GLOSSARY OF TERMS AND ACRONYMS 

AQI Air Quality Index, daily forecast to the public about air quality on a 24-hour basis. 

Air Quality Monitor Device measuring ozone and PM levels at various locations throughout the 

Washington region. 

APU Auxiliary Power Units, an electrical device that provides a low-emission 

alternative to constant idling for large diesel engines. 

ASIP Association for Southeastern Integrated Planning. 

Attainment A designation given to an area that does meet the federal health-based air quality

standard for a pollutant. 

Attainment (1-hour ozone) The expected numbers of days per calendar year with maximum hourly average 

concentrations above 0.12 ppm is equal to or less than 1. 

Attainment (8-hour ozone) The 3-year average of the annual fourth-highest daily maximum 8-hour average 

ozone concentration is less than or equal to 0.08 ppm.

Attainment (Annual PM2.5) The 3-year average of the annual means is less than or equal to 15.0 μg/ m3

. This 

comparison shall be based on 3 consecutive, complete years of air quality data. 

Attainment (24-hour PM2.5) The 3-year average of the 98th percentile values at each monitoring site is less 

than or equal to 65 μg/m3

. This comparison shall be based on 3 consecutive, 

complete years of air quality data. 

AQPAC Air Quality Public Advisory Committee.

BACT Best available control technology. 

Bump-up/Reclassification Process by which areas failing to attain the air quality standard by the assigned 

date are redesignated to a more stringent nonattainment category. 

CAAA Clean Air Act Amendments of 1990. 

Classification Federal designation indicating the severity of a region's air quality problem. A 

region's classification determines the date on which a region must attain the 

CAAA requirements. 

Clean Air Partners Non-profit regionally-sponsored organization in the Baltimore-Washington metro 

area that educates businesses and the public to take actions to reduce ozone, 

especially on Air Quality Code Red Action Days. 

CLRP Constrained Long Range Plan; lists expected changes to transportation 

infrastructure over the next 20 years. 

Control Measures Pollution control measure implemented as part of a regional air quality plan. 

Contingency Measures Pollution control measures to be implemented after the fact if the region fails to 

demonstrate rate of progress toward or attainment of an air quality standard. 

CTG Control Technique Guidance, comes in the form of documents from EPA. 

DCDOE District of Columbia Department of the Environment. 

Design Value The U.S. EPA’s official definition: “a design value is the mathematically

determined pollutant concentration at a particular site that must be reduced to, or 

maintained at or below the National Ambient Air Quality Standard to assume

attainment.” The design value number tells us how a particular site or area 

compares with the National Ambient Air Quality Standards (NAAQS). 

Design Value (1-hour

Ozone) 

The 1-hour ozone design value is the fourth highest 1-hour maximum ozone 

concentration at a monitoring site during a continuous three year period. Values 

of 125 ppb and above are exceeding the 1-hour ozone health standard. 

Design Value (8-hour

Ozone) 

The 8-hour ozone design value is the fourth highest 8-hour maximum ozone 

concentration at a monitoring site averaged over a continuous three year period. 

Values of 85 ppb and above are exceeding the 8-hour ozone health standard. 

EPA U.S. Environmental Protection Agency.

Emission Inventory A document that details the amounts of projected emissions from area sources 

MWAQC Ozone SIP Glossary-1 Draft May 23, 2007 
GLOSSARY OF TERMS AND ACRONYMS 

over time. Includes four types of emission sources: stationary point sources, area

sources, nonroad sources, and on-road mobile sources. 

Exceedance Condition created when an air quality monitor registers ozone or PM levels 

exceeding the federal health standard. 

FHWA Federal Highway Administration. 

General Conformity Federally-required process during which Federal projects are evaluated to ensure 

that they are consistent with the region's air quality plans. 

IAD Dulles International Airport, site of a weather monitor. 

IAQC Interstate Air Quality Council; a council, consisting of the chief environmental 

appointees of the Chief Executives and the chief transportation appointees of the 

Chief Executives. 

I/M Inspection and Maintenance programs that require vehicle owners to have their 

vehicles' emission systems regularly tested and repaired, if necessary. 

Lead Monitor The monitor in the region with the highest Design Value. 

LDT Light-duty trucks.

LTOs Landing and Take-Off cycles for aircraft. 

MACTEC An engineering and consulting firm under contract to OTC. 

MDE Maryland Department of the Environment. 

Mid-Course Review The Mid-Course Review is intended to show the progress being made to improve 

air quality in a nonattainment area and the efforts underway to assure that all 

necessary steps are taken to reach the federal health standard for the relevant 

standard by the attainment date. 

MDPC Metropolitan Development Policy Committee; a COG committee of planning 

directors. 

MSA/CMSA Metropolitan Statistical Area/Consolidated Metropolitan Statistical Area; serve as 

the presumptive boundary for nonattainment areas. 

MOBILE6 EPA model used to estimate levels of mobile emissions. 

Mobile Budget Cap on mobile emissions set in the SIP and used in transportation conformity. 

MWAQC Metropolitan Washington Air Quality Committee. 

MWAQC TAC Technical Advisory Committee, advices MWAQC on technical issues. 

MARAMA Mid-Atlantic Regional Air Management Association; an RPO. 

MWAA Metropolitan Washington Airports Authority.

NAA Non-Attainment Area.

NAAQS National Ambient Air Quality Standard. Ambient standards for six pollutants 

including ozone, carbon monoxide, nitrogen dioxide, lead, particulate matter, and 

oxides of sulfur specifically regulated under the U.S. Clean Air Act of 1990. 

Areas designated as nonattainment must adopt State Implementation Plans to 

reduce emissions in order to comply with the standard by the attainment date. 

NEI National Emissions Inventory. The National Emissions Inventory is the most 

comprehensive estimate of criteria pollutant emissions in the United States. The 

inventory represents a major effort by the individual states to quantify their local 

and regional contributions to air quality. Data from the NEI are used for air 

dispersion modeling, regional strategy development, regulation setting, and

tracking trends in emissions over time. 

NESCAUM Northeast States for Coordinated Air Use Management. 

Nonattainment A designation given to an area that does not meet the federal health-based air 

quality standard for a pollutant. 

NOx Nitrogen oxide, a precursor to ozone formation. 

Organic Carbon Carbon emission, a precursor to PM formation. 

OTC Ozone Transport Commission, a commission of air directors from northeastern 

MWAQC Ozone SIP Glossary-2 Draft May 23, 2007 
GLOSSARY OF TERMS AND ACRONYMS 

and mid-Atlantic states affected by transported ozone pollution; an RPO. 

Ozone A pollutant (O3) formed from chemical reactions in the atmosphere involving 

precursors (NOx and VOC) in the presence of sunlight and heat. 

PEI Periodic Emissions Inventory. The Clean Air Act [under Section 182(a)(3)(A)]

requires that state and local agencies develop a periodic emission inventory (PEI) 

for ozone nonattainment areas classified as marginal and above. The PEI is a tool 

used to monitor a nonattainment area’s progress in attaining the National Ambient 

Air Quality Standards (NAAQS) for ozone. A PEI for an ozone nonattainment 

area is required to contain emissions of ozone precursor pollutants (specifically

VOC and NOx) from Point Sources, Area Sources, On-road Mobile Sources, 

Non-road Mobile Sources, and Biogenic Sources. A PEI is to be compiled every

three years until attainment of the National Ambient Air Quality Standards 

(NAAQS) for ozone is reached. 

PJM Distribution grid for electricity that includes Pennsylvania, New Jersey and 

Maryland. 

PM2.5 Particulate matter, fine particulate. Particles of less than 2.5 microns in diameter 

are referred to as fine particulate. 

RACM Reasonably available control measure. 

RACT Reasonably available control technology. 

REC Renewable Energy Certificate. 

Retrofit Installation of pollution control devices on existing equipment, such as particulate 

filters and catalytic converters. 

RFP Reasonable Further Progress. 

ROP Rate of Progress. 

RPO Regional Planning Organization in CAAA, such as OTC, NESCAUM. 

RPS Renewable Energy Portfolio Standard Act of 2004, a District of Columbia law. 

RSD Remote sensing device, used in the field to detect motor vehicles with emissions 

exceeding allowable limits. 

SI Spark-Ignition engines, such as gasoline marine engines, including outboard, 

personal watercraft and jet boat. 

SIP State Implementation Plan, the air quality plan. 

1-hour Standard Ozone standard setting the maximum average ozone concentration over a onehour period. 

8-hour Standard Ozone standard setting the maximum average ozone concentration over an eighthour period. 

24-hour Standard PM standard setting the maximum average concentration over a 24-hour period.

Annual Standard PM standard setting the maximum average concentration over a one-year period.

Sulfates/SO2 Sulfur dioxide, a precursor to ozone and PM formation. 

TAC Technical Advisory Committee of the MWAQC. 

TCM Transportation Control Measure. 

TDM Transportation Demand Model; a TPB model used to estimate travel demand in 

the Washington region. 

TERM Transportation Emission Reduction Measure. 

TPB National Capital Region Transportation Planning Board, body responsible for 

development of regional transportation plan. 

tpd tons per day.

tpy tons per year.

TIP Transportation Improvement Plan; a short term transportation plan produced by

TPB, usually covering a five-year period.

Transportation Conformity Federally-required process during which the regional transportation planning 

MWAQC Ozone SIP Glossary-3 Draft May 23, 2007 
GLOSSARY OF TERMS AND ACRONYMS 

board ensures that expected transportation emissions are consistent with the 

region's air quality plans. 

VADEQ Virginia Department of Environmental Quality. 

VISTAS Visibility Improvement State and Tribal Association of the Southeast; an RPO. 

VMT Vehicle Miles Traveled. 

VOC Volatile organic compound, a precursor to ozone formation. 

Voluntary Measure Pollution control measures that are not regulatory in nature. 

WOE Weight of Evidence. 

MWAQC Ozone SIP Glossary-4 Draft May 23, 2007