Radioactive Aerosols - Aerosols: Measurement, Dosimetry, and Health Effects - page 385

(or groups) of miners, we ind that the total uncertainty in this case will be in hundreds of percent.
This fact makes the data on dosimetry, and consequently on the risk assessment, open to question.
Because the error cannot exceed 100% in the negative direction, it is better to say that the true value
(of concentration, and consequently exposure) can be an order (or even more) of magnitude greater
or smaller than the current estimated value. A broad discussion of some (not all) sources of uncer-
tainties in dosimetry is presented in BEIR VI (NAS, 1999).
We were not surprised that the accuracy in the measurement of radon decay product concen-
trations in mines was in tens of percent (40%-50%), because in mines the instrumentation must
be portable and easy to operate. Such poor accuracy is necessarily acceptable under some ield
conditions.
What was not acceptable from a dosimetric point of view was the fact that the air concentration
of radon decay products (or exposure) measured by a standard procedure, especially in real mining
conditions, was not the physical parameter that is directly responsible for the biological effect, that
is, lung cancer.
Moreover, no serious attempt was made to study the correlation between radon and its decay
product measurement in real mining conditions, and the damaging biological factor, the activity or
dose to the lungs of miners.
According to standard metrological terminology, the uncertainty estimate in such cases is called
the propagation of the uncertainties. From a metrological point of view, the worst scenario in the
assessment of the physical value is not when the error (uncertainty) is large, because very often by
analyzing the sources of the errors we can ind a way of introducing the corresponding corrections.
The worst scenario is when the analysis shows that the uncertainty is itself uncertain. This is exactly
what takes place in the dosimetry of miners.
The (NRC, 1999) report “Health Effect of Exposure to Radon” (BEIR VI, 1999) discussed this
problem briely as a heterogeneity of the exposure—response trends among the various miner stud-
ies. That is, there were very different results from the 11 underground mining cohorts studied to
determine the relationship between radon decay product exposure and lung cancer.
Still, it seems that the assessment of miner dosimetry appears more qualitative than quantitative
because no serious attempt to simply follow the rules of metrology was practiced.
Another question arises. Are there different approaches, that is, methods in improving this
situation, to diminish partial and consequently total uncertainty? It seemed to us that such an
opportunity to at least diminish the uncertainty existed in using a direct measurement on miners'
lungs, and this technique was subsequently proved in measurements on miners in Tadjikistan.
Most of the results of these studies were not published, and exist only in a few dissertations and my
Radioactive Aerosols (2001, in Russian).
We had access to the health effects data in these same miners on whom lung measurements were
made. We decided it could clarify the risk in mines from radon and its decay product if we carried
out a study on the health effects as a function of radon and especially the detailed decay product
exposure.
Some (if not most) of the studies on exposure present effect results without error bars on both
vertical and horizontal axes, that is, without any serious attempt to assess the reliability of the
dosimetric and consequently risk data, as well as the death data.
Decreasing the statistical uncertainty in the biological effect (lung cancer mortality in the case
of miners) is usually achieved by choosing a substantial number of miners with reported exposure
histories. The uncertainties in exposure in most of the studies are not mentioned at all. The irony is
because the uncertainty is so large and undetermined, we simply ignore it.
If someone suggested that in grouping many mines, averaging of the various exposure factors
takes place, and that there is therefore no problem in risk assessment, we can respond, “Maybe.” But
such a point of view should be validated by statistical modeling or on-site experimentation in the
mines. We should also remember that miner data are the only source of quantitative risk assessment
in the epidemiology of radon and its decay product.