ICAO recognizes that airport-related sources of emissions have the ability to emit pollutants that can contribute to the degradation of air quality of their nearby communities. As such, national and international air quality programmes and standards are continually requiring airport authorities and government bodies to address air quality issues in the vicinity of airports. Similarly, attention must also be paid to other possible airport-related environmental impacts associated with noise, water quality, waste management, energy consumption and local ecology in the vicinity of airports, to help ensure both the short- and the long-term welfare of airport workers, users and surrounding communities.
One the initiatives that ICAO has undertaken to improve air quality are the creation and continued updating of the guidance Document 9889 "Airport Air Quality Manual". The manual provides guidance to assist with the assessment of airport emission sources, emission inventories and emissions allocation. The first step to addressing local air quality is to obtain an accurate estimate of the types and amounts of contaminants being introduced to the airshed. Then efforts to reduce these emissions can be pursued. The two main areas of an air quality assessment are: the emissions inventories; and the dispersion modelling of pollution concentrations.
An emissions inventory gives the total mass of emissions released into the environment and provides a basis for reporting, compliance, mitigation planning, and can be used as input for modelling pollution concentrations. In order to link emissions to pollution concentrations, the spatial and temporal distribution of the emissions have to be assessed as well. This combined approach of using emissions inventories and dispersion modelling enables the assessment of historical, existing and/or future pollution concentrations in the vicinities of airports or from individual emissions sources.
The emissions inventory, concentration modelling and ambient measurement elements of an air quality assessment can be used individually or in combination to aid the process of understanding, reporting, compliance and/or mitigation planning by providing information on overall conditions as well as specific source contributions. Subsequent air quality mitigation or other implemented measures (with proper consideration of the interrelationship with, primarily, noise and other airport environmental impacts) can have beneficial results for the total emissions mass, the concentration model results and measured concentrations.