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Mesothelioma Risk and the Timing of Asbestos Exposure

The timing of a person’s exposure to asbestos may play a bigger role in the development of malignant pleural mesothelioma than previously thought.

A new French study has found that asbestos exposure earlier in a worker’s career appeared to raise their risk of developing pleural mesothelioma more than asbestos exposure later in their work life.

Exposure Timing and Mesothelioma Risk

The study evaluated the cases of 1,196 male workers who were exposed to asbestos on the job between 1987 and 2006. These cases were matched with 2,369 men of their same age who had not been exposed.

The researchers used an asbestos exposure matrix organized by job to calculate the amount of asbestos exposure and the timing of each man’s exposure over the length of their careers and compare it to their mesothelioma risk.

Their conclusion? While all asbestos exposure is dangerous, asbestos exposure early on is potentially even more detrimental, in terms of mesothelioma risk, than later exposure. Even after asbestos exposure declines, the mesothelioma risk posed by that early exposure lingers.

Writing in the journal Occupational and Environmental Medicine, lead investigator Aude Lacourt of the University of Bordeaux explains it this way:

“Due to much stronger weights of early doses of asbestos exposure, subjects who accumulated 20 fibres/mL over the entire job history with high doses during the first years and low doses thereafter were at higher risk of pleural mesothelioma than those who accumulated most of the doses later.”

Later Exposure is Better

This is not the first time that researchers have attempted to better understand the link between asbestos exposure timing and mesothelioma development. In 2012, another University of Bordeaux team led by Dr. Lacourt reached a similar conclusion.

After evaluating 1,041 male workers who had been exposed to asbestos and 1,425 who had never been exposed, Lacourt and colleagues concluded that “the risk of pleural mesothelioma was lower for subjects first exposed after the age of 20 years and continued to increase until 30 years after cessation of exposure.”

In that study, the total duration of a man’s asbestos exposure had less to do with his risk of developing malignant mesothelioma than his age at first exposure. 

The Importance of Timing

There are a number of instances of people who were exposed to mesothelioma briefly as teenagers and developed mesothelioma decades later. There are even more cases of people who worked around asbestos their whole work lives and never contracted mesothelioma.

While scientists are not entirely sure why some asbestos-exposed people get pleural mesothelioma and others do not, or why younger people are at higher risk, some speculate that people who are exposed when they are younger simply have more time to develop the disease. Mesothelioma can take 50 years or more to develop.

Certain genetic anomalies are also known to have an impact on a person’s likelihood of developing mesothelioma if they are exposed to asbestos.

Lacourt and her colleagues conclude that their latest report highlights the importance of taking the timing of asbestos exposure into account when trying to assess mesothelioma risk.


Lacourt, A, et al, “Dose-time-response association between occupational asbestos exposure and pleural mesothelioma”, May 13, 2017, Occupational and Environmental Medicine, Epub ahead of print

Lacourt, A, et al, “Temporal patterns of occupational asbestos exposure and risk of pleural mesothelioma”, June 2012, pp. 1304-1312

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