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HOW MUCH NO2 IS SAFE?

Nitrogen dioxide comes from vehicles, power plants, industrial emissions and off-road sources such as construction, lawn and gardening equipment. 

All of these sources burn fossil fuels.  

The US Environmental Protection Agency has issued guidance for safe levels of inhalation of Nitrogen Dioxide, measured in parts per billion breathed over the course of an hour.

Safe to moderate levels range from zero to 100 parts per billion per hour.  

EPA GUIDANCE ON AIR QUALITY
Air Quality Index (ppb) Likely impact
Good (0-50) No health impacts are expected when air quality is in this range
Moderate (51-100) Individuals who are unusually sensitive to nitrogen dioxide should consider limiting prolonged outdoor exertion
Unhealthy for Sensitive Groups (101-150) People with lung diseases, such as asthma, as well as children and older adults, should limit prolonged outdoor exertion
Unhealthy (151-200) Sensitive groups should avoid outdoor exertion and everyone else should limit prolonged exertion
Very Unhealthy (201-300) Sensitive groups should avoid outdoor exertion and everyone else should limit theirs

Scientific evidence links short-term NO2 exposures, ranging from 30 minutes to 24 hours, with adverse respiratory effects including airway inflammation in healthy people and increased respiratory symptoms in people with asthma. 

Studies also show a connection between short-term exposure and increased emergency room visits and hospital admissions for respiratory illnesses.

Individuals who spend time on or near major roads can experience NO2 exposures considerably higher than occur away from roads. 

These exposures are of particular concern for sensitive groups, such as people with lung disease including asthma, children and older adults.

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