Originally Posted By: Caoimh?n P. Connell
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Hello folks ?
I confess that I haven?t read all of the questions posed on this board since my last posting. And I did not read a lot of the repeated material by Dr. Fields. However, let me address some of the questions I did read, and also address some of the off-line issues that have been raised. (Please, post your questions to me here, as I don?t always get around to answering direct emails on the subject.)
For a start, Brian Kelly, your question is a good one, and Dr. Field?s response helps to underpin my position that he hasn?t quite got an handle on the technical aspects of the issue. For example, Dr. Fields opines that
?Risks are all relative. What one person considers safe another person may not.? In making this statement, Dr. Fields begins to indicate his unfamiliarity with the terms of the business ? in that his answer confuses ?risk? and ?safety.? It simply is not true that all risks are relative, and in many cases we have absolute risk, and indeed we can quantify those risks as absolute. However, what we cannot quantify is ?safety? since the issue of
safety is perceptual and subjective, and frequently even irrational. It is partially because of statements like this that I realize that Dr. Field is, well, out of his field. Dr. Fields answers your question by saying
?So to answer your question, even very low radon exposures HAVE THE POTENTIAL to cause cancer.? But he does not go on to clarify that that potential may be so low as to be non-existent from a practical perspective. In other words, it is equally true to say that
Eating a single peanut (exposure to a single peanut) HAS THE POTENTIAL to cause cancer. However, without the benefit of placing that statement within the context of the actual risk ? what kind of a conclusion will you draw? Answer: Peanuts are dangerous at all levels. But are they?
Dr. Fields also brings up the recent North American and European Pooling of Residential Radon Studies paper (in fact he brings up the reference more than once). Now, to be honest, Dr. Fields is a minor author (listed sixth on the list) of that study, and so I won?t state that he has a vested interest in it. But frankly, I have to conclude that either Dr. Fields did not read the study, or lacks the technical ability to understand what the study found. I say this because in a nut-shell, ?his? study provides far more support for my argument that his!
Let?s see what ?his? study says ? For a start, he states that the study DIRECTLY examines the relationship between residential radon exposure and lung cancer. This statement is ABSOLUTELY not correct. The study in question is called a ?metaanalysis? study which is an analysis of an analysis or an analysis ? etc. In such a study, the errors associated with the foundational study used in the analysis are often ignored, and frequently compounded (and the probability of systematic errors increases).
So let?s see what ?his? study says, and why it supports my argument, not his: (by the way, as a risk modeler myself, I am not casting stones at the actual authors, rather, I am casting stones at the inappropriate interpretations of the study by Dr, Fields). The Pooled Study states:
To date, 20 case? control studies of residential radon and lung cancer have been completed, including 7 studies in North America, 11 in Europe, and 2 in China (Table 1). Some of these studies reported a positive or weakly positive association between lung cancer risk and residential radon concentrations, whereas others have reported results consistent with no association.
OK? in layman?s terms this statement acknowledges that not all studies have shown that exposure to radon, at concentrations associated with household exposures, produces a risk of cancer ? indeed some studies show
no increased risk of cancer.
The study then contains a terrible logic gaffaw which I am rather surprised to see survive the peer review process:
?To date, no case? control study has reported a statistically significant negative association.?
The lack of a negative correlation study, cannot ever, ever, EVER be used as support for an argument of causation or hypotheses test (even a null hypothesis test) since, in an argument known as
reductio ad absurdem , it requires one to prove a negative; which is impossible. It is rather like saying ?
To date, no case? control study has reported a statistically significant negative association between looking at a blue chair, and developing glaucoma. Ergo, we have found evidence that looking at blue chairs can cause glaucoma.? Essentially what we have is a terrible editing problem in an otherwise interesting (but largely uninformative) paper.
Dr.Fields own study makes it very clear that:
Although excess odds ratios for all but 2 studies (West Germany and Shenyang, China) were positive, confidence limits included the null value of zero in all but 4 studies...
(Layman?s terms: The studies failed to show evidence that radon exposure results in significant cancer risk!) and continues with?
These results reflect a range of lung cancer risks, including the possibility of no risk , suggesting the need for an overall assessment of the findings from different studies.
This IS
EXACTLY what I have been saying ? and which Dr. Fields argues against. If it was wrong, why then did he not object to the inclusion of the statement in a paper that bears his name? (I have the answer in my back pocket, and it will remain there, in deference to professional courtesy toward Dr. Fields, who may choose explain for himself, or not). I don?t care to go there.
Further, this recent study, that is held up as a banner by Dr. Fields, which openly tells us that 1) a lot of studies show that radon doesn?t cause a problem as concentrations seen in houses, and those that do only show a ?weak? correlation, the study starts right off by telling us that:
Underground miners exposed to high levels of radon have an excess risk of lung cancer. Residential exposure to radon is at much lower levels, and the risk of lung cancer with residential exposure is less clear.
No kidding. This is what I have been saying ? quite in contrast to the definitive nature of Fields? statements here on this thread which are entirely devoid of doubt and uncertainty. The reality is that Fields? own study makes it clear that we don?t have sufficient evidence to conclude that radon exposure at concentrations seen in houses results in a significant risk.
Fields study makes a statement that is DIRECTLY in opposition to his comments here on this board. Fields has stated in this thread that
?Additional studies are now complete DIRECTLY examining the relationship between residential radon exposure and lung cancer.?
This is absolutely NOT true, and in fact, in Fields? own study, the authors very clearly and unequivocally state EXACTLY the opposite:
The National Research Council has estimated that residential radon may account for 10% to 15% of the lung cancer burden in the United States. However, there has been no unambiguous direct evidence of an increased lung cancer risk associated with residential exposures.
That?s worth repeating since it is PRECISELY what I have been saying here, and it is exactly the opposite of what Fields has been saying here. So to repeat Fields
OWN study states:
However, there has been no unambiguous direct evidence of an increased lung cancer risk associated with residential exposures.
I respectfully submit that either Dr. Fields did not read the study which he references, or possibly that he lacks the technical expertise to understand what the study says. And as a personal note, to Dr. Fields, I say that with all due respect ? but what other conclusion can I possibly draw, when your own words on this thread are entirely inconsistent with the study to which you allude?
Dr. Fields further states in this thread:
Residential radon studies do not require linear no threshold extrapolations, so this is not an issue.
Of course they don?t, that is the whole bloody point, for heaven?s sake. Not only do they not require linear no threshold extrapolations, they should NOT be used since they are grossly inappropriate (which is what Bernie Cohen?s studies demonstrated ? all the rest of Dr. Field?s talk about hypothesis testing indicates further evidence that Dr. Fields is terribly confused and doesn?t understand the nature of these issues). In any event, apparently Dr. Fields is not aware of the fact that in ?his? own study, the lower confidence interval in the overall data gave a
negative correlation; with the mean value ever so slightly positive; even in the restricted data set, the LCI was flat (indicting no risk). I?m am not sure that Dr. Fields understands this since it argues completely against what he has attempted to state on this board. Still further, if these exposure studies not require linear no-threshold extrapolations, and they should not be used, then why, in the name of good science, did Fields attribute his name to a metaanalysis that relied EXCLUSIVELY on linear no threshold extrapolations? The Pooled Study to which he alludes states:
All analyses were conducted using conditional likelihood regression with a linear model for the odds ratio (OR) of the form OR(x) =1+Bx, where x is the mean residential radon concentration in the exposure time window in Bq/m3 and B is the excess odds ratio
Dr Fields, if its inappropriate, and its not required ? why was it used, and why did you argue in favour of it in one place and agin it here? Why are there so many glaring contradictions between what you have presented here on this thread and what you have presented in ?your? paper? And how, in the light of such GLARING inconsistencies do you have the gumption, to call my challenges a ?disservice.? It would be an act of disservice to ignore this kind of behaviour.
Fields paper tells us:
Although radon is one of the most extensively investigated human lung carcinogens, the weight of evidence for radon carcinogenicity derives largely from occupational studies of underground miners exposed to much higher radon levels than those typically encountered in homes.
Don?t we know it. This was EXACTLY the same data set which the NRC stated
This information would be appropriate for predicting the risks to the public if everyone was a miner, everyone lived in mines, and a large fraction of the general population smoked cigarettes.
But folks, we don?t. It?s that simple. We don?t. And when the foundational data set upon which the metaanalyses are performed are flawed, those metaanalyses are also necessarily flawed unless corrected ? which in the case of the Pooled data study ? they absolutely were NOT.
(I need to slow down a bit, and take a break, my wife tells me I?m furiously pounding the keyboard again?) Pauses to breath? OK. I?m back. Where was I? Oh yes, pontificating?
Dr Fields ?own? study states speaks to the issue of those challenged data:
There are also marked differences between the conditions of exposure in mines and in houses. These differences include the relative proportion of radon itself to its decay products (which affects the amount of energy deposited in the lung), respiratory rate (which affects the rate radon and its decay products are inhaled and retained in the lung), and particle size distributions (which affect the fraction of radon progeny attached to particles and the depth of penetration and site of deposition within the lung). All of these factors complicate the direct extrapolation of occupational data on radon lung cancer risks to residential settings.
No kidding. Isn?t this what I?ve been saying?
Dr. Field?s study tells us:
Metaanalyses of published odds ratios from North American and other residential radon case? control studies found a statistically significant increase in lung cancer risk. However, the odds ratios in 13 studies included in the more recent metaanalysis exhibited heterogeneity among studies, possibly as a result of the inability to directly adjust for other confounding factors.
Folks, the subtlety and profound importance of this statement cannot be overstressed ? since within the cause of the heterogeneity lies the crux of the problem, and the foundation of my argument. For example, smoking remained a confounder in four of the seven studies and in NONE of the studies was there a negative control.
Let?s look briefly at the validity of the data sets used in the metaanalysis:
The Iowa study also measured only one home?.
OUCH!
?and historical profiles of radon concentrations in houses based on detector measurements or on the original investigators? best estimates.
OUCH!
Results are based on the best estimates of radon concentrations, including both measured and imputed radon values supplied by the collaborating investigators.
OUCH!
The residential radon measurements in these case?control studies are subject to measurement error. No formal adjustment for this source of error was attempted. Such adjustments require repeated radon measurement in the same
OUCH!
The authors are honest and tell us:
The analysis is inherently limited by the quality and reporting of the original residential radon studies, as well as the need for a common data format.
The tautology of the argument was not overlooked by the authors who stated,
It is possible that the findings for the restricted data were the consequence of differentially excluding participants in the negative studies.
Look; I?m not trying to slam Dr. Field, I am sure he is now rather embarrassed about referencing a paper which he obviously didn?t read or didn?t understand. Neither am I casting stones at the primary authors (Fields was only a minor author, listed sixth), who performed a metaanalysis and appeared to be quite open with their assumptions. Indeed overall, the paper was important in that it reemphasied many of the things that I have argued in these radon threads.
Ultimately, my problem lies with policy wonks and others who parade poor science as fact, and present conclusion not supported by their data, and or conclusions bereft of context and/or perspective. I would like to thank Dr. Fields for referencing a study, indeed participating in a study that very effectively argues my point.
Cheers ? I?m going fishing.
Caoimh?n P. Connell
www.forensic-applications.com
(The opinions expressed here are exclusively my personal opinions and do not necessarily reflect my professional opinion, opinion of my employer, agency, peers, or professional affiliates. The above post is for information only and does not reflect professional advice and is not intended to supercede the professional advice of others.)
AMDG
