Radioactive Aerosols - Aerosols: Measurement, Dosimetry, and Health Effects - page 388

Most of the mining industry in this region used artiicial ventilation. In the period of the pri-
mary study, only three mines did not have artiicial ventilation. Blind (cul-de-sac) mine shafts were
ventilated by ventilators (types VAM-450, BM-200). In most cases, suction-type ventilation was
used together with a dispersed set of ventilators in the pipelines. A substantial disadvantage to this
method is the possibility of contamination (pollution) of the clean air entering the mine working
with radon and also the possibility of suctioning polluted air from nonworking sites.
In general, numerous nonworking sites connected with working sites created a negative inluence on
ventilation and consequently on radon and its decay product concentration in the working sites, increas-
ing it. Due to the noise, often miners turn off ventilation during the shift and mine working takes place
without air replacement. The worst air conditions, therefore, took place in blind shafts, particularly in
shaft sinker (drifter) working sites. In cleaning sites, due to trough ventilation, air exchange was constant.
In the nonworking sites, air usually stagnates. These nonworking sites are visited from time to
time by geologists, mine surveyors, and others, who carry out different types of work, such as dis-
mantling, taking down the rail, pipes, cables, etc.
The main tool in the ight with dust, besides ventilation, was wet drilling. Even in mines where
the average dust concentration did not exceed the APC standard level in mine shafts, the dust con-
centration was substantially higher and therefore, in terms of dust, the worst situation was for ore
face-workers (getters).
Especially dificult working conditions arose for the geology-prospecting groups due to the
following reasons:

• Remoteness (distance) of this type of work from main transport arterial roads and indus-

trial centers

• Dificulties in energy supply

• Dificulties in alpine (mountain), arid (waterless), deserted, permafrost conditions

• Dificulties with maintenance equipment

• Absence of ventilation and mountain life-saving services

All these situations existed in Tadjikistan. The prospecting mine shaft is blind, that is, it has only
one exit to the surface, which makes the ventilation of such working sites very dificult. In addition, a
cross section of such sites is usually less than 5 m 2 , making it impossible to use ventilation pipes with
large diameters. A low cross section also makes it impossible to use loading mechanisms (gearing),
which resulted in most work being manual with a very high physical work load. All these circum-
stances came to our attention after we became closely acquainted with mine working conditions.
It became clear that mining conditions are very diverse and, therefore, too complicated to use
one or two measurements per month of radon and its decay product concentration (or exposure) as a
characteristic of the dose of individuals or a group of miners.

15.7 DIRECT METHOD: THE TADJIKISTAN STUDY AS AN OPPORTUNITY
TO REDUCE LUNG DOSIMETRIC UNCERTAINTY
Our irst underground experience was a very dramatic one. We arrived in the capital of Tadjikistan,
Dushanbe, after an 8 h light from Moscow, late in the evening. The next day, early in the morning,
we went to the mine located outside the city.
In order to obtain the best results, we asked the mining administration to show us the places with
the highest concentrations. At irst, our guide led us to the wrong site and it was only by chance that
we did not perish. We arrived at the site, where the concentrations were 10 4 -10 5 times higher than
permissible. We wore respirators, but I was so tired after the light and the almost sleepless night
that I had dificulty breathing, and so took off the respirator. Radon decay products were not only in
our lungs, they were on our faces, clothes, everywhere.