Litigation involving asbestos has extended over decades and has been at least one stated cause of many companies filing for bankruptcy protection. Currently, many complaints filed include allegations that exposure to asbestos was the cause of mesothelioma, a type of cancer often attributed to asbestos exposure. But the authors of Chronological trends in the causation of malignant mesothelioma: Fiber burden analysis of 619 cases over four decades present data that supports a changing trend for the presumed cause of the disease.
 
The purpose of the study was to show how lung fiber burdens [the process of identifying fibers in the lungs] in patients diagnosed with mesothelioma has changed over time, as well as other changing trends in the data. The authors noted that the primary goal of regulating the use of asbestos (i.e. the Occupational Safety and Health Administration in 1972) was to decrease or eliminate the occurrence of asbestosis in exposed workers. Due to the 30-40 year latency period for diagnosis of an asbestos exposure-related disease, their data spanning four decades is significant. 
 
The authors note that one type of cancer – diffuse malignant mesothelioma – is relatively rare, but strongly associated with prior asbestos exposure. According to the data collected from 619 cases spanning four decades, the authors conclude that there is a trend of a decreasing number of mesothelioma cases diagnosed each year that include a history of exposure to asbestos-containing products for the patient. Comparing the data across the four decades (1980’s through 2010’s), the authors also identify decreasing levels of asbestos bodies found in the lung tissue over time, with an increase in the median age of the patient at the time of diagnosis among other trends. 
 
The authors note that a certain percentage of mesothelioma cases have always appeared to be “iodiopathic” or without a known cause (i.e. no known exposure to asbestos). However, based on the data discussed in the article, including the increase in age of the patients and decrease in cases where fiber is found in the lungs, there is support for medical providers to consider an alternative cause for mesothelioma such as genetic susceptibility. The authors note genetic susceptibility is an important role that has become increasingly recognized in the past several years. The authors further conclude that “[o]ne of the great challenges facing the scientific community in the future will be the distinction between cases caused by genetic susceptibility alone and those for which the individual is unusually susceptible to relatively low levels of asbestos exposure.” 
 
The evaluation of whether there was exposure to asbestos during a particular patient’s lifetime is a question asked and answered on a case-by-case basis, but the data discussed by Dr. Roggli, et al., at a minimum, shows not all mesothelioma cases involve exposure at all.