The Environmental Health Perspectives journal has released a new report that analyzed mesothelioma cases worldwide. What they discovered is startling: around 20% of all mesothelioma cancer cases are not reported.

Mesothelioma is an aggressive cancer with a discouraging prognosis; once one receives a diagnosis, they will likely pass away within a year or two. Furthermore, mesothelioma cancer is a disease with an astonishing latency period. The disease usually develops decades following one’s exposure to asbestos, and is usually not able to be diagnosed until well into the advanced stages of the cancer.

The authors of this study looked extensively at data from 56 countries. This provided them with information on 174,300 deaths from mesothelioma between 1994 and 2008. Due to the typical distance in time between asbestos exposure and mesothelioma’s diagnosis, often 20 to 50 years, the authors also looked at the level of asbestos use within the 56 countries between 1920 and 1970. The resulting figures allowed the authors to conclude that a country’s use of asbestos reliably indicated and predicted the later deaths from mesothelioma cancer in that country.

There were 33 countries that used asbestos from 1920 to 1970 that did not report any cases of mesothelioma from 1994 to 2008. Using the statistical evidence that was compiled allowed the study’s authors to conclude that in those 33 countries there were a probable 38,900 mesothelioma deaths that went unreported. Ken Takahashi, from Japan’s University of Occupational and Environmental Health, says that their “most important finding is the magnitude of unreported mesothelioma in countries that used asbestos at substantial levels but report no cases of the disease.” Of the top 15 asbestos using countries, Kazakhstan, China, Russia, and India all neglected to report a single case of mesothelioma.

The best way to prevent mesothelioma is to eliminate the use of asbestos. Surprisingly, asbestos continues to be mined. According to the British Geological Survey of world mineral production, in 2006 there were 2.3 million tonnes of asbestos mined worldwide. Perhaps most surprising is Canada’s 10.3% share in this production. Other producing countries include Russia at 40.2%, China at 19.9%, Kazakhstan at 13.0%, and Brazil at 9.9%.