WCAS/monitoring/NOx
Oxides of nitrogen (NOx), mostly in the form of nitrogen oxide (NO) and nitrogen dioxide (NO2), are produced by the high temperature combustion of fossil fuels. Nitrogen oxide is the predominant species emitted by combustion sources but it is rapidly changed to nitrogen dioxide in the atmosphere.
Nitrogen dioxide is a reddish-brown gas with a pungent irritating odour. It has been linked to respiratory disease and contributes to acid rain. It plays a major role in atmospheric photochemical reactions and ground level ozone formation and destruction.
Exposure of vegetation to high concentrations of nitrogen oxides results in silvering of the lower leaf surface. A waxy appearance appears shortly after exposure followed by bronzing after two or three days.
The primary emitting sources are transportation sources (e.g. on-road and off-road motor vehicles and engines, rail), fossil-fuelled electric power plants as well as upstream oil and gas industry (e.g. natural gas plants, oil sands).
Alberta Environment and Parks guideline are based on the prevention of human health effects. They are equal to the most rigorous of Environment Canada's ambient air quality objectives.
The Alberta Guidelines for nitrogen dioxide, the major component of nitrogen oxides in the ambient atmosphere are:
| Concentration (ppb) | Exposure Time | Human Symptoms and Other Effects |
| 300,000 | — | Rapid death |
| 150,000 | — | Death after 2 or 3 weeks by bronchiolitis fibrosa obliterans |
| 50,000 | — | Reversible, nonfatal bronchiolitis |
| 10,000 | — | Impairment of ability to detect odour of NO2 |
| 5,000 | 15 min | Impairment of normal transport of gases between the blood and lungs in health adults |
| 2,500 | 2 hours | Increased airway resistance in healthy adults |
| 2,000 | 4 hours | foliar injury to vegetation |
| 1,000 | 15 min | Increased airway resistance in adults with bronchitis |
| 1,000 | 48 hours | Slight leaf spotting of pinto bean, endive, and cotton |
| 300 | — | Brownish color of target — 1 km distant |
| 250 | — | Decrease of growth and yeild of tomatoes and oranges |
| 210 | 1 hour | Alberta ambient air quality guideline |
| 200 | 8 hours | Yellowing of white fabrics |
| 120 | — | Odour perception threshold |
| 110 | 24 hours | Alberta ambient air quality guideline |
| 100 | 12 weeks | Fading of dyes on cotton and rayon |
| 100 | 20 weeks | Reduction of growth of Kentucky bluegrass |
| 30 | annual | Alberta ambient air quality guideline |
| 30 | — | Brownish color of target — 10 km distant |
| 3 | — | Brownish color of target — 100 km distant |