Appendix Air Pollution Legislation

The legislative basis for air pollution abatement in the United States is the 1963 Clean Air Act and its amendments. The Clean Air Act was the first modern environmental law enacted by the U.S. Congress. The original act was signed into law in 1963, and major amendments were made in 1970, 1977, and 1990. The act establishes the federal-state relationship that requires the U.S. Environmental Protection Agency (EPA) to develop National Ambient Air-Quality Standards (NAAQS) and empowers the states to implement and enforce regulations to attain them. The act also requires the EPA to set NAAQS for common and widespread pollutants after preparing criteria documents summarizing scientific knowledge of their detrimental effects. The EPA has established NAAQS for each of six criteria pollutants: sulfur dioxide, particulate matter, nitrogen dioxide, carbon monoxide, ozone, and lead. At certain concentrations and length of exposure these pollutants are anticipated to endanger public health or welfare. The NAAQS are threshold concentrations based on a detailed review of the scientific information related to effects. Concentrations below the NAAQS are expected to have no adverse effects for humans and the environment. Table 2.21 presents the U.S. national primary and secondary ambient air quality standards for ozone, carbon monoxide, nitrogen dioxide, sulfur dioxide, suspended particulate matter, and lead.

The 1990 amendments of the Clean Air Act establish an interstate ozone transport region extending from the Washington, DC metropolitan area to Maine. In this densely

TABLE 2.21 United States National Ambient Air Quality Standards

Pollutant

Primary Standards

Averaging

Times

Secondary Standards

Carbon monoxide

9 ppm (10 mgrrT3)

8-ha

None

35 ppm (40 mg m~3)

l-h°

None

Lead

1.5 pg m~3

Quarterly average

Same as primary

Nitrogen dioxide

0.053 ppm

Annual (arithmetic mean)

Same as primary

(100 pgnT3)

Particulate matter (PM10)

50 pg m~3

Annual'' (arithmetic mean)

Same as primary

150|igm"3

24-h°

Same as primary

Particulate matter (PM2.5)

15.0 pgm"3

Annual^ (arithmetic mean)

Same as primary

65pgm~3

24-hd

Ozone

0.08 ppm

8-he

Same as primary

0.12 ppm

1-1/

Same as primary

Sulfur oxides

0.03 ppm

Annual (arithmetic mean)

0.14 ppm

24-h°

3-h"

0.5 ppm

(1300 ng m~3)

"Not to be exceeded more than once per year.

''To attain this standard, the expected annual arithmetic mean PMjo concentration at each monitor within an area must not exceed 50|rgm~3.

cTo attain this standard, the 3-year average of the annual arithmetic mean PM2.5 concentrations from single or multiple community-oriented monitors must not exceed 15 pg m~3.

dTo 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 65 (rgm~3.

fTo attain this standard, the 3-year average of the fourth-highest daily maximum 8-h average ozone concentration measured at each monitor within an area over each year must not exceed 0.08 ppm. ^(a) The standard is attained when the expected number of days per calendar year with maximum hourly average concentration above 0.12 ppm is < 1; (b) the 1-h NAAQS will no longer apply to an area one year after the effective date of the designation of that area for the 8-h ozone NAAQS; the effective designation date for most areas is June 15, 2004 [40 CFR 50.9; see Federal Register of April 30, 2004 (69 FR 23996)].

"Not to be exceeded more than once per year.

''To attain this standard, the expected annual arithmetic mean PMjo concentration at each monitor within an area must not exceed 50|rgm~3.

cTo attain this standard, the 3-year average of the annual arithmetic mean PM2.5 concentrations from single or multiple community-oriented monitors must not exceed 15 pg m~3.

dTo 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 65 (rgm~3.

fTo attain this standard, the 3-year average of the fourth-highest daily maximum 8-h average ozone concentration measured at each monitor within an area over each year must not exceed 0.08 ppm. ^(a) The standard is attained when the expected number of days per calendar year with maximum hourly average concentration above 0.12 ppm is < 1; (b) the 1-h NAAQS will no longer apply to an area one year after the effective date of the designation of that area for the 8-h ozone NAAQS; the effective designation date for most areas is June 15, 2004 [40 CFR 50.9; see Federal Register of April 30, 2004 (69 FR 23996)].

populated region, ozone violations in one area are caused, at least in part, by emissions in upwind areas. A transport commission is authorized to coordinate control measures within the interstate transport region and to recommend to the EPA when additional control measures should be applied in all or part of the region in order to bring any area in the region into attainment. Hence areas within the transport region that are in attainment of the ozone NAAQS might become subject to the controls required for nonattainment areas in that region.

The Clean Air Act requires each state to adopt a plan, a State Implementation Plan (SIP), which provides for the implementation, maintenance, and enforcement of the NAAQS. It is, of course, emission reductions that will abate air pollution. Thus the states' plans must contain legally enforceable emission limitations, schedules, and timetables for compliance with such limitations. The control strategy must consist of a combination of measures designed to achieve the total reduction of emissions necessary for the attainment of the air quality standards. The control strategy may include, for example, such measures as emission limitations, emission charges or taxes, closing or relocation of commercial or industrial facilities, periodic inspection and testing of motor vehicle emission control systems, mandatory installation of control devices on motor vehicles, means to reduce motor vehicle traffic, including such measures as parking restrictions and carpool lanes on freeways, and expansion and promotion of the use of mass transportation facilities.

APPENDIX 2.2 HAZARDOUS AIR POLLUTANTS (AIR TOXICS)

Hazardous air pollutants or toxic air contaminants ("air toxics") refer to any substances that may cause or contribute to an increase in mortality or in serious illness, or that may pose a present or potential hazard to human health. Title III of the Clean Air Act Amendments of 1990 completely overhauled the existing hazardous air emission program. Section 112 of the Amendments defines a new process for controlling air toxics that includes the listing of 189 substances, the development and promulgation of Maximum Achievable Control Technology (MACT) standards, and the assessment of residual risk after the implementation of MACT. Any stationary source emitting in excess of lOtonsyr 1 of any listed hazardous substance, or 25 tons yr 1 or more of any combination of hazardous air contaminants, is a major source for the purpose of Title III and is subject to regulation. Congress established a list of 189 hazardous air pollutants in the CAA itself. It includes organic chemicals, pesticides, metals, coke-oven emissions, fine mineral fibers, and radionuclides (including radon). This initial list may be revised by the EPA to either add or remove substances. The EPA is required to add pollutants to the list if they are shown to present, through inhalation or other routes of exposure, a threat of adverse human health effects or adverse environmental effects, whether through ambient concentrations, bioaccumulation, deposition, or otherwise.

Congress directed the EPA to list by November 15, 1995, the categories and subcategories of sources that represent 90% of the aggregate emissions of

• Alkylated lead compounds

• Polycylic organic matter

• Hexachlorobenzene

• Polychlorinated biphenyls

• 2,3,7,8-Tetrachlorodibenzofuran

• 2,3,7,8-Tetrachlorodibenzo-/j-dioxin

Congress further directed the EPA to establish and promulgate emissions standards for such sources by November 15, 2000. The emissions standards must effect the maximum degree of reduction in the listed substance, including the potential for a prohibition on such emissions, taking into consideration costs, any non-air-quality health and environmental impacts, and energy requirements. In establishing these emissions standards, the EPA may also consider health threshold levels, which may be established for particular hazardous air pollutants. Each state may develop and submit to the EPA for approval a program for the implementation and enforcement of emission standards and other requirements for hazardous air pollutants or requirements for the prevention and mitigation of accidental releases of hazardous substances.

TABLE 2.22 Substances Either Confirmed or under Study as Hazardous to Human Health by State of California Air Resources Board (1989)

Concentrations

TABLE 2.22 Substances Either Confirmed or under Study as Hazardous to Human Health by State of California Air Resources Board (1989)

Concentrations

Substance

Qualitative Health Assessment"

Manner of Usage/ Major Sources

Atmospheric Residence Time

Ambient Average*

Hotspot

Benzene

Human carcinogen

Gasoline

12 days

4.6 ppb (SoCABf

Ethylene dibromide

Probable carcinogen

Gasoline, pesticides

50 days

7.4 ppt (SoCAB)

Ethylene dichloride

Probable carcinogen

Gasoline, solvents,

42 days

19-110 ppt

pesticides

Hexavalent chromium

Human carcinogen

Chrome plating,

0.5 ng m"3 (SoCAB)

corrosion inhibitor

Dioxins

Probable carcinogen

Combustion product

1 yr in soil

1.0 pgm"3

Asbestos

Human carcinogen

Milling, mining

Unknown; removed

8-80 fibers m"3

50-500 fibers m

by deposition

Cadmium

Probable carcinogen

Secondary smelters,

7 days; removed by deposition

1-2.5 ng m"3

40 ngm"3

fuel combustion

Carbon tetrachloride

Probable carcinogen

CCI4 production,

42 yr

0.13 ppb

0.63 ppb

grain fumigant

Ethylene oxide

Probable carcinogen

Sterilization agent,

200 days

50 ppt (SoCAB)

17 ppb

manufacture of

surfactants

Vinyl chloride

Human carcinogen

Landfill byproduct

2 days

0.08-0.34 ppb

Inorganic arsenic

Human carcinogen

Fuel combustion,

Unknown; removed by

2.4 ngnT3 (SoCAB)

200 ngm"3

pesticides

deposition

Methylene chloride

Probable carcinogen

Solvent

0.41 yr

1.1-2.4 ppb

10.7 ppb

Perchloroethylene

Probable carcinogen

Solvent, chemical

0.4 yr

0.71 ppb

22 ppb

intermediate

Trichloroethylene

Probable carcinogen

Solvent, chemical

5-8 days

0.22 ppb

Nickel

Probable carcinogen

Alloy, plating ceramics,

Unknown, removed

7.3 ngm"3

23 ng m"3

dyes intermediate

by deposition

Formaldehyde

1.3-Butadiene

Acetaldehyde Acrylonitrile

Beryllium

Dialkylnitrosamines p-Dichlorobenzene

Di-(2-ethylhexyl) phthalate

1.4-Dioxane

Dimethyl sulfate Ethyl acrylate

Hexachlorobenzene Lead

Mercury

4,4' -Methylenedianiline TV-Nitrosomorpholine

Probable carcinogen

Probable carcinogen Probable carcinogen

Probable carcinogen Probable carcinogen

Probable carcinogen

Probable carcinogen

Probable carcinogen

Probable carcinogen Probable carcinogen

Probable carcinogen Possible carcinogen

Probable carcinogen Blood system toxic, neurotoxicity Neurotoxic

Possible carcinogen Probable carcinogen

Solvent, chemical intermediate Chemical

Chemical feedstock, resin production Motor vehicles Feedstock, resins, rubber Metal alloys, fuel combustion Chemical feedstock Room deodorant, moth repellent Plasticizer, resins Solvent stabilizer, feedstock Chemical reagent Chemical intermediate Solvent, pesticide Auto exhaust, fuel additive Electronics, paper/ pulp manufacture Chemical intermediate Detergents, corrosion inhibitor

10 days to be removed 0.11-0.22 ng m 1

by deposition

7-30 days; removed by deposition 270-820 ng m~3

0.3-2 yr; removed by deposition 0.37-0.49 ppb

10 ppb

0.016 ppb 35 ppb

0.3 ppb

105-1700 pgnT3

1.2 ppb

0.1 ngm-3 OContinued)

TABLE 2.22 (Continued)

Concentrations

Qualitative Health Manner of Usage/ Atmospheric

Substance Assessment" Major Sources Residence Time Ambient Average* Hotspot

Qualitative Health Manner of Usage/ Atmospheric

Substance Assessment" Major Sources Residence Time Ambient Average* Hotspot

PAHs

Probable carcinogen

Fuel combustion

0.4-40 days; removed by deposition

0.46 ngm 3

-

PCBs

Probable carcinogen

Electronics

3-1700 days;

0.5-14 ngnT3

-

Propylene oxide

Probable carcinogen

Resin manufacture, surfactant

6 days

-

-

Styrene

Probable carcinogen

Chemical feedstock

lOppb

-

Toluene diisocyanates

Possible carcinogen

Raw material Polyurethane

26 h

-

-

2,4,6-Trichlorophenol

Probable carcinogen

Herbicide, wood preservative

"Human carcinogen = sufficient evidence in humans (International Agency for Research on Cancer). Probable human carcinogen = limited human or sufficient animal evidence using IARC criteria or EPA guidelines for carcinogen risk assessment. Possible human carcinogen = limited animal evidence using IARC criteria or EPA guidelines for carcinogen risk assessment. ^Values presented by the California ARB relevant to California. "South Coast Air Basin of California (Los Angeles metropolitan area).

"Human carcinogen = sufficient evidence in humans (International Agency for Research on Cancer). Probable human carcinogen = limited human or sufficient animal evidence using IARC criteria or EPA guidelines for carcinogen risk assessment. Possible human carcinogen = limited animal evidence using IARC criteria or EPA guidelines for carcinogen risk assessment. ^Values presented by the California ARB relevant to California. "South Coast Air Basin of California (Los Angeles metropolitan area).

The California Air Resources Board (ARB) (1989) has developed a list of substances of concern in California, called "Status of Toxic Air Contaminant Identification." This list and the organization of substances within it are subject to periodic revision, as needed. The February 1989 Status List grouped substances into three categories. Category I includes identified toxic air contaminants: asbestos, benzene, cadmium, carbon tetrachloride, chlorinated dioxins and dibenzofurans (15 species), chromium (VI), ethylene dibromide and ethylene dichloride, and ethylene oxide. Category IIA contains nine substances that were in the formal review process (1,3-butadiene, chloroform, formaldehyde, inorganic arsenic, methylene chloride, nickel, perchloroethylene, trichloroethylene, and vinyl chloride). Category IIB contains 23 substances not yet reviewed at the time (acetaldehyde, acrylonitrile, beryllium, coke-oven emissions, dialkylnitrosamines, p-dichlorobcnzene, di(2-ethylhexyl)-phthalate, 1,4-dioxane, dimethyl sulfate, environmental tobacco smoke, ethyl acrylate, hexachlorobenzene, inorganic lead, mercury, 4,4'-methylenedianiline, V-nitrosomorpholine, PAHs, PCBs, propylene oxide, radionuclides, styrene, toluene diiosocyanates, and 2,4,6-trichlorophenol). Category III includes substances for which additional health information was needed prior to review. These are acrolein, allyl chloride, benzyl chloride, chlorobenzene, chlorophenols/ phenol, chloroprene, glycol ethers, maleic anhydride, manganese, methyl bromide, methyl chloroform, nitrobenzene, vinylidene chloride, and xylenes. Available information on these compounds is summarized in Table 2.22.

PROBLEMS

2.1A Methane (CH4) has an atmospheric mixing ratio of about 1745 ppb. Carbon monoxide (CO) has a global average mixing ratio in the neighborhood of 100 ppb. Global annual emissions of CH4 are about 600 Tg (CH4)yr 1 (Table 2.10); global annual CO sources are estimated as 2780Tg (CO)yr-1 (Table 2.14). How can the atmospheric concentration of CH4 be almost 20 times higher than that of CO given their relative emissions? (Problem suggested by T. S. Dibble.)

2.2A Figure 2.6 shows ozone molecular number concentration and mixing ratio versus altitude. Why do the molecular number concentration and mixing ratio peak at different altitudes?

2.3a The total estimated global sink of nitrous oxide (N20) is 12.6TgNyr_1. The global mean N20 mixing ratio in 2000 was 315 ppb. On the basis of these two values, estimate the mean lifetime of N20 in the atmosphere.

2.4A Calculate the number of DU assuming that the entire atmospheric 03 column is at a uniform concentration of 3 x 1012 molecules cm-3 between 15 km and 30 km and zero elsewhere.

2.5A Singh et al. (2003) reported airborne measurements of hydrogen cyanide (HCN) and methyl cyanide (CH3CN, also known as acetonitrile) over the Pacific Ocean in 2001. Mean HCN and CH3CN mixing ratio of 243 ppt and 149 ppt, respectively, were measured. On the basis of these findings and other information, they prepared global budgets for both compounds.

a. Compute the mean tropospheric column burdens, in molecules cm-2, of each compound according to these values.

b. The authors estimated the following quantities for the two compounds:

HCN CH3CN

Annual mean atmospheric burden, Tg (N) 0.44 0.30

Residence time due to OH reaction, months 63 23

Calculate the residence time of each compound due to the oceanic sink and the overall global mean residence time of each compound, assuming that OH reaction and deposition to the oceans are the only loss processes.

2.6a Table 2.10 presents the global methane budget, in which sources are estimated to exceed sinks by 22 Tg (CH4) yr~1. Show that this difference corresponds to an increase of 8 ppb vr of CH4.

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  • jens bauer
    How does an increase in 22Tg of methane/ year correspond to an increase of 8ppb/year?
    9 years ago

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