level, to weave one more complication into a nest of complications, El Dorado County's explosive growth could be masking any effect there, raising the possibility that a problem could be detectable only years from now.
So far, the incidence of mesothelioma doesn't seem out of the ordinary in the county, said William Wright, chief of the cancer surveillance section of the California Department of Health Services.
From 1998 through 2002, the last five-year period for which statistics are complete, eight cases of mesothelioma were diagnosed in El Dorado County and reported to the state's cancer registry, he said.
That is within the range reported annually statewide - 1.1 new cases of mesothelioma for every 100,000 people, Wright said.
Some are concerned, though, that El Dorado and other fast-growing foothill areas may face a particularly high risk because constructing vast new communities moves so much earth that it might more accurately be compared to quarrying or mining.
Dr. Bruce Case, a Canadian pathology professor, is one of those most alarmed by the dangers that could be churned up in El Dorado.
Case has looked at the way the county's population rapidly exploded, at the virulence of the tremolite asbestos present there, and at the long delay in cancer onset, and come up with a date.
The year 2020, he believes, is when exposures dating back to the 1980s will start producing statistically detectable levels of disease.
"This is the real thing," he said. "Eventually, you're going to have an epidemic."
He cannot guess how many people that epidemic could fell, but says the upper end he worries about involves mesothelioma causing about one death in every hundred in the county.
Case's darker fears, using county death rates projected by California's state demographer, translate to 22 mesothelioma deaths in El Dorado County annually by 2020, and probably fewer, because many areas of the county have no asbestos.
Even a single death, though, raises an ethical issue for the community, said Dr. Hugh Dame, a retired surgeon and a Camino resident.
Dame is a skeptic. He hates that his county today has cut library hours to a bare minimum, while hiring asbestos control workers to deal with a problem that hasn't yet been quantified.
And yet, as a doctor, he cannot disregard the importance of acting to save a life.
"If I saw that there was one specific thing we could isolate, that with a reasonable amount of money we could mitigate, I would do that," Dame said.
He can't imagine what that one thing would be.
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