United States
Environmental Protection
Agency
Atmospheric Research and
Exposure Assessment Laboratory
Research Triangle Park, NC 27711
Research and Development
EPA/600/SR-93/050
May 1993
&EPA Project Summary
Particle Total Exposure
Assessment Methodology
(PTEAM): Riverside, California
Pilot Study - Volume I
E. D. Pellizzari, K. W. Thomas, C. A. Clayton, R. W. Whitmore, R. C. Shores, H.
S. Zelon, and R. L. Peritt
EPA's Atmospheric Research and
Exposure Assessment Laboratory
(AREAL) and the California Air Re-
sources Board sponsored a study of
human exposure to inhalable particles
in the Los Angeles Basin. A total of
178 residents of Riverside, CA, wore
specially designed personal monitors
for a day, and allowed their homes and
back yards to be monitored concur-
rently, in the fall of 1990. Personal ex-
posures averaged 150 ng/m3 during the
day, compared to indoor and outdoor
concentrations of 94-95 |ig/m3. Daytime
personal exposures to 14 of 15 ele-
ments were also significantly increased
compared to indoor and outdoor con-
centrations. Housework (vacuuming,
dusting, cooking) and sharing a home
with a smoker were two activities asso-
ciated with significantly increased ex-
posures to particles and metals.
This Project Summary was developed
by EPA's Atmospheric Research and
Exposure Assessment Laboratory, Re-
search 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
In 1986, Congress mandated that the
USEPA undertake a study of exposure to
particles. EPA's Atmospheric Research
and Exposure Assessment Laboratory
(AREAL) joined with California's Air Re-
sources Board to sponsor a study in the
Los Angeles Basin. Small portable per-
sonal monitors were designed to measure
inhalable particles (aerodynamic diameter
less than 10 |im or PM10) In addition,
stationary microenvironmehtal monitors
were designed to sample both PM10 and
PM . (fine particles <2.5 jim in diameter).
Following a 9-home study to test the mea-
surement methods in the Azusa, CA, area,
a study of 178 residents of Riverside, CA,
was carried out in the fall of 1990.
Procedure
Measurement Methods
A personal exposure monitor (PEM) was
designed to collect PM10 using a sharp-cut
impactor with a circular set of holes 1.9
mm in diameter. Particles are collected at
a flow rate of 4 Lpm on a 37-mm Teflon
filter mounted below a greased impactor
plate. The PEM consists of a soft canvas
bag containing the pump and battery pack
that can be worn on the hip, stomach,
lower back, or over the shoulder. A broad
shoulder strap supports the sampling head,
which can be moved to a comfortable
position near the collarbone using a Velcro
fastener. When worn on the body, the
pump/battery pack slides freely on a belt,
allowing it to be shifted to the most com-
fortable position depending on people's
activities or changes of posture. A leather
backing for the sampling head was added
to prevent it from being accidentally turned
toward the body, and a 2-inch guard
shaped like a hooded traffic light was
added to the top of the sampling head to
protect against skin flakes, hairs, or fibers
from clothes.
A small quiet monitor for concurrent in-
door and outdoor sampling was also cre-
ated. This monitor is called the Stationary
Ambient Monitor (SAM) when used out-
Printed on Recycled Paper
-------
doors and the Stationary Indoor Monitor
(SIM) when used indoors. The monitor
employs identical sampling heads and flow
rates as the PEM to collect PM10, but
operates off line current instead of batter-
ies. The sampling head can be replaced
with one having holes 1.4 mm in diameter
to collect fine particles (PM ). Laboratory
studies indicate that the PEM and the
SAM10 have a sharp outpoint at about 11
urn, while the SAM25has a sharp outpoint
at 2.5 |im.
Study Design
The City of Riverside, CA, was selected
for study because it is known to have
highly variable outdoor PM10 concentra-
tions and because the socioeconomic char-
acteristics of the community appeared to
provide a reasonably representative mi-
crocosm of the southern California popu-
lation. A wide range of outdoor concentra-
tions offers the best chance of determin-
ing the contribution of outdoor levels to
indoor levels and personal exposures. The
fall season was selected since Santa Ana
winds occur then; such winds can have
strong effects on the outdoor concentra-
tions of particles.
The main goal of the study was to esti-
mate the frequency distribution of expo-
sures to PM10 particles for all nonsmoking
Riverside residents aged 10 and above,
based on a probability sample of 178 resi-
dents. A second major objective was to
estimate the frequency distribution of con-
centrations of PM10 and PM25 in residences
and nearby outdoor air (e.g., back yards).
Other objectives included determining the
effect of outdoor air on indoor concentra-
tions, and the contribution of personal ac-
tivities to exposure.
A three-stage probability sampling pro-
cedure was adopted. Thirty-six areas within
Riverside were selected for study follow-
ing socioeconomic stratification. Several
homes from each area were sent letters
explaining the study. Interviewers then col-
lected information about each household
and invited eligible residents to partici-
pate. Respondents represented 139,000
± 16,000 (S.E.) nonsmoking Riverside resi-
dents aged 10 and above.
Smokers were excluded from participat-
ing, but nonsmoking members of their fam-
ily were not. Employed persons were
slightly oversampled, since employment
was thought to be a possible risk factor
for exposure to particles.
Each participant wore the PEM for two
consecutive 12-hour periods. Concurrent
PM10 and PM samples were collected
by the indoor SIM and outdoor SAM at
each home. This resulted in 10 samples
per household (day and night samples
from the PEM10, SIM10, SIM25, SAM10, and
SAM25). Air exchange rates were also cal-
culated for each 12-hour period, using the
perfluorotracer technique.
Participants were asked to note activi-
ties that might involve increased particle
levels (nearby smoking, cooking, garden-
ing, etc.). Following each of the two 12-
hour monitoring periods, they answered
an interviewer-administered recall ques-
tionnaire concerning their activities and
locations during that time.
Up to four participants per day could be
monitored, requiring 48 days in the field.
A central outdoor site was maintained over
the entire period (Sept. 22-Nov. 9, 1990).
The site had two high-volume samplers
(Wedding & Assoc.) with 10-|j.m inlets (ac-
tual outpoint about 9.0 urn), two dichoto-
mous PM10 and PM25 samplers (Sierra-
Andersen) (actual outpoint about 9.5 |im),
one PEM and one SAM.
All filters were weighed on-site and then
analyzed for elements by x-ray fluores-
cence (XRF). An additional set of about
600 citric-acid treated filters from personal
and indoor samplers was analyzed for
nicotine.
Filters were weighed before use and
again within 48 hours of collection at an
on-site weighing facility with controlled tem-
perature and humidity. Replicate weighings
were required to be within 4 ^g/filter. Blank
filters were weighed, sent out with field
samples, and reweighed along with the
field samples. Duplicate indoor and out-
door samples were collected at 10% of
the homes. Duplicate SAM and PEM
samples were also collected at the central
. site. Duplicate PEM samples were also
collected by EPA, RTI, and Harvard sci-
entists while on site.
Results
Of 632 permanent residences contacted,
443 (70%) completed the screening inter-
view. Of these, 257 were asked to partici-
pate and 178 (69%) agreed. More than
2750 particle samples were collected,
about 96% of those attempted.
Quality of the Data
Blank PEM and SIM/SAM filters (N =
51) showed consistent small increases in
mass of 5-10 jig. Blanks (N = 9) placed
near ungreased impactor plates had simi-
lar increases of 7 jig. Blank dichot filters
(N = 41) showed increases averaging 4
p.g. Blank SSI filters had increases of about
170 |ig. XRF analyses indicated that the
increase was not due to aerosol; possibili-
ties include water vapor or electric charge,
although stringent efforts were made to
control humidity and static charge in the
on-site weigh room. The effect of the in-
crease is small (0.4-4 jig/m3) and was
corrected for by subtracting the mean blank
value from all samples. Limits of detection
(LODs), based on three times the stan-
dard deviation of the blanks, were on the
order of 10 ng/m3. All field samples ex-
ceeded the LOD.
Duplicate samples (N = 363) showed
excellent precision for all types of sam-
plers at all locations, with median relative
standard deviations ranging from 2-4%.
The collocated samplers at the central
site showed good agreement, with corre-
lations ranging from 0.96 to 0.99. As had
been noted in the pilot study, the PEM
and SAM collected about 12% more mass
than the dichotomous samplers (Figure
1), perhaps due to their higher outpoint
(11 jam compared to 9.5 |j.m) or to a par-
ticle "bounce" effect, measured in the labo-
ratory at less than 9%. The Wedding sam-
plers collected about 13% less mass than
the dichots at night, but about the same
level during the day, reflecting a possible
temperature dependency on the part of
the Wedding. Although these small differ-
ences were significant, they do not affect
the main conclusions.
All PEM, SIM, SAM, and dichotomous
sampler filters (about 2500) were ana-
lyzed by XRF for a suite of 42 elements.
The analysis was carried out at EPA's
Atmospheric Research and Exposure As-
sessment Laboratory in Research Triangle
Park, NC. Some filters were analyzed twice
under blind conditions. A subset of about
100 filters was analyzed by the Lawrence
Berkeley Laboratory (LBL) for quality as-
surance purposes.
Background levels on laboratory and
field blanks were very low for 19 of 20
elements. Blank levels for iron were slightly
higher but were 4 to 100 times lower than
observed concentrations. Analyses of stan-
dard reference materials (SRM 1832 and
1833) were within 7% of the correct val-
ues for all 12 elements contained. Median
relative standard deviations (RSD) for du-
plicates analyzed blindly by the principal
laboratory were less than 15% for all 15
prevalent (more than 30% of samples with
measurable quantities) elements. Median
RSDs for duplicates analyzed by the two
laboratories were less than 21% for all
elements except manganese (76%) and
copper (27%). The LBL laboratory reported
10-20% higher average values for 13 of
14 elements. All filters analyzed by LBL
had been first analyzed by EPA.
-------
Comparison of Methods
PEM-SAM vs. Dichot
250
100
Mean of Dichots (\ig/m 3)
150
200
Figure 1.
The collocated PEM and SAM showed good precision but a positive bias
with respect to the dichotomous samplers.
Concentrations
Outdoor 12-h PM10 concentrations at
the central site ranged from 20-200 |ig/
m3, with the fine particles accounting for
most of the variation (Figure 2). On the six
windiest (16-20 mph) days, the coarse
particles accounted for most of the PM10
mass.
Population-weighted daytime personal
PM10 concentrations averaged about 150
ng/m3, compared to concurrent indoor and
outdoor mean concentrations of about 95
p.g/m3 (Table 1; Figure 3). The overnight
personal PM10 mean was much lower (77
|j.g/m3) and more similar to the indoor (63
|ig/m3) and outdoor (86 jig/m3) means (Fig-
ure 4). Approximately 25% of the popula-
tion was estimated to have exceeded the
24-h National Ambient Air Quality Stan-
dard for PM10 of 150 jig/m3. Over 90% of
the population exceeded the California
Ambient Air Quality Standard of 50 ng/m3.
Fine (PM25) particles accounted for about
50% of the total PM10 mass both indoors
and outdoors.
The measurements at the central site
showed good agreement with the outdoor
measurements at homes throughout the
City of Riverside (Figure 5), indicating that
a single central-site PM10 monitor can char-
acterize a large urban area adequately.
Although the correlations of indoor air con-
centrations with outdoor air are lower, there
is evidence (Figure 6) that outdoor air
PM10 concentrations can affect indoor air
concentrations.
Population-weighted mean elemental
concentrations for 15 prevalent elements
are provided in Table 2. As with the par-
ticle mass, daytime personal exposures
were consistently higher than either in-
door or outdoor concentrations of all the
elements save sulfur. At night, levels were
similar in all three types of samples. The
weighted mean element/particle mass ra-
tios are provided in Table 3. The personal
and indoor PM10 samples are depleted in
the crustal elements (Si, Al, Fe) compared
to the outdoor samples, by amounts rang-
ing from 15 to 25%. The indoor PM25
samples show no depletion in any ele-
ments and may be slightly enriched in Ca,
K, Cl, and (night only) S.
Models of Exposure
Questionnaires were analyzed to detect
activities associated with increased expo-
sure. Housework (dusting, vacuuming,
cooking) was associated with significantly
increased personal exposures and indoor
air concentrations during the day (Table
4). Sharing a home with one or more
smokers also led to increased personal
exposures and indoor air concentrations
during the night. Persons who commuted
to work had significantly lower exposures
than those who stayed at home, perhaps
due to the housework activities of the lat-
ter group.
Discussion
Source of Excess Personal
Exposure
The source or sources of the roughly
50% increase in daytime personal expo-
sure compared to the indoor and outdoor
air concentrations remain unclear. Sev-
eral possibilities include
1) The apparent increase is due to differ-
ent sampling characteristics of the per-
sonal monitor.
2) The increase is due to skin flakes or
clothes fibers accumulating on the per-
sonal monitor.
3) The increase is due to increased expo-
sures encountered while participants are
out of the house.
4) The increase is due to generation or
reentrainment of particles during per-
sonal activities.
The first possibility has been tested in
several ways. The only difference between
the PEM and the SIM is the pump (Casella
vs. Medo). Laboratory tests of the two
pumps failed to show any difference in
sampling characteristics on a test aerosol.
Wind speed and direction were also tested
and had little effect on either the PEM or
the SIM. Particle bounce should affect both
the PEM and SIM equally, since the sam-
pling heads are identical. It remains pos-
sible that the constant motion of the PEM
may somehow affect its sampling charac-
teristics compared to the fixed SIM.
The second possibility was tested by
scanning electron microscopy (SEM) on
three sets of personal, indoor, and out-
door filters. Although skin flakes were
found in large numbers on one personal
filter, their mass seemed insufficient to
explain the mass difference. Also, if most
of the increased mass were due to skin
flakes or fibers, increases in elements other
than carbon would not be expected; how-
ever, 14 of 15 elements were also el-
evated in the personal samples.
The third possibility has been partially
tested by comparing persons who went to
work on the day of monitoring with those
who did not. Even though their daytime
exposures included round-trip commutes
in Los Angeles County traffic, their expo-
sures were significantly lower than those
of participants who stayed at home.
The fourth possibility seems likely. Per-
sons engaging in activities such as vacu-
uming, dusting, and cooking had signifi-
cantly higher exposures than the other
participants. House dust is a mixture of
airborne outdoor aerosols, tracked-in soil
and road dust, and aerosols produced by
-------
Central Site: PM-10 and Coarse Particles
200
20
40 60 80
12-Hour period beginning Sept. 22, 1990
100
Figure 2.
During the 48-day sampling period, two extended peaks characterized by elevated
fine particles (PM-2.5) occurred. Coarse particles were elevated on days with high
wind speeds.
Table 1. Population-Weighted' Concentrations and Standard Errors (iig/m3)
Sample Type
Daytime PM10
Personal
Indoor
Outdoor
Overnight PMW
Personal
Indoor
Outdoor
Daytime PM25
Indoor
Outdoor
Overnight PM2S
Indoor
Outdoor
N
171
169
165
168
163
162
173
167
166
161
Median
130 ±8
82 ±8
83 ±5
66±4
52 ±4
74 ±4
34 ±4
36±4
26 ±2
35 ±2
Arithmetic
Mean
150 ±9
95 ±6
94 ±6
77 ±4
63 ±3
87 ±4
48 ±4
49 ±3
36 ±2
51 ±4
Percentile
90%
260 ± 12
180 ±11
160 ± 7
140 ± 10
120 ± 5
170 ± 5
100 ± 7
100 ±6
83 ±6
120 ±5
98%
380
240
240
190
160
210
170
170
120
160
'Personal samples weighted to represent nonsmoking population of 139,000 Riverside residents
aged 10 or above. Indoor-outdoor samples weighted to represent 61,500 homes with at least one
nonsmoker aged 10 or above.
indoor sources. As such, it should contain
crustal elements from soil, lead and bro-
mine from automobiles, and other elements
from combustion sources. This would be
consistent with the observation that nearly
all elements were elevated in personal
samples. The fact that personal overnight
samples showed smaller mass increases
than the personal daytime samples is also
consistent with the fact that the partici-
pants were sleeping for much of the 12-
hour overnight monitoring period and were
thus not engaging in these particle-gener-
ating or reentraining activities. There re-
mains the problem of sulfur, which showed
no increase in personal samples compared
to indoor or outdoor samples. This may
be because sulfate ions have a much
smaller mass median diameter and a lower
deposition velocity than other ionic con-
stituents of fine particles. Thus, sulfur
would not tend to accumulate in house
dust as much as other elements. Also,
smaller particles may be harder to dis-
lodge from surfaces, due to electrostatic
or Van der Waals forces.
Conclusions and
Recommendations
The personal and microenvironmental
monitors designed especially for this study
performed well. About 96% of all samples
attempted were collected and median pre-
cision was 2-4%. A positive bias of about
12% was noted with respect to the refer-
ence dichotomous sampler method.
The major finding of the study was the
50% increase in daytime personal expo-
sures to PM10 compared to indoor and
outdoor concentrations. The increase ap-
pears to be due to personal activities such
as dusting, vacuuming, cooking, and shar-
ing a home with a smoker. This suggests
that reduction of dust levels in the home
could decrease exposure to airborne par-
ticles.
Future Publications
Volume II of this three-volume series
presents the results of measurements of
polyaromatic hydrocarbons (PAH) and
phthalates in 120 of the 178 homes in this
study. Entitled "PTEAM: Monitoring of
Phthalates and PAHs in Indoor and Out-
door Air Samples in Riverside, Califor-
nia—Volume II," it is available from the
California Air Resources Board, Sacra-
mento, CA.
Volume III will present the results of
additional statistical analyses and physi-
cal modeling. It will also contain the re-
sults of the nicotine analyses and the air
exchange rate measurements. Volume III
will be available in 1993 from the National
Technical Information Service (NTIS).
-------
Particle Levels: Daytime PTEAM Study: Riverside, CA
1000
co
100
10
_L
1000
Figure 3. Population- or household-weighted frequency
distributions of 12-h average concentrations of
PM-10 and PM-2.5 show a nearly log-normal
shape for personal, indoor, and outdoor air.
Daytime personal levels are 50% higher than
concurrent indoor/outdoor levels.
100
25%
50
10
75
90 95
98 99%
In 2.5
Pers 10
-O-- Out2.5
—•— In 10
—- Out 10
Particle Levels: Overnight PTEAM Study: Riverside, CA
WOO
100
10
Figure 4. At night, personal concentrations sink to levels
comparable with outdoor air. Indoor levels of
both PM-10 and PM-2.5 also fall to 60-70% of
outdoor levels.
25%
1000
100
50
Pers 10
In 2.5
75
—•— In 10
--O- Out 2.5
90 95 98 99%
--- Out 10
10
-------
Outdoor PM-10: Homes vs. Central Site
250
200
150
100
50
0 50
The line is the 1:1 line.
100 150
SAM-10(\ig/m3)
200
250
Figure 5. Outdoor PM-10 levels near homes were also well characterized by the identical
monitor at the central site.
Indoor vs. Outdoor PM-10: Overnight
200
100 150
Outdoor (\ig/m 3)
200
250
Figure 6. Although there is considerable scatter due to indoor sources and activities,
outdoor concentrations near the home appear to have considerable impact on
indoor concentrations.
-------
Table 2.
Element
Si
Al
Ca
Fe
Mn
K
Br
Pb
S
Zn
Cl
Ti
Cu
Sr
P
Mean Elemental Concentrations (ng/m3) in Personal,
Daytime
PJ
SAM
740.
b
330.
400.
12.
230.
8.8
20.
1500.
41.
83.
-
-
-
-
SIM
700.
-
380.
340.
9.8
260.
9.1
17.
1300.
42.
130.
-
11.
-
-
SAM
7700.
3100.
2300.
2300.
51.
1100.
10.
30.
1800.
65.
230.
210.
15.
18.
-
PM10
SIM
6300.
2300.
2300.
1800.
38.
1100.
13.
27.
1700.
86.
410.
190.
22.
15.
-
Indoor, and Outdoor Samples'
PEM
12000.
4700.
4300.
3400.
69.
1900.
25.
40.
1800.
150.
840.
390.
41.
25.
230.
P/l
SAM
380.
-
170.
260.
9.9
150.
11.
23.
1600.
38.
170.
-
9.6
-
-
J25
SIM
360.
.
200.
200.
7.5
200.
8.6
20.
1300.
34.
100.
.
8.9
.
-
Nighttime
SAM
5000.
2000.
1500.
1700.
37.
800.
13.
32.
1900.
56.
500.
140.
17.
14.
-
PMW
SIM
3300.
1200.
1200.
990.
22.
650.
11.
27.
1500.
60.
290.
100.
15.
9.8
-
PEM
4200.
1400.
1700.
1200.
24.
800.
14.
26.
1500.
67.
440.
130.
19.
11.
-
"Results are weighted to reflect the target population of individuals (PEM samples) or households (SIM and SAM samples).
"Fewer than 30% of samples with concentrations greater than the uncertainty limit.
Table 3. Mean Ratios of Element/Particle Masses (%) in Personal, Indoor, and Outdoor Samples'
Element
Si
Al
Ca
Fe
Mn
K
Br
Pb
S
Zn
Cl
Ti
Cu
Sr
P
P/l
SAM
2.16
b
0.94
1.17
0.04
0.60
0.02
0.06
3.30
0.13
0.16
-
-
-
-
SIM
2.37
-
1.19
1.09
0.03
0.69
0.02
0.05
3.22
0.13
0.27
-
0.04
-
-
Daytime
SAM
9.04
3.63
2.70
2.72
0.06
1.27
0.01
0.03
1.92
0.08
0.28
0.25
0.02
0.02
-
PMW
SIM
7.15
2.56
2.57
1.99
0.04
1.18
0.01
0.03
2.01
0.11
0.44
0.21
0.03
0.02
-
PEM
7.57
2.88
2.85
2.14
0.04
1.22
0.02
0.03
1.36
0.11
0.58
0.25
0.03
0.02
0.15
Nighttime
PM25 PM,0
SAM
1.39
-
0.58
0.83
0.03
0.47
0.02
0.06
3.62
0.12
0.40
-
0.03
-
SIM
1.74
-
0.90
0.85
0.03
0.72
0.03
0.07
4.28
0.15
0.34
-
0.04
-
SAM
7.02
2.78
2.12
2.25
0.05
1.09
0.02
0.04
2.23
0.07
0.68
0.19
0.02
0.02
SIM
5.97
2.08
2.14
1.71
0.04
1.11
0.02
0.04
2.73
0.11
0.52
0.18
0.03
0.02
PEM
5.72
1.87
2.31
1.56
0.03
1.09
0.02
0.03
2.16
0.10
0.61
0.18
0.03
0.02
"Results are weighted to reflect the target population of individuals (PEM samples) or households (SIM and SAM samples). Estimated means < 0 are
reported as 0.
"Fewer than 30% of samples with concentrations greater than the uncertainty limit.
'ftV.S. GOVERNMENT PUNTING OFFICE: 1993 • 7S047I/IMM07
-------
Table 4. Effects of Activities on Mean Personal and Indoor Air PM10 Concentrations
Activity
and Sample
Type
Housework (Day)
Personal
Indoor
Smoking (Night)
Personal
Indoor
Work (Day)
Personal
Homes/Persons
With Activity
N
110
111
29
30
59
Mean
162'
106'
104'
93'
127
(SE)
(11)
(8)
(8)
(9)
(12)
Homes/Persons
Without Activity
N
61
58
139
131
111
Mean
125
71
71
55
162'
(SE)
(11)
(6)
(3)
(3)
(10)
"Both arithmetic mean (shown) and geometric mean significantly (p<0.05) higher than correspond-
ing value for other group.
E. D. Pellizzari, K. W. Thomas, C. A. Clayton, P. W. Whitmore, R. C. Shores, H. S.
Zelon, and R. L. Peritt are with Research Triangle Institute, Research Triangle
Park, NC 27709-2194
Lance A. Wallace is the EPA Task Manager (see below).
The complete report, entitled "Particle Total Exposure Assessment Methodology
(PTEAM): Riverside, California Pilot Study-Volume I" (Order No. PB93-166 957/
AS; Cost: $44.50, 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 Task Manager can be contacted at:
Atmospheric Research and Exposure Assessment Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, NC 27701
United States
Environmental Protection Agency
Center for Environmental Research Information
Cincinnati, OH 45268
BULK RATE
POSTAGE & FEES PAID
EPA
PERMIT No. G-35
Official Business
Penalty for Private Use
$300
EPA/600/SR-93/050
------- |