tration is attributed to US sources.  The reminder
from Windsor and vicinity were attributed to
vehicles (12 percent) and wood burning stoves (21
percent)
Prior to this study, benzo(a)pyrene levels were
considered to be higher, as the coke ovens in the
Detroit area were shut down for most of  this study
period, although dispersion modelling suggested a
very minimal contribution to ambient levels of
B(a)P in Windsor from the retrofitted coke ovens in
Detroit, which resumed operation in 1992.
chromium concentrations are mainly attributed to
point sources (i.e. 50 percent from the steel industry
in Detroit and 16 percent from the automobile
manufacturing sector in Windsor)
sources of cadmium include road dust from
Windsor and Detroit (35 percent), the motor vehicle
manufacturing sector in Windsor (27 percent), and
the steel industry in Detroit (13 percent).
most of  the formaldehyde in Windsor is attributed
to photochemical reactions and long range transport
of  air pollutants.
carbon tetrachloride was found to originate prima-
rily from long range transport.
the highest concentrations of 1,3-butadiene and
benzo(a)pyrene were found in northwest Windsor.
North-central Windsor has the highest concentra-
tions of  benzene, chromium, and cadmium, mostly
attributable to local source contributions from the
automobile manufacturing sector.
31