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

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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.

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                               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

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                        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).

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                  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

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                          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.

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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

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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
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