Does anything other than asbestos exposure cause mesothelioma?The titular question of this article is tricky, and those who ask it often fall into one of several camps. They may be (a) simply curious, (b) scientifically inquiring into the cellular nature of malignant pleural mesothelioma (MPM), (c) questioning a well-established fact for their own professional gain, or (d) some combination of the above. We leave it to you to judge the merits of each of these mindsets.
As an example of inquiries of this nature, consider a literature review that recently weighed the potential for substances other than asbestos to cause MPM. Published in the journal Archives of Pathology, the paper seems to fall nicely into camps (a) and (b).
Asbestos: The sole proven cause
The potential of asbestos to lead to lung scarring, asbestosis and mesothelioma is thoroughly established. The Environmental Protection Agency lists it as a dangerous carcinogen, and the National Cancer Institute calls asbestos the only proven cause of MPM. Each year, 3,000 cases of mesothelioma are diagnosed in the U.S., and most of them involve a history of asbestos exposure.
But what about the ones that don't? That is the thought that drove UK scientists to conduct the recent review.
In the paper, the authors described searching the available medical literature for reports of mesothelioma caused by non-asbestos substances. The results indicate that while exposure to a few other carcinogens may increase the risk for MPM, asbestos is still the only substance conclusively proven to cause mesothelioma.
The usual (and unusual) suspects
Researchers began by addressing a few of the perennially suspected agents, including radiation therapy, viruses and non-asbestos minerals. In each case, prior studies could not establish a solid connection to mesothelioma.
For example, the team noted that the inhalation of several distinct minerals has been suggested to independently cause MPM. While studies suggested that these ores seriously damage lung tissue, the minerals that seemed most dangerous were, unsurprisingly, those that most resembled asbestos in fibrousness and carcinogenicity.
Likewise, radiotherapy and viruses (especially the simian virus 40) each has the capacity to damage DNA and increase the risk of malignancy. But, to date, only case studies and small, non-randomized reports have made the claim that these agents cause MPM.
The report also addressed some of the more unusual suspects, such as carbon nanotubes and common minerals like nickel, beryllium and silica. Researchers explained that "these observations have either been based on intraserosal implantation experiments in animals, which are highly artificial and sometimes very misleading, or on rare case reports with poorly documented histopathology."
No case of MPM has yet been linked to nanotubes, and there is no evidence that connects nickel or other common minerals to the disease, the group concluded. For now, when it comes to mesothelioma, asbestos is still public enemy number one.
Copper thefts may increase locals' risk of asbestos exposure, http://www.heraldnews.com/newsnow/x1922376864/Asbestos-spread-by-copper-thieves-will-cost-Fall-River-Housing-Authority-78-000, 12/14/12
Massachusetts school custodians learn about asbestos exposure, http://www.wickedlocal.com/norwell/news/x2105847083/Norwell-participates-in-asbestos-awareness-training#axzz2Ese9TA66, 12/14/12
Experts question integrity of asbestos exposure reports, international collaboration, https://www.rightoncanada.ca/?p=1761, 12/14/12
Northern Ireland campaign will educate tradespeople, others about asbestos exposure, http://m.u.tv/news/300-NI-asbestos-deaths-in-five-years/e3426c38-0a85-47ff-b68f-3e2d4fbbe3cd, 12/11/12