Pure Air

Air is a mixture of various gases (Table 1.1). However, rapid industrialization, population explosion, high-scale combustion of fossil fuel, and several other factors has led to the intensification of air pollution, putting atmospheric balance into an erratic state.

Table 1.1: Composition of air in percent by volume

US: Ambient Air Quality Standards

On December 31, 1970, the US government, introduced the Clean Air Act, to “foster the growth of a strong American economy and industry while improving human health and the environment”. The act was last amended in 1990, that required the US Environmental Protection Agency (EPA) to set up the National Ambient Air Quality Standards (NAAQS) for six principal pollutants (Table 1.3), which are called “criteria” air pollutants.

Periodically, these standards get reviewed and revised. In Table 3 are also listed the reference values for the pollutants. These benchmarks help industries, agencies and governments to formulate policies, standards for pollutant emission, and take necessary initiatives to maintain air quality standards. It helps us in giving the estimations of how far we have ascended in the pollution graph and what will be the picture of future pollution levels.

However, more than 80% of people living in urban areas are breathing unfit air over and above the levels set by the World Health Organization (WHO). Low-income generating cities have been found to be at a higher risk. For instance, almost 14 out of 15 of the most air-polluted cities in the world are in India alone (Table 1.2), as per WHO’s Global Ambient Air Quality Database (Update 2018). This survey is mostly based on findings of a high amount of Particulate Matter in ambient air.