AW: [ RadSafe ] query

Rainer.Facius at Rainer.Facius at
Fri Jan 11 03:54:37 CST 2008




Relative risk is a ratio (the risk of cancer for a given radiation dose, divided by the background risk)

Another way of expressing risk is excess relative risk. This is figured by subtracting 1 (that is, the background risk) from the relative risk.



R(D) = R(0) [ 1 + k D ]

RR(D) (relative risk) =: R(D)/R(0)

ERR(D) (excess relative risk) =: RR(D) - 1

ERR(D)= RR(D) -1 = R(D)/R(0) - 1 = k*D;  q.e.d.

"But this is hard to believe"

Mathematics (fortunately) is the one exception in science, where belief is irrelevant - once the definitions are set.


Check your paper whether the definitions pertain.


Best regards, Rainer


Von: radsafe-bounces at im Auftrag von Bernard L. Cohen
Gesendet: Do 10.01.2008 18:59
An: RadiatSafety
Betreff: [ RadSafe ] query

Can someone help me on this question -- please reply to  blc at
    If rhe risk of cancer, R, is expressed as
                            R = R(0) [ 1 + k D ]
where R(0) is the risk with no exposure, D is the dose in Sv, and k is a
constant, what is the excess relative risk, ERR. I thought it would be
ERR = k. In that case, a finding that ERR = 1.0 / Sv would mean that the
risk is 2R(0) for an exposure of 1.0 Sv,         3 R(0) for an exposure
of  2.0 Sv,  4R(0) for a dose of  3.0 Sv, etc. But this is hard to
believe in a paper I am trying to understand. Any help on this would be

Bernard L. Cohen
Physics Dept., University of Pittsburgh
Pittsburgh, PA 15260
Tel: (412)624-9245  Fax: (412)624-9163
e-mail: blc at  web site:

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