Robert A Corbitt, P.E.*
AIR QUALITY OBJECTIVES
The goal of the Clean Air Act is to protect the public health and welfare from the harmful effects of air pol- lutants. To this end, national ambient air quality standards were developed as a quality reference point. Also, state implementation plans were required to manage and regulate the provisions of the act, including permit- ting. Table 3.1 provides a reference list of U.S. Environmental Protection Agency (EPA) regulations for im- plementing the Clean Air Act.
Ambient Air Quality Standards
Congress mandated that the EPA promulgate national ambient air quality standards as maximum levels of selected pollutants that would lead to unacceptable air quality. These numerical standards were to be based
TABLE 3.1 Air Program Regulations
40 CFR Part Topic
50 National primary and secondary ambient air quality standards
51 Requirements for preparation, adoption, and submittal of implementation plans 52 Approval and promulgation of implementation plans
53 Ambient air monitoring reference and equivalent methods 54 Prior notice of citizen suits
55 Outer continental shelf air regulations 56 Regional consistency
57 Primary nonferrous smelter orders 58 Ambient air quality surveillance
59 [Reserved]
60 Standards of performance for new stationary sources 61 National emission standards for hazardous air pollutants
62 Approval and promulgation of state plans for designated facilities and pollutants 63 National emission standards for hazardous air pollutants for source categories 66 Assessment and collection of noncompliance penalties by EPA
67 EPA approval of State noncompliance penalty program 68 Chemical accident prevention provisions
69 Special exemptions from requirements of the Clean Air Act 70 State operating permit programs
71 Federal operating permit programs 72 Permits regulation
73 Sulphur dioxide allowance system 74 Sulfur dioxide opt-ins
75 Continuous emission monitoring
76 Acid rain nitrogen oxides emission reduction program
77 Excess emissions
78 Appeal procedures for acid rain program 79 Registration of fuels and fuel additives 80 Regulation of fuels and fuel additives
81 Designation of areas for air quality planning purposes 82 Protection of stratospheric ozone
85 Control of air pollution from motor vehicles and motor vehicle engines
86 Control of air pollution from new and in-use motor vehicles and new and in-use motor vehicle engines: Certification and test procedures
87 Control of air pollution from aircraft and aircraft engines 88 Clean-fuel vehicles
89 Control of emissions from new and in-use nonroad engines 90 Control of emissions from nonroad spark-ignition engines
91–92 [Reserved]
93 Determining conformity of federal actions to state or federal implementation plans
94 [Reserved]
95 Mandatory patent licenses
on background studies that included control technology, costs, energy requirements, emission reduction benefits, and environmental impacts.
The national primary ambient air quality standards are judged necessary, with an adequate margin of safety, to protect public health. Secondary standards were developed to protect the public welfare from any known or anticipated adverse effects of a pollutant, such as impaired vision or damage to buildings and life- forms.
The pollutant levels of the national primary and secondary ambient air quality standards are presented in Table 3.2. The reference condition for these standards is a temperature of 25°C and a pressure of 760 mm Hg.
The promulgation of the standards stated that they should not in any way be considered to allow signifi- cant deterioration of an area’s existing air quality. Furthermore, the states may establish statewide or region- al ambient air quality standards that are more stringent than the national standards.
In 1997, the ambient air quality standards were revised to include particulate matter that is 2.5 microns or less in diameter (PM2.5). While the standards for particulate matter that is 10 microns or less in diameter
(PM10) retain the same values as the prior National Ambient Air Quality Standards, their forms are new. Pre- viously, the particulate material applied to the highest 24-hour or annual averages found within a planning area, and monitoring networks were often designed to measure these highest values. These networks did not
TABLE 3.2 National Primary and Secondary Ambient Air Quality Standards (1)
Pollutant Air Quality Standard
Sulfur Dioxide
Primary 80 g/m3 0.03 ppm Annual arithmetic mean
365g/m3 0.14 ppm Maximum 24-h concentration not to be exceeded more than once per year Secondary 1300 g/m3 0.5 ppm Maximum 3-h concentration not to be
exceeded more than once per year Particulate Matter
PM2.5 150g/m3 — Annual arithmetic mean, 3-year averaging,
spatial averaging
65g/m3 — 24-h 98th percentile, 3-year averaging, at each monitor
PM10 50g/m3 — Annual arithmetic mean
150g/m3 — 24-h 99th percentile, averaged over 3 years Carbon Monoxide
Primary and secondary 10,000 g/m3 9 ppm 8-h average concentration not to be exceeded more than once per year
40,000g/m3 35 ppm 1-h average concentration not to be exceeded more than once per year
Ozone
Primary and secondary 157 g/m3 0.08 ppm 8-h average concentration, 3-year average of annual fourth-highest daily maximum 8-h average
Nitrogen dioxide
Primary and secondary 100 g/m3 0.53 ppm Annual arithmetic mean Lead
Primary and secondary 1.5 g/m3 — Maximum arithmetic mean averaged over a calendar quarter
necessarily represent the overall exposure of populations to excessive particulate matter concentrations. Some data from these networks were disregarded by epidemiologists as being unrelated to health indicators, such as hospital admissions and death. The new forms for these standards are intended to provide more ro- bust measures for the particulate indicator. The new PM2.5standards will enhance the value of compliance
measurements for evaluating health effects.
The implementation steps for the revised PM2.5and PM10ambient standards include:
앫 PM2.5and PM10standards promulgated by the EPA
앫 PM2.5compliance networks installed and operating and PM10networks revised. Many PM10compliance
sites will be discontinued in favor of new PM2.5sites.
앫 Metropolitan Planning Areas (MPA) defined and designated as unclassifiable with respect to PM2.5and
PM10standards. MPAs must be defined for Metropolitan Statistical Areas (MSAs) containing more than
200,000 inhabitants. States may define additional MIPAs with smaller populations. Areas with existing or pending PM10State Implementation Plans (SIPs) are obligated to implement the measures in those
plans.
앫 Collect compliance data and conduct special studies. Compliance data are PM2.5and PM10measurements
with Federal Reference Methods or Federal Equivalent Methods. Fifty sites in the United States will ac- quire PM2.5samples amenable to chemical characterization for elements, ions, and carbon year after year.
Two hundred and fifty sites will acquire chemical data for shorter time periods and may be moved from one area to another.
앫 Five-year evaluation of particulate matter health criteria completed by the EPA. By presidential order, no planning areas will be declared in nonattainment until the technical basis for the new standards is reeval- uated in light of new research.
앫 Presuming the current PM standards are justified by the reevaluation, planning areas exceeding the stan- dards will be assigned attainment or nonattainment status.
앫 SIPs are formulated and submitted to demonstrate how planned emissions reductions will bring an area into attainment of the standard. SIPs will be based on measured concentrations and source apportionment studies.
앫 Emissions reduction measures are implemented and attainment is demonstrated by measured PM2.5and
PM10concentrations below the National Ambient Air Quality Standards levels.
The regulatory schedule to implement these standards is on par with the three- to ten-year schedule need- ed to extract the relevant science from health effects and field studies. Of particular note is that nonattain- ment areas will not be designated prior to a reevaluation of the scientific basis for a particulate standard. This provides business, governmental, and scientific groups with sufficient time to complete experiments that will better elucidate the relationships between emissions, human exposures to particles, and adverse health effects.
Air Quality Regions
Regions within a state are designated as either attainment or nonattainment areas. When the air quality ex- ceeds national ambient air quality standards, the region is an “attainment area.” The designations are pollu- tant-specific, which means an area may fall into both categories for different pollutants.
Permits are issued to new or modified existing major sources in attainment areas. These permits are part of the “prevention of significant deterioration” program and apply to facilities expected to emit over 100 tons per year of national ambient air quality standard pollutants or 250 tons per year of other pollutants fol- lowing application of emission controls.
Also, the states are required to issue permits for controlling emissions from major stationary sources in nonattainment areas. The principal considerations for issuance of the permit are
1. A net reduction in the total relevant pollutant emissions by regulation of a source or areawide controls 2. Compliance with the lowest achievable emission rate
3. Compliance of all sources owned or operated by the applicant in the state with applicable state and feder- al regulations
4. Determination that the applicable implementation plan is being carried out for the subject nonattainment area