Air pollution is formally defined as the presence in the atmosphere of any substance, or combination of substances, that is detrimental to human health and welfare, offensive to human senses, or indirectly affects human well-being (Parker, 1977). The substances responsible for this atmospheric degradation are known as air pollutants. For environmental engineers, compliance officers, and public health officials, a systematic understanding of these pollutants—their characteristics, origins, and control mechanisms—is of strategic importance. This report provides a detailed technical overview of air pollutants, their classification systems, primary sources, and the abatement technologies available for their control.

Pollutants enter the atmosphere from both natural and anthropogenic (human-made) sources. Natural phenomena such as volcanic eruptions and soil erosion release considerable quantities of pollutants. However, it is the pollutants derived from human activities—those associated with industrial societies, community living, and rising standards of living—that pose the most significant and concentrated threat to human health and property. These activities primarily include the combustion of fuel for heat and power, the industrial processing of materials, and the disposal of waste.

The presence of these pollutants represents a dual challenge: they are a direct threat to environmental and public health, and they often constitute a waste of valuable resources. While the technological means to control most sources of air pollution are available today, their implementation is not without consequence. The economic costs are significant, and achieving healthful air quality in densely populated urban centers may necessitate substantial changes in lifestyle and industrial practice. To effectively manage and mitigate the impacts of air pollution, it is first necessary to classify pollutants into logical categories, a framework this report will now explore.