might be for subjects who spend time
commuting to and working in other locations
during the day. We chose three panels located
near two of the monitors, at Odean Circle and
at Chulalongkorn Hospital. The Odean
Circle area, known as the Chinatown of
Bangkok, is a densely populated residential
and commercial area with small streetside
shops located on intertwining narrow roads.
Business dealings, which may begin as early as
4 AM and extend beyond 9 PM, usually take
place on the ground floor, and the upper
floors are used as residences. As a center for
wholesale business, Odean Circle is congested
with vehicles for a large part of the day.
Therefore, the residents in this area are likely
to be exposed to high concentrations of air
pollution. The Chulalongkorn site is located
near the city center and is surrounded by wide
streets often congested throughout the day.
The three groups of subjects recruited
were adults who lived and worked in the
Odean Circle area, children who lived and
attended school in the Odean Circle area, and
nurses and student nurses at Chulalongkorn
Hospital who lived in nurses’ dormitories
near the hospital. A preselection interview
was conducted to identify potential adult subjects
in the Odean Circle area with the following
criteria: a) they lived and spent most
of the day within 2 km of the air monitoring
station; b) they did not smoke; c) their main
work area or daytime living space was not air
conditioned; and d ) their work area did not
have obvious or dominating indoor air pollution
sources (e.g., motorcycle repair). Ninetytwo
people who met the above criteria agreed
to participate in the study. We expected this
panel would have a relatively high exposure to
air pollution.
The nurse group was selected because we
expected they would provide high compliance
and accuracy of reporting because of their
training in the health field. We expected them
to have lower air pollution exposures than the
adults in the Odean Circle panel as a result of
working at least some of the time in air-conditioned
areas of the hospital. However, to
ensure the nurses chosen for this study did not
spend all their indoor time in air-conditioned
environments, only nurses who lived in the
first five floors of the dormitories without air
conditioning were recruited. In addition, to
be included in the study, nurses had to be
nonsmokers and had to remain in Bangkok
on most days off from work. Sixty nurses and
20 fourth-year student nurses who met the
criteria agreed to participate.
Children were included because they may
have different exposure (e.g., spending more
time outdoors) and different sensitivity to air
pollution. A preselection questionnaire was
sent home with the third- to fifth-grade students
who attended the only public school
(Wat Thrimit) in the Odean Circle area.
Those who met the specific criteria of living
within the Odean Circle area and having
parental consent were selected. Consequently,
79 children ranging in age from 8 to 12 years
participated in the study.
All subjects (and parents of the children)
consented in writing to participate in the
study after being informed about what their
participation entailed. The adult subjects
started their symptom diaries as they were
recruited from mid-December 1995 to early
January 1996. The children started their
diaries on January 9, 1996. The adults were
asked to participate over a 90-day period,
whereas the children, because of school holidays,
were involved for 69 days. The selected
subjects were also offered a small monetary
incentive paid at the completion of the diary
period. Three instruments were developed for
the diary study: a subject screening questionnaire
for adult subjects, a daily symptom
diary form for the adult participants and a
simplified version for the children, and a
background questionnaire for all study participants.
All of the diary work was conducted
in Thai. Survey instruments from many previous
studies were used as a starting point for
the development of these symptom diary
instruments, but careful translation was
needed to ensure they were easy to understand
and use by the local study sample.
In the Odean Circle area, field staff
interviewers visited each adult subject daily
and recorded responses to the diary questions.
This was necessary to maintain reasonable
response rates and compliance for
this panel. The nurses completed the diaries
on their own, with weekly contacts from
selected nurses recruited to help supervise
the diary execution and periodic contacts
from the study team. Schoolchildren completed
the diaries at school with the supervision
and assistance of their teachers. They
took the diaries home on weekends and holidays
and were encouraged to fill them out
on their own. Diaries were completed
regarding symptoms on the previous day.
Up to 2-day recall was allowed if a day was
missed for any reason.