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National Ambient Air Quality Standards
Does Massachusetts Air Meet Federal Standards ?
Ozone is the only pollutant for which Massachusetts monitors indicate nonattainment with a National Ambient Air Quality Standards (NAAQS). Massachusetts is in attainment for the other criteria pollutants, including carbon monoxide, lead, nitrogen dioxide (NO2), sulfur dioxide (SO2), and particulate matter (including PM10 and PM2.5).
The Clean Air Act (CAA) established timeframes and milestones for states to meet and maintain NAAQS for criteria pollutants. Each state is required to monitor the ambient air to determine whether it meets each standard. If the air quality does not meet a standard, the state must develop and implement pollution control strategies to attain that standard. Once air quality meets a standard, a state must develop a plan to maintain that standard while accounting for future economic and emissions growth. Taken together, these plans and control strategies constitute the State Implementation Plan (SIP).
Ozone
In 1997, EPA set a new stricter ozone standard of 0.08 ppm averaged over an eight-hour period, but implementation was delayed due to legal challenges to the standard. EPA designated Massachusetts as "moderate nonattainment" for the 8-hour standard effective June 15, 2004. The previous 1-hour ozone standard (0.12 ppm averaged over one hour), which had been in place for almost two decades, was revoked on June 15, 2005. Massachusetts had been classified as "serious nonattainment" for the 1-hour ozone standard since the early 1990s. However, with the adoption of numerous control programs, Massachusetts has made significant progress in reducing the number and severity of 1-hour ozone exceedances. Mitigation programs that were put in place to attain the 1-hour standard continued as part of MassDEP's strategy to attain the 8-hour standard. In January 2008 MassDEP submitted to USEPA an 8-hour Ozone SIP including strategies for attaining the 8-hour ozone standard by 2010.
On March 12, 2008 USEPA lowered the primary ozone standard to 0.075 ppm (from 0.08 ppm) and set the secondary standard identical to the primary standard. In March 2009, Massachusetts recommended to EPA that the entire state be designated as nonattainment for the new standard.
Standards Attained
Sulfur Dioxide, Nitrogen Dioxide & Lead
Massachusetts has been in attainment for sulfur dioxide, nitrogen dioxide, and lead for a number of years based on decades of monitoring.
On May 1, 2008, EPA revised the lead standard from 1.5 ug/m3 to 0.15 ug/m3, and set the secondary standard identical to the primary standard. By October 2009 Massachusetts must recommend to EPA whether the state attains the new lead standard.
Carbon Monoxide
Prior to the mid-1980s, Massachusetts was in violation of the carbon monoxide (CO) standard. However, with the adoption of numerous control programs, CO emissions have significantly decreased, and the last violation in the state of the CO NAAQS occurred in 1986. The entire state has been officially designated as attainment since 2002.
Particulate Matter
There are currently two sets of NAAQS for particulate matter: one for PM10 and one for PM2.5. Massachusetts has been in attainment of the PM10 standard for several years. PM2.5 standards were first established in 1997. In December 2004, EPA designated Massachusetts "Attainment/Unclassifiable" for PM2.5 statewide based on monitoring data.
In December 2006, EPA revised the PM10 and PM2.5 standards. EPA retained the 24-hour PM10 standard (at 150 ug/m3) but revoked the annual PM10 standard. In addition, EPA retained the annual PM2.5 standard (at 15 ug/m3) and lowered the 24-hour PM2.5 standard to 35 ug/m3 (from 65 ug/m3). In October 2009, EPA designated Massachusetts as attainment/unclassifiable for the 2006 24-hour PM2.5 standard.
Current National Ambient Air Quality Standards
The table below shows the current NAAQS as of April 2009.
| Pollutant |
Averaging
Time |
Primary
Standard1 |
Secondary
Standard2 |
Sulfur Dioxide
SO2
|
Annual
Arithmetic
Mean |
0.03 ppm
(80 ug/m3) |
None |
| 24-Hour |
0.14 ppm
(365 ug/m3) |
None |
| 3-Hour |
None |
0.50 ppm
(1300 ug/m3) |
Carbon Monoxide
(CO) |
8-Hour |
9 ppm
(10 mg/m3) |
Same as
Primary Standard |
| 1-Hour |
35 ppm
(40 mg/m3) |
Same as
Primary Standard |
| Ozone |
8-Hour |
0.075 ppm
|
Same as
Primary Standard |
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Note: The 8-hour standard is met when the 3-year average of the 4th-highest daily maximum 8-hour average does not exceed 0.075 ppm at any one monitor. |
| Lead |
Calendar
Quarter
Arithmetic
Mean |
0.15 ug/m3 |
Same as
Primary Standard |
Nitrogen Dioxide
NO2 |
Annual
Arithmetic
Mean |
0.053 ppm
(100 g/m3) |
Same as
Primary Standard |
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PM2.5 Particulates up to 2.5 microns in size |
Annual
Arithmetic
Mean |
15.0 ug/m3 |
Same as
Primary Standard |
| 24-Hour |
35 ug/m3 |
Same as
Primary Standard |
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The annual standard is met when the annual average of the quarterly mean PM2.5 concentrations is less than or equal to 15 ug/m3 (3-year average). If spatial averaging is used, the annual average from all monitors within the area may be averaged in the calculation of the 3-year mean.
The 24-hour standard is met when the 98th percentile value is less than or equal to
35 ug/m3 (3-year average). |
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PM10 Particulates up to 10 microns in size |
24-Hour |
150 ug/m3 |
Same as
Primary Standard |
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The PM10 standard is based upon estimated exceedance calculations described in 40 CFR Part 50, Appendix K.
The 24-hour standard is attained if the estimated number of days per calendar year above 150 ug/m3 does not exceed one per year on average over 3 years. |
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1Primary Standard: designed to protect public health against adverse health effects with a margin of safety.
2Secondary Standard: designed to protect against damage to crops, vegetation, and buildings.
ug/m3 = micrograms per cubic meter
ppm = parts per million
mg/m3 = milligrams per cubic meter
* Standards based on averaging times other than the annual arithmetic mean must not be exceeded more than once per year.
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