For decades, mesothelioma has predominately affected white men older than 60 years of age.
This is largely because of the rare cancer’s connection to occupational asbestos exposure and its long latency period of 20 to 50 years.
But as worldwide use of asbestos continues to decline and more industrialized countries continue to ban the toxic mineral, scientists are noticing a shift in age and gender when it comes to mesothelioma cases.
University of New Caledonia epidemiologist Francine Baumann designed and performed a study analyzing environmental risk of mesothelioma in the U.S. and its effect on women and young people.
“In countries where asbestos is no longer used by the industry, and where there are other fibrous minerals present in the natural environment, I think that the proportion of environmental causes of exposure is very likely increasing, and that the proportion of female and young mesothelioma cases is also very likely to rise,” Baumann told Asbestos.com.
The Journal of Toxicology and Environmental Health recently published the results of Baumann’s study.
Environmental asbestos exposure generally occurs from natural deposits of fibrous minerals found in specific geographic areas.
Over time, these deposits can become disturbed through construction of roads, commercial development or natural erosion. These factors, combined with dry conditions and high winds, send toxic asbestos fibers in the air, which become deadly if inhaled.
“The [U.S. Geological Survey] recently updated their maps of asbestos and other fibrous deposits, showing that the soil of California and other western states contain large deposits of these minerals,” Baumann said.
Other countries at high risk for environmental asbestos exposure include Mexico, Greece, Turkey, Italy, Australia, South Africa and Corsica, a French-owned Mediterranean island.
Because environmental exposure occurs naturally, it has become a primary cause for asbestos-related diseases among demographic groups normally not associated with industrial-asbestos disease.
“Studying an environmental exposure is very challenging, because people don’t know that they have been exposed, when they have been exposed, and to what they have been exposed,” Baumann said.
This makes it impossible to have a personal history of environmental exposure, Baumann explained. The rarity of mesothelioma, diagnosed in 3,000 Americans annually, also makes it difficult to separate occupational cases from environmental cases.
“For this reason, individual studies [for environmental exposure] cannot be used, contrarily to the studies of occupational diseases,” she said. “Environmental epidemiology is developing its own methods, which are often based on ecological studies, using small geographical areas as units instead of individuals.”
While Baumann was in charge of the Cancer Registry in New Caledonia, she discovered a high incidence of mesothelioma in some tribal areas. There was no use of asbestos in those areas, and men and women were equally concerned about developing the rare cancer at a very young age — as early as 30 years old.
“These people were exposed to carcinogenic mineral fibers that were present in their environment,” Baumann said. “I discovered that rocks called serpentinite were present in these areas, and that they were used to cover nonpaved roads.”
Asbestos comes in six naturally occurring fibrous minerals: Chrysotile, amosite, crocidolite, tremolite, anthophyllite and actinolite.
But the fibrous mineral Baumann found in New Caledonia was antigorite, which is not among the six regulated asbestos minerals. Antigorite is among the three most common serpentine minerals, along with lizardite and chrysotile, which comprises 90 percent of the asbestos used commercially in the world.
“With this study, I showed that mineral fibers, other than the six known asbestos, could be carcinogenic, and that a high percentage of women and young people among mesothelioma cases could be an indicator of environmental exposure.”
Despite predictions of a decline in malignant mesothelioma because of a decrease in occupational exposures, Baumann’s study shows environmental asbestos exposure is causing the gender gap to shrink significantly.
Because environmental epidemiology has to focus on geographic areas instead of individuals, Baumann analyzed all mesothelioma deaths reported to the Centers for Disease Control and Prevention during 1999 to 2010.
Men born in the 1920s significantly outweighed the reported deaths and younger deaths declined with time, suggesting a decline in occupational exposure. But the incidence and mortality rates among women increased over time, suggesting an increase proportion of environmental cases.
Among occupational asbestos exposure, the mesothelioma sex ratio is generally 4-8 male cases for every one female case. For environmental exposure, it’s a 2-1 ratio. When both types of exposure exist in a certain area, the male to female ratio is less than 4-1.
Additionally, the median age of diagnostic for occupational exposure is generally higher compared to environmental exposure.
The study follows a 2015 report from Baumann and researchers at the University of Hawaii Cancer Center that linked environmental asbestos exposure to a growing number of mesothelioma cases among women and younger residents of southern Nevada counties, including Las Vegas.
Baumann examined the distribution of mesothelioma by sex and by age group in the counties by analyzing governmental statistics, as well as soil, rock and air samples.
“I discovered that, in southern Nevada, the percentage of female and young people among mesothelioma cases was significantly elevated, compared to other Nevada regions and to the U.S., in general,” Baumann said. “This indicated the presence of environmental exposure to carcinogenic fibers.”
In the findings, southern Nevada residents under 55 accounted for nearly double the percentage of mesothelioma deaths in that age group compared to the national average. The male to female ratio was significantly closer in the region compared to the rest of Nevada and the U.S.
This news was particularly alarming for residents of Las Vegas, a worldwide resort destination reliant on tourism.
Although the two papers raised awareness about environmental asbestos exposure among public health authorities and residents of Nevada, Baumann noted there is still a lot to learn, along with some limitations.
“Some studies funded by the asbestos industry still continue to try to minimize the risk due to fibers exposure, and to spread doubts among the people,” she said.
Baumann said the first step to remediate the problem of environmental exposure is to carry out other studies combining epidemiological, geological and environmental data in all regions where the soil might contain fibrous minerals, in order to highlight the areas and populations most at risk.
“We just need funds for that,” she said. “Then we need to communicate with local authorities and with the population in order to teach which materials may be dangerous, and how contaminated soils may be remediated.”