United States
Environmental Protection
Agency
Air and Energy Engineering
Research Laboratory
Research Triangle Park NC 27711
Research and Development
EPA/600/S2-87/102 Feb. 1988
SERA Project Summary
Evaluation of the Effectiveness
of Chemical Dust Suppressants
on Unpaved Roads
G. E. Muleski and C. Cowherd, Jr.
The long-term effectiveness of five
unpaved-road chemical dust suppres-
sants was measured. Effectiveness at
controlling total particulate emissions
in three size fractions ( < 15, < 10,
and < 2.5 fjm] was determined over
several cycles of chemical application,
control effectiveness decay, and chem-
ical reapplication. All five chemicals
were tested on the same road with each
chemical used on separate, abutting
road segments. The chemicals were
applied in quantities that spanned the
range of common practice in the steel
industry. Traffic parameters were
typical of the steel industry. Over a 30-
day period, control effectiveness of
each chemical decreased: in some
cases by as much as 50%, and in others
by as little as 10%. Control effective-
ness for all chemicals was greater than
95% immediately after chemical appli-
cation or reapplication. The rate of
decay was approximately the same for
all particle size ranges investigated.
Road surface silt loading was found to
be a reliable indicator of relative
effectiveness for some chemicals.
This Project Summary was devel-
oped by EPA's Air and Energy Engi-
neering Research Laboratory. Research
Triangle Park, NC. to announce key
findings of the research project that is
fully documented in a separate report
of the same title (see Project Report
ordering information at back).
Introduction
Many studies of the iron and steel
industry have shown that open dust
sources (e.g., vehicular traffic on paved
and unpaved roads, material handling,
and wind erosion) merit prime consid-
eration in the development of particulate
emission control strategies. This conclu-
sion has been based on (a) industry-wide
comparisons between uncontrolled
emissions from open dust sources, and
(b) typically controlled fugitive emissions
from major process sources such as
steelmaking furnaces, blast furnaces,
coke ovens, and sinter machines. In
addition, preliminary cost-effectiveness
(dollars expended per unit mass of
reduced particulate emissions) analysis
of promising control options for open dust
sources has indicated that control of
these sources might result in signifi-
cantly improved air quality at a lower cost
compared to the control of process
sources.
Of open dust sources, vehicular traffic
on paved and unpaved roads generally
account for the vast majority of partic-
ulate emissions in the iron and steel
industry. For the 1970s, unpaved surfa-
ces were estimated to account for
roughly 70% of open source particulate
emissions in the industry. By the early
1980s, the contribution was considera-
bly less. This reduction was due to
implementation of dust control programs
which, in addition to chemical treatment
of unpaved roads, included paving many
roads and using shuttle buses to reduce
emissionsfrom employees commuting to
their work stations.
Some unpaved roads in the iron and
steel industry are, by their nature, not
suitable for paving. These roads are
normally used by very heavy vehicles or
may be subjected to considerable spil
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lage. Because of the additional mainte-
nance costs associated with a paved road
under this type of service environment,
emissions from these roads generally are
controlled with regular reapplications of
chemical treatments.
Besides water, petroleum resins (such
as Coherex®) have historically been the
products most widely used in the indus-
try; however, considerable interest has
been shown at both the plant and
corporate level in alternative chemical
dust suppressants. As a result of this
continued interest, several new dust
suppressants have been introduced
recently, including asphalt emulsions,
acrylics, salts, and adhesives. In addition,
the generic petroleum resin formulations
developed at the Mellon Institute with
funding from the American Iron and Steel
Institute (AISI), have gained considerable
attention. These generic suppressants
were designed to be produced on-site at
iron and steel plants.
The overall objective of this study was
to provide data that document the
reduction of paniculate emissions (in
several particle size ranges) generated by
vehicular traffic on representative
unpaved roads in the iron and steel
industry following control application.
The data were used to provide average
control efficiencies for common road dust
suppressants, over ranges of averaging
periods and application parameters that
span typical values used in the iron and
steel industry. Information of this type
is valuable to both industry and regula-
tory personnel in developing and mon-
itoring dust control programs.
Secondary objectives, which largely
supported the primary objective stated
above, included: (a) a survey of current
and projected industry practices in
unpaved road dust control; (b) character-
ization of traffic on unpaved roads in the
industry; (c) collection of cost data to
develop relative cost-effectiveness
values for the suppressants evaluated;
(d) examination of less expensive mea-
sures to monitor control performance;
and (e) analysis of previous studies to
develop a model to estimate control
performance.
Summary and Conclusions
The purpose of this study was to obtain
data characterizing the average control
performance of dust suppressants com-
monly used by the iron and steel industry
to mitigate particulate emissions from
unpaved roads. Vehicular traffic on
unpaved roads has been estimated to
contribute more than half of the sus-
pended particulate emissions from open
sources in the industry.
Control efficiency values were deter-
mined not only for total particulate (TP),
but also for particles < 15 /um in aero-
dynamic diameter (inhalable particulate,
IP), < 10 //m in aerodynamic diameter
(PMio), and < 2.5 fjm in aerodynamic
diameter (fine particulate, FP). The study
focused on PMio control performance of
dust suppressants in particular, because
this size fraction is anticipated to form
the basis of any revised National Ambient
Air Quality Standard for particulate
matter.
To make the control performance test
results as useful as possible to the
industry, unpaved road vehicular traffic
characteristics and dust control tech-
niques used in the industry were sur-
veyed early in the study. Subsequently
these results formed the basis for the
design of the field testing program so that
commonly used suppressants could be
evaluated under service conditions
representative of typical iron and steel
industry unpaved roads.
The exposure profiling method deve-
loped by MRI was the technique utilized
to measure uncontrolled and controlled
emission factors for vehicular traffic on
unpaved roads. Exposure profiling of
roadway emissions involves direct iso-
kinetic measurement of the total passage
of open dust emissions about 5 m
downwind of the edge of the road by
means of simultaneous sampling at four
points distributed vertically over the
effective height of the dust plume.
Downwind particle size distributions
were measured using cyclone precollec-
tors followed by parallel-slot cascade
impactors. Upwind particle size distribu-
tions were also determined using impac-
tion. A total of 64 tests of controlled and
uncontrolled particulate emissions from
vehicular traffic on unpaved roads were
conducted at two iron and steel plants.
Five chemical dust suppressants were
evaluated during the study: PetroTac, an
emulsified asphalt; Coherex®, a petro-
leum resin; Soil-Sement, an acrylic
cement; Generic 2 (QS), a generic
petroleum resin product developed at the
Mellon Institute; and Liquidow, a salt
(calcium chloride). All products, except
Generic 2, have been used in iron and
steel plants. In addition, industry person-
nel have expressed considerable interest
in the use of Generic 2.
These suppressants were applied ii
quantities that generally span the rang
of common practice in the industry
manufacturers' recommendations, ani
previous field evaluations. Control effi
ciency was measured over periods up t
70 days after application, although thi
main averaging period of interest wa
about 1 month. The latter is represen
tative of time periods between contrc
applications in the industry.
All chemicals tested exhibited averagi
control efficiencies of about 50% or mon
over the first 30 days after application
These tests were conducted using appli
cation and traffic parameters that ma'
be considered typical in the iron and stee
industry. Note that, while the contrc
provided by some suppressants showei
significant temporal decay, others exhi
bited a relatively constant level of contro
over the time period.
Statistical analyses of the data mdicati
that reapplication results in a signifi
cantly higher level of control and tha
only one suppressant exhibited signifi
cant differences in control between th<
various particle size fractions. Compar
isons between the control efficiencies fo
different chemicals indicate that rela
lively few suppressant/size fractioi
combinations could be considered signif
icant at the 5% level.
Comparison of the relative cost
effectiveness reveals only a slight vari
ation between the suppressants othe
than calcium chloride. In terms of cost
effectiveness, the salt did not compan
favorably with the other products; how
ever, this is at least a partial result o
the abnormally high precipitation durini
the field exercise.
Several road surface material proper
ties were discussed as possible tndica
tors of control performance. Whil<
reasonably strong relationships betweer
silt loading and control were found fo
some of the suppressants, the clustere(
nature of the entire data set preclude!
development of a reliable performanc<
indicator. However, the data suggest tha
the industrial paved road emission facto
equation may be used to conservatively
overestimate emissions from controlle(
unpaved roads.
Finally, results of previous tests were
combined with data from the presen
study to develop an average contro
performance model for petroleum resins
The model was designed to meet typica
needs in the iron and steel industry ir
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terms of averaging periods and service
environments.
G. Muleski and C. Cowherd. Jr. are with Midwest Research Institute, Kansas
City. MO 64110.
Robert C. McCrillis is the EPA Project Officer (see below).
The complete report, entitled "Evaluation of the Effectiveness of Chemical Dust
Suppressants on Unpaved Roads," (Order No. PB 88-139 936/AS; Cost:
$14.95, subject to change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Air and Energy Engineering Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
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Environmental Protection
Agency
Center for Environmental Research
Information
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