Environmental Engineering Reference
In-Depth Information
and radon progeny in mines. The degree of equilibrium varies substantially in time and space, both
for underground workers and the general population.
Unfortunately, even after concentration (exposure) of decay products (not of radon) was estab-
lished as a measure of the irradiation of the lung more than 40 years ago, no discussion and experi-
mental study in mines were conducted to determine the degree of correlation between the measured
concentration and the actual dose (intake) for individuals and a group of miners.
To assess the reliability of dosimetric data for miners, we should carefully consider every factor
related to dose (activity) calculated or measured together with assessment of the uncertainties for
every partial factor and the total error (uncertainty).
It seems that a lack of such careful consideration of the metrological aspects in the assessment
of the dose to the lungs of miners from radon decay products in the past resulted in large uncer-
tainty in the dose to the lung, and correspondingly unreliable data in estimating the risk of lung
cancer.
It is obvious that because irradiation of the lung by radioactive aerosols, and particularly radon
decay products, depends on physical activity, there are some biological factors that will contribute
to the total uncertainty in the dose assessment. In order to simplify the task, we will put aside, at
least for now, the biological factors and focus only on the physical factors, especially because the
uncertainty in physical factors is very large in itself.
Let us call all these factors that contribute to the release of energy to the lung tissue as “dosi-
metric factors.” There are two groups of dosimetric factors. The irst group—radioactive dosimetric
factors—determines the total energy of radiation in the air or in the lung. The second—nonradioactive
group—is mainly responsible for the portion of this energy deposited in the lung.
The following are the factors in the irst group—radioactive parameters:
1. Concentration measured by standard procedure
2. Breathing zone concentration
3. Concentration of unattached radon decay products
4. Exposure
5. Activity in the lung
6. Energy of the alpha and beta particles
7. Integral absorbed dose
8. Absorbed dose
The parameters of the second nonradioactive group are
1. Counting, surface area, and weighted aerosol concentration
2. Aerosol particle size distribution
3. Breathing rate (minute volume)
4. Deposition coeficient
5. Filtration ability of the lung (FAL)—combination of the volume breathing rate and deposi-
tion coeficient
6. Eficiency in using respirators (when applicable)
7. Parameters of biokinetic processes
Besides all these factors, mention of the “work itinerary” (“scenario of exposure”) is also a neces-
sary element for correct dose assessment.
In the NRC Report, the structure of the lung inner surface layers from the point of view of alpha-
dosimetry was studied.
It is well known that the dose to lung tissue from the inhalation of radon progeny cannot
be measured. It must be calculated by modeling the sequence of events involved in inhalation,
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