WHILE NITROGEN compounds potentially pollute every element of our ecosystem, air is the most critical medium in terms of damage through nitrogen pollution. Agriculture, transport, energy production and combustion in industry contribute to emissions of nitrogen pollutants into the air.
The release of ammonia and nitrogen oxides into the lower atmosphere has significant health impacts. Nitrogen oxides are formed through a combination of nitric oxide and nitrogen dioxide. These two nitrogen compounds form fine particulate matter (PM) that has been noted to be a significant contributor towards lung damage, respiratory ailments and reduction of life expectancy. Nitrogen oxides also cause photochemical smog in which high level of tropospheric ozone is produced. This ozone, which is closer to the Earth's surface, is harmful for both humans and the environment. It has been found to cause adverse short-term and chronic impacts on respiratory functions. It is detrimental to agriculture and causes damage to crop production of up to five per cent every year globally.
Nitrous oxide (N O), another oxide of nitrogen, is a greenhouse gas that is 300 times more reactive than carbon dioxide and has a lifespan of 120 years in the atmosphere. An American study in 2012 found that over a period of 100 years, the heating effects of N O far outweighed any short-term cooling impact that reactive nitrogen might have. Further, N O has a potential of ozone depletion in the stratosphere— this ozone protects us from the harmful ultraviolet rays of the sun—that is comparable to the potential of hydrochloroflourocarbons which were phased out in the 1990s as a highly ozonedepleting substance.
Nitrogen can be blamed to a large extent for India's poor air quality. According to media reports, 13 of the 17 most polluted cities in the world are in India. Delhi and Kolkata far exceed the World Health Organization's (WHO's) standard of 40 micrograms per cubic metre for N O. Chennai and Bengaluru are the only metro cities that are safely within prescribed limits. Twenty-seven Indian states, for which data is available, exceed the WHO limit of 20 micrograms per cubic metre for annual mean PM.