Ann. occup. Hyg., Vol. 41, Supplement 1, pp. 700-706, 1997
© 1997 British Occupational Hygiene Society
Published by Elsevier Science Ltd. All rights reserved
Printed in Great Britain
0003-4878/97 $17.00 + 0.00
Inhaled Particles V11I
PII: S0003-4878(96)00175-5
PERSONAL EXPOSURE MEASUREMENTS OF THE GENERAL
PUBLIC TO ATMOSPHERIC PARTICLES
D. Mark,* S. L. Upton,t C. P. Lyons,! R. Appleby,* E.J. Dyment,t
W.D. Griffith! and A.A. Foxt
* Institute of Occupational Health, University of Birmingham, Birmingham, U.K.;
tAerosol Science Centre AEA Technology, Harwell, Didcot, U.K.; and ^Environmental Pollution Unit,
Birmingham City Council, Birmingham, U.K.
INTRODUCTION
Airborne particles in ambient atmospheres in the U.K. are continuously monitored
using tapered element oscillator microbalances (TEOM) (Patashnick and Rupprecht, 1991), equipped with inlets that select the thoracic aerosol fraction according
to the PM10 definition. These are part of the Automatic Urban Network (AUN) of
the U.K. Department of the Environment, which is a network of sites located in
cities throughout the U.K. In order to use this information to estimate the exposure
and potential dose of particles to the general public, it is necessary to understand
the relationship between these measurements and actual exposure as measured
with personal samplers. These personal samplers are worn on the upper part of the
chest close to the nose and mouth of the wearer and are specially designed to mimic
the aerodynamic behaviour of the human respiratory system. The aim of this
project is to obtain a reliable assessment of the particle exposures of a representative group of the general public and to use this information to determine how
effectively data from the fixed site TEOM monitors can estimate that exposure.
PREVIOUS PERSONAL EXPOSURE DATA TO PM10 PARTICLES
So far, most of the published data on the personal exposure of the general public
to ambient airborne particles has been carried out in the U.S.A. Since the early
1980s, a small number of long-term studies have been initiated to estimate the
exposure of the general public to airborne pollutants, including particles. One of
the major studies carried out in the U.S.A. during this period was the Six City study
(Spengler, 1985), carried out by investigators mainly from the Harvard School of
Public Health. In this study, estimates of respirable particle exposures in six cities
in the U.S.A. were obtained using both personal samplers and microenvironmental and/or outdoor fixed-site monitors. In the total human environmental exposure study (THEES) (Lioy, et al., 1990) personal, indoor and outdoor
concentrations of thoracic (PM10) particles were measured for the first time. The
total exposure assessment methodology (TEAM) study (Wallace et al., 1993)
involves the measurement of PM10 particles in a large number of residents in
Riverside, California.
700
Exposure measurements of the public to atmospheric particles
701
However, despite the existence of these three large exposure studies, the number
of measurements of particle exposure made with actual personal samplers is
relatively small (250 respirable and 530 PM10). Instead, most of the exposure
estimates were based on the use of exposure models in which particle levels in a
number of micro-environments (normally five), measured using static monitors,
are used in combination with information from activity diaries to build up exposure
profiles for each subject. However, whilst these models may effectively estimate
individual exposures to gases such as CO, NO2 and SO2 there is very little evidence
concerning their validity for estimating particulate exposures. Consequently, many
authors expressed a preference for personal sampling, but argued against largescale personal monitoring studies on the grounds of excessive cost.
THE PERSONAL SAMPLER USED FOR THE STUDY
The choice of sampler used in this study was severely limited by the lack of
suitable samplers. Consequently, a modified version of the prototype personal
sampler, reported by Mark et al. (1988), was used. The sampling head has an
internal cassette with an inhalable aerosol entry followed by a cylindrical plug of
porous polyester foam to select the thoracic fraction of the inhaled particles, which
are collected on a 37 mm diameter filter. A specially-built (small, light and quiet)
sampling pump was used, capable of sucking air at 2 1 min"1 for at least 16 h each
day with a fast battery charging system that enabled the sampler to be used the next
day. Particular attention was paid to making the sampler as quiet as possible. An
unobtrusive, easily removable carrier harness, based around a small camera case,
was used to carry both the pump and the sampler. The sampler itself was fixed to
the carrying strap and was maintained in the lapel position by a combination of
removable loops and clips.
THE SAMPLING CAMPAIGN
The sampling campaign was based around the two AUN sites within the City of
Birmingham. One is situated in the centre of the city in the corner of a car park
close to the Centenary Square, whilst the other is in the playground of a school
within a suburban area of the city.
Sampled population
The sampled population comprised 15 members of the general public at each
site, although some volunteers dropped out after the first exercise and were
replaced with substitutes. The main criterion for the choice of subjects was that of
reliability, to ensure that the samples obtained did represent actual personal
exposure measurements for the periods specified. At each site we were able to
identify three main sub-groups, who have similar living and working arrangements
(called lifestyle in the analysis of the results), and therefore may have similar
exposures. They were: (1) retired people who live very close to the AUN stations;
(2) people who also live close to the AUN stations, but who work at least 3 miles
away; and (3) people who work close to the AUN stations (Centre—office workers,
702
D. Mark et al.
East—teachers), but who live at least 3 miles from the site. The gender of the
volunteers was: Centre, 15 male, 3 female; East, 12 female, 3 male.
Sampling programme
For each group of subjects, three sampling surveys were carried out: Survey 1 in
August/September 1995, Survey 2 in October/November/December 1995 and
Survey 3 in February/March 1996. For each survey, a target of five replicate
exposure periods for each subject was set. These were of variable duration from 16
to 33 hours, with the samplers being switched off during sleep time, and at some
workplaces. Subjects completed an initial questionnaire about their housing,
heating, method of cooking, occupation, hobbies and kept a diary of their major
activities during the exposure measurements.
Experimental analysis
Glass fibre filters were used to collect the sampled particles. The mass of
particles collected on each filter was determined by weighing the filter before and
after sampling twice on a six-place electronic balance. A rigid system of filter
conditioning and controls was employed to enable the maximum accuracy to be
achieved with the expected small particulate masses (expected to be around
50-1000 u.g).
The mean outdoor PM10 mass concentration levels were calculated from the 15
min averages of continuous measurements given by the TEOM instruments at the
two AUN sampling stations. The raw data have been modified following the agreed
acceptance criteria for the AUN network, but must still be considered as
provisional at this stage. These were calculated for each personal exposure sample
for the periods during which the personal samplers were in operation.
Statistical analysis
Two main statistical analyses were carried out. Firstly, descriptive statistics were
calculated for the personal exposure measurements, subdivided according to
survey, smoking status and lifestyle. In order to stabilise the variances, the natural
logarithms of the personal exposure measurements have been used for all models
tested. Regression analyses were carried out to investigate the relationship between
the personal exposure measurements and the AUN measurements. Factors such as
exposure to tobacco smoke or lifestyle were treated as confounders in some
analyses and their effects on the relationship between personal exposure measurements and AUN measurements were explored using analyses of covariance.
RESULTS
The results of the descriptive statistics for the personal exposure measurements
for both sites are shown in the box plots of Fig. 1 (a)-(c). In Fig. l(a), significant
differences between surveys was found both between sites and between seasons
(survey 1 being in the summer and 2 and 3 being in the winter). The effects of
smoking on exposures can be seen in Fig. l(b), where for both sites, the differences
were highly statistically significant, with smokers exposed to almost twice as much
mass of thoracic particles as the non-smokers. Levels for the passive smokers at
Exposure measurements of the public to atmospheric particles
BIRMINGHAM CENTRE
703
BIRMINGHAM EAST
Extreme data < 3 interquartile range
450
250
Data < 1.5 Interquartile range
200
75th Perccntile
Sample mean*
50th perccntile (median)
400
350
300
150
BOX PLOT KEY
250
200
100
150
E
50
100
00
A
Q
u
50
a) ALL DATA
0
1
2
3
SURVEY NO
04
o
x
w
450
400
250
Z
UJ
350
UJ
300
200
So -50
!-Ll
b) SMOKING STATUS
200
100
150
OJ
100
O
cu
X
T
50
o
1
2
3
SMOKING STATUS
SMOKING STATUS
<
z
o
1 - Active smoker
2 - Passive smoker
3 - Non - smoker
450
250
400
350
200
300
250
150
c) LIFESTYLE
200
100
150
100
50
50
1 - Live and work in vicinity
2 - Live in area and work away
3 - Work in area and live away
0
1 2 3
LIFF STYLE
Fig. 1. Box plots of personal exposure measurements.
704
D. Mark et al.
• SubjectCOl
• Subject C06
A Subject C07
X Subject C08
XSubjectCIO
• Subject Cll
+ Subject Cl 2
-Subject Cl 3
-Subject C14
O Subject Cl 5
D Subject C16
A Subject Cl 7
Co Subject Cl 8
a) Birmingham Centre - All Data
450
5b
«?
400
350
tnora
o
300
1
u
250
a
3
200
«
150
;ure
e
100
a
u
50
X
a
c
s
- x
°
•,
X O
x -r
•°
A
•
x
- *•
•;? Subject C19
O Subject C20
:: Subject C21
• Subject C22
0
10
20
30
40
50
60
80
70
AUN PM10 Concentration Levels (ng/m3)
b) Birmingham East: - All Data
• Subject E01
250
• Subject E02
A Subject E03
2
200
X Subject E04
X Subject E05
5
• Subject E06
150
+ Subject E07
-Subject E08
— Subject E09 i
O Subject E10 I
DSubjectEll
A Subject E!2 i
• Subject E13 ;
• >SubjectE14 j
Z
0
;; Subject EI5
20
40
60
100
80
3
AUN PM10 Concentration Levels (|ig/m )
Regression equation: In (personal exposure) = intercept + AUNx
No of Samples
CENTRE
All subjects
Non smokers
EAST
All subjects
Non smokers
128
76
173
143
slope
Intercept
ln(ug/m3)
Slope
P
R~
4.262
4.077
0.009
0.009
0.0035
0.0086
0.066
0.09
3.576
3.438
0.02
0.022
0.0001
0.0001
0.144
0.145
Fig. 2. Relationship between personal exposure and AUN measurements.
East were only slightly higher than those for the non-smokers. In Fig. l(c), the
effects of where people live and work in relation to the AUN sites, can be seen. For
Centre, those subjects living and working in the area and those living in the area,
but working away are exposed to approximately twice as much mass of thoracic
particles as those working in the area and living away. For East, the picture was
slightly different, with those subjects living and working in the area experiencing
Exposure measurements of the public to atmospheric particles
705
the lowest exposures and those living in the area but working away appeared to
have the highest. These effects were statistically significant with P values < 0.001.
The results of all the measurements of personal exposure and corresponding
PM10 levels from AUN monitors for Centre and East are given in Fig. 2(a) and (b),
respectively. Regression analyses carried out to investigate the relationships
between the data are given on the figures. For centre, the overall positive
association between personal exposure measurements and AUN PM10 values, just
fell short of statistical significance both for the model with all subjects and for that
with smokers excluded. For East, the overall positive association between personal
exposure measurements and AUN values was statistically significant (P = 0.0001),
both for the model with all subjects and that with smokers excluded. However,
there is a wide spread of results with the regression relationship explaining only
14% of the variability (R2 = 0.14).
DISCUSSION
This is the first systematic study carried out in the U.K., to determine the
personal exposure of members of the general public to airborne particles. It
represents a 50% increase in the number of actual personal samples reported
irrespective of size fraction measured and a 60% increase in measurements of the
thoracic fraction. The main conclusion from this short study is that there is no
simple relationship between PM10 levels obtained from the AUN particle monitors
at Birmingham and the thoracic particle exposures of a small group of the general
public living and/or working in the area. However, there is increasingly strong
evidence of a correlation between PM10 levels in the ambient atmosphere and
certain ill-health in the general public (Schwartz, 1991; Dockery et al., 1993). As
people spend on average over 90% of their time indoors (confirmed in this study),
the question that immediately springs to mind is: "Is there high penetration of
outdoor aerosols into indoor environments?" If the answer to this question is "yes",
then it is conceivable to suggest that it is the fine outdoor particles that are mainly
responsible for the ill-health reported. This suggestion would lend some support to
the proposition by Seaton et al. (1995) that ultra-fine particles (< 100 nm) are the
main causative agents for the reported circulatory health effects. However, there
are also many potentially harmful particles that are derived solely from indoor
sources such as: particles from gas cookers and heaters, environmental tobacco
smoke, mould spores, house dust mite faeces, dander, skin, cat, bird and insect
allergens. These are variously reported to have potential allergenic, pathological
and carcinogenic properties. Therefore, if the main aim of particle monitoring is to
provide information for the minimisation of all particle-related ill-health, then it
may not be sufficient just to monitor the ambient atmosphere via the AUN system.
Further work is required.
Acknowledgements—The authors would like to acknowledge the support both financially and technically of the U.K. Department of the Environment for this work. Our special thanks go to those people in
Birmingham, who willingly and responsibly participated in the exposure measurements.
706
D. Mark et al.
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