Re: Fw: Glass-Based Radon Measurements

[hflong@postoffice.pacbell.net]

Kai and Radsafers,

I, too, have trouble understanding the permutations of case control studies and

radon variability, glass -based measures, etc.



Looking at the larger picture helps me fit them into the puzzle. In Iowa

(Field), the lesser radon (c4ppCi/L) of controls  than cases of lung cancer

(c5pCi/L) in that 1% highest USA radon location, fits the larger picture of a

"U" curve. The usual USA radon doses (Cohen) are much lower (mean 1.3pCi/L). The

less the radon, the higher lung cancer mortality rates (with or without

smoking).



Both Field and Cohen could be correct about the effect of radon on lung cancer -

Field that, generally, less radon in homes would be better in Iowa and Cohen

that, generally, more radon in homes would be better for 90% of the USA.



Howard Long



Kai Kaletsch wrote:



> Friends,

>

> As a result of my request, a radsafer has sent me a copy of the Lagarde et

> al. paper. I still seem to have a problem wrapping my head around this

> case - control stuff. I would very much appreciate it if someone could take

> the time to help me out (if you want to see the paper, you can get to a pdf

> version from

> http://www.nature.com/jea/journal/v12/n5/index.html ):

>

> According to the first row of Table 4 of the Lagarde et al. paper there are

> 33 cases and 58 controls in the 50 to 80 Bq/m3 category ( i.e. 1.76 controls

> per case) and 24 cases and 55 controls in the 80 to 140 Bq/m3 category (

> i.e. 2.29 controls per case). Relatively speaking, there are 30 % more

> healthy people (controls) in the higher dose category than in the lower dose

> category. Yet, the authors calculate a higher relative risk for the 80 to

> 140 Bq/m3 category than in the 50 to 80 Bq/m3 category (1.42 vs. 1.28).

>

> To me, that doesn't make any sense. If you asked me if I wanted to belong to

> a group that is full of sick people or to a group that is full of healthy

> people, I would answer: "I want to belong to the group that has lots of

> healthy people, because that means my risk of becoming sick is lower."

>

> Could someone please try to explain this in common sense terms?

>

> Thanks in advance,

> Kai

>

> ----- Original Message -----

> From: "Kai Kaletsch" <info@eic.nu>

> To: <epirad@mchsi.com>; <radsafe@list.vanderbilt.edu>

> Sent: Saturday, August 31, 2002 9:42 AM

> Subject: Re: Glass-Based Radon Measurements

>

> > Bill and Friends,

> >

> > I'm still trying to wrap my head around what the actual observables are in

> a

> > case - control study. The way I understand it, case - control studies work

> > like this:

> >

> > 1.    Find people with a disease (cases).

> > 2.    Match people to the cases that are similar (controls).

> > 3.    See if there is a difference in exposure to a suspected causal

> agent.

> > 4.    If there is a difference in exposure, you calculate an excess

> relative

> > risk (ERR) per unit exposure.

> >

> > The only observables are related to step 3, i.e. differences in exposure.

> >

> > My question is: Is there any way that we can infer the observables

> > (differences in exposure) from the reported calculated results? (I don't

> > have ready access to J Expo Anal Environ Epidemiol 2002 Sep;12(5):344-54)

> >

> > For example, could the statement:

> >

> > "...the excess relative risk (ERR) of 75% (-4% to 430%) per 100 Bq m(-3)

> > obtained when using a continuous variable for surface-based average radon

> > concentration estimates, were about twice the size of the corresponding

> > relative risks obtained among these subjects when using air-based average

> > radon concentration estimates."

> >

> > mean:

> >

> > "surface-based average radon concentration estimates showed only 1/2 as

> much

> > excess radon concentration of cases vs. controls than using air-based

> > average radon concentration estimates."?

> >

> > In physics, the authors of studies usually put their raw data somewhere so

> > that anyone can download it, re-analyze it, check for errors in arithmetic

> > etc etc. Is this not usual in epidemiology? (Obviously one would have to

> > hide the personal info of the participants, but that shouldn't be a

> > problem.)

> >

> > To me, this would add more credibility to the studies. If the same people

> > are designing the study and collecting the data and analyzing the data and

> > writing conclusions about the data, would that not tend to amplify any

> > biases these people might subconsciously have by a factor of 4?

> >

> > Best Regards,

> > Kai

> >

> > ----- Original Message -----

> > From: <epirad@mchsi.com>

> > To: <radsafe@list.vanderbilt.edu>

> > Sent: Thursday, August 29, 2002 3:14 PM

> > Subject: Glass-Based Radon Measurements

> >

> >

> > > Two recent papers that may be of interest.

> > >

> > > Regards, Bill Field

> > > bill-field@uiowa.edu

> > >

> > > J Expo Anal Environ Epidemiol 2002 Sep;12(5):344-54

> > >

> > > Glass-based radon-exposure assessment and lung cancer

> > > risk.

> > >

> > > Lagarde F, Falk R, Almren K, Nyberg F, Svensson H,

> > > Pershagen G.

> > >

> > > Institute of Environmental Medicine, Karolinska

> > > Institutet, Stockholm, Sweden.

> > >

> > > Lung cancer risk estimation in relation to residential

> > > radon exposure remains uncertain, partly as a result of

> > > imprecision in air-based retrospective radon-exposure

> > > assessment in epidemiological studies. A recently

> > > developed methodology provides estimates for past radon

> > > concentrations and involves measurement of the surface

> > > activity of a glass object that has been in a subject's

> > > dwellings through the period for exposure assessment.

> > > Such glass measurements were performed for 110 lung

> > > cancer subjects, diagnosed 1985 to 1995, and for 231

> > > control subjects, recruited in a case-control study of

> > > residential radon and lung cancer among never-smokers in

> > > Sweden. The relative risks (with 95% confidence

> > > intervals) of lung cancer in relation to categories of

> > > surface-based average domestic radon concentration

> > > during three decades, delimited by cutpoints at 50, 80,

> > > and 140 Bq m(-3), were 1.60 (0.8 to 3.4), 1.96 (0.9 to

> > > 4.2), and 2.20 (0.9 to 5.6), respectively, with average

> > > radon concentrations below 50 Bq m(-3) used as reference

> > > category, and with adjustment for other risk factors.

> > > These relative risks, and the excess relative risk (ERR)

> > > of 75% (-4% to 430%) per 100 Bq m(-3) obtained when

> > > using a continuous variable for surface-based average

> > > radon concentration estimates, were about twice the size

> > > of the corresponding relative risks obtained among these

> > > subjects when using air-based average radon

> > > concentration estimates. This suggests that surface-

> > > based estimates may provide a more relevant exposure

> > > proxy than air-based estimates for relating past radon

> > > exposure to lung cancer risk.

> > > --------------------------------------------

> > >

> > >

> > > Health Phys 2002 Aug;83(2):261-71

> > >

> > >

> > > 210Po implanted in glass surfaces by long term exposure

> > > to indoor radon.

> > >

> > > Steck DJ, Alavanja MC, Field RW, Parkhurst MA, Bates DJ,

> > > Mahaffey JA.

> > >

> > > Physics Department, St. John's University, Collegeville,

> > > MN 56321, USA. dsteck@csbsju.edu

> > >

> > > Recent epidemiologic investigations of the relationship

> > > between residential radon gas exposure and lung cancer

> > > relied on contemporary radon gas measurements to

> > > estimate past radon gas exposures. Significant

> > > uncertainties in these exposure estimates can arise from

> > > year-to-year variation of indoor radon concentrations

> > > and subject mobility. Surface implanted 210Po has shown

> > > potential for improving retrospective radon gas exposure

> > > estimates. However, in previous studies, the ability of

> > > implanted 210Po activity to reconstruct cumulative radon

> > > gas exposure was not tested because glass was not

> > > available from homes with known radon-gas concentration

> > > histories. In this study, we tested the validity of the

> > > retrospective radon gas reconstruction using implanted

> > > 210Po surface activity by measuring glass surfaces from

> > > homes whose annual-average radon gas concentrations had

> > > been measured almost every year during two decades.

> > > Regression analysis showed a higher correlation between

> > > measured surface activity and cumulative radon gas

> > > exposure in these homes (R2>0.8) than was observed in

> > > homes where only contemporary radon gas measurements

> > > were available. The regression slope (0.57 ky m(-1)) was

> > > consistent with our earlier retrospective results.

> > > Surface activity measurements were as reliable for

> > > retrospective radon gas exposure reconstruction as

> > > yearlong gas measurements. Both methods produced

> > > estimates that were within 25% of the long-term average

> > > radon gas concentrations in a home. Surface measurements

> > > can be used for home screening tests because they can

> > > provide rapid, reliable estimates of past radon gas

> > > concentrations. Implanted 210Po measurements are also

> > > useful in retrospective epidemiologic studies that

> > > include participants who may have been exposed to highly

> > > variable radon concentrations in previously occupied or

> > > structurally modified homes.

> > >

>

>



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