1
24-071
Practical Application of Surfactants for Respirable
Silica Dust Control
Barbara J. Arnold
The Pennsylvania State University,
University Park, PA
Randy Reed
NIOSH Pittsburgh Mining Research Division,
Pittsburgh, PA
ABSTRACT
Respirable crystalline silica poses a significant health risk,
with the American Lung Association estimating that 2.3
million workers are exposed to silica in the workplace.
This includes mine workers as well as those in many other
industries. Reducing dust formation is sometimes not pos-
sible so other methods to reduce exposure are critical. These
methods include the use of surfactants to reduce airborne
dust particles. However, it is the proper selection and appli-
cation of surfactants that leads to reduced dust exposure.
A discussion of how surfactants work, especially for silica
dust, leads to guidance for surfactant selection followed by
a review of technologies for their application.
INTRODUCTION
Respirable crystalline silica has been studied as a potential
carcinogen in dusts from many sources, including those
produced in mines. Whether mining specifically for silica
or mining other minerals, it is likely that silica is in the
mined product as it is an accessory mineral phase in many
common commodities as indicated in Table 1 (1). While
coal is not on the list, it is certainly well known that coal
also contains quartz, with a 1990 US Bureau of Mine work,
Sources and Characteristics of Quartz Dust in Coal Mines,
initiating some of the research on silica in coal (2).
Researchers have also indicated that quartz cannot be
treated as a single mineral phase as there are many variations
in contaminants and associated minerals (see, for example,
3, 4, 5). In general, however, it appears that the issue with
crystalline silica, most notably α-quartz, is the formation of
reactive oxygen species (ROS) on the surface of dust par-
ticles, forming “silanols” that interact with lung tissue to
cause fibrosis and lung cancer (3, 4, 5). These works and
others along with the increase in the occupational respira-
tory diseases silicosis and coal worker’s pneumoconiosis (6,
7, 8, 9) spawned new research, including recent interna-
tional papers by Azam et al. (10), LaBranche et al. (11),
and Li et al. (12). These and many other papers document
research regarding respirable dust and, especially, silica dust.
As this paper takes a practical look at surfactants for respira-
ble silica dust, this is not the place to document these many
papers, though Arnold and her team have a review paper in
progress. Suffice it to say that respirable silica dust and its
toxicity is the subject of many current National Institute
of Occupational Safety and Health (NIOSH) studies (13).
In addition, it is important to note that the US Mine
Safety and Health Administration has put forth new silica
dust regulations for comment (14). The use of surfactants
to control dust and, especially, silica dust, is a timely topic
to review.
24-071
Practical Application of Surfactants for Respirable
Silica Dust Control
Barbara J. Arnold
The Pennsylvania State University,
University Park, PA
Randy Reed
NIOSH Pittsburgh Mining Research Division,
Pittsburgh, PA
ABSTRACT
Respirable crystalline silica poses a significant health risk,
with the American Lung Association estimating that 2.3
million workers are exposed to silica in the workplace.
This includes mine workers as well as those in many other
industries. Reducing dust formation is sometimes not pos-
sible so other methods to reduce exposure are critical. These
methods include the use of surfactants to reduce airborne
dust particles. However, it is the proper selection and appli-
cation of surfactants that leads to reduced dust exposure.
A discussion of how surfactants work, especially for silica
dust, leads to guidance for surfactant selection followed by
a review of technologies for their application.
INTRODUCTION
Respirable crystalline silica has been studied as a potential
carcinogen in dusts from many sources, including those
produced in mines. Whether mining specifically for silica
or mining other minerals, it is likely that silica is in the
mined product as it is an accessory mineral phase in many
common commodities as indicated in Table 1 (1). While
coal is not on the list, it is certainly well known that coal
also contains quartz, with a 1990 US Bureau of Mine work,
Sources and Characteristics of Quartz Dust in Coal Mines,
initiating some of the research on silica in coal (2).
Researchers have also indicated that quartz cannot be
treated as a single mineral phase as there are many variations
in contaminants and associated minerals (see, for example,
3, 4, 5). In general, however, it appears that the issue with
crystalline silica, most notably α-quartz, is the formation of
reactive oxygen species (ROS) on the surface of dust par-
ticles, forming “silanols” that interact with lung tissue to
cause fibrosis and lung cancer (3, 4, 5). These works and
others along with the increase in the occupational respira-
tory diseases silicosis and coal worker’s pneumoconiosis (6,
7, 8, 9) spawned new research, including recent interna-
tional papers by Azam et al. (10), LaBranche et al. (11),
and Li et al. (12). These and many other papers document
research regarding respirable dust and, especially, silica dust.
As this paper takes a practical look at surfactants for respira-
ble silica dust, this is not the place to document these many
papers, though Arnold and her team have a review paper in
progress. Suffice it to say that respirable silica dust and its
toxicity is the subject of many current National Institute
of Occupational Safety and Health (NIOSH) studies (13).
In addition, it is important to note that the US Mine
Safety and Health Administration has put forth new silica
dust regulations for comment (14). The use of surfactants
to control dust and, especially, silica dust, is a timely topic
to review.