Natural Asbestos, Cancer Linked

A new study has found that everyday exposure to naturally occurring asbestos boosts the chances of developing a deadly form of cancer but added that the risks are relatively low.

The statewide study by a team of UC Davis researchers is expected to affect the ongoing debate over how to tackle the problem in fast-growing communities in the Sierra foothills where asbestos fibers embedded in the ground are being unearthed by new housing tracts.

In California, researchers determined that the risk of contracting mesothelioma -- a rare and lethal form of cancer -- is about 1 in 100,000 people each year, though those chances increase for residents who live near pockets of natural asbestos.

Although the overall danger is low, researchers encouraged public officials to press ahead with efforts to reduce the likelihood of breathing the spear-shaped fibers, particularly in areas of the state where new housing developments are pushing into terrain dotted with the type of rock that acts as a seedbed of naturally occurring asbestos.

Marc Schenker, chairman of the UC Davis department of public health sciences and lead author of the study released last week, called the threat in such spots “a health hazard” that should be “considered seriously.”

The battle over what to do has been most intense in El Dorado Hills, a fast-growing upscale community about 30 miles east of Sacramento.

Although some residents are alarmed that veins of asbestos uncovered by development could be risking lives, others contend that the threat has been overblown.

Throughout the region, officials have tried to gauge the threat of asbestos or have taken precautions to control its spread. Last year, to prevent asbestos-laden dust from being stirred up, almost all the exposed ground at a high school in El Dorado Hills was capped with concrete or ground cover -- at a cost of $2.5 million.

Officials with the federal Environmental Protection Agency conducted tests in El Dorado Hills in October to see how much asbestos-laden dust is kicked up by normal recreation.

EPA workers rode bikes, played baseball and kicked soccer balls -- to mention just a few activities -- while wearing air monitors, respirator masks and protective moon suits.

The tussle over asbestos has boiled over at the state Capitol, where legislation that could require tougher standards for builders to ensure that asbestos deposits are left untouched or sealed up has run into opposition from the building industry.

But when releasing the new study, Schenker mostly steered clear of politics and focused on science.

Funded by the National Cancer Institute, the research effort used public health records, geologic maps and satellite mapping to pinpoint victims of mesothelioma across California over a 10-year period concluding in 1997.

Researchers found that the risk increased closer to deposits of naturally occurring asbestos, which is most prevalent in the Sierra foothills, the Coast Range and the Klamath Mountains in the state’s far north.

A person living within four miles of an asbestos deposit had about double the chance of contracting mesothelioma as someone about 40 miles away.

Mesothelioma has a long latency period of about three decades, but then it strikes with a vengeance. Patients typically die within a year of diagnosis.

Given the possibility of a jump in mesothelioma 30 years from now, Schenker said public efforts should focus on protecting people from the disease, a type of cancer that is preventable. “Our biggest efforts should be to reduce those future cancers,” he said, adding that it is “less costly to prevent now than treat later.”

Nationwide, mesothelioma is rare. A person is about eight times more likely to get pancreatic cancer. The annual death toll from mesothelioma is estimated to be about on par with fatalities linked to secondhand tobacco smoke.

Researchers found that mesothelioma death rates in Los Angeles, Orange, Riverside and San Bernardino counties fall below the state average. The highest rates are in Trinity and Sierra counties.

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Times staff writer Marla Cone contributed to this report.