In the medical and scientific literature, a finding of asbestosis is clear evidence that asbestos at least contributed to cause a person’s lung cancer. Many medical experts regard a finding of asbestosis as essential to any finding that asbestos caused any lung cancer. Other experts look for sufficient exposure to cause asbestosis, even if not evident from radiology or pathology. Still others take a position contrary to both views.
Too little attention has been paid to controlling for the increased risk of lung cancer from cigarette smoking. Without appropriate controls for all aspects of cigarette smoking which affect the risk of lung cancer, the increased risk apparently from asbestos exposure is actually an increased risk from cigarette smoking. The factors affecting the risk of lung cancer from smoking, the methodology of the studies relied, on and which of these factors have not been taken into account are key questions for expert witnesses in asbestos cases.
Factors That Influence Smoking Habits
Any study attempting to determine risk of lung cancer attributable to asbestos exposure versus smoking must control appropriately for smoking-related factors that increase the risk of lung cancer: gender; age; occupation; education; and duration of smoking. Failure to do so overstates the effect of asbestos exposure.
The gender differences in smoking habits between men and women are well established. Greater percentages of men smoke more frequently and more heavily than women. Blue-collar occupations are male-dominated. Calculation of lung cancer risk by comparing blue-collar workers to the general population without adjustment for gender will lead to erroneous findings of an excess risk of lung cancer that are actually due to the greater smoking habits of males.
Age is also associated with cigarette smoking habits. The likelihood that someone will ever have smoked increases with age. The likelihood that someone is a current smoker also increases with age until the 55-64 age range.
Doubling the amount of smoking doubles the risk of lung cancer. The lifetime risk of lung cancer among moderate smokers is approximately 10 percent while the risk among heavy smokers is 20 percent. Any study of smoking by blue collar employees using the general population as a control group ignores the fact that blue-collar workers smoke more heavily, begin smoking at a younger age, and are less likely to quit. Certain blue-collar occupations, particularly construction workers, are more likely to be smokers.
Education is also strongly associated with smoking habits, and must be considered in comparing smoking habits of a control group to subjects under study. Persons with only some high school education are 4.2 times more likely to be current smokers, 2.6 times more likely to be ever smokers, 1.6 times more likely to be heavy smokers and 0.3 times less likely to cease smoking than those with 16 or more years of education (essentially an undergraduate college degree).
Duration of smoking
The risk of lung cancer is much more influenced by the duration of smoking than by the number of cigarettes smoked per day. The risk of lung cancer increases by the fourth to fifth power from the duration of smoking, but only by the second power from the number of cigarettes smoked per day.
Studies of Lung Cancer Without Asbestosis
Numerous studies have attempted to show that asbestos-related lung cancer will occur without asbestosis, or without sufficient exposure to cause asbestosis. These studies suffer from methodology defects, particularly concerning the confounding effects of smoking versus asbestos on the risk of lung cancer described above, and are therefore unreliable.
In deposing experts, counsel should explore the studies relied on to support a causation opinion. Those studies should be challenged regarding control for cigarette smoking and any other problem with methodology, and the expert should be questioned in detail about the problems with the studies relied upon. The deposition testimony can then be effectively used to exclude the causation opinion.