Nitrogen Dioxide(NO2)

Several combinations of Nitrogen oxide gases add up to become the highly reactive Nitrogen Dioxide. Nitrogen Dioxide is one of the compounds of the nitrogen oxide along with nitrous acid and nitric acid. In a general case, the major source of NO2 is combustion processes. An appreciable quantity of NO2 is present in rural and urban environments making it very accessible for problems related to lungs.


Causes of Nitrogen Dioxide?

Nitrogen Dioxide is generally caused by the fumes of cars, trucks and other such vehicles and other off-road equipment. It is also caused by burning fossil fuels, coal, oil, and gas. It is also the major cause of photochemical smog. It is also caused by petrol and metal refining.

Health Effects caused by Nitrogen Dioxide.

The main cause of inhaling Nitrogen Dioxide are the problems in the respiratory system. NO2 exposure can cause a decrement in lung function (i.e. increased airway resistance). This gas also reduces the immunity of lungs infections causing problems such as asthma and leading to respiratory symptoms such as coughing, wheezing or difficulty breathing. Chronic exposure of NO2 may lead to chronic lung disease and variety of structural/morphological changes in lung epithelium conducting airways and air -gas exchange region. People with asthma, as well as children and the elderly, are generally at greater risk for the health effects of NO2, especially the people who have heart-related conditions. Asthmatics are more susceptible to the acute effects of nitrogen dioxide as they have higher baseline airway responsiveness

Standards set for NO2.

The standards are highly marginal where a 50% margin of safety is proposed because of the reported statistically significant increase in response to a bronchoconstrictor (increased airway responsiveness) with exposure to 190 μg/m3 and a meta-analysis suggesting changes in airway responsiveness below 365 μg/m3 showed by a study of WHO in 2000.  

The table provides the details of breakpoints for IND-AQI and breakpoints of USEPA, China and EU for NO 2 are given.