Introduction
An atmospheric pollutant may be defined as any atmospheric substance which is not normally present in the atmosphere, or is present at a greater concentration or in a different location from usual. Generally, air pollutants are known to have deleterious effects on human and animal health, vegetation, materials and buildings, and are known to affect the atmospheric transfer of radiation with consequences on visibility and climate. Knowledge of the levels of atmospheric pollutants forms an essential aspect of the assessment, and mitigation, of their adverse impacts on human health and wider ecosystems, and provides the data to monitor compliance with regulatory controls, and to advise the general public of current air quality levels and pollution warnings as appropriate.