While the data reviewed were not the most current
With regard to hazardous air pollutants (HAPs), of
nor comprehensive, it is clear that, in all three
those tracked by the Commission in 1991, there is
regions, during episodes that occur with some
evidence that emissions of  several of  these may
frequency, particularly in the summer months, smog
have declined over the ensuing period.  However,
(ozone and fine particulate) achieves levels that
emissions of  trichloroethylene and xylene com-
would affect the well being of  the entire population
pounds appear to be at or above previous estimates.
and have an immediate, pronounced negative impact
Many organic HAPs are Volatile Organic Com-
on the most sensitive elements of  the populations
pounds (VOCs) and, as such, also contribute to the
youth and the elderly.  Similar conditions are evident
formation of  ozone.  There is some evidence of
in the past few years and appear to persist to this
particular HAPs in excess of  the levels associated
with the one-in-one-million lifetime cancer risk
benchmark in the US Clean Air Act.
The two southerly regions are the subject of  a
greater number of  Ontario MOE smog alerts, while
Concentrations of hazardous air pollutants are more
the northern locale has a higher annual average
strongly associated with local sources and further
ozone concentration. Continued non conformance
regional reductions from both mobile and stationary
with the Ontario interim 24 hour PM10 objective
sources would be required to lower these concentra-
and the annual Total Suspended Particulate ambient
air quality criterion (AAQC) is evident in Sault Ste
Marie Ontario, particularly at the monitoring site
Additional assessment of the health impact of these
adjacent to the Algoma Steel facility.  Concentra-
HAPs individually is complicated by the differences
tions of  benzo-a-pyrene at this industrial site were
among the various guidelines and standards prevail-
also in excess of  the provincial AAQC for this
ing among the jurisdictions; however, the risk
assessment now underway under the US Ten City
Study may offer some further guidance on this issue.
Sources of  smog are both regional (Chicago-
Quebec City corridor) and local (mobile, point and
A more comprehensive overview of  the current
areal sources).  Improvement in local and downwind
prevailing situation would require a joint co-
air quality, particularly in the two southern locales,
ordinated effort by the federal, state and provincial
would require significant reductions from all local
source segments, including gasoline and diesel
powered vehicles in the mobile sector.