Sander Greenland and others have raised various theoretical objections to the argument that relative risks should exceed two before attribution can be made in specific cases. In large part, Greenland’s objections turn on conjecture that risks are not stochastically distributed in the population samples studied in epidemiologic studies. These objections are potentially true, but the burden remains on the proponent. When there is serious evidence of latency or bimodal distribution, then epidemiologic studies or clinical trials can be adapted to examine the risk in the relevant subgroup. When this is done, the relative risk argument once again is unavoidable. For many exposures and conditions of interest, epidemiologic studies have evolved to accommodate the relevant model of risk distribution.
Despite Greenland’s speculative objections, the concept of a doubling dose has been widely advocated by scientists. The following are a few of such endorsements:
Philip Enterline, “Attributability in the Face of Uncertainty,” 78 (Supp.) Chest 377, 377, 378 (1980);
Otto Wong, “Using Epidemiology to Determine Causation in Disease,” 3 Natural Resources & Env’t 20, 23 (1988); Ben Armstrong, Claude Tremblay, and Gilles Theriault, “Compensating Bladder Cancer Victims Employed in Aluminum Reduction Plants,” 30 J. Occup. Med. 771 (1988);
Joshua Muscat & Michael Huncharek, “Causation and disease: Biomedical science in toxic tort litigation,” 31 J. Occup. Med. 997 (1989);
Troyen A. Brennan, “Can Epidemiologists Give Us Some Specific Advice?” 1 Courts, Health Science & the Law 397, 398 (1991)(“This indeterminancy complicates any case in which epidemiological evidence forms the basis for causation, especially when attributable fractions are lower than 50%. In such cases, it is more probable than not that the individual has her illness as a result of unknown causes, rather than as a result of exposure to hazardous substance.”);
Mark R. Cullen & Linda Rosenstock, “Principles and Practice of Occupational and Environmental Medicine,” chap. 1, in Linda Rosenstock & Marc Cullen, eds., Textbook of Clinical Occupational and Environmental Medicine 1, 13-14 (Phila. 1994);
David F. Goldsmith & Susan G. Rose, “Establishing Causation with Epidemiology,” in Tee L. Guidotti & Susan G. Rose, eds., Science on the Witness Stand: Evaluating Scientific Evidence in Law, Adjudication, and Policy 57, 60 (OEM Press 2001)(“A relative risk greater than 2.0 produces an attributable risk (sometimes called attributable risk percent10) or an attributable fraction that exceeds 50%. An attributable risk greater than 50% also means that ‘it is more likely than not’, or, in other words, there is a greater than 50% probability that the exposure to the risk factor is associated with disease.”)
Below, I have updated once again the case law on the issue of using relative and attributable risks to satisfy plaintiff’s burden of showing, more likely than not, that an exposure or condition caused a plaintiff’s disease or injury.
See Reference Manual on Scientific Evidence on Relative Risk Greater Than Two For Specific Causation Inference (April 25, 2015), for the updated the case law on the issue of using relative and attributable risks to satisfy plaintiff’s burden of showing, more likely than not, that an exposure or condition caused a plaintiff’s disease or injury.
