Environmental Engineering Reference
In-Depth Information
The authors mention that the results presented in Ruzer and Sextro (1997a,b) can have a possible
impact on and contribution to the discussion on the value of radiation mortality risk. It was shown in a
study of American miners that the mortality risk was several times lower than in an analogous study of
Czechoslovakian mines. Such a discrepancy can at least be partially explained by different strategies of
measurement. This would lead to an overestimation of miners' expected exposure and, consequently,
to the obtaining of a much lower mortality risk for American miners than for Czechoslovakians.
Summing up, Domanski et al. (1989) declared the following opinion:
The postirradiation lung cancer risk factor due to exposure to radon progeny should be thoroughly
reconsidered in the light of discovered effects. The correctness of the miners' exposure can be provided
only by the IDS.
Based on the results the following conclusions were drawn:
•
Since the beginning of the study of the health effects of radon and its decay products, con-
centration and exposure were chosen as an adequate measure of the irradiation of the lungs
of miners. No serious and systematic attempts were made to establish the individual dosi-
metric control for underground workers from alpha-emitters of radon series despite the fact
that for low-LET radiation in occupational exposure such individual control is mandatory.
•
In the majority of dosimetric and epidemiological studies on miners, no quantitative con-
siderations were made according to the rules of metrology for accuracy in the evaluation of
exposure, intake, and dose to the lungs for every dosimetric parameter, that is, concentra-
tion in the breathing zone of miners, volume breathing rate, and deposition for different
degrees of the load of work.
•
Routine methods of assessment of exposure (intake, dose) in the lungs of miners are very
sensitive to the strategy of the measurements and consist of errors (uncertainties) in hun-
dreds of percent, which make the correct risk assessment of miners, and consequently of
the general population, very uncertain.
•
Direct measurements of the activity (dose) in the lungs of miners permit one to assess
dosimetric factors with an accuracy close to the statistical error in the assessment of lung
cancer mortality.
•
Because practically it is impossible to provide individual measurements for every miner,
an intake for the group of miners is proposed, which takes into account diversities of mine
environment as an alternative to exposure as a characteristic of miners' irradiation.
15.10.2 M
etHod
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d
irect
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easureMent
oF
tHe
a
ctivity
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ose
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ungs
oF
M
iners
The determination of the absorbed radiation dose in the lungs of miners due to the inhalation of
radon and its decay products can in principle be estimated from the air concentration of radon
progeny at the work sites, the rate of inhalation and the retention in the lung airways. However, the
value of the rate of inhalation is indeinite, since it depends on the physical load (the nature of the
work) and varies within broad limits from 10 L/min for the rest to 30-40 L/min for the hard work.
The air concentration varies with time and the value of the lung deposition fraction depends on
the particle size of the inhaled aerosols and the inhalation rate and was not measured under actual
working conditions.
The accurate measurement of the air concentration during exposure is complex. First the con-
centration at the same working site is subject to substantial variations. For example, a variation of
the intensity of ventilation even for a short time period of time leads to a change in the radon and
its progeny concentration of several-fold. Moreover, the content of aerosols directly in the breathing
zone may differ substantially from the value measured by an instrument, located in another part of
the working area.
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