Thursday, March 3, 2016

I Say There, Old Chap

A final study on weapons workers and nuclear power workers comes from England's National Radiological Protection Board. The study, involving 95,100 workers over 3,237,378 person-years was conducted by G.M. Kendall, et. al. and caused a recent stir in the United States. [Kendall, G.M., et al. Mortality and occupational exposure to radiation: first analysis of the National Registry for Radiation Workers. British Medical Journal, 304, 220, 1992.]

T.D. Luckey has taken exception to the manner in which the data was presented, in particular that it dramatically increased the apparent cancer risk by not differentiating between the doses received by certain workers. The English authors have objected to Luckey's objection and are apparently unwilling to undertake any revision that would jeopardize their conclusion. [Not only are they uninterested in considering a revision, they don't want Luckey doing so either and have refused to supply specific age information, as it might identify particular workers. (Interestingly, in the report, fewer than 2% of the workers requested anonymity.)]

What conclusion is that?

"There is evidence for an association between radiation exposure and mortality from cancer, in particular leukemia (excluding chronic lymphatic leukemia) and multiple myeloma, although mortality from these diseases in the study population was below that in the general population." [Emphasis added.]

So, considering the data presented in Figure 20, how can the report claim a positive correlation between radiation and cancer? You guessed it: "There is strong evidence of a healthy worker effect." Why? Because, according to the report, "Mortality is lower in radiation workers than in the general population of England and Wales - overall and for most specific causes, including cancer."

Caption and source for Figure 20 Mortality Among British Nuclear Workers: The "lagged analysis excludes the first two years (leukemia) or first ten years (other cancers) after the start of radiation work. Source: Kendall, G.M., Muirhead, C.R., MacGibbon, B.H., O'Hagan, J.A., Conquest, A.J., Goodill, A.A., Butland, B.K., Fell, T.P., Jackson, D.A., Webb, M.A., Haylock, R.G.E., Thomas, J.M., and Silk, T.J. Mortality and occupational exposure to radiation: first analysis of the National Registry for Radiation Workers. British Medical Journal, 304, 220, 1992.

One might suggest there is a case of circular reasoning here: There is evidence of healthy worker effect since the workers are healthier. As in the study by Dr. Gilbert, no controls of unexposed co-workers were used; nor was any consideration given to the possibility of hormesis.

The LNT dies hard.

For those who have, or may contemplate, working around radioactive materials, you might be pleased to read the following:

There was a 66% decrease in the death rate from infection and parasitic disease in exposed workers at the Savannah River Plant when compared with unexposed controls within the same area. [Cragle, D.L. et al. Mortality among workers in a nuclear fuel products facility. American Journal of Industrial Medicine, 14, 397, 1988.]

Los Alamos workers exposed to greater than 1 mGy (100 mrem) were compared with the U.S. population. The exposed group had only 58% as much total cancer mortality as controls, although brain cancer mortality exceeded controls by 17%. Other cancer categories were: lymphopoietic, 56%; respiratory, 57%; digestive, 67%; leukemia, 75%; no thyroid or bone cancer mortality was found in exposed persons. [Acquavella, J.F., et al. A melanoma case-control study at the Los Alamos National Laboratory, Health Physics, 45, 587, 1988.]

"The total number of deaths experienced by Union Carbide employees in the three Oak Ridge atomic energy facilities over the past 16 years, 1950 through 1965, was compared with the deaths which would be expected or predicted by applying U.S. Bureau of Vital Statistics (BVS) mortality rates to the employee population over this period of time. There were 692 deaths among the plant population over this period, which involved over 200,000 man-years of employment. Based upon the BVS mortality rates, one would have predicted 992 deaths. It is therefore concluded that these employees are experiencing a signficantly lower death rate than the average of the white population [the employees were predominately white] throughout the United States." [Larson et al. Comparison of Union Carbide employees in Oak Ridge atomic energy facilities with U.S. Bureau of Vital Statistics Mortality, UCC Report K-A-708, issued June 9, 1966.]

"Up-to-date cancer incidence data for those cohorts [weapons plant workers] are reviewed and continue to show rates below those expected in the general population. This, in a population of workers exposed during their occupations over many years to radiation doses that would be considered unacceptable today, and studied as a 'bellwether' for predicting risk to current workers, there is evidence at a cellular level of their having received that exposure, but as yet no evidence of unpredicted harm." [Emphasis added.] [Berry, R.J., et al. Biological markers, morbidity, and mortality in a long-serving radiation worker population. American Nuclear Society Transactions, November 1994.]

Mortality studies of plutonium workers at Rocky Flats [Colorado] involving 7,112 workers from 1952 to 1979 gave cancer deaths at 64% of the expected number in the general population. [Nuclear News, December 1981, pp. 135-38.]

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I would hate to be a regulator these days and to be required to continually come up with excuses as to why the data are wrong, and why my opinion is right. But then, perhaps things would look differently if my prestige and paycheck were on the line.