quality regulators, the academic research community, and nongovernmental organization advocacy
groups. Some individuals would quickly note that
this enterprise is counterbalanced by corporations
and industrial groups advocating for the status quo
or “dirty air.” This polarized approach has frequently resulted in the focus being on a single
risk factor, air quality, rather than the overall
well-being of the health of societies around the
world.
Air Quality Guidelines and Standards, Table 6 National Ambient Air Quality Standards for criteria pollutants
Primary standards
Secondary standards
Pollutant
Level
Averaging time
Level
Averaging time
Carbon monoxide
9 ppm (10 mg/m
3
)
8-h
a
None
35 ppm (40 mg/m
3
)
1-h
a
Lead
0.15 mg/m
3 b
Rolling 3-month average
Same as primary
Nitrogen dioxide
53 ppb
c
Annual (arithmetic average)
Same as primary
100 ppb
1-h
d
None
l
Particulate matter (PM 10 )
150 mg/m
3
24-h
e
Same as primary
Particulate matter (PM 2.5 )
15.0 mg/m
3
Annual
f (arithmetic average)
Same as primary
35 mg/m
3
24-h
g
Ozone
0.075 ppm (2008 std)
8-h
h
Same as primary
0.08 ppm (1997 std)
8-h
i
0.12 ppm
1-h
j
Sulfur dioxide
0.03 ppm
Annual (arithmetic average)
0.5 ppm
3-h
a
0.14 ppm
24-h
a
75 ppb
k
1-h
None
l
Source: Taken from US EPA Website, July 26, 2011
a Not to be exceeded more than once per year
b
Final rule signed October 15, 2008. The 1978 lead standard (1.5 mg/m
3 as a quarterly average) remains in effect until
1 year after an area is designated for the 2008 standard, except that in areas designated nonattainment for the 1978
standard, the 1978 standard remains in effect until implementation plans to attain or maintain the 2008 standard are
approved
c The official level of the annual NO 2 standard is 0.053 ppm, equal to 53 ppb, which is shown here for the purpose of
clearer comparison to the 1-h standard
d
To attain this standard, the 3-year average of the 98th percentile of the daily maximum 1-h average at each monitor within
an area must not exceed 100 ppb (effective January 22, 2010)
e Not to be exceeded more than once per year on average over 3 years
f
To attain this standard, the 3-year average of the weighted annual mean PM 2.5 concentrations from single or multiple
community-oriented monitors must not exceed 15.0 mg/m
3
g
To attain this standard, the 3-year average of the 98th percentile of 24-h concentrations at each population-oriented
monitor within an area must not exceed 35 mg/m
3 (effective December 17, 2006)
h
To attain this standard, the 3-year average of the fourth-highest daily maximum 8-h average ozone concentrations
measured at each monitor within an area over each year must not exceed 0.075 ppm (effective May 27, 2008)
i
(a) To attain this standard, the 3-year average of the fourth-highest daily maximum 8-h average ozone concentrations
measured at each monitor within an area over each year must not exceed 0.08 ppm(b) The 1997 standard – and the
implementation rules for that standard – will remain in place for implementation purposes as EPA undertakes rule making
to address the transition from the 1997 ozone standard to the 2008 ozone standard(c) EPA is in the process of
reconsidering these standards (set in March 2008)
j
(a) EPA revoked the 1-h ozone standard in all areas, although some areas have continuing obligations under that standard
(“antibacksliding”)(b) The standard is attained when the expected number of days per calendar year with maximum hourly
average concentrations above 0.12 ppm is 1
k
Final rule signed June 2, 2010. To attain this standard, the 3-year average of the 99th percentile of the daily maximum 1-h
average at each monitor within an area must not exceed 75 ppb
l
On July 12, 2011, the EPA Administrator proposed to set Secondary NAAQS for NO 2 and SO 2 for a 1-h averaging time at
concentrations equal to the Primary Standards, NO 2 – 100 ppb and SO 2 – 75 ppb (Note: This footnote was added by Roger
O. McClellan)
Air Quality Guidelines and Standards
39
groups. Some individuals would quickly note that
this enterprise is counterbalanced by corporations
and industrial groups advocating for the status quo
or “dirty air.” This polarized approach has frequently resulted in the focus being on a single
risk factor, air quality, rather than the overall
well-being of the health of societies around the
world.
Air Quality Guidelines and Standards, Table 6 National Ambient Air Quality Standards for criteria pollutants
Primary standards
Secondary standards
Pollutant
Level
Averaging time
Level
Averaging time
Carbon monoxide
9 ppm (10 mg/m
3
)
8-h
a
None
35 ppm (40 mg/m
3
)
1-h
a
Lead
0.15 mg/m
3 b
Rolling 3-month average
Same as primary
Nitrogen dioxide
53 ppb
c
Annual (arithmetic average)
Same as primary
100 ppb
1-h
d
None
l
Particulate matter (PM 10 )
150 mg/m
3
24-h
e
Same as primary
Particulate matter (PM 2.5 )
15.0 mg/m
3
Annual
f (arithmetic average)
Same as primary
35 mg/m
3
24-h
g
Ozone
0.075 ppm (2008 std)
8-h
h
Same as primary
0.08 ppm (1997 std)
8-h
i
0.12 ppm
1-h
j
Sulfur dioxide
0.03 ppm
Annual (arithmetic average)
0.5 ppm
3-h
a
0.14 ppm
24-h
a
75 ppb
k
1-h
None
l
Source: Taken from US EPA Website, July 26, 2011
a Not to be exceeded more than once per year
b
Final rule signed October 15, 2008. The 1978 lead standard (1.5 mg/m
3 as a quarterly average) remains in effect until
1 year after an area is designated for the 2008 standard, except that in areas designated nonattainment for the 1978
standard, the 1978 standard remains in effect until implementation plans to attain or maintain the 2008 standard are
approved
c The official level of the annual NO 2 standard is 0.053 ppm, equal to 53 ppb, which is shown here for the purpose of
clearer comparison to the 1-h standard
d
To attain this standard, the 3-year average of the 98th percentile of the daily maximum 1-h average at each monitor within
an area must not exceed 100 ppb (effective January 22, 2010)
e Not to be exceeded more than once per year on average over 3 years
f
To attain this standard, the 3-year average of the weighted annual mean PM 2.5 concentrations from single or multiple
community-oriented monitors must not exceed 15.0 mg/m
3
g
To attain this standard, the 3-year average of the 98th percentile of 24-h concentrations at each population-oriented
monitor within an area must not exceed 35 mg/m
3 (effective December 17, 2006)
h
To attain this standard, the 3-year average of the fourth-highest daily maximum 8-h average ozone concentrations
measured at each monitor within an area over each year must not exceed 0.075 ppm (effective May 27, 2008)
i
(a) To attain this standard, the 3-year average of the fourth-highest daily maximum 8-h average ozone concentrations
measured at each monitor within an area over each year must not exceed 0.08 ppm(b) The 1997 standard – and the
implementation rules for that standard – will remain in place for implementation purposes as EPA undertakes rule making
to address the transition from the 1997 ozone standard to the 2008 ozone standard(c) EPA is in the process of
reconsidering these standards (set in March 2008)
j
(a) EPA revoked the 1-h ozone standard in all areas, although some areas have continuing obligations under that standard
(“antibacksliding”)(b) The standard is attained when the expected number of days per calendar year with maximum hourly
average concentrations above 0.12 ppm is 1
k
Final rule signed June 2, 2010. To attain this standard, the 3-year average of the 99th percentile of the daily maximum 1-h
average at each monitor within an area must not exceed 75 ppb
l
On July 12, 2011, the EPA Administrator proposed to set Secondary NAAQS for NO 2 and SO 2 for a 1-h averaging time at
concentrations equal to the Primary Standards, NO 2 – 100 ppb and SO 2 – 75 ppb (Note: This footnote was added by Roger
O. McClellan)
Air Quality Guidelines and Standards
39