A new Turkish study is shining a spotlight on the role of environmental asbestos exposure in the development of malignant mesothelioma, an aggressive malignancy with no known cure.
Malignant mesothelioma, which occurs on the membranes around the lungs, the abdominal organs or, more rarely, the heart, is most often associated with occupational asbestos exposure.
But a new study in the Archives of Environmental and Occupational Health cautions that “Environmental asbestos exposure is as important as occupational exposure to develop malignant mesothelioma.”
In addition, after studying 21 groups of Turkish mesothelioma patients with either environmental or occupational exposure, the researchers concluded that environmental exposure is different from occupational exposure in some notable ways.
Asbestos Exposure and Mesothelioma Diagnosis
Doctors have known since as early as the 1930s of the possible connection between the mineral asbestos and a previously-unknown type of lung cancer.
The fact that the incidence of mesothelioma was (and remains) low, made it difficult to study. It was not until the 1960s that it became clear that asbestos exposure was the primary cause of mesothelioma and some companies began to taper off their use of asbestos-containing materials.
From the very first study on mesothelioma and asbestos, published in the British Journal of Medicine in 1960, researchers acknowledged that both occupational and environmental exposure to asbestos could be deadly.
Other studies followed, showing that people who either worked or lived around asbestos or products that contained it, were more likely than the general public to die of malignant mesothelioma.
This is because when they are inhaled or swallowed, asbestos fibers get trapped in the tissues, triggering inflammation and irritation that can lead to a mesothelioma diagnosis even decades later.
Occupational vs Environmental Asbestos and Mesothelioma Risk
In the newest study on asbestos exposure and mesothelioma incidence, researchers with Turkey’s Eskisehir Osmangazi University examined 21 groups or “cohorts” of asbestos-exposed mesothelioma patients.
Eight of the groups included patients whose only known exposure to asbestos or a similar mineral called erionite was environmental. Erionite is especially common in some areas in Turkey and many homes in these regions have been constructed with rocks that contain it, putting both the builders and the occupants of these homes at risk for mesothelioma.
The remaining 13 groups of mesothelioma patients analyzed for the new study included patients whose only known exposure to mineral fibers was in their work.
Results of the Mesothelioma Study
Although exposure to asbestos or erionite was clearly implicated in the illnesses of all of the study participants, the researchers discovered that how and where one was exposed could play a role in the development and progression of their mesothelioma.
Among the environmentally-exposed mesothelioma patients, incidence was higher in women. In contrast, groups of patients exposed at work tended to contain more men.
Among the environmentally-exposed mesothelioma patients, the rate of mesothelioma increased as the median exposure time increased, but the incidence of mesothelioma appeared to decrease as median cumulative exposure dose increased.
In the work-exposed groups, the opposite was true—the rate of malignant mesothelioma went up as their median cumulative exposure to asbestos increased. The findings prompted the researchers to conclude that environmental exposure “has its own unique features on the risk of malignant mesothelioma.”
In the US, environmental exposure to asbestos may include things like living near a decommissioned asbestos mine, laundering the clothes or equipment of someone who worked around asbestos, hiking in an area where asbestos occurs naturally, or living in a home with disintegrating asbestos insulation.
Metintas, S, “A review of the cohorts with environmental and occupational mineral fiber exposure”, April 2018, Archives of Environmental Occupational Health, Epub ahead of print