Re: Ecological studies and population shifts

["H.Wade Patterson" <hwade@talltown.com>]

David Scherer wrote, in part:
 
> With the A-bomb survivors, we are at least sure that all the subjects were
> in fact exposed to some radiation, approximated by their distance from
> ground zero.  In the radon study there is no individual verification that
> the subjects were actually exposed to the radon levels suggested by the
> county in which they died.

Dave and others:
This being so, it's interesting to look at the data from one of the most
recent RERF reports. Please read my comments at the end of the abstract.
Pierce, D. A.; Shimizu, Y.; Preston, D. L.; Vaeth, M.; Mabuchi, K.
Studies of the mortality of atomic bomb survivors. Report 12, Part I. 
Cancer: 1950-1990. Rad. Res. 146:1-27; 1996.
Abstract: This continues the series of periodic general reports on
cancer mortality in the cohort of A-bomb survivors followed by the
Radiation Effects Research Foundation. The follow-up is extended by the
5 years 1986-1990, and analysis includes an additional 10,500 survivors
with recently estimated radiation doses. Together these extensions add
about 550,000 person-years of follow-up. The cohort analyzed consists of
86,572 subjects, of which about 60% have dose estimates of at least
0.005 Sv. During 1950-1990 there have been 3086 and 4741 cancer deaths
for the less than and greater than 0.005 Sv groups, respectively. It is
estimated that among these there have been approximately 420 excess
cancer deaths during 1950-1990, of which about 85 were due to leukemia.
For cancers other than leukemia (solid cancers), about 25% of the excess
deaths in 1950-1990 occurred during the last 5 years; for those exposed
as children this figure is nearly 50%. For leukemia only about 3% of the
excess deaths in 1950-1990 occurred in the last 5 years. Whereas most of
the excess for leukemia occurred in the first 15 years after exposure,
for solid cancers the pattern of excess risk is apparently more like a
life-long elevation of the natural age-specific cancer risk. Taking
advantage of the lengthening follow-up, increased attention is given to
clarifying temporal patterns of the excess cancer risk. Emphasis is
placed on describing these patterns in terms of absolute excess risk, as
well as relative risk. For example: (a) although it is becoming clearer
that the excess relative risk for those exposed as children has declined
over the follow-up, the excess absolute risk has increased rapidly with
time; and (b) although the excess relative risk at a given age depends
substantially on sex and age at exposure, the age-specific excess
absolute risk depends little on these factors. The primary estimates of
excess risk are now given as specific to sex and age at exposure, and
these include projections of dose-specific lifetime risks for this
cohort. The excess lifetime risk per sievert for solid cancers for those
exposed at age 30 is estimated at 0.10 and 0.14 for males and females,
respectively. Those exposed at age 50 have about one-third these risks.
Projection of lifetime risks for those exposed at age 10 is more
uncertain. Under a reasonable set of assumptions, estimates for this
group range from about 1.0-1.8 times the estimates for those exposed at
age 30. The excess life-time risk for leukemia at 1 Sv for those exposed
at either 10 or 30 years is estimated as about 0.015 and 0.008 for males
and females, respectively. Those exposed at age 50 have about two-thirds
that risk. Excess risks for solid cancer appear quite linear up to about
3 Sv, but for leukemia apparent nonlinearity in dose results in risks at
0.1 Sv estimated at about 1/20 of those for 1.0 Sv. Site-specific risk
estimates are given, but it is urged that great care be taken in
interpreting these, because most of their variation can be explained
simply by imprecision in the estimates.

Comment:
>From Table II, "Observed and Expected Deaths for Solid Cancers", the
observed deaths at and below 0.1 Sv are 5808, while the expected deaths
are 5765. The excess deaths for this dose range are then 43, or less
than 1%.
>From Table V," Observed and Expected Deaths for Leukemia", the observed
deaths at and below 0.2 Sv are 143, while the expected deaths are 137. 
The excess deaths for this dose range are then 6, or less than 5%.
No Japanese wore a dosimeter. They have simply been assigned doses,
solely on the basis of distance categories. The resulting dose
uncertainties are 30-50% within the distance categories.
Additionally, Pierce, et al have fitted their data to a risk vs.
exposure model whose origin is at zero,  and whose slope is everywhere
positive. This guarantees that all estimated risks will be positive.
Therefore, to cite this paper as supporting the LNT is circular
reasoning.
Finally, they show no evidence for risk of cancer below 0.1 Sv.
-- 
Best wishes,

Wade

<hwade@talltown.com>

H.Wade Patterson
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Lakeview OR 97630
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