People who have been exposed to asbestos remain at risk of developing mesothelioma for the rest of their lives no matter how long they live, according to a new study published in the British medical journal Thorax.
The study examined eight patient groups from Italy and Australia, including both occupational and secondhand exposure, and found that the toxicity of asbestos within the body does not decrease or decline. No amount of asbestos exposure is considered safe.
The risk of malignant mesothelioma (MM) increases proportionally to the cumulative exposure to asbestos. But little is known about the risk of MM after more than 40 years since first exposure because most epidemiological studies have not had follow-up for sufficient periods of time.
The researchers pooled the data from six cohort studies of exposed workers and two cohorts with residential exposure. Conditional logistic regression modelled the relationship between time since first exposure and risk of MM.
The combined data consisted of 22,048 people with asbestos exposure, 707 cases of pleural MM and 155 cases of peritoneal MM. Median time following first exposure for pleural MM cases was 38.4 years. The rate and risk of pleural MM increased until 45 years following first exposure, and then appeared to increase at a slower power of time since first exposure.
Exposure to asbestos confers a long-term risk of developing pleural and peritoneal mesothelioma which increases following cessation of exposure, the scientists wrote. While the rate of increase appears to start to level out after 40 to 50 years, no one survives long enough for the excess risk to disappear.
The study’s lead author is Alison Reid, Associate Professor at the School of Public Health at Curtin University in Western Australia.
The report is “Mesothelioma Risk After 40 Years, Since First Exposure to Asbestos: A Pooled Analysis” can be found here.