United
Environmental Protection
Agency
Air and Radiation
Washington, DC 20460
EPA-456/F-97-004
July 1997
to
and Pi
Air Stamen
fit Matter
r / /' //1"\
/// / / ; rotecting public health, the environment and the quality of life from the detrimental
// of air pollution has a strong national priority since 1970, when Congress
^ the Clean Air Act. Under this authority, the U.S. Environmental Protection Agency (EPA) has
-air quality standards—S
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EPA published revisions to the ozone standards in
July 1997. The table on page 4 compares the current and
revised standards. Highlights of the changes to the primary
standard for ozone include:
® A In time. The new standard is
based on averaging air quality measurements over 8-
hour blocks of time, instead of the ! -hour blocks of
time required by the current standard. Eight-hour
averaging is more consistent with the health informa-
tion that prompted EPA to propose revisions to the
standard. Also, by averaging over 8 hours, the stan-
dard helps protect people who spend a significant
amount of time working or playing outdoors—a
group that is particularly vulnerable to the effects of
ozone.
© tie EPA has adopted an 8-hour
standard with a level of 0.08 ppm to provide greater pro-
tection to public health than the current standard.
The new ozone standard would help
protect people who spend a significant
amount of time working or playing
outdoors—a group that is particularly
vulnerable to the effects of ozone.
To account for the fact that the
concentration of a pollutant In air
varies over time, an afr quality
standard ss as an aver-
age concentration over a specific
time period (an hour, a day, or a
year, for example). The concentra-
tion is In parts per
million fppmj* or micrograms of
pollutant per cubic meter of air
f^g/m3). (For example, the current
primary standard for ozone Is
0.12 ppm over 1' hour.)
The standard also specifies
whether the limit applies to a
specific concentration (for exam-
pie, the fourth-highest In a year)
or a number of times the can
be during the calendar
year,
Is for
ing air
are responsible for prepar-
ing and implementing "State
Implementation Plans" to achieve
and maintain the air quality stan-
dards within their borders. As
part of plans, divide
their total into "Air Quality
Control Regions/' and local
air pollution control authorities
ments for controlling air pollution
within region.
are
Implementation Plans must
be approved by EPA, Under
plans, and local authorities
monitor the air quality In
control region. If the air quality In
a region falls below any of the air
quality standards, EPA
that region as a "nonattainment
area." The Is then required
to develop and Implement plans
to improve Its air quality.
then establish individual require-
1 One drop of water in a fulf bathtub is analogous to one part per million.
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The paniculate matter standards were last revised in 1987.
Since that time, many important new studies have been
published which show that breathing particulate matter at
concentrations allowed by the current primary standard
can likely "cause significant health effects—including prema-
ture death and an increase in respiratory illness. Also, EPA
believes that the current secondary standard does not ade-
quately protect visibility (our ability to clearly perceive dis-
tance, color, contrast, and detail).
EPA estimates that the new
particulate matter standards, along
with clean air programs already
planned, will reduce premature deaths
by about 15,000 a year and
serious respiratory problems in
children by about 250,000 cases a year
s©
EPA published final revisions to the particulate matter stan-
dards in July, 1997. The table on page 4 compares the cur-
rent and revised standards.
The current standards apply to particles up to 10 microns
in diameter. (One thousand particles of this size could fit
into the period at the end of this sentence.) A review of the
scientific data indicate, however, that it is the smaller (or
fine) particles—less than 2.5 microns in diameter—that are
largely responsible for the health effects of greatest con-
cern and for visibility impairment (for example, obscuring
scenic views).
Based on this information, EPA has issued final revisions to
strengthen the particulate matter standards by keeping the
current 10-micron standards and adding new standards
.that provide more stringent goals for fine particles in air.
EPA estimates that the new standards, along with clean air
programs already planned, will reduce premature deaths
by about 15,000 a year and serious respiratory problems in
children by about 250,000 cases a year.
Fine particles in air not only can impact human health but,
because they scatter and absorb light -effectively, also can
affect the quality of life by impairing visibility. Impaired visi-
bility in all directions over a large area is called "regional
haze."
EPA proposed a new program to control regional haze in July
1997. This program will help achieve a national visibility goal
that Congress established when it amended the Clean Air Act
in 1977. This goal calls for improving current visibility and pre-
venting future visibility problems due to pollution in several
national parks and wilderness areas. EPA is soliciting comments
on the proposed regional haze program and expects to finalize
it in 1998.
@w D
SSnencSuPcSgl?
More information about ozone and particulate matter and
related programs can be found on the Internet at EPA's
Office of Air Quality Planning and Standards home page:
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for
Ozone
1 -Hour To attain this standard, the daily
0.12 ppm maximum 1 -hour average concen-
tration measured by a continuous
ambient air monitor must not
exceed 0.12 ppm more than once
per year, averaged over 3 consecu-
tive years.
8-Hour
0.08 ppm
To attain this standard, the 3-year
average of the fourth-highest daily
maximum 8-hour average of contin-
uous ambient air monitoring datab
over each year must not exceed
0.08 ppm.
Diameter fPMl0f
Annual
5Qjtig/m3
To attain this standard, the arith-
metic average of the 24-hour
samples for a period of I year,
averaged over 3 consecutive
years, must not 50 jjg/m3.
Annual Same as existing standard for PM
10-
24-hour To attain this standard, the con- 24-hour
150 jjg/m3- centration of samples taken for 24- 150
hour periods at each monitor fjg/m3
within an must not exceed
150/jg/tn3, more than once per
year, averaged over 3 years.
To attain this standard, the 99th
percentllec of the distribution of the
24-hour concentrations for a period
of 1 year, averaged over 3 years,
must not 150 ^g/m3 at each
monitor within an area.
No
Annual
! 5 jucj/fn3
To this standard, the 3-year
of the annual arithmetic
mean of the 24-hour concentrations
from single or multiple population-
oriented monitors^ must not
24-hour To this the
•65 |jg/m3 of the distribution of the
...;.. -.. 24-hour concentrations for a period
of 1 year, over 3 years,
:::". - must not 65 pg/m3 at each
monitor within an
a The current and revised secondary standards for ozone and particulate mat-
ter are the same as the primary standards described here.
k The new approach of focusing on actual monitored concentrations rather
than the number of days on which the standard is exceeded (regardless of the
magnitude of the exceedance) better accounts for the effects on public health.
c The revised 24-hour PM, 0 standard is very similar to the current standard.
However, by using the 99th percentile concentration approach, the revised
standard better accounts for the effects on public health and inherently com-
pensates for missing data. In this way, it reduces or eliminates the need for
complex procedures that now are needed to adjust for missing samples. Thus,
the revised approach for the 24-hour PA/1,0 standard simplifies the data han-
dling requirements.
^ The focus on population-oriented monitors stems from the health informa-
tion that formed the basis for the annual PM2 5 standard. This information
relates area-wide health statistics to area-wide air quality as measured by one
or more monitors.
U.S.
58
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