This section discusses the purposes for which this  Aviation Emissions and Air Quality Handbook  (the  Handbook ) was prepared, the intended audience, its primary objectives, and its contents.  This  Handbook  has been published by the Federal Aviation Administration (FAA) explanatory guidance, and is a tool and resource designed to assist the FAA and others that are  responsible for the planning, organization, and completion of air quality assessments aviation-related projects and/or actions. Following the guidance in this  Handbook  will help to  ensure that air quality assessments for these projects/actions are comprehensive, consistent, and  appropriate for use in the disclosure and decision-making processes.  The effects on air quality from aviation and aviation-related developments and operations have  long been an important and significant subject matter. On one hand, airports perform vital civic  and economic functions by serving scheduled and unscheduled  operations of air carriers which  enable the transportation of passengers and cargo safely and efficiently across the count ry and  throughout the world. For over 100 years, airports  (including general aviation [GA] airports)  have remained among the enabling resources for progress and prosperity within the communities  they serve. On the other hand, air pollutants associated with aircraft and other airport emission  sources are an inevitable consequence of these activities and can have  impacts on local and  regional air quality.  This long-term connection between aviation and air quality has been growing in im portance as  the aviation industry seeks to (i) develop, expand, and/or improve their facilities, equipment, and  procedures; (ii) repair /replace aging infrastructure; and/or (iii) accommodate the forecasted  growth in air traffic; while implementing sustainable practices. Meanwhile, air quality regulatory  agencies continually strive to safeguard human health and the natural environment from effects of air pollution – including the air emissions associated with aviation.  Historically, the junction where aviation and air quality most often intersect s is in the federal  Clean Air Act (CAA) and other environmental-related regulations and directives which are often  discussed in environmental documents prepared in accordance with the National Environmental  Policy Act (NEPA) (discussed in greater detail in  Section 2 , Regulatory Framework ). In short,  such rules and requirements mandate that the air quality impacts associated with federal actions  and projects do, in the case of the CAA, not cause, or worsen, violations of relevant air quality  standards, criteria and/or thresholds and environmental impacts are disclosed under NEPA to the  public.  For the FAA, these demonstrations of disclosure and compliance for air quality are regul arly  accomplished in conjunction with the more encompassing environmental  analyses of aviation- related projects/actions conducted under NEPA as part of Environmental Assessments Environmental Impact Statements (EA s/EISs) and/or in association with General Conformity  Determinations performed under the CAA. In many cases, the air quality analysis is an integral  component of these assessments. Therefore, in support of the documentation of these air quality  assessments, the purpose of this  Handbook  is essentially three-fold:  1$_{ }$ 1.  Introduction and Background  1.1. Purpose of This Handbook  Aviation Emissions and Air Quality Handbook 