Page 224 - Advances In Productive, Safe, and Responsible Coal Mining

Diesel particulate matter: Monitoring and control improves safety and air quality 203

PEL for M/NM mines was implemented in May 2008. MSHA monitor DPM by
employing a sampling methodology developed by NIOSH to measure total carbon
(TC) concentration [44]. TC is the cumulative mass of both EC and OC. TC is used
as a measure of DPM because reported studies have shown that DPM is generally
(70%–90%) made up of TC [45–47]. The relationship between EC and OC fractions
in untreated exhaust from diesel engines depends on operating conditions, type of
engine, fuel composition, and many other factors. The EC fraction in DPM increases
with engine speed and operating load. A study conducted in underground metal mines
where diesel-powered equipment is extensively used in the mining process reported
that EC concentrations average about 75% of TC concentrations; whereas TC concen-
trations were found to make up, on average, 72% of total DPM concentrations [10,48].
Another study conducted in several underground M/NM mines showed strong linear
correlation between EC and DPM and between EC and TC concentrations when
Diesel Particulate Filter (DPF) systems were not used [49]. The PEL for TC on an
3
average eight-hour shift basis is 160μg/m . TC is defined as the sum of EC and
OC when both EC and OC are analyzed by using the standard NIOSH 5040
method [32,50].
Contrary to M/NM mines, DPM regulations implemented in underground coal
mines are not compliance based, as the primary focus is to control DPM concentration
by utilizing different available technologies that reduce DPM at the point of genera-
tion. Therefore, MSHA does not enforce DPM monitoring for compliance determina-
tions in underground coal mines.

11.6 DPM exposure measurements

In underground M/NM mines, MSHA and operators routinely measure ambient con-
centrations and personal exposure to CO, CO 2 , NO, NO 2 , DPM, and other pollutants to
verify compliance with exposure limits [32,44]. Routine measurements of in-use
emissions of CO and measurements of personal exposures to CO and NO 2 are a
requirement when operating diesel engines in underground coal mines [51].
In order to assess the potential environmental and health impact of diesel emissions,
ambient and indoor exposure measurement is primarily used. In occupational settings,
three basic types of sampling techniques are used: (a) personal, (b) breathing zone, and
(c) general air [52]. In the case of personal sampling, a measurement or sampling device
is worn by the miner during his normal work shift. In breathing zone sampling, other
individual samplers not worn by the miner measure concentrations from the breathing
zone of the miner for whom exposure is to be obtained. These are typically hung from
the roof and moved from place to place as the miner’s work location changes. Area sam-
pling or mine air sampling is a technique where concentrations are sampled or measured
from fixed locations in the mine. In underground M/NM mines, a miner’s exposure is
usually determined by the personal sampling technique [32,51]. This is due to the non-
existence of an established relationship between area sampling and personal sampling
concentrations [52,53]. The following section describes methods used to determine
DPM concentrations in US M/NM mines as coal mines do not use ambient exposure
monitoring for DPM compliance.