Workers are losing out because of a common test of whether a condition is occupational is based on bad calculations. Sander Greenland, writing in the American Journal of Public Health, said the doubling of relative risk (RRx2) requirement, commonly used to establish whether a cancer is occupational and to determine whether compensation is payable, was “a methodologic error that has become a social problem.” He explained: “The first problem is that the probability of causation cannot be computed solely from the relative risk. In particular, when exposure accelerates the time of disease occurrence, the standard epidemiological estimates of probability of causation will tend to underestimate that probability. The second problem is that the exposure dose at which the probability of causation exceeds 50 per cent (the point at which exposure causation is more likely than not) may fall well below the ‘doubling dose’ (the dose at which the incidence of disease is doubled).”

Greenland S (1999). Relation of probability of causation to relative risk and doubling dose: a methodologic error that has become a social problem. American Journal of Public Health, volume 89(8), pages 1166-9.