Workers exposed to both asbestos and another insulation material called refractory ceramic fiber (RCF) are more than 4 times as likely to develop malignant pleural mesothelioma as are workers who were only exposed to asbestos. That is the conclusion of a new study from a team of French scientists at the University of Bordeaux.
Asbestos, a fibrous mineral used in insulation and building materials, has been known for decades to increase the risk of mesothelioma. RCF is a manmade aluminum-silicate-based material that is also used for insulation, particularly in high-heat industrial applications. Although some animal studies on RCF have suggested that the material might also cause cancer, a 2012 study in Inhalation Toxicology found no increase in lung cancer or mesothelioma incidence in exposed workers.
In the latest study, French researchers attempted to find out if RCF might have a synergistic effect with asbestos in the development of mesothelioma. They examined the work histories of 988 French workers who had developed mesothelioma between 1987 and 2006. One group of workers had only been exposed to asbestos while the second group had a history of exposure to both asbestos and RCF.
Reporting in the European Respiratory Journal, lead author Aude Lacourt writes, “A dose-response relationship was observed in both groups but it was stronger in Group 2.” In fact, the researchers found that the risk of developing mesothelioma after asbestos exposure was more than 4 times higher among workers who had also been exposed to RCF – from an odds ratio of 2.6 in the asbestos-only exposure group to 12.4 in the group exposed to both materials.
“Our results suggest that the pleural carcinogenic effect of occupational asbestos exposure may be modified by additional exposure to RCF,” concludes the article. Mesothelioma is an aggressive and usually lethal cancer of the membranes surrounding internal organs.
Asbestos was used from the 1930s to about the 1980s and RCFs were launched on the European market in the 1960s. Although asbestos is now banned or restricted in most developed countries, workers may encounter asbestos containing materials and refractory ceramic fibers together during demolition or remodeling projects.
Lacourt, A et al, “Co-exposure to refractory ceramic fibres and asbestos and risk of pleural mesothelioma”, July 17, 2014, European Respiratory Journal, Epub ahead of print