United States Department of Health and Human Services. June 2006
“The Health Consequences of Involuntary Exposure to Tobacco Smoke: A Report of the Surgeon General.”
For heart disease and for lung cancer the independent additional risk from ETS exposure is of the order of 25%. Those who regard exposure to risk being equivalent to material contribution would probably regard this as compensable but, so far, legal precedent in the UK would tend to exclude this as a cause of action in its own right.