Environmental Health Criteria 214

HUMAN EXPOSURE ASSESSMENT
Indoor Air Quality in the Basse Area, The Gambia (WHO/UNEP, 1988)
Table 38. (continued)
An introductory guide to human exposure field studies: survey methods and
statistical sampling (WHO/UNEP, 1992a)
Endemic fluorosis: a global health issue (WHO/UNEP, 1992b)
Human Exposure to Pollutants. Report on the pilot phase of the Human
Exposure Assessment Locations Programme (UNEP/WHO, 1991)
Los Angeles. Another goal was to determine particle concentrations in
the participants' homes and immediately outside the homes.
The study had a three-stage probability sampling procedure
(Ozkaynak et al., 1996). Ultimately 178 residents of Riverside, took
part in the study in the fall of 1990. Respondents represented
139 000 ± 16 000 (SE) non-smoking Riverside residents aged 10 and
above. Their homes represented about 60 000 Riverside homes.
Each participant wore a personal exposure monitor (PEM) for two
consecutive 12-h periods. Concurrent PM 10 and PM 2.5 samples were
collected by a stationary indoor monitor (SIM) and stationary outdoor
monitor (SAM) at each home. The SIM and SAM were essentially identical
to the PEM. A total of 10 particle samples were collected for each
household (day and night samples from the PEM 10 , SIM 2.5 , SIM 10 ,
SAM 2.5 , SAM 10 ). Air exchange rates were also determined for each 12-h
period.
Up to 4 participants per day could be monitored, requiring
48 days to conduct the study. A central outdoor site was maintained
over the entire period (22 September-9 November 1990). The site had 2
high-volume samples with 10 µm inlets (actual cut-point about 9.0 µm),
2 dichotomous PM 10 and PM 2.5 samples (actual cut-point about 9.5 µm),
1 PEM 10 , 1 SAM 10 and 1 SAM 2.5 .
More than 2750 particle samples were collected, about 96% of
those attempted. All filters were analysed by XRF for a suite of
40 metals. More than 1000 12-h average air exchange rate measurements
were made. A complete discussion of the quality of the data is found
in Thomas et al. (1993a). LODs, based on 3 times the standard
deviation of the blanks, were of the order of 7-10 µg/m 3 . All field
samples exceeded the LOD. Duplicate samples ( n = 363) showed
excellent precision for all types of particle samplers at all
locations, with median relative standard deviations ranging from 2 to
4%.
Daytime mean personal PM 10 concentrations (150 µg/m 3 ) were more
than 50% higher than either indoor or outdoor levels (95 µg/m 3 ).
Overnight mean personal PM 10 concentrations (77 µg/m 3 ) were similar
to the indoor (63 µg/m 3 ) and outdoor (86 µg/m 3 ) levels. The higher
personal concentrations do not appear to be due to skin flakes or
clothing fibres; many skin flakes were found on filters (up to an
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