In Italy, mesothelioma cases spike even as asbestos use hits zeroBanning asbestos use is a first step toward reducing the prevalence of malignant pleural mesothelioma (MPM), but it isn't the only one. That's because, once the fiber has been made illegal, cases of the disease tend to increase for the next few decades before gradually tapering off.
This effect is caused by mesothelioma's long latency period - or the time between initial asbestos exposure and diagnosis of the condition. For a good illustration of the phenomenon, scientists have looked to Italy, a nation that banned asbestos use in 1992.
Comparing expectations to reality
Italian researchers are quite aware of these circumstances themselves. In a study recently conducted at the Sapienza University of Rome, a team of biostatisticians derived the standardized mortality rate (SMR) associated with mesothelioma from data collected in 11 Italian regions between 1974 and 2006.
The SMR is a simple ratio that compares the expected number of deaths caused by a disease (in this case, MPM) to the actual number of deaths attributed to the illness.
So, say American scientists expect to tally 3,000 new mesothelioma cases this year in the U.S. (and they do, according to the American Cancer Society). If, when they add up the total number, they get 3,000, then the SMR is 3,000/3,000, or 1. If they were to note 6,000 cases, the SMR = 6,000/3,000 = 2.
Clearly, double the expected number of MPM cases would be a terrifying increase. Yet, that is just what's happening in Italy, where some regions have seen up to a sixfold increase in mesothelioma's incidence.
Standard mortality ratios go up, and up, and up...
The new study, which appeared in the journal International Archives of Occupational and Environmental Health, analyzed information collected in all 20 Italian regions. Unlike the U.S., which has no formal mesothelioma registry, Italy keeps track of the disease via the Italian National Agency for New Technologies, Energy and the Environment (ENEA), an agency that tabulates data noted in death certificates provided district by district to the National Institute of Statistics.
In all, over the 32-year study period, the team found that 11 of 20 Italian regions had SMRs higher than 1 - which is a very bad sign.
Even though Italy banned asbestos in 1992, the rate of mesothelioma has risen considerably, thanks to the decades-long lag time between exposure to asbestos and MPM diagnosis.
The areas hit the hardest are found in Northern Italy, where regions like Piedmont and Friuli-Venezia Giulia had a mesothelioma SMR of about 3, and Liguria - a coastal region that specializes in shipbuilding - had an SMR of 6!
Scientists say it may be two or three more decades before these numbers finally subside.
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