Environmental Science 3(3+0)

Introduction

• Air is necessary for the survival of all higher forms of life on earth. On an average, a person needs at least 30 lb of air every day to live, but only about 3 lb of water and 1.5 lb of food. A person can live about 5 weeks without food and about 5 days without water, but only 5 minutes without air. Naturally, everyone likes to breathe fresh, clean air. But the atmosphere, that invisible yet essential ocean of different gases called air, is as susceptible to pollution from human activities as are water and land environments.


• Any undesirable change in the physical, chemical and biological properties of air that adversely affects the life is called air pollution. Air pollution may be simply defined as the presence of certain substances in the air in high enough concentrations and for long enough duration to cause undesirable effects. “Certain substances” may be any gas, liquid or solid, although certain specific substances are considered significant pollutants because of very large emission rates or harmful and unwanted effects. “Long enough durations” can be anywhere from a few hours to several days or weeks; on a global scale, durations of months and years are of concern.