Outdooor pollutants and Ozone

Pollution is not a recent phenomenon. Air pollution has been a problem since the appearance of our earliest ancestors. But over the past few centuries, the rising human activities associated with population growth and industrialization have negatively contributed to the air quality. Atmospheric air can be considered as an aero-disperse system, containing primarily nitrogen, oxygen, other minor gases together with water vapour. In addition to these components, more than 3,000 substances, known as air pollutants and able to change the base composition of the atmosphere, are also present. Usually pollutants are classified in several ways according to their origin, phase, formation mechanism and their effect on human health. This chapter will examine the six major air pollutants designated by the U.S. Environmental Protection Agency (EPA) as “criteria pollutants”. They include particulate matter, carbon monoxide, sulfur oxides, nitrogen oxides, lead and trophospheric ozone. It will be also described the contribution to the air pollution of halogens, halogenated hydrocarbons and the singular case of cigarette smoke, now considered part of the air pollutants. Since most air pollutants act directly as prooxidants of lipids and proteins or as free radical generators, their common cellular mechanism of injury involves the promotion of oxidative stress and induction of inflammatory responses. Despite the advances that were reached, many questions remain. Humans are exposed to several pollutants simultaneously, but as consequence of different factors, such as genetic predisposition, age, nutritional status and time of exposure, not everybody that is exposed to toxicants develops diseases or the same diseases. Therefore, all these variables make the understanding of pollution effects in human health very difficult. Nevertheless, in view of the enormous burden estimated from exposure to air pollution, it would be of utmost importance to conduct researches in this field for the development of different and specific strategies to counteract the negative health and social impacts. Furthermore, sensitizing the institutions to air pollution control policy is of strategic importance for air quality in worldwide.