A few thoughts on life in the city

NOx – The dangerous silent killer

07 Jul 2013, Posted by Frangipani Country Estates in City vs Country

The American Environmental Protection Agency (EPA) has established National Ambient Air Quality Standards (NAAQS) for NOx and tropospheric ozone. The NAAQS define levels of air quality that are necessary, with a reasonable margin of safety, to protect public health (primary standard) and public welfare (secondary standard) from any known or anticipated adverse effects of pollution. The primary and secondary standard for NOx is 100 μg per cubic metre, annual arithmetic mean concentration. The acceptable standard as per Indian pollution control standards is 60 ug per cubic metre. NOx reacts with ammonia, moisture, and other compounds to form nitric acid vapor and related particles. Small particles can penetrate deeply into sensitive lung tissue and damage it, causing premature death in extreme cases. Inhalation of such particles may cause or worsen respiratory diseases, such as emphysema or bronchitis, or may also aggravate existing heart disease.

NOx reacts with volatile organic compounds in the presence of sunlight to form Ozone, which can cause adverse effects such as damage to lung tissue and reduction in lung function mostly in susceptible populations (children, elderly, asthmatics). NOx destroys ozone in the stratosphere. Ozone in the stratosphere absorbs ultraviolet light, which is potentially damaging to life on earth.