Nitrogen dioxide, mainly emitted by power generation, industrial and traffic sources, is an important constituent of particulate matter and ozone. There is growing evidence that independently, it can increase symptoms of bronchitis and asthma, as well as lead to respiratory infections and reduced lung function and growth. Evidence also suggests that NO2 may be responsible for a large disease burden, with exposure linked to premature mortality and morbidity from cardiovascular and respiratory diseases.


Nitrogen Dioxide

Time-weighted average

660 (0.35) -100 (0.05) µg/Nm3 (ppm)

Averaging time

1 hour-Annual

Time –weighted average Averaging Time Number of allowable exceedances
350 ppb 1-hour 2 times within 30 days
50 ppb annually None
Number of allowable exceedances

2 times per 30 days N/A