Environmental Health Criteria 214

HUMAN EXPOSURE ASSESSMENT
30 µg/dl. The study also found a significant correlation between high
blood lead levels and proximity of the household to dense traffic. In
a 1990-1991 study of exposure to lead among schoolchildren in Manila,
Subida & Torres (1991) found that mean blood lead concentrations were
14 µg/dl ( n = 387), with 10% having levels over 10 µg/dl. The same
study measured blood lead levels among child street vendors. Mean
blood lead level for a sample of 101 vendors was 17.8 µg/dl, with 33%
having levels over 20 µg/dl.
Muangnoicharon (WHO, 1995b) reports on a lead exposure study of
bus drivers in Bangkok. The study was a cooperation between the WHO
HEAL Project and the Department of Medical Science, Ministry of Public
Health of Thailand and was designed to assess exposure in a high risk
group. Subjects were bus drivers assigned to traffic routes in Bangkok
where ambient lead levels exceeded 1 µg/m 3 . Lead was analysed in 24-h
air samples, duplicate food for each meal for 6 days and faeces for 5
days, as well as blood collected on the day 7.
Average personal air exposures were 0.117 µg/m 3 , which yielded
an estimated 0.936 µg/day absorption by inhalation at an estimated
absorption rate of lead via inhalation of 40% and 20 m 3 /day
respiratory air. Intake by food was 87.92 µg/day (27.32 SD). Thus, the
estimated average lead absorption from air, food and water was 13.325
µg/day at an estimated absorption rate via ingestion of 10%.
Researchers suggested that meals consumed from roadside restaurants
and food stands resulted in higher than expected lead levels in food.
Blood lead levels for bus drivers ranged between 5 and 12 µg/dl.
The results for the Thai study were compared to other HEAL
sponsored studies in China, Sweden and Yugoslavia (Table 41).
One of the HEAL projects investigated lead and cadmium exposure
among small groups of non-smoking women (Vahter & Slorach, 1990).
Subjects kept activity diaries. Duplicate portions of food and
corresponding faeces samples were collected along with personal air
samples. Food was found to be the main source of both lead and
cadmium. Faecal concentrations could be used for validation of the
duplicate portion samples because of the low uptake in the
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Table 40. Weighted estimates of air and breath concentrations of 19 prevale
residents (February 1984); 330 000 Los Angeles residents (May 1984);
(June 1984)
Compound LA1 (February) LA2 (May)
Personal Outdoor Breath Personal Outdoor B
air air air air
(n = 110) (24) (110) (50) (23) (
1,1,1-Trichloroethane 96 a 34 a 39 b 44 5.9 23
m,p-Xylene 28 24 3.5 24 9.4 2
m,p-Dichlorobenzene 18 2.2 5.0 12 0.8 2
Benzene 18 16 8.0 9.2 3.6 8
Tetrachloroethylene 16 10 12 15 2.0 9
o-Xylene 13 11 1.0 7.2 2.7 0
Ethylbenxene 11 9.7 1.5 7.4 3.0 1
Trichloroethylene 7.8 0.8 1.5 6.4 0.1 1
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