2
process blasting, drilling, crushing, screening, transferring,
and processing into the final product all release dust into
the air, which will have varying amounts of crystalline silica
depending on the region and commodity being mined [3].
The National Institute for Occupational Safety and
Health (NIOSH) has a recommended exposure limit for
RCS of 50 µg/m3 as a time-weighted average (TWA) con-
centration for an 8-hour working shift. Additionally, the
Mine Safety and Health Administration (MSHA) has an
RCS permissible exposure limit that equates to 100 μg/m3,
with a new proposed rule that would lower the exposure
limit to 50 μg/m3 as TWA as well. In the mining environ-
ment, the concentration of airborne RCS can be determined
using time-integrated samples, collected with portable,
wearable sampling instruments and laboratory analysis or
end-of-shift analysis with portable infrared spectrometers
[4–7]. Both technologies, unfortunately, do not produce
data in real-time. In this context, it becomes imperative to
delve deeper into the risks associated with silica exposure in
respirable dust and the technologies available to monitor
respirable dust in the working areas of those who labor in
environments where exposure to silica is a prevalent threat.
Monitoring the workers’ personal exposure to respi-
rable dust or the respirable dust concentration level pres-
ent in an occupational environment, such as a mine, is a
fundamental step to understanding and characterizing the
hazard and risk for overexposure conditions, to assess the
compliance with company-based or regulatory exposure
limits, and to select and verify a proper dust mitigation
strategy. Traditional and established monitoring method-
ologies involve collecting time-weighted average represen-
tative samples, which are then sent for costly and lengthy
laboratory analysis. The monitoring apparatus includes
an aerosol sampler which must comply with the required
respirable convention, generally the ISO/CEN/ACGIH
[8], a medium for collecting the aerosol sample which is
generally a filter, and a calibrated sampling pump set up
at a proper volumetric flowrate which assures the proper
functioning of the aerosol sampler and correct determina-
tion of the volume sampled. At the laboratory, the samples
can be analyzed by a variety of analytical techniques if the
respirable dust mass concentration is the metric of interest,
then a gravimetric analysis can be employed [8]. Thanks to
the standardization of the monitoring apparatus and the
analytical methods, filter-based monitoring methodologies
for respirable dust provide operators with accurate data on
average exposure or hazard concentration levels during a
specific period of time.
Industrial hygienists or health and safety professionals
at the mine site periodically collect data on respirable dust
concentration and workers’ exposure throughout the oper-
ation. The frequency and sampling strategies are different
from company to company and are based on several fac-
tors such as the results of previous samples and the current
priorities of the company. It is uncommon for an industrial
hygienist to collect more than a handful of samples in a year
from the same location in a mine or from the same similar
exposure groups. These results ultimately provide a limited
number of data points to the industrial hygienist profes-
sional who conducts all the activities such as understand-
ing and characterizing the hazard and risk for overexposure
conditions, assessing the compliance with company-based
or regulatory exposure limits, and selecting and verifying
the proper mitigation strategy. These methodologies can-
not capture real time variability in dust levels, such as fluc-
tuations during work shifts or in response to operational
changes.
Other monitoring technologies based on aerosol sen-
sors have been available for health and safety practitioners
in the mining industry for several years. These technolo-
gies, such as area monitors or personal monitors, can pro-
vide time-series data throughout the sampling event, and
they can assist industrial hygienists in a variety of activi-
ties. Many publications report their potential added value
[9–12]. These technologies require substantial work from
the professional in terms of set-up, data download, data
manipulation, and interpretation. Recent technological
advancements have introduced an additional option—
relatively inexpensive aerosol sensors, referred to here as
low-cost dust monitors (LCDMs). These sensors might
enable researchers and industrial hygienist practitioners
to generate time-series area hazard monitoring data with
unprecedented spatial and temporal granularity and the
opportunity for targeted and timely intervention, open-
ing new possibilities in hazard monitoring [13, 14]. This
article documents how NIOSH has been able to harness
the potential of LCDMs in establishing baseline respirable
hazard levels and monitoring changes following remedia-
tion interventions on both seasonal and real-time bases. To
obtain an extended evaluation of sensor utility, NIOSH
researchers have conducted a 12-month study at a sand
mine in Wisconsin, USA, and present the findings here as
a general framework when using LCDMs in occupational
environments.
The advent of LCDMs has brought about signifi-
cant advantages for occupational hazard monitoring, and
these types of sensors offer compelling benefits that make
them an appealing way to augment traditional methods,
including: 1. Cost-effectiveness and accessibility, 2. Real-
time data generation, 3. Increased spatial and temporal
process blasting, drilling, crushing, screening, transferring,
and processing into the final product all release dust into
the air, which will have varying amounts of crystalline silica
depending on the region and commodity being mined [3].
The National Institute for Occupational Safety and
Health (NIOSH) has a recommended exposure limit for
RCS of 50 µg/m3 as a time-weighted average (TWA) con-
centration for an 8-hour working shift. Additionally, the
Mine Safety and Health Administration (MSHA) has an
RCS permissible exposure limit that equates to 100 μg/m3,
with a new proposed rule that would lower the exposure
limit to 50 μg/m3 as TWA as well. In the mining environ-
ment, the concentration of airborne RCS can be determined
using time-integrated samples, collected with portable,
wearable sampling instruments and laboratory analysis or
end-of-shift analysis with portable infrared spectrometers
[4–7]. Both technologies, unfortunately, do not produce
data in real-time. In this context, it becomes imperative to
delve deeper into the risks associated with silica exposure in
respirable dust and the technologies available to monitor
respirable dust in the working areas of those who labor in
environments where exposure to silica is a prevalent threat.
Monitoring the workers’ personal exposure to respi-
rable dust or the respirable dust concentration level pres-
ent in an occupational environment, such as a mine, is a
fundamental step to understanding and characterizing the
hazard and risk for overexposure conditions, to assess the
compliance with company-based or regulatory exposure
limits, and to select and verify a proper dust mitigation
strategy. Traditional and established monitoring method-
ologies involve collecting time-weighted average represen-
tative samples, which are then sent for costly and lengthy
laboratory analysis. The monitoring apparatus includes
an aerosol sampler which must comply with the required
respirable convention, generally the ISO/CEN/ACGIH
[8], a medium for collecting the aerosol sample which is
generally a filter, and a calibrated sampling pump set up
at a proper volumetric flowrate which assures the proper
functioning of the aerosol sampler and correct determina-
tion of the volume sampled. At the laboratory, the samples
can be analyzed by a variety of analytical techniques if the
respirable dust mass concentration is the metric of interest,
then a gravimetric analysis can be employed [8]. Thanks to
the standardization of the monitoring apparatus and the
analytical methods, filter-based monitoring methodologies
for respirable dust provide operators with accurate data on
average exposure or hazard concentration levels during a
specific period of time.
Industrial hygienists or health and safety professionals
at the mine site periodically collect data on respirable dust
concentration and workers’ exposure throughout the oper-
ation. The frequency and sampling strategies are different
from company to company and are based on several fac-
tors such as the results of previous samples and the current
priorities of the company. It is uncommon for an industrial
hygienist to collect more than a handful of samples in a year
from the same location in a mine or from the same similar
exposure groups. These results ultimately provide a limited
number of data points to the industrial hygienist profes-
sional who conducts all the activities such as understand-
ing and characterizing the hazard and risk for overexposure
conditions, assessing the compliance with company-based
or regulatory exposure limits, and selecting and verifying
the proper mitigation strategy. These methodologies can-
not capture real time variability in dust levels, such as fluc-
tuations during work shifts or in response to operational
changes.
Other monitoring technologies based on aerosol sen-
sors have been available for health and safety practitioners
in the mining industry for several years. These technolo-
gies, such as area monitors or personal monitors, can pro-
vide time-series data throughout the sampling event, and
they can assist industrial hygienists in a variety of activi-
ties. Many publications report their potential added value
[9–12]. These technologies require substantial work from
the professional in terms of set-up, data download, data
manipulation, and interpretation. Recent technological
advancements have introduced an additional option—
relatively inexpensive aerosol sensors, referred to here as
low-cost dust monitors (LCDMs). These sensors might
enable researchers and industrial hygienist practitioners
to generate time-series area hazard monitoring data with
unprecedented spatial and temporal granularity and the
opportunity for targeted and timely intervention, open-
ing new possibilities in hazard monitoring [13, 14]. This
article documents how NIOSH has been able to harness
the potential of LCDMs in establishing baseline respirable
hazard levels and monitoring changes following remedia-
tion interventions on both seasonal and real-time bases. To
obtain an extended evaluation of sensor utility, NIOSH
researchers have conducted a 12-month study at a sand
mine in Wisconsin, USA, and present the findings here as
a general framework when using LCDMs in occupational
environments.
The advent of LCDMs has brought about signifi-
cant advantages for occupational hazard monitoring, and
these types of sensors offer compelling benefits that make
them an appealing way to augment traditional methods,
including: 1. Cost-effectiveness and accessibility, 2. Real-
time data generation, 3. Increased spatial and temporal