Combining relative risks:additive or multiplicative e.g lung cancer and RRSmoking 25 pack years and asbestos occupational exposure 40 years
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- Answered 1 Oct 2019 Conflict of interest declaration: None In 2011 the UK’s Health and Safety Executive published “The joint effect of asbestos exposure and smoking on the risk of lung cancer mortality for asbestos workers (1971-2005)” . This is available as full-text via the link below. However, in the executive summary they report: “The interaction between asbestos exposure and smoking for asbestos workers was greater than additive, and the hypothesis that asbestos produces an effect proportional to the effect of smoking (multiplicative) could not be rejected. For those asbestos workers who smoked, an estimated 3% of lung cancer deaths were attributable to asbestos only, 66% to smoking only, and 28% to the interaction of asbestos and smoking.” See section 4.6 on page 39 for further details. The US National Cancer Institute says roughly the same : “Many studies have shown that the combination of smoking and asbestos exposure is particularly hazardous. Smokers who are also exposed to asbestos have a risk of developing lung cancer that is greater than the individual risks from asbestos and smoking added together…” References 1) http://www.hse.gov.uk/research/rrpdf/rr833.pdf 2) https://www.cancer.gov/about-cancer/causes-prevention/risk/substances/asbestos/asbestos-fact-sheet#how-does-smoking-affect-risk