by Carole Jackson, Bottom Line Health
A long ride down a gravel road in the country might have you conjuring up visions of a remote campsite or a picturesque pond at its end, but if you live in Dunn County, North Dakota — or in certain parts of 11 other states — the gravel road is more likely to stir up the harmful mineral erionite. Itâs an asbestos-like fiber that can cause mesothelioma, a type of cancer that affects the tissues that surround the lungs and abdominal organs. In fact, erionite is much more potent than asbestos in terms of causing mesothelioma. Talk about dangerous dust!
Whatâs even scarier is that while the government has imposed severe restrictions on how asbestos can be used in the US, it has not taken any similar action with erionite — at least not yet. Investigators at the University of Hawaii Cancer Center in Honolulu hope that their recent research on the dangers posed by this mineral will change all that.
A HIGHER RISK FOR CANCER
Over the past few decades, geologists have discovered that natural erionite deposits exist in the rock of at least 12 western states — North Dakota, South Dakota, Arizona, California, Colorado, Idaho, Montana, Nevada, New Mexico, Oregon, Utah and Wyoming. When this rock is made into gravel, carcinogenic fibers are released into the air — and these carcinogenic fibers continue to be released into the air whenever the gravel is disturbed, like when a car drives over a road (or a driveway!) that is made of erionite-containing gravel.
If you breathe in these fibers, they can become lodged in your lungs, where they can cause abnormal cell development. Decades later — usually 30 to 60 years after exposure — this may lead to mesothelioma. Unfortunately, our current medical therapies have little impact on this lethal type of cancer, which has an average survival rate from diagnosis of just four to 18 months.
It sure was disheartening to learn that something as simple as a stone could cause such a life-threatening disease. To find out more, I spoke with Michele Carbone, MD, PhD, lead author of the study that made these discoveries, and Haining Yang, PhD, a member of the research team led by Dr. Carbone.
To explore the potential health risks that are associated with inhaling erionite gravel, Dr. Carbone and his team — in partnership with scientists at the Environmental Protection Agency, the National Institute of Environmental Health Sciences and several universities — turned their focus on Dunn County, North Dakota, where more than 300 miles of roads have been surfaced with erionite-containing gravel over the past 30 years.
The researchers measured airborne concentrations of Dunn County erionite and evaluated its physical and chemical properties. Then they compared their results with earlier findings from Turkish villages, where erionite gravel is commonly used and 6% to 8% of all deaths in those villages have been attributed to mesothelioma. In their analysis of the data, Dr. Carbone and his colleagues found that…
- On Dunn County roadsides, and even in nearby indoor areas and inside vehicles that were regularly driven on erionite gravel roads — including school buses — levels of erionite equaled or exceeded the levels that were found in the Turkish villages.
- The physical and chemical properties of North Dakota and Turkish erionite were almost identical. Therefore, Dr. Carbone and his colleagues theorized that erionite from Turkey and North Dakota would have the same carcinogenic effects. When they injected mice with Dunn County erionite, they found that, sure enough, their theory was correct. Inflammation and abnormal cell growth — early signs of mesothelioma — occurred in the lungs of the mice.
These findings, which were published in the July 25, 2011 issue of Proceedings of the National Academy of Sciences, are alarming. To make matters worse, with the increasing development of rural areas in the US, erionite exposure is likely to rise, said Dr. Carbone.
Up until a few decades ago, it had been thought that no erionite existed in US rock — and, in any case, it wasnât used on US roads or driveways, said Dr. Carbone. Since both the discovery and the use of erionite in the US are relatively new, the potential health consequences of erionite exposure in the US hadnât been explored until this study — so these results may trigger more research on the topic. Since it usually takes decades for mesothelioma to develop, Dr. Yang said that we are now approaching the time when erionite-related mesothelioma may start to be detected. She said she wouldnât be surprised if Dunn County (and other parts of the US exposed to erionite) saw a rise in mesothelioma in the years to come.
Right now, there is no easy way to know if the gravel road that you are walking or driving on contains erionite, since erionite gravel doesnât look, smell or feel different than many other types of gravel. Fortunately, most gravel does not contain erionite.
Even if you do know for sure that youâre walking or driving on an erionite-gravel road, unfortunately scientists know of no good way that you can protect yourself. When I asked Dr. Carbone whether it might help to roll up the car windows and set a vehicleâs climate controls on “recirculate” — which is supposed to block all or most outside air from entering — he said that this might help lessen exposure, but it wouldnât eliminate it, since no carâs recirculation system is 100% efficient. You could also try calling your county or state health department to see if erionite exposure rates are being measured and if erionite gravel is being replaced. Since research on this topic is new, not all governments may take action yet, but you can at least help raise awareness about the problem. Paved roads made of asphalt in affected areas may also contain some erionite gravel bits (they werenât studied), but while traveling on those types of roads, youâre less likely to inhale as many harmful erionite fibers, so take asphalt roads if and when you can.
Also, if you experience any of the common symptoms of mesothelioma — trouble breathing… pain in the lower back or side of chest… trouble swallowing… swelling in face and arms… pain or swelling in the abdomen… or unexplained weight loss — call your doctor immediately, especially if you live in an affected area.
Michele Carbone, MD, PhD, professor of pathology, director, University of Hawaii Cancer Center, Honolulu.
Haining Yang, PhD, assistant professor of pathology, University of Hawaii Cancer Center, Honolulu.