Environmental Engineering Reference
In-Depth Information
1. A minimum of 40 lung cancer deaths. This criterion established the level of uncertainty in
lung cancer mortality in the range of 15%-20%.
2. Estimates of Rn progeny exposure in units of WLM for each member of the cohort based
on historical measurements of either Rn or Rn progeny.
We will try to assess the uncertainties in every step of the calculation from the air concentration to
the activity (intake, dose) of radon decay products in the lung, assuming that activity (intake) is the
main physical value responsible for the biological effect in this case.
1. In some of the studies mentioned, assessment of radon progeny was made based on recon-
struction and some assumptions (China, New Foundland, Sweden, Beaverlodge). In such
cases, it is impossible even to determine the uncertainty (errors). The use of these data
should be called into question. It seems that criterion 2 was not applied in this case because
it was impossible to estimate exposure for each member of the cohort. In the Workshop on
Uncertainty in Estimating Exposure to Radon Progeny Studies of Underground Miners
(BEIR VI, E—Annex 2), questions were raised about removing certain cohorts, ranking of
cohorts, and obtaining additional information.
2. In many of the earliest studies, only radon concentration was measured. It is well
known that the contribution of radon itself to the dose is negligible in comparison to
its decay products. It was shown that the equilibrium factor varies in mines and has a
wide range from 0.2 to 0.9; Domanski et al. [1989], Poland). Therefore, assuming that
the average equilibrium factor is 0.5 for all situations, we can have uncertainties on the
order of 100%.
3. Measurements of radon decay products are directly related to irradiation of lung tissue.
Errors in calibration and measurements should be taken into account. Assessment of the
errors related to radon progeny measurements was the topic of discussion in the special
workshop (BEIR VI, E—Annex 2). It was estimated that uncertainty in this case was about
50%. This is consistent with the standard adopted in the former Soviet Union for radon
decay products measurements in mines—the errors should be on the order of 30%-40%
(Antipin et al., 1980).
4. Another source of error is the correlation between concentration measured by a standard
procedure (or area monitor) and that in the breathing zone. In BEIR VI (1998), the sug-
gestion was made that in some cases there are no substantial differences in these two
concentrations. But in Domanski et al. (1989), results were also presented on the correla-
tion between these two factors. The one measured by the air sampling system (ASS) was
based on the ield monitoring of radon progeny in air; the second one, called the individual
dosimetric system (IDS), was based on the individual dosimeter worn by miners. The ratio
ASS/IDS varies from 11.0 to 0.14. that the ratio of concentrations measured by a personal
aerosol sampler (PAS) and a standard aerosol sampler (SAS) depends substantially on the
strategy of measurements and sampler location. In short, this means that if the concentra-
tion was measured only by standard procedure and the ratio PAS/SAS is not known, addi-
tional uncertainty in the assessment of the concentration related to lung irradiation can be
on the order of hundreds of percent.
5. By deinition, irradiation of the lung by radon decay products should depend on physical
activity. The data on the breathing rate for different types of physical activity are presented
in Alterman (1974), Ruzer et al. (1995), and Layton (1993). The problem for miners is
that this parameter changes substantially within the shift from 10 to 30-40 L/min, and
by using the average value for the breathing rate an error of 100% can be made. It should
be mentioned that the measurement of the actual breathing rate was usually made only
for low physical activity because the measurement method itself disturbs real breathing
conditions, especially in the case of hard work.
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