The driving conditions that were tested for the in-vehicle concentrations o
f selected volatile organic compounds (VOCs) included transport modes, fuel
distributions, vehicle ventilation conditions, driving routes, commute sea
sons, car models, and driving periods. This study involved two sampling sea
sons (winter and summer). The in-auto/in-bus/fixed site ratio of the winter
time mean concentrations was about 6/3/1 for total VOCs and 8/3/1 for benze
ne. On the median, the in-auto/in-bus exposure ratio ranged from 1.5 to 2.8
for the morning commutes, and ranged from 2.4 to 4.5 for evening commutes,
depending on the target compounds. The wintertime in-auto concentrations w
ere significantly higher (p < 0.05), on the average 3-5 times higher, in a
carbureted engine than in the three electronic fuel-injected cars. For the
summertime in-auto concentrations of the target compounds except benzene, t
here were no significant differences between low and high ventilation condi
tions on the two urban routes. The urban in-auto benzene concentration was
significantly higher (p < 0.05) under the low ventilation condition. For th
e rural commutes, the in-auto concentrations of all target compounds were s
ignificantly higher (p < 0.05) under the low ventilation condition. The in-
auto VOC concentrations on the two urban routes did not differ significantl
y, and they were greater than the rural in-auto concentrations, with the di
fferences being significant (p < 0.05) for all target compounds. The summer
time in-auto concentrations of benzene and toluene were greater than the wi
ntertime in-auto concentrations, with the difference being significant(p <
0.05), while the concentrations of the other target compounds were not sign
ificantly different between the two seasons. Neither car models nor driving
periods influenced the in-auto VOC concentrations. (C) 1998 Elsevier Scien
ce Ltd. All rights reserved.