21

Mining Environment 

Aleksandar D. Bugarski and Robert J. Timko 

National Institute for Occupational Safety and Health, Pittsburgh Research Laboratory 

Abstract 

Despite extensive research efforts conducted in the past decades, occupational health risks associated with exposure 

to nano and ultrafine aerosols emitted by diesel power equipment are still not completely understood. The 

complexity of physical and chemical properties of diesel aerosols, constantly changing with the implementation of 

advanced diesel emissions control technologies, make this task rather challenging. The objective of this paper is to 

identify and characterize nanometer and ultrafine aerosols emitted by diesel engines in the underground environment 

and evaluate the effects of selected contemporary control technologies on physical properties, chemical composition, 

and in-vitro toxicology of diesel aerosols. The physical and chemical properties of the nanometer and ultrafine diesel 

aerosols are to be characterized through a test series in the NIOSH Lake Lynn Laboratory experimental mine. The 

crucial part of the study has been development of a facility that allows researchers to generate field results with 

precision and accuracy characteristics of a laboratory environment. The knowledge obtained from this study should 

strengthen our understanding of the health implications related to exposure to diesel particulate matter and aid in 

assessing the potential of various control technologies for reducing this exposure. 

Introduction 

In recent years, health effects associated with exposure to diesel particulate matter (DPM) and 

other combustion-generated nanometer and ultrafine aerosols received substantial attention 

globally from public, academia, and government sources. Pope and coauthors (2002) established 

that long-term exposure to combustion-related fine particulate pollution is an important risk 

factor for cardiopulmonary and lung cancer mortality. Donaldson and Stone (2003) concluded 

that there is good toxicological evidence that ultrafine particles cause inflammation in the lungs, 

even when composed of relatively low toxicity material. There is growing evidence suggesting 

that particle number, surface area, size, or perhaps some associated structural properties may 

affect nanoparticle toxicity, in comparison with larger respirable particles of the same 

composition (Donaldson and Stone. 2003). In general, occupational health risks associated with 

exposure to nano and ultrafine aerosols are not yet clearly understood. 

Diesel particulate matter (DPM) is a common term describing a complex mixture of solid and 

liquid aerosols emitted by diesel engines. Size distribution and chemical composition vary 

widely with a number of engine and aftertreatment parameters. The primary constituents of DPM 

are elemental carbon (EC), numerous organic carbon species (including several that are known 

carcinogens), sulfates, and transitional metals. A large portion of these aerosols, primarily 

generated due to incomplete combustion in diesel engines, ideally falls into the nanometer (D50< 

50 nm) and ultrafine (D50<100 nm) size ranges (Kittelson 1998). Typically, ultrafine and 

nanometer aerosols emitted by diesel engines contribute between 1 and 20% of total DPM mass 

but comprise more than 90% of the total particle number and surface area. 

Recent U.S. surveys revealed that, of all occupations, underground metal and nonmetal miners 

are exposed to the highest concentrations of diesel aerosols. Total carbon concentrations in 

underground metal mines were found to be as high as 3300 μg/m3 (Cash and Baughman 2005). 

In January 2001, the U.S. Mine Safety and Health Administration (MSHA) promulgated rule 30 
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strategies and technologies, rather than on established health effects of DPM. These limits are 

based on total DPM and EC mass concentrations. Mass-based exposure assessments are not 

always predictive of disease risk; in some cases respirable particle surface area and detailed 

surface compositional or morphological properties better correlate with toxicity or offer an 

explanation of seeming anomalies in epidemiological findings of disease risk (Wallace et al., 

1990). Recent results (Donaldson et al. 2000, Tran et al. 2000, Oberdörster et al. 2000 and 2004, 

Englert 2004,) emphasize the importance of complementing mass-based monitoring exposure to 

nanometer and ultrafine aerosols with measurements of aerosol size, number, and surface area to 

better assess the adverse health impact of ultrafine aerosols. 

Since the introduction of 30 CFR 57.5060, the U.S. underground mining community has been 

working on identifying and implementing technically and economically feasible strategies and 

technologies to curtail emissions from existing and new diesel-powered vehicles and reducing 

miners’ exposures to DPM. Some tools available to control DPM emissions are the replacement 

of older diesel engines with cleaner powerplants, more efficient mine ventilation, advances in 

diesel engine maintenance, and the implementation of various diesel emission control methods. 

As a result of the high demand for aftertreatment systems, a number of new emission control 

technologies have emerged to reduce diesel emissions from on- and off-road vehicles. Several 

studies (McGinn et al. 2002, Bugarski et al. 2006a and b) have shown that DPM concentrations 

can be substantially reduced by using modern engines, reformulated fuels, and exhaust 

aftertreatment technologies. The health effects of nanometer and ultrafine aerosols with altered 

size and chemical composition remain to be established. 

Studies (Maricq et al. 1999, Khalek et al 2000, Kittelson et al. 2005) determined that the total 

mass, size distribution, size-resolved chemical composition, and genotoxicity of diesel aerosols 

depend on engine parameters, aftertreatment methods, and aerosol interaction with the 

environment. Since a majority of nanometer particles emitted by a diesel engine are volatile 

(Vaaraslahti et al. 2004), parameters such as dilution ratio, temperature, humidity, aerosol 

concentrations, and residence time were found to strongly influence their formation and 

transformation (Shi and Harrison 1999, Khalek et al. 2000). Although a majority of the work on 

characterizing diesel aerosol is done in the laboratory, this evidence suggests that the best way to 

characterize them is to sample directly in either an occupational setting or other environments 

where the aerosols are formed and transformed. 

Objective 

Through a Nanotechnology Safety and Health Research Program at the National Institute for 

Occupational Safety and Health (NIOSH), researchers from the Pittsburgh Research Laboratory 

(PRL) began an extensive study that characterizes the physical, chemical, and toxicological 

properties of diesel aerosols in an occupational setting. The specific objectives of the project are: 

•	 Describing nano and ultrafine particles emitted in work environment by typical light- and 

heavy-duty diesel engines; 
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•	 Studying the effects of the aerosol aging process on diesel aerosol properties; 

•	 Evaluating currently available instrumentation and methods for monitoring worker exposure 

to diesel aerosols 

•	 Investigating the potential for establishing a new metric for monitoring worker exposure to 

DPM. 

Methodology 

Previous studies, conducted in operating underground metal mines (Bugarski et al. 2006 a, b), 

suffer from logistic and technical difficulties that prevent conducting detailed long-term studies 

on the characterization of DPM. Therefore, it was necessary to develop a facility capable of 

generating field results with precision and accuracy characteristics of a laboratory environment. 

The result of these efforts is the NIOSH Diesel Laboratory. 

NIOSH Diesel Laboratory 

The NIOSH Diesel Laboratory has integrated a transportable dynamometer into the NIOSH Lake 

Lynn Laboratory (LLL) experimental mine (Figure 1). LLL is an established underground 

limestone mine situated in Fairchance, Pennsylvania, about 97 km (60 miles) southeast of 

Pittsburgh, PA, and 16 km (10 miles) northeast of Morgantown, WV (Tribsch and Sapko 1990). 

Figure 1. NIOSH Lake Lynn Laboratory Experimental Mine 

The NIOSH Diesel Laboratory is located in the D-drift. This drift is approximately 530 m (1750 

ft) long, 6 m (20 ft) wide, and 2 m (7 ft) high. A schematic layout of the laboratory is shown in 

Figure 2. The major components are engine/dynamometer systems, three sampling and 

measurement stations, and a ventilation measurement and control system. 

Dynamometer/Engine Systems 

Two dynamometer/engine systems are built around two water-cooled eddy-current 

dynamometers; a 150 kW (201 bhp) Model SE150 and a 400kW (536 bhp) Model SE 400 (SAJ, 

Pune, India). The 150 kW-dynamometer is coupled to a naturally aspirated, mechanically 
24

Figure 2. NIOSH Diesel Laboratory 

Figure 3. 150 kW dynamometer/Isuzu C240 system 

SE400 dynamometer is coupled to an electronically-controlled turbocharged Mercedes Benz OM 

904 3MT32 engine. 

Measurement and Sampling Stations 

Ambient concentrations of selected gases and aerosols are sampled in the mine air upstream and 

downstream of the dynamometer. The upstream ambient monitoring and sampling station is 

located approximately 60 m (197 ft) inby the dynamometer. This station is designed to measure 

background aerosol concentrations. The downstream ambient monitoring and sampling station is 

located about 60 m (197 ft) downstream of the dynamometer. This station is designed to sample 

concentrations of aerosols, carbon monoxide (CO), carbon dioxide (CO2), nitric oxide (NO), 

nitrogen dioxide (NO2), sulfur dioxide (SO2), and total hydrocarbons (HC). At both locations 

ambient concentrations of total particulate matter with aerodynamic diameters under 0.8 μm are 

monitored using a Series 1400a tapered element oscillating microbalance (TEOM) (Thermo 

Electron Corp., East Greenbush, NY). 
25

horizontal stratification, each sample is obtained at five different locations on the sampling grid 

(Figure 4). 

Figure 4. Downstream sampling station 

Five identical preclassifiers, each consisting of a 10-mm Dorr-Oliver cyclone 

followed by a single stage diesel impactor, are used to remove coarse aerosol. A flow rate of 

approximately 2.2 l/min (0.1 cfm) is maintained through each preclassifier. At this flow rate 

only particles with geometric mean diameters smaller then 0.75 μm are deposited on the filters 

(Olson 2001). The five preclassifiers are attached to a symmetrical plenum that distributes a total 

flow rate of about 11.0 l/min (0.4 cfm) uniformly to the five streams. Each preclassifier 

assembly is connected to the plenum chamber by a 0.9 m (3 ft) long section of conductive 

tubing. The plenum outlet is directly connected to either a 25 mm stainless steel filter holder or a 

37 mm cassette. Sampling train airflow is maintained with a Model 1023 rotary vane pump (Gast 

Manufacturing Inc., Benton Harbor, MI). 

Tissue quartz fiber (TQF) filters (Pall Corporation, Ann Arbor, MI) are used for collecting 

samples for carbon analysis. Teflon coated glass fiber (TCGF) filters (Pall Corporation) and 0.8 

μm polyvinyl chloride (PVC) filters (Millipore Corp., Billerica, MA) collect DPM for ion and 

metal analysis. TCGF and PVC filters are conditioned in an environmental chamber/weighing 

room at 20 °C and 50% relative humidity for at least 8 hours, then pre- and post-weighed in a 

weighing room. When weighed, each filter is placed on an NRD model 2U500 anti static strip 

(NRD LLC, Grand Island, NY) and finally onto a Mettler Model MT5 balance (Mettler-Toledo, 

Inc., Columbus, OH). 

Downstream, aerosol size distributions and concentrations are measured using a Model 3936 

Scanning Mobility Particle Sizer (SMPS) (TSI, St. Paul MN), a Model 3091 Fast Mobility 

Particle Sizer (FMPS) (TSI), and a Model DAS 3100 Electrical Low Pressure Impactor (ELPI), 

(Dekati, Finland). Samples for genotoxicity analysis are collected using a custom-designed 

system. Two sampling trains collect samples on two 90mm TCGF filters. Coarse particles (larger 

then 1 μm) are removed from the air stream by a URG-200-30EH cyclone (URG, Chapel Hill, 

NC). Sierra Model XXX mass flow controllers (Sierra Instruments, Inc., Monterey, CA) 

maintain a 50 l/min (1.8 cfm) flow rate in each sampling stream. A Gast Model 1023 rotary vane 

pump provides flow for both streams. 
26

ionization detector (HFID) (California Analytical Instruments, Inc., Orange, CA) measures 

gaseous-phase hydrocarbons. A Model 1312 photoacoustic multi-gas monitor (INNOVA 

AirTech Instruments, A/S, Ballerup, Denmark) monitors CO, CO2, and SO2. Gases are recorded 

by a Model 34970A data acquisition system (Agilent Technologies, Inc., Santa Clara, CA). 

The tailpipe monitoring station detects and records CO and CO2 concentrations in the engine 

exhaust. A Model 602 non-dispersive infrared (NDIR) analyzer (California Analytical 

Instruments, Inc.) is used to measure CO and CO2. Data from the analog outputs of this 

instrument are collected using a data acquisition system (Logic Beach Inc., La Mesa, CA). 

Samples collected on TQF filters are analyzed for EC content at the PRL analytical laboratory 

using the NIOSH Analytical Method 5040 (NIOSH 1999, Birch and Cary 1996, Bugarski 2006). 

Samples collected on TCGF filters are analyzed by Clayton Laboratories (Clayton Group 

Services, Novi, MI) for various ions following NIOSH Method 6004 (NIOSH 1994). The same 

laboratory analyzes samples collected on PVC filters for metals following NIOSH Method 7300 

(NIOSH 2003). Samples collected on 90 mm TCGF filters are assayed for standard in-vitro 

bacterial and mammalian cell genotoxicity by the NIOSH-Health Effects Laboratory DivisionMolecular Biophysics Team, Morgantown, WV. 

Ventilation Measurement and Control 

Fresh ventilation air is supplied from the ventilation shaft located in E-drift, situated immediately 

upwind and normal to D-drift. Air quantities supplied to D-drift can be regulated with sliding air 

doors positioned at the upstream end of D-drift and downstream end of E-drift. The total flow 

through the D-drift is measured using a subsonic Venturi meter (Primary Flow Signal, Inc., 

Tulsa, OK). The engine-specific ventilation flow rate is maintained by a Series 2000 Model 48­

26-1770 Axivane fan (Joy Technologies, Inc., New Philadelphia, OH). 

Preliminary Results 

Tests were conducted to establish sampling procedures. The objective of these was important to 

determine specific locations at the downstream sampling grid. SMPS downstream aerosol 

concentrations showed pronounced vertical stratification (Figure 5). These measurements 

indicated that the Isuzu C240 engine exhaust plume was strongly influenced by a strong vertical 

temperature gradient. Vertical stratification was minimized using a deflector curtain, installed 

30.5 m (100 ft) downstream of the tailpipe. With the deflector curtain in position, results show 

minimal vertical and horizontal stratification at the downstream grid location. 

SMPS and CO2 studies of exhaust plume propagation in the drift were conducted at various 

cross-sectional locations downstream of the tailpipe. Figure 6 average size distributions and 

concentrations of diesel aerosols illustrate the change in peak and total concentrations as well as 

physical properties of aerosols relative to distance from the tailpipe. For a given condition, most 

particle formation and transformation processes occur within the first 30 m (100 ft). 
1.20E+06 x=58 cm, y=140 cm W/O deflector 

x=58 cm, y=112 cm W/O deflector 

] 3

1.00E+06 

m^

x=58 cm, y=84 cm W/O deflector 

c/# [8.00E+05 x=58 cm, y=168 cm with deflector )p_D

x=58 cm, y=140 cm with deflector 

g(

6.00E+05 

/dlo

x=58 cm, y=112 cm with deflector 

dN

4.00E+05 x=58 cm, y=84 cm with deflector 

2.00E+05 

0.00E+00 

10 100 1000 

D_p [nm] 

Figure 5. Diesel aerosol size distributions of Isuzu C240 engine emissions when operated at 2000 rpm and 107 Nm 

(79 lb-ft) measured 61 m (200 ft) downstream of the tailpipe with and without the deflector in place.

1.20E+06 

x=140 cm, y= 102 cm I50 

1.00E+06 x=140 cm, y=127 cm 

] 

x=140 cm, y=157 cm 

m^3

8.00E+05 x=102 cm, y=140 cm 

cp) [#/

x=0 cm, y=140 cm 

_

6.00E+05 x=191 cm, y=140 cm 

og(DdN/dl 4.00E+05 

2.00E+05 

1.00E+00 

10 100 1000 

D_p [nm] 

Figure 6. Diesel aerosol size distributions of Isuzu C240 engine emissions when operated at 2000 rpm and 36.6 Nm 

(27 lb-ft) at various locations 61 m (200 ft) downstream of the tailpipe 

27

The NIOSH Diesel Laboratory enables diesel studies be conducted under field conditions with 

precision and accuracy characteristics of a laboratory environment. This approach should 
28

 

 

 

 

 

 

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