A New Mesothelioma Threat: Cancer Causing Chemicals in Road Gravel

Over the past several years scientific studies, such as the one done by the California Department of Toxic Substances Control (DTSC), have produced findings concluding that roads and driveways covered with serpentine gravel which contain naturally occurring asbestosmust be resurfaced. The mission of the Department of Toxic Substances Control is to ensure public health, protect, restore and enhance the environment, and conduct cleanups.

Roads surfaced with gravel in the California study pose a significant health hazard from airborne asbestosgenerated from vehicle traffic. Once paved or resurfaced, results showed that concentrations of airborne asbestos were nearly eliminated; they were reduced by 98 percent. Air sampling in this particular study was done in the summer of 2002, so researchers have known of the potential mesotheliomacancer causing risk of gravel on driveways and roadways. As part of the California study, a human health risk assessment was completed and became part of the DTSC report. This health risk assessment was based on measurements of airborne asbestos fibers caused by simulated traffic conditions before the repaving of the road with a four-inch limestone aggregate cover which reduced asbestos concentrations by an average of 98 percent.

• The study first looked at the risk of mesothelioma cancer from exposure to asbestos to use as a baseline.
• The risk of cancer was estimated in a person exposed to gravel dust in two conditions. The first was from five feet away. The second was from 190 feet away from the graveled road.
• Based on an estimated typical scenario of road travel (ten vehicles each hour traveling ten miles per hour), they found that 16 hours of exposure at a distance of five feet increased the risk of developing mesothelioma by 3 in 1,000.
• When tested at 190 feet, the additional lifetime risk of developing mesothelioma was three in 100,000.

So the fact that gravel dust can increase the risk of contracting mesothelioma cancer has been known for several years now.

A mineral called erionite which contains similarities to asbestos has been found in gravel on roads in many U.S. states. Erionite has physical similarities with cancer-causing asbestos. Just as is the case with asbestos, when erionite is disturbed by human activity, in the case of erionite-containing road gravel, vehicle traffic, fibers become airborne and may embed themselves into human lungs. There they may lie dormant for more than twenty years before symptoms develop illustrating the presence of mesothelioma cancer. Embedded erionite fibers, like embedded asbestos fibers, over time cause the cells of the pleura—the lining of the lung or of the lung itself to grow abnormally, leading to mesothelioma.

Miles of U.S. roads are paved with gravel containing the mineral erionite. So far the mineral has been discovered in road gravel in twelve states, but with further investigation, that number is expected to grow. The newest study was done by Michele Carbone, M.D., PhD, director of the University of Hawaii Cancer Center in Honolulu, Hawaii. The director of the University of Hawaii study had previously linked exposure to erionite in villages in Turkey to an abnormally high number of cases of mesothelioma. This most recent study was published in the July 25, 2011 issue of Proceedings of the National Academy of Sciences (PNAS). It is the first one of its kind to study the potential risks associated with exposure to erionite through gravel dust in the United States.

Erionite found in North Dakota was compared to the same mineral found nearby Turkey’s cities where there were abnormally high numbers of cases of mesothelioma. Various settings were utilized in order to measure the mineral’s airborne concentrations. The mineral’s chemical composition and biological activity were studied as well. The size of erionite fibers studied under a microscope in Turkey was similar to the size of the fibers found in Dunn County, North Dakota. Mice injected with erionite obtained from North Dakota had lungs which developed signs of inflammation and abnormal cell growth—both signs of future development of mesothelioma cancer. Rocks which contain erionite have been used in the state of North Dakota to produce gravel for the past 30 years. It can take up to 30 years or more for exposure to develop into mesothelioma. Since erionite deposit mining is only a relatively recent occurrence, the number of mesothelioma cases should be increasing in the future. Levels of airborne erionite in North Dakota were similar to levels found in villages in Turkey where there was an 8-percent mortality rate from the contraction of mesothelioma cancer.

• Arizona
• California
• Nevada
• North Dakota
• Oregon

Although other states have erionite mineral deposits as well, the possibility of human exposure in those other states has yet to be investigated. Asbestos has long been known to cause mesothelioma even in lower rates of exposure. As a result health benchmarks have been put into place in the U.S. for safe exposure tolerances. No such benchmarks have been established for exposure levels to erionite because until recently researchers believed cancer-causing erionite to exist only in Turkey where prior investigation was performed. There discoveries of the presence of the mineral both naturally occurring and in gravel led to residents being relocated away from areas known to contain erionite in high levels of concentration.

The latest University of Hawaii Cancer Center study reported in July’s issue of Proceedings of the National Academy of Sciences demonstrates that precautionary measures should be put into place in the United States to reduce exposure to this mesothelioma cancer-causing material.