Asbestos News

Natural Asbestos Tied to Mesothelioma

By Ian Hoffman, Red Orbit

For the first time, scientists have linked living close to a likely natural deposit of asbestos to a rare, highly lethal cancer.

Drawing on California's cancer registry, a database covering about a tenth of the nation's population, researchers found a slightly elevated chance of contracting mesothelioma among people who live within eight miles of places where construction or road building can disturb natural veins of asbestos.

"It says yes, this is a health hazard. Yes, it should be taken seriously," said the study's lead author, Marc Schenker, chairman of epidemiology and preventive medicine at the University of California, Davis.

The study adds to growing concern in California and other states where homes and schools are being built close to natural deposits of asbestos. Most recently, El Dorado County, near Sacramento, has struggled with fast-paced development and mounting evidence that the resulting dust is carrying asbestos into the lungs of residents.

But clear evidence of health effects has been lacking or at least difficult to discern. Mesothelioma, a malignancy of the lining of the lungs, is thought to be almost exclusivelytriggered by breathing asbestos fibers. Yet the disease is very uncommon -- on average, a single case for every 100,000 people per year -- and symptoms can take 20 years or more to appear after exposure to asbestos.

To get a meaningful picture of disease and residency, Schenker and colleagues at Davis and Harvard examined a decade's worth of data for all California cases of mesothelioma and compared them with similar cases of pancreatic cancer, which has no known link to asbestos exposure.

They examined the occupations of the mesothelioma victims and where they lived. After accounting for work such as shipbuilding or insulation installing that exposed victims to asbestos, they found a close association between residential proximity to likely asbestos veins and mesothelioma.

"In every case the relationship held up," said Laurel Beckett, chief of biostatistics at UC Davis. "This is quite unlikely to be due to chance."

In El Dorado County, where population is expected to triple over the next 30 years, scientists found about two cases a year.

"That number could go up substantially, and that's something we'd like to prevent," Schenker said.

Napa County also had about two cases a year. Every other county in the Bay Area has some scattered deposits and roughly one additional case of mesothelioma over the national average every two years.

In the Davis-Harvard study, scientists found that the odds of contracting mesothelioma diminished by 6.3 percent for every eight miles of distance from a likely asbestos deposit. That means that people who live 40 miles or more away from a deposit face roughly half as much risk of contracting mesothelioma as people who live within a few miles of a deposit.

"This is beginning to open the door to some of the vital questions that have been asked by communities that have been exposed to naturally occurring asbestos," said Earl Withycombe of the American Lung Association.

Federal study on environmental asbestos and mesothelioma.

Related: Asbestos: Are more rules in the air?