Leaving Las Vegas

The Journal of the National Cancer Institute recently published a curious article about what appears to be unpublished research that suggests a non-asbestos environmental cause of malignant mesothelioma in Clark County, Nevada.  Leslie Harris O’Hanlon, “Researchers Explore Possible Link Between Mesothelioma and Dust Emissions in Southern Nevada,” J. Nat’l Cancer Instit., doi: 10.1093/jnci/djt033,  published ahead of print (Feb. 12, 2013).

The researcher appears to have been Francine Baumann , an epidemiologist at the University of Hawaii Cancer Center, who has worked with Michele Carbone, on occasion.  Analyzing Nevada’s cancer registry data from 1995 to 2008, Baumann found what she believed to be an increase in earlier age at diagnosis, and a reduced ratio of male-to-female cases for Clark County.   She interpreted these data to show that an environmental exposure was at work, but she professed ignorance of what the exposure might be.

The article also quotes the Nevada state epidemiologist, Ihsan Azzam, M.D., Ph.D., as saying:

“We analyzed the data and used the same data set as the researcher and came to completely different conclusions and findings. Their interpretation of data and their representation of it is wrong.”

The article presents no data or statistical analysis.  Given that Baumann’s work is unpublished, and apparently contradicted, it is curious that the Journal would publish any story about it.  Some of the raw data can be found online at Nevada Central Cancer Registry, including an online database, and Reports From The Office of Public Health Informatics and Epidemiology.

The O’Hanlon article is even more curious considering the nature of the research.  There are 16 counties in Nevada,  so Baumann presumably was canvassing counties without a pre-specified hypothesis as to whether Clark County was different from the others, or from the national rates.  This seems like post-hoc data dredging, but the Journal does not provide sufficient information to assess the validity of Baumann’s work.

The O’Hanlon article bizarrely talks about an unknown environmental cause in Clark County, but does not mention erionite, a zeolite.  The article discusses erionite-associated mesothelioma in Turkey, and an investigation into erionite occurrences in the United States.  Remarkably, O’Hanlon fails to mention that erionite occurs in Clark County, and in many other counties, throughout Nevada.  The NIOSH Science Blog fills in the missing information by showing how widespread erionite deposits are throughout Nevada.  See David Weissman, MD, and Max Kiefer, MS, CIH, “Erionite: An Emerging North American Hazard,” (Nov. 22, 2011).  Of course, the widespread deposits argue against erionite as a causal explanation for the putative environmental trigger in Clark County.  See also Arthur J. Gude & Richard Sheppard, “Wooly Erionite from the Reese River Zeolite Deposit, Lander County, Nevada, and its Relationship to Other Erionites,” 29 Clays and Clay Minerals, 378-384 (1981); Keith Papke, “Erionite and Other Associated Zeolites in Nevada,” Bulletin 79, Nevada Bureau of Mines and Geology (1972).

Erionite occurs in several mineralogical forms, including non-fibrous and various fibrous forms.  The erionite associated with environmental cases in Turkey has been studied and found to be fibrous, but there are many variations in fibers, including length, and length-to-diameter aspect ratio.  Erionite is a zeolite mineral and has the ability to absorb metal ions, including chromate, uranyl, and other ions, which may be an independent source of potential carcinogenicity.

There are many reasons to leave Las Vegas, but Dr. Baumann probably has not found a new one.

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