Craftsmen who cut granite for kitchen countertops can be at risk of radiation exposure thousands of times above the federal safety limit, according to new research.

The danger results from inhaling the airborne granite dust, which sometimes contains significant quantities of uranium and other dangerous isotopes, scientists say.

“What we found scared the daylights out of us,” said co-author Linda Kincaid, an industrial hygienist in Saratoga, Calif.

The study, “Implications of Granite Counter Top Construction and Uses,” raises concerns that the stone dust could be exposing America’s estimated 24,000 granite fabricators to elevated cancer risks, according to Kincaid. People living in homes with granite countertops face no health concerns from the dust, which is generated when the stone is cut.

At issue is the potential threat to workers who process granite. Kincaid and co-authors Al Gerhart, an Oklahoma City stonecutter, and Dave Bernhardt, a Salt Lake City health physicist, contend that when workers cut slabs of stone, they sometimes release radioactive dust into the air. In turn, that dust is inhaled, reaching the workers’ lungs.

The contaminated dust bombards the lungs with so called alpha particles — a particularly damaging form of radiation, according to Kincaid, who said lung tissue is especially vulnerable. “It’s very delicate, very fragile, very easily damaged,” she said.

While public health officials have for decades focused on the elevated risk of respiratory diseases for those working in dusty conditions, the study unveiled at the Health Physics Society’s annual meeting July 13 in Minneapolis is the first look at how a granite byproduct could be harming workers.

The Marble Institute of America, a leading trade group for stone industry, slammed the new research.

“This report has no scientific credibility and cannot be relied upon,” said Jim Hieb, vice president of the Marble Institute, which is based in Cleveland, Ohio.

But, responding to the findings, a spokeswoman for the U.S. Department of Labor called for more research.

“Little research has been performed on the radiation hazards for granite cutting,” said Diana Petterson, a department spokeswoman. “But with the increasing residential use of granite countertops, more studies are underway.”

Co-author Kincaid called on granite workers to be especially careful to keep their workspaces clean. The authors also want more research on the topic, admitting that they have raised more questions than answers.

Long known to contain natural deposits of uranium, granite became a topic of concern last summer when fears were aired in the media that stone countertops could generate elevated levels of radon gas in the home. Those radioactive fumes, if not properly ventilated, could pose an increased cancer risk, Gerhart said.

The new finding focuses not on this risk to the general public, but rather on the dust danger for industrial workers. To assess that threat, Kincaid tested the air quality in Gerhart’s Oklahoma City granite-cutting shop. While he cut granite, she captured air samples.

 

Analyzing the results, Bernhardt found that full-time granite workers could be exposed to radiation levels of up to 320 rem per year — more than 3,000 times above the U.S. Nuclear Regulatory Commission’s radiation exposure limit of 0.1 rem per year for members of the general public.

About 5 percent of granite is radioactive, Gerhart said. Bernhardt estimates that half of granite cutters receive a radiation dose above the federal exposure limit for the general public.

“We’re looking at something that is a huge radiation exposure,” Kincaid said.

Gerhart says the research underlines the importance of ensuring that work environments are free of excess dust.

Because of longstanding concerns about ailments triggered by airborne contaminants, state and federal authorities have rules on dust levels in workplaces. But enforcement can be spotty.

The Marble Institute contends that almost three-quarters of stone fabricators use advanced, water-based cutting techniques to minimize dust exposure most or all of the time. According to Jim Martinez, an institute spokesman, stone-cutting facilities are taking precautions to keep their air clean — and that those precautions should lessen the inhalation of radioactive dust. Even if there is a risk, he contends, the current safeguards would minimize it.

Federal figures tell a different story. Inspecting 133 of the nation’s 64,000 stone cutting facilities from October 2007 to September 2008, authorities from the Occupational Safety and Health Administration — part of the U.S. Department of Labor — issued 185 citations for respiratory violations and 54 citations for air contaminants, according to OSHA data.

“There are a significant number of facilities that continue to operate with no or inadequate engineering controls,” said Petterson, the Labor Department spokeswoman. “This is why OSHA continues to target these industries.”

Research conducted in California echoes that. Bob Senchy, an associate safety engineer at the California state OSHA, inspected granite shops from 2001 to 2008 and found that 40 percent of granite cutting facilities had unacceptably dusty conditions.