Measuring Air Pollution : NACAA Positions| Related Documents| Related Links

Air pollution can be directly measured as it is emitted by a source (e.g., grams/second) or in the atmosphere as a concentration (e.g., micrograms/m3). Ambient air monitoring data is used to determine air quality, establish the extent of air pollution problems, assess whether established standards are being met, and characterize the potential human health risk in an area. Alternatively, air pollution concentrations can be simulated using computer models, and then validated using data collected from direct measurements at selected monitors or sources. Air pollution data and models are used together to examine the impacts of control strategies on the ambient air.

NACAA Positions

NACAA Comments on Emissions Factors Program Improvements Announced Notice of Proposed Rulemaking (December 14, 2009)
NACAA submitted comments on EPA’s Announced Notice of Proposed Rulemaking for the Emissions Factors Program Improvements, which was published in the Federal Register on October 14, 2009. NACAA’s comments provided input on each of 14 specific questions EPA had included in the notice, as well as several general points. Most importantly, NACAA expressed concern that the existing Emissions Reporting Tool is not based on current technology and would not be an effective platform on which to base a national emission factor program. NACAA recommended that EPA instead employ a web-enabled technology platform. Additionally, NACAA recommended that EPA use a system that provides state and local agencies with access to raw emissions data. Since data quality is a critical component of an effective emissions inventory program, the existing system, which relies on AP-42 and WebFIRE and lacks quantitative measures to assess data quality, should be improved upon. NACAA also noted that emission factors are used for many purposes and that determinations about the appropriateness of using them should be evaluated in the context in which they are applied and decided upon by state and local agencies on a case-by-case basis.
NACAA Comments on Emissions Factors Program Improvements Announced Notice of Proposed Rulemaking (December 14, 2009)
NACAA submitted comments on EPA’s Announced Notice of Proposed Rulemaking for the Emissions Factors Program Improvements, which was published in the Federal Register on October 14, 2009. NACAA’s comments provided input on each of 14 specific questions EPA had included in the notice, as well as several general points. Most importantly, NACAA expressed concern that the existing Emissions Reporting Tool is not based on current technology and would not be an effective platform on which to base a national emission factor program. NACAA recommended that EPA instead employ a web-enabled technology platform. Additionally, NACAA recommended that EPA use a system that provides state and local agencies with access to raw emissions data. Since data quality is a critical component of an effective emissions inventory program, the existing system, which relies on AP-42 and WebFIRE and lacks quantitative measures to assess data quality, should be improved upon. NACAA also noted that emission factors are used for many purposes and that determinations about the appropriateness of using them should be evaluated in the context in which they are applied and decided upon by state and local agencies on a case-by-case basis.
NACAA Comments on Emissions Factors Program Improvements Announced Notice of Proposed Rulemaking (December 14, 2009)
NACAA submitted comments on EPA’s Announced Notice of Proposed Rulemaking for the Emissions Factors Program Improvements, which was published in the Federal Register on October 14, 2009. NACAA’s comments provided input on each of 14 specific questions EPA had included in the notice, as well as several general points. Most importantly, NACAA expressed concern that the existing Emissions Reporting Tool is not based on current technology and would not be an effective platform on which to base a national emission factor program. NACAA recommended that EPA instead employ a web-enabled technology platform. Additionally, NACAA recommended that EPA use a system that provides state and local agencies with access to raw emissions data. Since data quality is a critical component of an effective emissions inventory program, the existing system, which relies on AP-42 and WebFIRE and lacks quantitative measures to assess data quality, should be improved upon. NACAA also noted that emission factors are used for many purposes and that determinations about the appropriateness of using them should be evaluated in the context in which they are applied and decided upon by state and local agencies on a case-by-case basis.
Change is in the Air: NACAA Recommendations to the New Administration on Improving Our Nation’s Clean Air Program (December 16, 2008)
STAPPA/ALAPCO Comments on EPA Exceptional Events Proposal (May 25, 2006)
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Air Quality Modeling : NACAA Positions| Related Documents| Related Links

As an alternative to or in conjunction with direct monitoring, computer models are often used to predict the levels of pollutants emitted from various types of sources, and how these emissions eventually impact ambient air quality over time. The models themselves vary in terms of sophistication, accuracy and precision of their outputs. Different models are used to estimate emission rates, source activity levels, and ambient air quality impacts. For example, models are available for estimating emissions from mobile and stationary sources, predicting meteorological factors and the likely photochemical and dispersion characteristics of air pollution, as well as predicting traffic patterns and congestion. In addition, emissions models and preprocessors can be used to provide input data for air quality models that need emissions based on chemical species, and broken down into very fine temporal (e.g., grams/second) and spatial (1 km x 1 km grid) resolution.

NACAA Positions

Monitoring : NACAA Positions| Related Documents| Related Links

Air pollution monitoring activities are typically separated into two classifications: source monitoring and ambient air monitoring. Both source and ambient air measurements can be made directly using continuous measurement instrumentation or manual methods, or remotely using optical sensing systems. Source monitoring involves the measurement of emissions directly from a fixed or mobile emission source, typically at the point of exhaust, vent, stack or chimney. Stationary source data is used to determine whether established permit limits are being met, and as input to ozone and/or health risk prediction models. Major stationary sources may have continuous emissions monitors (CEMs) installed to report real-time emissions based on pre-established reporting cycles. Ambient air monitoring involves the measurement of specific pollutants present in an immediate surrounding atmosphere. Most major urban areas will operate several ambient air monitoring instruments, each dedicated to measuring specific target pollutants.

NACAA Positions