QUALITY CHANGES, DUST GENERATION, AND COMMINGLING ...

The Lignotester uses a sample of 100 g of pellets and blows them around a perforated
chamber for 30 s (Winowiski, 1998). Pellets come out at the end of the cycle because the fines
are removed as they are generated.
The DURAL tester, which was developed for hard alfalfa pellets, subjects 100 g of
pellets to impact and shear forces for 30 s at 1600 rpm (Larsen et al., 1996; Sokhansanj and
Crerar, 1999; Adapa et al., 2004). In all of the abovementioned methods, PDI was calculated as
the percentage of the mass of remaining whole pellets after the PDI test over the total mass of
whole pellets before the test.
2.1.5 Grain Dust: Health and Safety Hazard and Air Pollutant
Handling of grain generates dust, which can be a safety and health hazard as well as an
air pollutant. Grain dust is composed of approximately 70% organic matter, which may include
particles of grain kernels, spores of smuts and molds, insect debris (fragments), pollens, and field
dust (US EPA, 2003).
Concentrations of grain dust above the minimum explosive concentration (MEC) pose an
explosion hazard (US EPA, 2003) due to the high organic content and a substantial suspendible
fraction. Published MEC values ranged from 45 to 150 g·m -3 (Jacobsen et al., 1961; Palmer,
1973; Noyes, 1998).
Moreover, grain dust is not only a safety hazard but also a health hazard (NIOSH, 1983).
Prolonged exposure to grain dust can cause respiratory symptoms in grain-handling workers and
in some cases affect workers’ performance and sense of well-being. The American Conference
of Governmental Industrial Hygienists (ACGIH, 1997) has defined three particulate mass
fractions in relation to potential health effects: (1) inhalable fraction (PM with a median cut point
aerodynamic diameter of 100 µm that enters the airways region), (2) thoracic fraction (PM with a
median cut point aerodynamic diameter of 10 µm that deposits in the tracheobronchial regions),
and (3) respirable fraction (PM with a median cut point aerodynamic diameter of 4 µm that
enters in the gas-exchange regions), herein referred to as PM-4.
The US EPA (2007), on the other hand, regulates PM-2.5 or fine PM (i.e., PM with
equivalent aerodynamic diameter of 2.5 µm or less) and PM-10 (i.e., PM with equivalent
aerodynamic diameter of 10 µm or less). PM-2.5 has been linked to serious health problems
ranging from increased symptoms to premature death in people with lung and heart disease (US
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