EPA/600/Ar93/l|4
INDOOR, OUTDOOR/ AND PERSONAL AIR EXPOSURES TO PARTICLES,
ELEMENTS, AND NICOTINE FOR 178 RESIDENTS OF RIVERSIDE,
CALIFORNIA.
Lance A. Wallace1, Haluk Ozkaynak2, John D. Spengler2, Edo D.
Pellizzari3 and Peggy Jenkins2
1	Atmospheric Research and Exposure Assessment Laboratory,
Environmental Protection Agency, Warrenton, VA, USA
2	Harvard University School of Public Health, Boston, MA, USA
3	Research Triangle Institute, Research Triangle Park, NC, USA
* California Air Resources Board, Sacramento, CA, USA
ABSTRACT
Personal, indoor, and outdoor concentrations of inhalable
particles and 15 elements were measured for a probability sample
of 178 persons representing 139,000 nonsmoking residents of
Riverside, California. Newly designed personal monitors were
employed. Personal exposures often exceeded concurrent indoor
and outdoor concentrations, both for particles and for 14 of 15
associated elements. The increase appears to be due to personal
activities such as dusting, vacuuming, cooking, and sharing a
home with a smoker. This suggests that reduction of dust levels
in the home could decrease exposure to airborne particles.
INTRODUCTION
In 1986, Congress mandated that the US EPA undertake a study of
exposure to particles. EPA's Atmospheric Research and Exposure
Assessment Laboratory (AREAL) joined with California's Air
Resources Board to sponsor a study in the Los Angeles Basin.
Small personal monitors were designed to measure inhalable
particles (aerodynamic diameter less than 10 jim, or PM10) . The
same monitors were used (with interchangeable sampling nozzles)
to sample both inhalable (PM10) and fine (PM2 5) particles indoors
and outdoors.
Following a 9-home study to test the measurement methods in the
Azusa, CA area, a full-scale study was carried out in Riverside,
CA in the fall of 1990. The main goal of the study was to
estimate the frequency distribution of exposures to PM10
particles for all nonsmoking Riverside residents aged 10 and
above, based on a probability sample of 178 residents. A second
major objective was to estimate the frequency distribution of
concentrations of PM10 and PM2 5 in residences and nearby outdoor
air (e.g., back yards). Other objectives included determining
the effect of outdoor air on indoor concentrations, and the
contribution of personal activities to exposure.

-------
METHODS AMD STUDY DESIGN
A personal exposure monitor (PEM) was designed to collect PM,0
using a sharp-cut impactor with a circular set of holes each 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.
A backup filter coated with citric acid collected nicotine vapor.
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.
The same monitor, modified to operate with line current, was used
to collect indoor and outdoor samples. This monitor is called
the Stationary Ambient Monitor (SAM) when used outdoors and the
Stationary Indoor Monitor (SIM) when used indoors. The sampling
head can be replaced with one having holes 1.4 mm in diameter to
collect fine particles (PM2 5) . Laboratory studies indicate that
the PEM and the SAM10 have a sharp cutpoint at about 11	while
the SAM25 has a sharp cutpoint at 2.5 jm*
A central site was selected to provide a record of temporal
changes in outdoor particle levels for the duration of the study
(48 days). The site had two high-volume samplers (Wedding &
Assoc.) with 10-/xm inlets (actual cutpoint about 9.0 /xm) , two
dichotomous PM10 and PM2 5 samplers (Sierra-Andersen) (actual
cutpoint about 9.5 /im and 2.5 /im) , one PEM and one SAM.
The city of Riverside, CA was selected for study because it is
known to have highly variable outdoor PM10 concentrations (1).
A wide range of outdoor concentrations offers the best chance of
determining 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 concentrations of particles (1).
A three-stage probability sampling procedure was adopted.
Thirty-six areas within Riverside were selected for study
following socioeconomic stratification. Several homes from each
area were sent letters explaining the study. Interviewers then
collected information about each household and invited eligible
residents to participate. Respondents represented 139,000 +
16,000 (S.E.) nonsmoking Riverside residents aged 10 and above.
Smokers were excluded from participating, but nonsmoking members
of their family 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 PM2 5 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 PEM.0,
SIM10, SIM, 5, SAM10, and SAM25.) Air exchange rates were also
calculated' for each 12-hour' period, using perfluorotracers (1) .

-------
Participants were asked to note activities that might involve
increased particle levels (nearby smoking, cooking, gardening,
etc.)- Following each of the two 12-hour monitoring periods,
they answered an interviewer-administered recall questionnaire
concerning their activities and locations during that time.
All filters were weighed on-site and then analyzed for elements
by x-ray fluorescence (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
temperature and humidity. Replicate weighings were required to
be within 4 /xg/filter. Blank filters were weighed, sent out with
field samples, and reweighed along with the field samples.
Duplicate indoor and outdoor samples were collected at 10% of the
homes. Duplicate SAM samples were collected at the central site.
Duplicate PEM samples (5% of the total) were also collected by
EPA, RTI, and Harvard scientists while on site.
RESULTS
Of 632 permanent residences contacted, 443 (70%) completed the
screening interview. Of these, 257 were asked to participate and
178 (69%) agreed. More than 2750 particle samples were
collected, about 9 6% of those attempted.
Blank PEM and SIM/SAM filters (N = 51) showed consistent small
increases in mass of 5-10 ng. XRF analyses indicated that the
increase was not due to particles? possibilities 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 increase is small (0.4-4 fig/m3) and was
corrected for by subtracting the mean blank value from all
samples. Limits of detection (LODs), based on three times the
standard deviation of the blanks, were on the order of 10 /ig/m3.
All field samples exceeded the LOD.
Duplicate samples (N = 363) showed excellent precision for all
types of samplers at all locations, with median relative standard
deviations ranging from 2-4%.
The collocated samplers at the central site showed good
agreement, with correlations 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, perhaps due to their
higher cutpoint (11 jim compared to 9.5 jxm) or to a particle
"bounce" effect, measured in the laboratory at less than 9%. The
Wedding samplers 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 differences were significant, they do not
affect the main conclusions.

-------
All PEM, SIM, SAM, and dichotomous sampler filters (about 2500)
vere analyzed by x-ray fluorescence (XRF) for a suite of 42
elements (1). The analysis was carried out at EPA's Atmospheric
Research and Exposure Assessment 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).
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 standard reference materials (SRM
1832 and 1833) were within 7% of the correct values for all 12
elements contained. Median relative standard deviations (RSD)
for duplicates 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%).
Outdoor 12-h PM-10 concentrations at the central site ranged from
20-200 /xg/m3, with the fine particles accounting for most of the
variation. On the six windiest (16-20 knots) days, the coarse
particles accounted for most of the PM10 mass.
Population-weighted daytime personal PM,q concentrations averaged
about 150 /xg/m , compared to concurrent indoor and outdoor mean
concentrations of about 95 /xg/m3 (Table 1). The overnight
personal PM10 mean was much lower (77 /xg/m3) and more similar to
the indoor (63 /xg/m3) and outdoor (86 /xg/m3) means. About 25% of
the population was estimated to have exceeded the 24-h National
Ambient Air Quality Standard for PM10 of 150 /xg/m3. Over 90% of
the population exceeded the California Ambient Air Quality
Standard of 50 /xg/m3. Fine (PM2^) particles accounted for about
50% of the total PM10 mass both indoors and outdoors.
The measurements at the central site showed good agreement (r =
0.93 at night, 0.66 during the day) with the outdoor measurements
at homes throughout the City of Riverside, indicating that a
single central-site PM10 monitor can characterize a large urban
area adequately. Although the correlations of indoor air
concentrations with outdoor air are lower (0.59 at night, 0.51
during the day), they provide some evidence that outdoor air PM10
concentrations can affect indoor air concentrations.
Air exchange rates varied from 0.15 to 4.74 h"1, with mean
(median) values of 1.24 (1.02) h"1 (daytime) and 1.09 (0.80) h'1
(overnight) in 174 homes. Nicotine levels ranged from 0.05 /xg/m3
to 14.9 /xg/m3, with a mean (median) value of 1.42 (0.45) /xg/m3.
Nicotine levels were measurable (mean of 2.2 /xg/m3) in 35 of the
39 homes reporting smoking, and were below detectable levels
(mean of .12 /xg/m ) in all but six homes without smokers.
Personal nicotine mean levels were similar to indoor means (1.48
/xg/ro3 vs. 1.39 /xg/m3).

-------
Table 1. Population-Weighted8 Concentrations (+ SE) (Mg/m3)
Arith.	Percentile
SamDle tvxse
li
Median
Mean

9 o%


98%
Daytime PM10










Personal
171
130
+
8
150
+
9
260
+
12
380
Indoor
169
82
+
8
95
+
6
180
+
11
240
Outdoor
165
83
+
5
94
+
6
160
+
7
240
Overnight PM10











Personal
168
66
+
4
77
+
4
140
+
10
190
Indoor
163
52
±
4
63
+
3
120
+
5
160
Outdoor
162
74
±
4
87
+
4
170
+
5
210
Daytime PM2 5











Indoor
173
34
±
4
48
+
4
100
+
7
170
Outdoor
167
36
±
4
49
+
3
100
±
6
170
Overnight PM2 5











Indoor
166
26
±
2
36
+
2
83
±
6
120
Outdoor
161
35
+
2
51
+
4
120
+
5
160
8 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.
Population-weighted mean elemental concentrations for 15
prevalent elements were calculated. As with the particle mass,
daytime personal exposures were consistently higher than either
indoor or outdoor concentrations of all the elements save sulfur.
At night, levels were similar in all three types of samples. The
personal and indoor PM10 samples are depleted in the crustal
elements (Si, Al, Fe) compared to the outdoor samples, by amounts
ranging from 15 to 25%. The indoor PM2, samples show no
depletion in any elements, and may be slightly enriched in Ca, K,
CI, and (night only) S.
Questionnaires were analyzed to detect activities associated with
increased exposure. Housework (dusting, vacuuming, cooking) was
associated with significantly increased personal exposures and
indoor air concentrations during the day. 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.

-------
DISCUSSION
The personal and microenvironmental monitors designed especially
for this study performed well. About 96% of all samples
attempted were collected and median precision was 2-4%. A
positive bias of about 12% was noted with respect to the
reference dichotomous sampler method.
The source of the roughly 50% increase in daytime personal
exposure compared to the indoor and outdoor air concentrations
appears to be generation or reentrainment of particles during
personal activities such as cooking, dusting, and vacuuming.
Other possible sources have been found to be unlikely. These
include 1) different sampling characteristics of the monitors (no
differences noted in laboratory tsts); 2) skin flakes or clothes
fibers accumulating on the personal monitor (does not account for
the observed higher elemental concentrations); and 3) increased
exposures encountered while participants are out of the house
(not supported by multivariate analyses).
House dust is a mixture of airborne outdoor aerosols, tracked-in
soil and road dust, and aerosols produced by indoor sources such
as combustion. As such, it should contain crustal elements from
soil, lead and bromine 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 participants were sleeping for
much of the 12-hour overnight monitoring period, and were thus
not engaging in these particle-generating or reentraining
activities. There remains the problem of sulfur, which showed no
increase in personal samples compared to indoor or outdoor
samples. This may be due to the fact that sulfate ions have a
much smaller mass median diameter and a lower deposition velocity
than other ionic constituents 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 dislodge from
surfaces, due to electrostatic or other forces.
REFERENCES
1. Pellizzari, E.D., Thomas, K.W., Clayton, C.A., Whitmore, R.W.,
Shores, R.C., Zelon, H.S., and Perritt, R.L. Particle Total
Exposure Assessment Methodology (PTEAM): Riverside, California
Pilot Study. Vol. 1. US EPA. Research Triangle Park, NC. 1992.
This paper has been reviewed in accordance with the U.S.
Environmental Protection Agency's peer and administrative review
policies and approved for presentation and publication. Mention
of trade names or commercial products does not constitute
endorsement or recommendation for use. This research was funded
in part by the California Air Resources Board.

-------
TECHNICAL REPORT DATA
(ntau teed Instructions On I he revtne b*fort ec
[t. REPORT NO.
EPA/600/A-93/144
|4. title and subtitle
Indoor, Outdoor, and Personal Air Exposures to
Particles, Elements, and Nicotine for 178
6. REPORT OATe
7/93
8. PERFORMING ORGANIZATION CODE
1	BpciHpnt!		
|7. AUTHQR(S)
L.A. Wallace, H. Ozkaynak, J. Spengler, E.
Pellizzari, P. Jenkins
B. PERFORMING ORGANIZATION REPORT NO.
PERFORMING ORGANIZATION NAME AND ADDRESS
Research Triangle Institute
Research Triangle Park, NC 27709
«0. PROGRAM ELEMENT NO.
11. contracV/grant NO.
68-02-4544
112. SPONSORING AGENCY NAME AND ADDRESS
US EPA
Research Triangle Park, NC 27711
13. TYPE OF REPORT AND PERIOO COVE REO
14. SPONSORING AGENCY CODE
EPA/600/09
16. SUPPLEMENTARY NOTES
[IB. ABSTRACT	~ ¦
Personal, indoor, and outdoor concentrations of inhalable
particles and 15 elements were measured for a probability sample
of 178 persons representing 139,000 nonsmoking residents of
Riverside, California. Newly designed personal monitors were
employed. Personal exposures often exceeded concurrent indoor
and outdoor concentrations, both for particles and for 14 of 15
associated elements. Tlie increase appears to be due to personal
activities such as dusting, vacuuming, cooking, and sharing a
home with a smoker. This suggests that reduction of dust levels
in the home could decrease exposure to airborne particles.
p. DESCRIPTORS
b.lOENTIFlCRS/OPEN ENDED TERMS
c. COSati Fitld/Group |



lie. distribution statement
19. SECURITY CLASS (This RtpO't)
ai. no. or PAOts 1
7 1
20. SECURITY CLASS (Thlt page)
25. PRICE 1
(PA Porm 2230.1 (R»v. 4-77) pncviout coition it eetftLCTC

-------