1. 1 INTRODUCTION
The modern mining industry, due to an ever increas-
ing intensity of production processes, including
more powerful diesel equipment and increased blast-
ing frequency and power, is experiencing an in-
crease in the risk of miners' exposure to potentially
harmful gases such as CO, CO2, NO and NO2.
With this in mind, as well as the lack of site-
specific data which would reflect the actual exposure
of miners to these gases, the largest national mining
companies through MMA - Macedonian Mining As-
sociation, in collaboration with Mining Engineering
Department at FTNS Goce Delcev University in
Stip, and MOHSA Macedonian Occupational Health
and Safety Association, launched an exposure as-
sessment campaign to address the issue at hand. The
campaign includes two hard rock metallic mines:
Mine A (an under-ground operation having a total
output of approximately 750.000 tons per year), and
Mine B (a surface operation having a total output
exceeding 8.000.000 tons per year).
The first step of the campaign was focused on de-
termining the miners' exposure to CO and NO2, with
the aim to provide solid exposure da-ta for a risk as-
sessment, to develop efficient, cost effective and
easily applicable assessment programs, as well as to
recommend additional protection/control measures
as needed.
A brief description of the methodology deployed,
and results gained, from Mine A are discussed be-
low.
2 DESCRIPTION OF THE MINING PROCESS
Mine A, which is an underground operation, is a
lead and zinc mine producing about 750.000 tons of
raw ore per year. This mine operates a fleet of about
50 diesel powered vehicles, as well as various other
diesel powered equipment, which results in the level
of installed diesel power reaching a combined total
of about 3000 kW. Due to the high power and utili-
zation time, the loaders and haulage trucks are the
most significant source of diesel emissions, while
production blasting is the most significant source of
blasting fumes. Most other production machines, i.e.
those used in blast-hole drilling, roof bolting and ex-
plosive loading, are powered by electricity. Thus,
the diesel engines are primarily used for the transfer
of workers, equipment, and materials from one
work-place to the other.
These vehicles, being primarily comprised of off-
road vehicles equipped with four-wheel-drive, have
been modified to suit their intended purposes. Other
service machines in operation, such as fork lifts,
cranes, and road graders are relatively smaller diesel
powered multipurpose machines.
Due to specific geological conditions, a sublevel
caving is applied. Ore body is assessed through hori-
Miner’s exposure to Carbon Monoxide and Nitrogen Dioxide in
underground metallic mines in Macedonia
D. Mirakovski, M. Hadzi-Nikolova, Z. Panov, Z. Despodov, S. Mijalkovski
Faculty of Natural and Technical Sciences (FTNS), Goce Delcev University Stip, Macedonia
G. Vezenkovski
Sasa Mines, Makedonska Kamenica, Macedonia
ABSTRACT: The largest mining companies in Macedonia, in collaboration with Goce Delcev University and
MOHSA, launched a campaign to measure the exposure of miners to CO and NO2 while working in under-
ground metallic mines. The aim of this campaign is to provide exposure data for risk assessment, and to de-
velop an effective assessment program. This study took place in two mines, where the subjects were groups of
workers that were involved in the operation of diesel powered equipment and blasting during a full shift of 8
hours of exposure. In each mine, two groups were assessed: workers in both production and develop-
ment/service areas. Average exposures differentiate between groups and working positions, indicating diesel
powered equipment as the main source of pollution. Ventilation efficiency played a significant role in the
overall exposure levels, which is clearly indicated for all working positions in the development group primari-
ly operating under local exhaust ventilation systems.

2. zontal drifts and access ramps, while shafts are used
for ventilation and the transport of ore. Production
and development processes are exclusively per-
formed by drill and blast methods (Fig.1).
Figure 1. Production/development process
The quality of the underground atmosphere is
controlled only by an exhaust ventilation system,
which is powered by one main fan (500 kW) and
two “buster” underground fans. Fresh air, having
been drawn through drifts and intake shafts, is guid-
ed to the individual production areas where it is then
distributed by local ventilation systems to the several
working areas on different active sublevels. Used air
is then returned back to the exhaust shafts in isolated
drifts.
Air quality requirements are strictly defined in
national mining regulation. Threshold limit values
for carbon monoxide and nitrogen dioxide are given
bellow (Tab. 1). The same regulations prescribe
minimal control measures and assessment proce-
dures.
Table 1.Treshold limit values
Threshold limit values
TWA (8 hours) in ppm STEL (15 minutes) ppm
CO 30 120
NO2 5 /
*valid at the time of investigations
3 MATERIALS AND METHODS
Within Mine A, an underground operation with 6 ac-
tive production areas, a group of exposed workers
includes operators of diesel powered equipment,
blasting specialist and production supervisors. Due
to a difference of working conditions, and a suspect-
ed level of exposure, two sub-groups where formed,
one to include workers from the production areas
under the general ventilation system, and another
comprised of workers from development areas
where auxiliary ventilation is usually applied. The
group of workers from the production areas included
two 2 diesel loader drivers, 2 jumbo drill operators,
and 2 blasting specialists, while the group of work-
ers from the underground construction areas consist-
ed of 1 diesel loader driver, 1 jumbo drill operator,
and 1 blasting specialist. The supervisor of each
group was also included in the assessment. Real full
shift exposure (spanning from the entry point, down
into the mine itself, and back to the point of exit) to
car-bon monoxide and nitrogen dioxide was deter-
mined. The workers were monitored for 3 consecu-
tive shifts (I, II and III), with each worker wearing a
Gastec direct-read dosimeter tube (Fig. 2) placed on
the lapel within the breathing zone.
The tubes provide simple and reliable direct-read
TWA (time-weighted average) monitoring of target-
ed chemicals. Since there is no need for user calibra-
tion, extra equipment, laboratory analysis or exten-
sive training, the dosimeter tubes reduce costs,
administrative and maintenance time, and the possi-
bility of user error. Dosimeter tubes operate by di-
rect diffusion exposure, and are highly sensitive and
selective to the targeted chemicals, as opposed to
other non-specific testing methods.
Figure 2. Carbon Monoxide dosimeter tube after 8 hours usage
As a quality control, one of the workers in each
shift wore a VRAE PGM 7800 hand-held monitor
with built-in electrochemical CO and NO2 sensors,
sampling pump and data logging. The monitor was
calibrated to clean air prior to each use, and span
gases calibration was performed once a week.
The data collected were used to calculate TWA
for 8 hour shifts and compared against the dositube
readings.
In general, there was good correlation between
TWA obtained from the tube (9,25 ppm) readings
against TWA calculated from real-time concentra-
tion measurements (7,97 ppm) as shown in Figure 3.
Due to the small amount of data obtained in the
first phase of the study, statistical processing was not
possible.
All data were recorded in predefined measure-
ment protocols, including photos of the tubes and
raw readings from the handheld monitor.

3. Figure 3. Carbon monoxide exposure during the shift of a su-
pervisor
4 RESULTS AND DISCUSSION
Compiled assessment data, including 36 readings for
each pollutant from Mine A, are given in the Table
2.
Although exposure above national regulations
was not noted, the average exposures determined
could be regarded as significant.
Table 2. 8 hour’s TWA exposure in Mine A
Shift I Shift II Shift III
Working
position
CO
ppm
NO2
ppm
CO
ppm
NO2
ppm
CO
ppm
NO2
ppm
Production Group
LHD
Driver 1
11,85 1,325 15,5 1,425 13,25 1,55
LHD
Driver 2
9,75 1,075 12,25 1,05 11,53 0,95
Drilling
operator 1
10,55 0,75 9,25 0,75 8,51 0,25
Drilling
operator 2
7,50 0,25 8,50 0,50 6,52 0,25
Blasting
operator 1
8,20 0,55 8,75 0,95 11,25 2,15
Blasting
operator 2
4,50 0,25 7,325 0,75 9,75 1,85
Supervisor
1
10,25 0,87 7,85 0,25 7,85 0,50
Supervisor
2
9,25 0,55 5,25 0,25 5,55 0,25
Development group
LHD
Driver
22,5 2,50 25,80 2,25 19,85 1,55
Drilling
operator
16,37 1,85 14,75 2,15 12,25 1,25
Blasting
operator
11,25 1,55 10,05 1,85 11,85 2,05
Supervisor 12,50 1,25 12,5 1,50 9,85 1,15
We have found that the average exposure levels
differentiate between the groups and working posi-
tions, indicating that diesel powered equipment was
the main source of pollution, thus the loader drivers
were shown to have the highest levels of exposure
during their 8 hour shifts (15,84 ppm for carbon
monoxide and 1,52 ppm for nitrogen dioxide) rela-
tive to employees working in other positions within
the same timeframe (Tab. 3).
Table 3. Average exposure of working positions in
different groups
Average exposure (8 hour’s TWA)
Production
Group
Development
Group
Working position
CO
ppm
NO2
ppm
CO
ppm
NO2
ppm
LHD drivers 12,41 1,23 15,84 1,52
Drilling operator 8,47 0,46 10,47 0,89
Blasting operator 8,30 1,08 9,21 1,33
Supervisor 7,67 0,45 8,98 0,73
The efficiency of underground ventilation also
plays a significant role in overall exposures, which is
clearly indicated for all working positions in the de-
velopment group usually operating under local ex-
haust ventilation systems. Workers in the develop-
ment group, on average, were exposed at a rate of
10-48% higher than corresponding positions in the
production group (Tab. 3).
Average exposures of different working positions
obtained in this study are generally higher, com-
pared to data from the extensive study in German
potash mines (Dahman, Monz, Sönksen 2007).
The full shift exposures of LHD drivers obtained
in our study are significantly higher compared to the
same in German potash mines as shown in Figure 4.
Figure 4. Average exposure of LHD drivers
Drilling operators exposures also show similar re-
lations, while other working positions are not com-
parable between studies.
The difference could be explained with different
mining conditions and methods applied, but
measures for improvement of the exposure situation

4. in Macedonian mines are still necessary to achieve
state of the art conditions as those found in German
potash mines.
5 CONCLUSIONS
The results of this study clearly indicate that diesel
equipment is the main source of carbon monoxide
and nitrogen dioxide in underground metal mines,
and although blasting can contribute to nitrogen di-
oxide generation, if proper ventilation is applied, ex-
posure to blasting fumes is rather insignificant.
Of all the working positions that were studied, diesel
loader drivers had the highest average expo-sure
compared with other working positions. In general,
the average exposures determined could be regarded
as significant, although exposure above national
regulations was not noted. Proper ventilation
measures are the most efficient method for con-
trolling underground atmosphere quality, thus con-
trolling workers exposure to harmful gases. As such,
every effort should be made to implement appropri-
ate ventilation in all underground work areas. As
part of the measurement campaign plan, 3 measure-
ment sessions, conducted according to the pattern
and methodology mentioned above, should be com-
pleted in each of the mines. The data collected
should allow for the proper evaluation of miners' ex-
posure in hard rock metal mines, and comparative
analysis of exposures between different groups of
workers at surface and underground operations. Ad-
ditionally, quantum data will support the use of di-
rect-read dosimeter tubes as an effective assessment
method within specific terms of usage.
6 REFRENCES
Coble, J. B., Stewart, P. A., Vermeulen, R., Yerebm, D.,
Stanevich, R., Blair, A., Silverman, D. T., Attfield, M.
2010. The Diesel Exhaust in Miners Study: II. Exposure
monitoring surveys and development of exposure groups.
The Annals of Occupational Hygiene: 54 (7):747-61.
Dabill, D. W. 2004. Controlling and monitoring exposure to
diesel engine exhaust emissions in non-coal mines. HSE
Books: Sudbury: HSE Information Services.
Dahmann, D., Monz, C., Sönksen, H. 2007. Exposure
assessment in German potash mining. International
Archives of Occupational and Environmental Health:
81(1):95-107.
Dahmann, D., Morfeld, P., Monz, C., Noll, B., Gast, F. 2009.
Exposure assessment for nitrogen oxides and carbon
monoxide in German hard coal mining. International
Archives of Occupational and Environmental Health:
82(10):1267-79.
Gastec. 2012. Environmental Analysis Technology Handbook
(12th ed.). Japan: Gastec Corporation.
Stewart, P. A., Coble, J. B., Vermeulen, R., Schleiff, P., Blair,
A., Lubin, J., Attfield, M., Silverman, D. T. 2010. The
diesel exhaust in miners study: I. Overview of the exposure
assessment process. The Annals of Occupational Hygiene:
54 (7): 728-46.
Stewart P.A, Vermeulen R, Coble JB et al. (2012) The diesel
exhaust in miners study: V. Evaluation of the exposure
assessment methods. The Annals of Occuptional Hygene:
56: 389–400.
US EPA. 2002. Health assessment document for diesel engine
exhaust. National Center for Environmental Assessment
EPA/600/8–90/057F: Washington, DC: US EPA.
Vermeulen R, Coble J. B., Lubin, J. H. et al. 2010. The diesel
exhaust in miners study: IV. Estimating historical
exposures to diesel exhaust in underground non-metal
mining facilities. The Annals of Occupational Hygiene: 54:
774–88.
Vermeulen, R., Coble, J. B., Yereb, D. et al. 2010. The diesel
exhaust in miners study: III. Interrelations between
respirable elementary carbon and gaseous and particulate
components of diesel exhaust derived from area sampling
in underground non-metal mining facilities. The Annals of
Occupational Hygiene: 54: 762–73
Yanowitz, J., McCormick, R. L., Graboski, M. S. 2000. In-use
emissions from heavy-duty vehicle emissions.
Environmental Science & Technology: 34: 729–40.
Zey, J. N., Stewart, P. A., Hornung, R. et al. 2002, Evaluation
of side-by-side pairs of acrylonitrile personal air samples
collected using different sampling techniques. Applied
Occupational and Environmental Hygiene: 17: 88–95