What are nitrogen oxides?
Nitrogen oxides (NOx) are a group of highly reactive gases, containing one atom of nitrogen and one or more oxygen atoms. Nitric oxide (NO) is a colorless, sharply sweet-smelling gas. In the atmosphere, it can gain another oxygen atom and become nitrogen dioxide (NO2). For this reason, NO2 can be used as an indicator for the other nitrous oxides. Our monitors are Breathe Easy Berkshires are scanning for NO2. Nitrogen dioxide has a strong, harsh odor and a reddish brown color. NO2 is also a very acidic, corrosive gas that can have significant effects on the environment, human health, and properties.
Where does nitrogen dioxide come from?
NOx is directly emitted into the air from the burning of fossil fuels. Emissions from cars, trucks, buses, power plants, and off-road equipment are major sources. Concentrations of NOx are typically higher in urban areas with high levels of traffic or industrial activity. Nitrogen oxides are also used in rocket fuels and the manufacture of explosives. In poorly ventilated situations, indoor domestic appliances like gas stoves or gas and wood heaters can be significant sources of nitrogen oxides.
Although differences exist between sources, nitric oxide (NO) generally accounts for 90-95% of the nitrous oxides released from combustion fuels. NO2 typically accounts for only 5-10%. But, in ambient conditions, NO finds available oxidants (such as ozone, volatile organic compounds, or oxygen itself) and transforms into NO2 in a matter of minutes. That’s why measuring NO2 relies on NO having a chemical reaction.
How is nitrogen dioxide measured?
Chemical concentrations in the air are measured by units of the substance (milligrams, micrograms, nanograms, picograms, or other tiny units of measurement) per volume of air as cubic meters or feet. NO2 is typically expressed as parts per billion (ppb) or micrograms per cubic meter (µg/m3).
Nitrogen dioxide sensors function via chemiluminescence analyzer. Chemiluminescence is the process by which a chemical reaction produces light. The sensor pulls in air, and the nitric oxide (NO) and ozone (O3) in the air react with each other to form nitrogen dioxide (NO2), oxygen (O2), and light. This method doesn’t actually measure the NO2 in the traditional sense. Instead, it calculates the airborne levels of nitric oxide and the total oxides of nitrogen, subtracts one reading from the other, and produces a result expressed as either ppb or µg/m3.
What are the standards for nitrogen dioxide in the United States?
National Ambient Air Quality Standards (NAAQS) for pollution specify a maximum amount of a pollutant to be present in outdoor air.
Currently, the EPA has primary (health-based), secondary (welfare-based), and short-term (24 hour) standards in place for NO2. These standards are based on average numbers over the course of three years. Having a longer-term measurement period like that is a better indicator of overall air quality than data collected from just one year.
| Pollutant | Standard Type | Mass per Volume | Terms | Date Established |
| NO2 | 1 hour | 100 ppb | 1 hour maximum per 24 hours not to be exceeded more than 2% of the time, as averaged over 3 years | 16 April 2018 |
| NO2 | Primary | 53 ppb | Annual average over a 3 year period | 16 April 2018 |
| NO2 | Secondary | 53 ppb | Annual average over a 3 year period | 3 April 2012 |
How does nitrogen dioxide affect people?
Breathing air with a high concentration of NOx irritates airways in the human respiratory system and causes health issues. It can cause symptoms like coughing, wheezing, and difficulty breathing. Controlled human exposure studies show that it can intensify responses to allergens in allergic asthmatics. A number of epidemiological studies have shown a connection between NO2 exposure and premature death, cardiopulmonary effects, decreased lung function growth in children, emergency room visits and hospital admissions for asthma, and intensified allergic responses.It may also affect the senses, for example, by reducing a person’s ability to smell odors.
Who is most at risk for adverse health effects from NOx exposure?
Infants and children are particularly at risk because they have disproportionately higher exposure to NO2 than adults.They have a higher breathing rate for their body weight and typically greater outdoor exposure duration. Several studies have shown that long-term NO2 exposure during childhood, the period of rapid lung growth, can lead to smaller lungs at maturity in children with higher compared to lower levels of exposure. In addition, children with asthma have a greater degree of airway responsiveness compared with adult asthmatics. In adults, the greatest risk is to people who have chronic respiratory diseases, such as asthma and chronic obstructive pulmonary disease.
How does nitrogen dioxide affect the environment?
There are a few different ways that having NOx in the atmosphere can harm both the environment and manmade objects. Nitrogen dioxide is incredibly acidic. It can injure crops, trees, forests, and other vegetation in the natural world. This has been reported when the cumulative duration of exposure was at least 0.2ppm for 100 hours or longer during the growing season. NO2 can fade and discolor furnishings and fabrics, and react with surfaces like paint on cars and buildings.
NO2 and other NOx interact with water, oxygen and other chemicals in the atmosphere to form acid rain. Acid rain is harmful to sensitive ecosystems like lakes and forests, and it also contributes to erosion on public utilities like bridges and roads.
Additionally, NOx can contribute to the reduction of visibility. It selectively absorbs the short blue wavelengths of visible light, leaving behind a yellow – red – brown smog; it can also contribute to the formation of a nitrate aerosol haze that decreases visibility, notably in California in the US.