impacts to human health from air quality than the
AQI and Public Health
former category, Suspended Particles.  Although data
available to the Board while compiling this report pre-
The Toronto Board of  Health conducted a study to
date the introduction of  this revised AQI, the Board
examine whether the air quality classifications under the
considers it prudent to highlight the Ministry’s current,
Ontario AQI values appropriately reflected the state of
revised AQI (Table 10).  Appendix A contains the AQI
the air quality and the associated burden of illness in
used in Ontario prior to August 23, 2002.
Toronto.  The study found that more than an estimated
92 percent of  premature mortality and hospitalization
occurs when the AQI was in the ŇVery Good” or
United States Air Quality Index
ŇGood” range, while the remaining eight percent of  the
burden of  illness occurred when the air quality is in the
ŇModerate” or ŇPoor-Very Poor” range.  This indicates
In United States, the Air Quality Index (AQI) is a
that the breakpoints (which are derived from the
national index, so the values and colors used to show
concentration range of  a single pollutant) used to
local air quality and the associated level of  health
classify the ŇGood” and ŇVery Good” AQI which do
concern would be identical throughout the country
not always correspond with pollutant levels that do not
(Table 11).  In large metropolitan areas (more than
cause significant adverse health effects (Ref. 20).
350,000 people), state and local agencies are required to
report the Air Quality Index to the public daily.  Al-
Air Pollution Index (API)
though it is not required, many smaller communities also
report the AQI as a public health service.  Concentra-
The Ontario Ministry of  the Environment is also
tions of  the major pollutants, including ground-level
responsible for the Air Pollution Index (API).  This
ozone, particulate matter, carbon monoxide, sulphur
index is derived from the 24-hour running averages of
dioxide and nitrogen dioxide are converted into AQI
sulphur dioxide (SO ) and suspended particles (SP).
values using formulas developed by the EPA.  The
These averages are evaluated in conjunction with the
highest of  the AQI values for the individual pollutants
current or expected meteorological conditions.  Various
becomes the AQI value for that day (Ref. 21).  If  two or
API values may result in emission reduction require-
more pollutants have AQI values above 100 on a given
ments from industries not essential to public health or
day, agencies report to all of  the sensitive populations
(e.g. children with asthma, people with heart disease)
affected by those pollutants.
The Minster of  the Environment is authorized under
the Ontario Protection Act (1971), to order non-
In the United States, the U.S. EPA will announce Ozone
essential point sources to reduce or cease operations
Action Days when weather forecasts predict days that
when air pollution levels are considered harmful to
are conducive to ozone formation; typically summer
human health.
days that are hot and sunny.  On these days, industries
and individuals will be asked to voluntarily reduce
In Sarnia, the Sarnia-Lambton Environmental Associa-
emissions that cause ozone pollution.
tion (SLEA) utilizes criteria similar to that described
above to advise industry to curtail or reduce emissions
of  sulphur dioxide.  This is referred to as a  Lambton
Industrial Meteorological Alert (LIMA).  Further
discussion regarding LIMA is provided in the Sarnia
section of  this report.
On August 23, 2002, the Ministry incorporated PM
into Ontario’s AQI.  PM2.5 is a better indicator of