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While asbestos exposure is the most commonly known cause for mesothelioma, it has also been discovered that a mineral called erionite can be a cause as well. One case of erionite-induced mesothelioma has been reported in a male living in North Dakota.1 Similar cases with eronite-induced mesothelioma have also been reported in areas of Turkey. Because chronic erionite exposure must last decades before mesothelioma develops in the cases in Turkey, this single case report suggested that North Dakota (ND) may have a source for chronic erionite exposure.
What is erionite?
Erionite is a naturally occurring, white, brittle, fibrous mineral found in some volcanic ash. Weathering of the volcanic ash and exposure to ground water helps in its formation. Eakle found irregular shaped blocks of white, straight, steel wool-like fibers in rhyolite lava in Oregon in 1898 and named them erionite. Geologists classify it as a type of zeolite mineral.
Erionite looks like a cage-like structure with six sides (hexagon). The crystal groups appear to radiate from a central line. Three main forms have been described: erionite bound with calcium (Ca), erionite bound with sodium (Na), and erionite bound with potassium (K). A fourth type of erionite is associated mainly with a mixture of silicon and aluminum (Si+Al). Erionite can absorb up to 20% of its weight in water. The blocks of erionite can be broken or shattered and its tiny sharp fibers can float in the air.2
Does the US contain any deposits of erionite?
Yes. Several rock deposits contain erionite in Nevada (n=14), California (n=8), Oregon (n=7), Arizona (n=7), Wyoming (n=5), and New Mexico (n=2).2
The following states contain 1 rock deposit with erionite: Colorado, Idaho, Montana, North Dakota, South Dakota, and Utah.2
Do towns exposed to erionite have higher rates of mesothelioma?
Yes. The citizens of Karain, Tuzkoy, and Sarihidir villages which are located in the middle of Turkey in the Cappadocia region have high rates of malignant mesothelioma. About 25% to 50% of these villagers die of mesothelioma.2,3 In comparison, the US has about 2700 deaths yearly or about 14 deaths due to mesothelioma per million in 2005.4 Thus, approximately 0.0014% of people die of mesothelioma in the US.
A major cause of the high rate of malignant mesothelioma in these Turkish villages turned out to be exposure to local rocks containing erionite.3 Many families had built their adobe houses from the local rocks.3 These homes were passed down from generation to generation. Only families living in homes built with adobe that contained erionite had high rates of mesothelioma.3
How are residents of North Dakota being exposed to erionite?
Since homes in North Dakota (ND) are not made of adobe, the search for a source of erionite widened. Carbone et al determined that Dunn County ND had used gravel from the North Killdeer Mountains which unfortunately contained erionite.2 Dunn County, ND had paved 300 miles of roads with the gravel during the 1980s.2 Some playgrounds, parking lots, baseball fields, and 32 miles of school bus routes contained the erionite-containing gravel in the northwest region of Dunn County, ND.2
Does the air above the pavement contain erionite?
Most air samples obtained inside cars and school buses that were traveling on the erionite-containing roads were positive for erionite fibers.2 The erionite fibers are measured with very powerful microscopes. The transmission electron microscope method found that 37 air samples from different vehicles out of 41 were positive (mean level was 0.235) and the phase contrast microscopy equivalent method found 26 out of 41 samples positive (mean level 0.022).2 Air samples from parked buses and cars adjacent to the roads (3 samples of 3 tested) had erionite fibers in their air by both methods. The erionite fiber levels in the parked vehicles were about half of that in moving vehicles.2
Garages contained erionite in most air samples. The transmission electron microscope (TEM) method found 4 of 5 air samples from different garages as positive (mean level was 0.207) and the phase contrast microscopy equivalent (PCME) method found 2 of 5 samples positive (mean level 0.061).2 Thus, the erionite levels in the garage air samples were similar to the air samples in vehicles moving on the erionite containing roads by the TEM method and about twice as high by the PCME method.
The concentration of erionite in air samples while people walked on playgrounds, ballfields, parking lot, and biked on residential alley ways were about 7-8 fold lower than the released erionite in moving school buses and cars.
How do these erionite levels in the air compare to the erionite levels in the villages of Cappadocia?
The erionite levels in air samples taken during indoor activity in ND ranged between those observed in the villages of Karlik and Boyali, which have rates of mesothelioma from 6% to 7%.2
The erionite levels in stationary air samples next to the ND streets containing erionite gravel were 10 times higher than those in any of these five Turkish villages in the Cappadocia region.2 This was not surprising since the roads in Cappadocia did not contain gravel with erionite.
As a comparative, these erionite levels in stationary air samples next to the ND streets containing erionite gravel were 2 times lower to 70 times lower than the air during indoor activity in the homes of four of these five Turkish villages in the Cappadocia region.2
Is the erionite in ND similar to erionite in the Coppadocia villages of Turkey where many residents developed mesothelioma?
Yes. The width and length of the erionite fibers in ND are similar to those erionite fibers found in the rocks in the villages of Turkey.2
The erionite in North Dakota mostly bound a mixture of Silicon and Aluminum (77% to 79%), similar to the erionite in the adobe homes in the villages in the Cappadocia region of Turkey (79% to 81%).2 The remaining erionites in both samples contained similar mixtures of Ca-erionite, Na+Ca erionite and K-erionite.2
Thus, the shape, width, length, and composition of the eronite fibers in ND were similar to those found in the Turkish villages with high rates of mesothelioma.2
Kliment CR, Clemens K, Oury TD. North american erionite-associated mesothelioma with pleural plaques and pulmonary fibrosis: a case report. Int J Clin Exp Pathol 2009;2(4):407-410.
Carbone M, Baris YI, Bertino P et al. Erionite exposure in North Dakota and Turkish villages with mesothelioma. Proc Natl Acad Sci U S A 2011;108(33):13618-13623.
Metintas M, Hillerdal G, Metintas S, Dumortier P. Endemic malignant mesothelioma: exposure to erionite is more important than genetic factors. Arch Environ Occup Health 2010;65(2):86-93.
Center for Disease Control. Malignant Mesothelioma Mortality --- United States, 1999--2005. 393-396 (Center for Disease Control Atlanta, 2009).
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