Nitrogen Dioxide is considered as one of the most polluting compounds in the air. NO2 is produced by automobiles and other kinds of combustion.
Long-term exposure to NO2 may cause a wide spectrum of severe health problems such as hypertension, diabetes, heart and
cardiovascular diseases, and even death.
NO2 can also form indoors when fossil fuels like wood or natural gas are burned. Current guidelines by the WHO says that one hour exposure to 106 ppb of Nitrogen Dioxide26 is acceptable.
At about twice this level, asthmatics may find it harder to breathe due to reduced pulmonary function. For normal people, breathing in NO2 at this level can cause slight difficulties in breathing.