Lung cancer

Synergism between smoking and occupational exposures a concern

Professor Fraser Brims

Smoking isn’t the only risk factor for lung cancer, delegates to the Australian Lung Cancer Conference on the Gold Coast were reminded last week.

Respiratory physician Professor Fraser Brims, from the Sir Charles Gairdner Hospital and Curtin University, told the meeting that at least 15% of lung cancer cases were attributable to occupational exposures.

Australian data [link here] has shown that 81% of Australians are exposed to at least one carcinogen in the workplace and about 25% are exposed to more than five carcinogens such as diesel engine exhaust, silica and wood dust.

He said diesel engine exhaust for example was an IARC class 1 carcinogen for humans which was associated with a 2-3 fold increase in the risk of lung cancer. Possibly 1.2 million Australians were currently exposed, he added.

However it’s the interaction between tobacco exposure and occupational exposures that should have people worried, he said.

Professor Brims, who Chairs the Western Australian Mesothelioma Registry, said there was a concerning additive synergism between tobacco and asbestos exposure.

“Asbestos itself in the absence of tobacco increases the relative risk of lung cancer but in combination with tobacco exposure, that risk is amplified. Asbestos raises the relative risk about 2-fold and tobacco about 10-fold, but the combined risk is out to about 25 fold.”

He said data from the Asbestos Review Program found 2.3% of exposed workers and their families had lung cancer despite modest exposure to asbestos and the fact that one-third were never smokers. Two-thirds of the cohort were not miners with heavy direct exposure to blue asbestos but people like tradies in construction and manufacturing who were exposed down the line.

The data suggested as little as 3 months of asbestos exposure probably warranted lung cancer screening.

Professor Brims said there were clear messages for public health, for physicians and for a future national lung cancer screening program.

“Many occupational exposures contribute to lung cancer. All of them are avoidable and to my mind, unacceptable in this day and age.”

He told the limbic that clinicians in primary and secondary care should be alert to the potential impact of occupational exposures on lung health.

“Ask the question and think that people might be exposed to fumes, dusts and chemicals at work.”

“We’ve seen data that some workers are exposed to multiple carcinogens at work and aside from the public health messaging that it has to change, respiratory physicians need to be asking the question and considering what that means.”

He said lung cancer screening programs were only effective from a population perspective if they were targeted to those at high risk. To date, the focus had been on smoking.

Professor Brims said most lung cancer screening models do not yet account for occupational exposures despite the significant interactions with smoking.

However a UK program announced in September 2022 proposes using the Liverpool Lung Project risk score which does include a binary “yes/no” question on exposure to asbestos.

“We need to include occupational exposures in lung cancer screening but for now we just need to get a program up and running.”

He said fine-tuning the program could follow later.

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