Wednesday, January 05, 2011

Concerns over erionite dust as cancer source

A report and news item in the journal Nature last month raised concerns over the possible health hazards from the zeolite mineral erionite which does occur in remote areas of Arizona and other states [right, photomicrograph of an erionite fiber from road gravel in North Dakota. Credit, K. Eylands/UND EERC].

"For generations, a handful of tiny villages in Cappadocia, Turkey, have been plagued by a rare and deadly lung disease. Five years ago, the cause of this disease, a naturally occurring mineral called erionite, was identified in the gravel paving hundreds of kilometres of roads in North Dakota. Researchers are now trying to get to grips with whether or not the exposure to people in North Dakota is dangerous." The article said researchers were working with geologists to "survey parts of Arizona, Nevada, Oregon, California and Idaho for the mineral."

That got us here at AZGS to see what we know about distribution of this mineral. There are six occurrences of the mineral noted in the book "Mineralogy of Arizona," all of them in generally remote areas. As AZGS Senior Geologist Jon Spencer says, "Erionite is known in Arizona, but occurrences other than near Bowie are, as far as I know, geologic curiosities associated with tuffaceous rocks, and are unlikely to be any more of a health hazard than all the asbestos outcrops that are typically rarely and briefly visited by geologists and curious citizens." Erionite is reported in the bedded lake deposits in the San Simon basin, 7 miles northeast of Bowie, in Cochise County.

There does not appear to be a situation here like was found in North Dakota where gravel used to pave some of the roads contains erionite.

An investigation launched by my colleague North Dakota State Geologist Ed Murphy has found "levels of exposure to erionite [a zeolite mineral with characteristics similar to asbestos] in North Dakota are the same as in some of the Turkish villages ravaged by mesothelioma" according to the report in Nature.

"The North Dakota study eventually grew into a global collaboration including cancer biologists, geologists, epidemiologists, environmental scientists and physicians." Results were presented earlier this month at the Chicago Multi­disciplinary Symposium in Thoracic Oncology.

"North Dakota doesn't seem to have a higher incidence of the disease than is normal nationwide," but it may take 30 years or more for effects to appear, so studies are underway on construction and quarry workers who may have had extended exposure to erionite dust used in road construction.

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