Research & Clinical Trials

Study: Time Doesn’t Affect Asbestos Toxicity

Written By:
May 30, 2014
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Written By: Tim Povtak,
May 30, 2014

The risk of developing mesothelioma cancer after exposure never leaves or subsides, regardless of how long you live, a new study shows.

The broad-based study that examined eight diverse patient groups from Italy and Australia, including both occupational and secondhand asbestos exposure, concluded the toxicity of asbestos within the body never expires.

There is no decrease or decline in risk, said lead author Alison Reid, Ph.D., Associate Professor at the School of Public Health, Curtin University in Western Australia. She and six others penned the study titled, “Mesothelioma Risk After 40 Years Since First Exposure to Asbestos: A Pooled Analysis.”

“We have always known that the risk of mesothelioma increases the longer it is since you were first exposed,” Reid told “What the study has shown is that even after 45 years, there still is risk for developing the disease.”

The typically long latency period (20-40 years) between asbestos exposure and definitive symptoms has been well chronicled in the past, but this is the first significant study detailing the indefinite risk of developing the cancer.

No One Outlives the Risk

“No one survives long enough for the excess risk to disappear,” the authors concluded in their analysis published in Thorax, one of the leading respiratory medical journals in the world. The study included 862 mesothelioma cases from more than 22,000 people who were exposed.

It’s an unsettling prospect for those who were exposed, knowing they are unlikely to outlive the risk of developing this rare cancer, which is diagnosed in an estimated 3,000 people annually in the U.S.

It helps to explain why the number of mesothelioma patients lately has remained steady each year, despite the dramatic drop in the use of asbestos materials during the last three decades. Those exposed in the ’60s and ’70s, at the height of the asbestos building boom in America, remain very much at risk today.

The collapse of the World Trade Center in the 2001 terrorist attack released an estimated 2,000 tons of pulverized asbestos in the air. Thousands of people in New York City who survived 9/11, despite that thick cloud of asbestos dust that engulfed them on that day, must live with the fact that their long-term risk for mesothelioma will never disappear.

No amount of asbestos exposure is considered safe.

Mesothelioma starts with the inhalation or ingestion of microscopic asbestos fibers, which can become lodged in the thin protective lining that covers the lungs, abdomen and heart. Those fibers can inflame or irritate the mesothelial cells within the lining, starting a slow chain reaction of metabolic and physical changes that can eventually lead to mesothelioma.

Proof Is in the Numbers

The study found that 44 percent of the pleural mesothelioma cases and 54 percent of the peritoneal mesothelioma cases were diagnosed at least 40 years after a first exposure.

There was a stunning 13.3 percent and 23.2 percent of pleural and peritoneal cases, respectively, found after 50 years. The median time from first exposure to diagnosis was 38.4 years for pleural.

“The rate and risk of pleural mesothelioma increased until 45 years following first exposure and then appeared to increase at a slower power of time since first exposure,” the authors wrote in the report. The rate of peritoneal over the 10-50 years since first exposure continued to increase.

One of the original goals of the study was to determine if the risk of developing mesothelioma decreased after 40 years from first exposure. The answer was a resounding no.

“For peritoneal mesothelioma, we didn’t find any such slowing down,” Reid said. “Instead, the risk continued to increase.”

Participants from the study came from six previous occupational group studies, one from a general environmental exposure study, and one from a study of stay-at-home, nonworking wives where were exposed through spouses who worked with asbestos.

The source of asbestos exposure included an amosite factory, an asbestos cement factory, an asbestos mine and an asbestos mill, along with environmental and railway stock exposure. The types of asbestos they were exposed to included crocidolite, amosite and chrysotile.

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