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Mesothelioma of “Unknown” Cause: Asbestos May Still Be the Culprit

26173732_worker4A new Italian study suggests that many cases of mesothelioma with “unknown” asbestos exposure may not be so mysterious after all.

Asbestos (and a similar mineral called erionite) is the top cause of mesothelioma worldwide. Almost everyone who is diagnosed with mesothelioma has come in contact with asbestos at some point.

 But in about a quarter of cases, no clear asbestos exposure can be identified. University of Milan researchers say it may be because no one has looked hard enough.

Sources of Mesothelioma-Causing Asbestos Exposure

Most mesothelioma patients have come in contact with asbestos on the job, which is why anyone suspected of having mesothelioma typically has to undergo a thorough work history as well as an  exam and various tests.

High risk occupations for mesothelioma include construction, plumbing and electrical work, shipbuilding and breaking. Many Naval veterans were exposed to asbestos on ships.

After asbestos was found to be a major cause of pleural mesothelioma, lung cancer, asbestosis and other diseases, many countries banned it. In the US, strict regulations were put on the use and handling of asbestos.

Overlooked Sources of Asbestos?

Because asbestos is so closely associated with mesothelioma, the University of Milan research team suspected that some asbestos exposure might be overlooked in at least some of those unclassified cases of mesothelioma.

The team reevaluated the cases of 364 mesothelioma patients who at first did not appear to have come in contact with asbestos.

After digging deeper, including looking at lifestyle habits, interviewing relatives and colleagues, contacting industrial hygienists, and analyzing production processes in the places where they worked, the team found that many of these mesothelioma cases could be reclassified.

Mesothelioma Risk and Asbestos

Of the 364 cases of malignant mesothelioma evaluated, a link to asbestos was found in 44 (12%) of them.

In fifteen percent of these cases, the asbestos exposure was confirmed and in almost  half of them, researchers identified “possible occupational exposure”.

The remaining 36 percent of previously unclassified mesothelioma cases were found to be related to asbestos exposure in homes, environments or leisure activities. Asbestos was once widely used in house construction and occurs naturally in the soil in some locations.

The detailed reconstruction of clinical and occupational history and of lifestyle habits of patients affected by malignant mesothelioma, close cooperation with Local Services of Occupational Medicine and literature review make it possible for previously overlooked asbestos exposure to be acknowledged,” the report concludes.

A connection to asbestos exposure is not only an important part of diagnosing mesothelioma but is also critical in determining whether a patient is eligible for compensation.


Mensi, C et al, “Malignant mesotheliomas with unknown exposure to asbestos: a re-examination”, January 20, 2015, La Medicina Del lavoro

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