United States
Environmental Protection
Agency
National Risk Management
Research Laboratory
Cincinnati, OH 45268
Research and Development
EPA/600/SR-01/039 August 2001
Project Summary D
Application of Pollution
Prevention Techniques to
Indoor Air Emissions
from Aerosol Consumer
Products
C. Bayer, R. Browner, S. Ho, L. Christiansen, L. Zhao, P. Heiselberg, M.
Tumbleson, and M. Cui
The report gives results of research,
undertaken to develop tools and meth-
odologies to measure aerosol chemical
and particle dispersion through space.
Georgia Tech Research Institute re-
searchers built an Aerosol Mass Spec-
tral Interface (AMSI), which is interfaced
with a mass spectrometer (MS), that
chemically characterizes aerosol con-
sumer products as they move through
space. University of Illinois research-
ers developed techniques for measur-
ing aerosol movement indoors by
tracking particle size changes via par-
ticle velocity measurements using par-
ticle image velocimetry (PIV). The AMSI
was designed, constructed, and opti-
mized to transfer a focused beam of
aerosol particles into a MS for chemi-
cal analysis. Experiments showed that
the AMSI can quantitatively detect com-
positional changes as the aerosol trav-
els through space. These data provide
important information for formulating
aerosol consumer products for pollu-
tion prevention strategies. The PIV sys-
tem demonstrated a correlation
between the material properties of the
aerosol components and the spray pat-
tern. These data were used to develop
a model for predicting the major char-
acteristics of aerosol spray patterns.
This Project Summary was developed
by the National Risk Management Re-
search Laboratory's Air Pollution Pre-
vention and Control Division, Research
Triangle Park, NC, to announce key find-
ings of the research project that is fully
documented in a separate report of the
same title (see Project Report ordering
information at back).
Introduction
The U.S. EPA has identified indoor air
quality (IAQ) as one of the most important
environmental risks to the Nation's health.
In the Pollution Prevention Act of 1990,
Congress declared that pollution should
be prevented or reduced at the source
whenever feasible. Modification of equip-
ment, processes, and procedures; refor-
mulations or redesign of products;
substitution of raw materials; and/or im-
provements in use procedures may ac-
complish source reduction.
Aerosol consumer products potentially
are amenable to pollution prevention
strategies that reformulate or redesign
products, substitute raw materials, and
improve use procedures. For example,
the tools developed under this project
may provide manufacturers with data
showing that products can be reformu-
lated, thereby reducing the required
amount of active ingredient. For example,
if 50% more of the active ingredient is
reaching the use site than is needed for
efficacy, the manufacturer may be able
reduce the amount of active ingredient in
the product accordingly.
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A basic understanding of the behavior
of aerosol consumer products can be used
to develop pollution prevention strategies,
which may reduce occupant exposures
and guide manufacturers in the develop-
ment of more efficacious products. The
spray cone is the dynamic three-dimen-
sional projection of the liquid aerosol par-
ticles ejected from the aerosol consumer
product spray nozzle into the air. The
length, particle sizes (and, potentially,
chemical composition), and the velocity
distribution are constantly changing as
the aerosol disperses through space. The
spray cone can be influenced by the lo-
calized air flow patterns in the space cre-
ated by natural and mechanical
ventilation. A basic understanding of the
spray cone behavior (both the chemical
composition and the particulate composi-
tion) is critical in understanding product
efficacy and in devising pollution preven-
tion strategies.
This research project was undertaken
to develop tools and methodologies to
measure aerosol chemical and particle
dispersion through space. EPA's National
Risk Management Research Laboratory
sponsored a cooperative agreement with
the Georgia Tech Research Institute
(GTRI) and the University of Illinois (Ul) to
develop tools and methodologies to mea-
sure aerosol chemical composition and
particle dispersion through space. These
tools can be used to devise pollution pre-
vention strategies that could reduce oc-
cupant chemical exposures and guide
manufacturers in formulating more effica-
cious products. GTRI researchers built an
Aerosol Mass Spectral Interface (AMSI),
which is interfaced with a mass spec-
trometer (MS), that chemically character-
izes aerosol consumer products as they
move through space. The AMSI/MS is
unique in that it measures the spatial
chemical composition of the aerosol
stream, rather than the more conventional
technique of measuring the chemical
composition of single aerosol particles.
Ul researchers developed techniques for
measuring aerosol indoors by tracking
particle size changes via particle velocity
measurements using particle image
velocimetry (PIV). This technique was used
to develop a model to predict the major
characteristics of aerosol spray patterns. In-
dustry Partners participated in this research
project to ensure that the technologies
developed would be useful to industry.
Surrogate Aerosols
The number of different aerosols is im-
mense. A major task was development of
a classification scheme representative of
most of the industry, but dividing the aero-
sol products into a manageable size for
meaningful data collection during the tools
and methods development. Also, to main-
tain the scientific integrity of the project
and the full cooperation of the Industry
Partners, it was important that the re-
search focus on generic products rather
than any specific manufacturers' formula-
tions. Since the purpose of the project
was to develop generic tools and meth-
ods that could be used by the industry as
a whole to develop pollution prevention
strategies, it was important to focus on
the end use of products rather than spe-
cific products.
The aerosol classification scheme de-
veloped for this project focuses on prod-
uct uses because they have the greatest
influence on spatial dispersion. A set of
12 surrogate aerosols, representing com-
mon formulations and uses, was devel-
oped by the Industry Partners. These fall
into three categories: 1) surface wipe aero-
sols (aerosol products that are sprayed
on a surface, then wiped off), 2) surface
non-wipe aerosols (aerosol products that
are sprayed on a surface and not wiped
off), and 3) air sprays. These are further
subdivided into the categories of lique-
fied hydrocarbon propellent and com-
pressed gas propellent aerosols, since
the propellent system can influence aero-
sol spatial dispersion and, therefore, could
be important in the design of pollution
prevention strategies. The surface wipe
and surface non-wipe surrogates were
tested both as pressurized and pump de-
livery systems. The surrogate aerosols
were designed, prepared, and supplied
by the Industry Partners.
Chemical Composition
The AMSI can be used by industry to
determine the chemical composition of
aerosol particles through space. Know-
ing the chemical composition and the
changes in the chemical composition dur-
ing particle dispersion through space may
guide the industry to make more effica-
cious products and devise pollution pre-
vention strategies through product
reformulation.
The AMSI was designed, constructed,
and optimized to transfer a focused aero-
sol beam of particles into a MS for chemi-
cal analysis. Experiments showed that the
AMSI could detect compositional changes
through space, and that the AMSI was
transferring aerosol particles into the MS.
The data obtained in this project indicate
that the AMSI/MS should be capable of
quantitative analysis, but further study is
required to confirm this. The AMSI/MS is
unique in that it can determine chemical
compositional changes as the aerosol
consumer product travels through space.
Most of the current MS research of aero-
sols measures the chemical composition
of individual aerosol particles rather than
looking at the complete stream of aerosol
particles.
The AMSI is essentially the momentum
separator portion of a particle beam (PB)
interface. The AMSI separates the aero-
sol particles from the propellents. This
was necessery since the propellents ere
the mejor components in the eerosol
sprey end overloeded the MS when the
eerosol wes spreyed directly into the MS.
The AMSI sends a focused eerosol beem
of eerosol perticles into the MS. The MS
response with AMSI wes found to be
within 5% of the stenderd devietion from
the meen peek eree.
The AMSI wes designed to relete
chemicel composition to perticle size. The
AMSI sends eerosol perticles in a streight-
line trajectory peth into the MS. A ges
flow wes epplied within the AMSI to
chenge the perticle size distribution en-
tering the MS. When no ges flow wes
epplied, the entire distribution of perticle
sizes wes transferred into the MS. When
a ges flow wes epplied, fewer of the
smeller perticles entered the MS, since
the ges flow pushed the smeller perticles
off of the streight-line trejectory peth.
One importent finding of this reseerch
project wes the detection of a contemi-
nent in the sterting meteriels used to meke
the test eerosol products. This contemi-
nent wes detecteble elso in the surrogete
eerosols. This finding cen provide impor-
tent dete for menufecturers in selecting
sterting meteriels to meke their products.
It wes found thet ion/molecule reec-
tions occur es the eerosol is ejected from
the sprey nozzle when components like
silicone ere ingredients of the eerosol
consumer product. Understending these
reections mey be importent in understend-
ing product efficecy.
Particulate Behavior
A PIV system wes used to determine
the perticulete cherecteristics of the sprey
cone of eerosol consumer products. The
PIV wes used to meesure perticle con-
centrations end velocity distributions.
These techniques were used in en envi-
ronmentel chember to investigete the ef-
fect of locelized eir flow petterns on perticle
concentretion distributions es the eero-
sols ere transported through spece in the
indoor environment.
Importent findings ebout the perticulete
behevior of eerosol consumer products
were thet compressed ges propellents
eppeered to result in e wider distribution
of perticle sizes then hydrocerbon pro-
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pellants, and that the velocity of the aero-
sol particles decreased with increasing
distance from the aerosol spray nozzle.
More than 90% of the particles were found
to be larger than 25 m. It was also found
that room air ventilation did have an ef-
fect on aerosol particle concentration dis-
tribution. The particle distribution was
stratified so that the particle distribution
was densest in the lower portion of the
room and more dilute in the upper por-
tions of the room.
A simplified engineering model was
developed to predict the mass, momen-
tum, and energy flux over space of aero-
sol consumer products - critical factors
for evaluating aerosol consumer product
efficacy. Applying the model, it was found
that the spray cone pattern showed a
correlation between material properties
of the liquids and the spray patterns. The
velocity of the aerosol particles in the
hydrocarbon propellent driven sprays ap-
peared to be increasing near the spray
nozzle. This may have been caused by
evaporation of the liquid propellents near
the spray nozzle. The velocity peaked at
a distance of 20 mm from the nozzle, and
then decreased as the distance from the
nozzle increased, probably due to air drag.
This mechanism appeared to control the
atomization process near the spray nozzle.
Technology Costs
Since the AMSI is not commercially
available and must be machined, the
costs depend on the individual machine
shop. In general, the cost of the AMSI
should be below $1000. The AMSI, in its
current form, must be interfaced with a
MS with PB or electrospray (or ion spray)
capabilities and preferably with MS/MS
capabilities. These systems range from
$150,000 to $500,000, depending on their
sophistication. Once the AMSI/MS is op-
erating, the analytical costs will range
from a few tens to a few hundreds of
dollars per sample.
The final costs of the PIV system de-
pend on the instrument manufacturer and
features of the components. Generally,
the cost of a system to measure aerosol
dispersion through space is about $75,000
to $90,000. The time required to measure
aerosol dispersion is considerable since
the data interpretation is labor-intensive.
Characterization of the aerosol spray pat-
tern requires approximately 1 hour for
data collection, approximately 6 hours to
calculate concentrations, and approxi-
mately 12 hours to calculate velocity dis-
tributions.
Technology Limitations
There are limitations to the tools devel-
oped under this project. However, most
of these limitations can be overcome with
additional research.
The AMSI is applicable only to aero-
sols that exit the nozzle in a spray form,
using either propellent or pump spray sys-
tems. Aerosols that are ejected as foams
or gels cannot be introduced into the MS
by the AMSI. Also, high viscosity aerosols
that are released primarily as dry par-
ticles, such as spray powders or paints,
will quickly contaminate the AMSI and
MS during analysis. This limitation will be
extremely difficult to overcome, and prob-
ably cannot be eliminated with the cur-
rent AMSI design. These types of products
will require a different type of sample in-
troduction method.
Particle size selection with the AMSI is
not currently calibrated. Experiments
showed that the numbers of smaller par-
ticles transferred into the MS from the
AMSI are reduced, but it is not possible to
give the range of particles that are being
transferred into the MS.
The developed PIV system allows for
the determination of two-dimensional
structures of full-scale room air flows and
particle concentration. Two cameras or
holograms are required to measure par-
ticle dispersion in three-dimensional
space. The current system measures par-
ticle velocities within 5% accuracy for par-
ticles larger than 100 m. A newer and
faster PIV system would increase speed
and simplify fate and transport measure-
ments, allowing smaller particles to be
measured with increased accuracy.
Study Results
The tools and methodologies devel-
oped under this research project can be
used to better understand aerosol con-
sumer product behavior. Once this un-
derstanding is achieved, effective pollution
prevention strategies can be designed.
Potential pollution prevention strategies
include product reformulation, raw mate-
rials substitution or more use of pure raw
materials, and modification of instructions
for users. These data can be obtained by
using the tools developed during this re-
search project.
When manufacturers begin using these
tools to study their products, they will be
able to determine the chemical composi-
tion of the products when they reach the
use site, and to determine the minimum
amount of active ingredients necessary
for efficacy. Manufacturers can investigate
the effects of product dispersion and the
effects of room air movement on disper-
sion, to better guide consumers on actual
use conditions. An understanding of the
chemistry of dispersion can lead to refor-
mulations that minimize cross-media
transference during use.
C. Bayer, R. Browner, and S. Ho are with Georgia Institute of Technology, Atlanta,
GA 30332-0400; and L Christiansen, L Zhao, P. Heiselberg, M. Tumbleson, and
M. Cui are with University of Illinois at Urbana-Champaign, Urbana, IL 61801.
Kelly W. Leovic is the EPA Project Officer (see below).
The complete report, entitled "Application of Pollution Prevention Techniques to
Reduce Indoor Air Emissions from Aerosol Consumer Products," (Order No.
PB2001-107254; Cost: $29.50, subject to change) will be available only from
National Technical Information ServiceO
5285 Port Royal RoadO
Springfield, VA 221610
Telephone: (703) 605-60000
(800) 553-6847 (U.S. only)
The EPA Project Officer can be contacted at
Air Pollution Prevention and Control Division
National Risk Management Research Laboratory
U. S. Environmental Protection Agency
Research Triangle Park, NC 27711
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