Smoking causes cardiovascular disease. Occupational or product contributions to this would be possible. Indivisible and divisible outcomes are both possible. Likely claims involving smoking would be when fine dust exposure is alleged to be a cause of indivisible heart disease. More speculative would occupational causes of debilitating high blood pressure or angina; both of which are divisible.
A report of the Surgeon General (2010) ISBN 978-0-16-084078-4
How Tobacco Smoke Causes Disease: The Biology and Behavioral Basis for Smoking-Attributable Disease
Different mechanisms would fall under different legal precedents. The list includes Bonnington, McGhee, Wilsher, Badger, Bailey, Barker, Gregg v Scott, Fairchild, Hotson, Holtby, Sienkiewicz, XYZ, Novartis and the recent EL triggers case. For example, exposure to multiple mutagens would be under Wilsher if they each operated independently and under McGhee if they somehow co-operated. Chronic inflammation would be added to by any and all irritants, Bailey might be cited if the outcome is indivisible, Holtby if it is divisible.