Pollution of the Atmosphere and Air Quality

In Chapter 6, the atmosphere was introduced as one of the five main parts of the environment. In this chapter, pollution of the atmosphere is discussed. Atmospheric quality is extremely important for human welfare, in part because of the intimate relationship that we have with air in the atmosphere. It is almost impossible in a practical sense to avoid breathing air as we find it around us. Toxic air pollutants will get into our lungs. In the innermost alveoli of the lungs where gases are interchanged between air that is inhaled and blood in the bloodstream, a layer only the thickness of a single human cell separates the blood from the air. If the air that we breathe is polluted, we may be harmed by it. 

In discussing atmospheric pollution, it is important to make the distinction between primary and secondary air pollutants. Primary air pollutants are those that are pollutants in the form in which they are emitted into the atmosphere. An example would be light-scattering fine ash particles ejected from a smokestack. Secondary air pollutants are those that are formed from other substances by processes in the atmosphere. A prime example of a secondary pollutant develops when otherwise relatively innocuous levels of hydrocarbons (including terpenes from pine and citrus trees) and NO are emitted into the atmosphere and subjected to ultraviolet radiation from the sun, resulting in a noxious mixture of ozone, aldehydes, organic oxidants, and fine particles called photochemical smog. 

Changing climatic conditions and atmospheric pollution that may result from such changes may have profound effects upon human health in the future. The health implications of climate change are discussed in more detail in Chapter 8, Section 8.2.6 

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