Air Pollution: A powerful Speech on Air Pollution!
“Air pollution” can be defined as the presence in the outdoor atmosphere of one or more contaminants (pollutants) in such quantities and of such duration as may be (or may tend to be) injurious to human, plant, or animal life, or to property (materials), or which may unreasonably interfere with the comfortable enjoyment of life or property, or the conduct of business.
It should be stressed that the attention in this definition is on the outdoor, or ambient, air, as opposed to the indoor, or work environment, air. Air pollution can be caused by the presence of one or more contaminants.
Examples of traditional contaminants include sulfur dioxide, oxides of nitrogen, carbon monoxide, hydrocarbons, ozone, oxidants, hydrogen sulfide, particulate matter, smoke, and haze. This list of air pollutants can be divided into two categories: gases and particulates.
Gases, such as sulfur dioxide and oxides of nitrogen, exhibit diffusion properties and are normally formless fluids which can be changed to the liquid or solid state only by a combined effect of increased pressure and decreased temperature.
Particulates represent any dispersed matter, solid or liquid, in which the individual aggregates are larger than single small molecules (about 0.0002 micrometers, µm, in diameter) but smaller than about 500 µm. (one micrometer is cm)
Of recent attention is particulate matter which is equal to or less than 10 µm in size, with this size range of concern relative to potential human health effects. Additionally, particles in the atmosphere can have a lifetime ranging from only a few minutes to several months; larger particles settle more rapidly than smaller particles.
The focus is on “air toxics,” or hazardous air pollutants. Air toxics are a class of compounds which may be present in the atmosphere and exhibit potentially toxic effects not only to humans but also to the overall ecosystem. In the 1990 Clean Air Act, the air toxics category includes 189 specific chemicals which may be of relevance in an air quality impact study (Quarles and Lewis, 1990).
This group of compounds represents typical compounds of concern in the industrial air environment, with these compounds and associated relevant quality standards being adjusted for outdoor atmospheric conditions.
The above definition also mentions the quantity or concentration of the contaminant in the atmosphere, and its associated duration or period of occurrence. This is an important concept in those pollutants that are present at extremely low concentrations and for short time periods may be insignificant in terms of the planning and conduction of an impact study.
Additional air pollutants or atmospheric effects which have become of concern include photochemical smog, acid rain, and global warming. “Photochemical smog” refers to the formation of oxidizing constituents, such as ozone, in the atmosphere as a result of the photo-induced reaction of hydrocarbons (or volatile organic chemicals) and oxides of nitrogen.
This phenomenon was first recognized in Los Angeles, California, in the period following World War II, and it has become a major air- pollution concern throughout the United States. “Acid rain” refers to atmospheric reactions which can lead to precipitation which exhibits a pH value less than the normal pH of rainfall (which is approximately 5.7 when carbon dioxide equilibrium is considered).
Within recent years, in central Europe and in several Scandinavian countries, along with Canada and the north-eastern United States, attention has been directed to potential environmental consequences of acid precipitation.
Causative agents in acid-rain formation are typically associated with sulfur dioxide emissions and, possibly, nitrogen oxide emissions, along with gaseous hydrogen chloride. From a worldwide perspective, sulfur dioxide emissions are the dominant precursor of acid-rain formation.
Another issue of importance from a global perspective is the influence of air pollution on atmospheric heat balances and associated absorption or reflection of incoming solar radiation.
As a result of increasing levels of carbon dioxide and other carbon-containing compounds in the atmosphere, there is a growing concern that the earth’s surface has already started exhibiting increased temperature levels, and this, in turn, can have major implications in terms of shifting climatic conditions throughout the world.