Re: Epidemiological musings of a non-biologist

[epirad@mchsi.com]

Clayton,



The limitations of ecologic studies can be found in most basic epidemiology 

text books or at: http://www.pitt.edu/~super1/



Causal effects in Epidemiology can be established using criteria such as 

Bradford Hill, see: Bradford-Hill, A. The environment and disease: Association 

or causation? President's address. Proceedings of the Royal Society of 

Medicine 1965; 9:295-300.



http://www.bruha.com/fluoride/html/bradford-hill.html



Other interesting related papers can be found here: 

http://www.aarst.org/radon_news.shtml





> 

> Are cancers dysfunctions of an organism, an organ, a cell or a molecule?  At

> which level of analysis should the "cause(s)" of a cancer be sought?  A

> common working hypothesis is that ionizing radiation induces cancers by

> means of insults to DNA molecules.   But since everyone receiving a

> specified dose does not develop cancer, other factors not necessarily

> related to radiation  must be intervening.  It seems a lot of things have to

> go wrong, in the right order, and at several levels (cellular, tissue and

> organism) for cancers to develop.   Each of these factors could (should) be

> considered as a confounder in any study of the relationship between

> radiation dose and cancer.  

> 

> To what extent then do case-control studies really avoid the statistical

> weaknesses of ecological studies?  The later looks at average doses to

> groups instead of doses to individuals.  But what is the "dose" to an

> individual? Depending on the level of analysis chosen, the whole body dose



> is the average dose to groups of organs/tissue systems, or to groups of

> cells, etc..  But we don't really know which dose is relevant to a

> particular cancer.   We assume that dose to the thyroid or the lung is

> relevant to the corresponding cancer, but dose  to which cell types in those

> organs are important?  How is the average dose to the organ related to the

> doses to individual cells/cell types?  Doesn't't a study which focuses on

> the organ doses to individuals suffer from an "ecological fallacy" when

> viewed from the cellular level? 

> 

> It is my view that epidemiological studies will never answer the LNT

> question.  We must first have a comprehensive theory of cancer before we can

> understand the relationship between cancer and radiation.  Epidemiology has

> done all it can by establishing an association.  It is incapable of anything

> more.

> 

> Clayton J. Bradt, CHP

> Principal Radiophysicist

> NYS Dept. of Labor

> Radiological Health Unit

> voice: (518) 457-1202

> fax:    (518) 485-7406



> e-mail: usccjb@labor.state.ny.us

> 

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B

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