[ RadSafe ] Can anyone help with this mystery?

[Bernard Cohen]

I took the standard deviation to be the sqare root of the number of 
cancer deaths, and confidence intervals to be +/- 2 standard deviations


John Jacobus wrote:

>Dr. Cohen,
>What do you mean by "as I crudely calculated from the
>data they presented?"
>
>--- Bernard Cohen <blc+ at pitt.edu> wrote:
>
>  
>
>> A paper by W.N. Sont et al in Am. J. Epidemiol.
>>154:309-318:2001 on 
>>radiation monitored Canadian workers in industrial,
>>medical, dental, and 
>>nuclear power jobs gives the following percentages
>>of people dying from 
>>cancer vs lifetime accumulated radiation dose (as I
>>crudely calculate 
>>from the data they present):
>>
>>          Dose        % who died      95% confid.   
>>         
>>
>>          in rem      from cancer      interval     
>>
>>            0.25             1.8%             1.8 -
>>1.8       
>>
>>             0.75            2.3%             1.9 -
>>2.7      
>>
>>             1.5              2.8%             2.4 -
>>3.2        
>>
>>             3.5              2.5%             2.1 -
>>2.9        
>>
>>              7.5             3.9%             3.2 -
>>4.6        
>>
>>              15              3.8%             2.9 -
>>4.7        
>>
>>              30              4.8%             3.3 -
>>6.3        
>>
>>            >40              6.8%             3.4 -
>>4.2        
>>
>>          On the face of it, these data give very
>>strong evidence in 
>>favor of a linear-no threshold dose response
>>relationship extending well 
>>below 1.0 rem.
>>
>>          However, by the time a person dies, he
>>receives a dose 
>>averaging about 20 rem from non-occupational
>>exposure, and these 
>>exposures vary widely, typically between about 10
>>rem and 30 rem, in a 
>>manner not correlated with occupational exposures.
>>Roughly speaking, 
>>that means that the numbers for dose in the first
>>column above should be 
>>increased by about 20 rem and assigned an
>>uncertaincy of about 10 rem.
>>
>>          Crudely, this converts the above table to:
>>
>>         
>>
>>          Dose        % who died      95% confid.   
>>         
>>
>>          in rem      from cancer      interval     
>>
>> 
>>
>>     10.25-30.25      1.8%             1.8 - 1.8    
>>
>>                                                    
>>              
>>10.75     -30.75      2.3%             1.9 - 2.7    
>> 
>>
>>      11.5-31.5         2.8%             2.4 - 3.2  
>>     
>>
>>      13.5-33.5         2.5%             2.1 - 2.9  
>>     
>>
>>      17.5-37.5         3.9%             3.2 - 4.6  
>>     
>>
>>         25-45             3.8%             2.9 -
>>4.7        
>>
>>          40-60            4.8%             3.3 -
>>6.3        
>>
>>            >50              6.8%             3.4 -
>>4.2            
>>
>> 
>>
>>          No one could claim that this table gives
>>any info on low level 
>>radiation in the dose range below 20 rem. But this
>>raises another 
>>question: why was the first table so deceiving?
>>
>>            Can anyone offer an explanation for
>>this?
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>>    
>>
>
>
>+++++++++++++++++++
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>
>-- John
>John Jacobus, MS
>Certified Health Physicist
>e-mail:  crispy_bird at yahoo.com
>
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