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Nitrogen Dioxide: Respiratory & Health Problems

Author: Thomas C. Weiss : Contact: Disabled World

Published: 2016-01-20 : (Rev. 2016-06-22)

Synopsis and Key Points:

Information regarding Nitrogen dioxide (NO2), an air pollutant that can aggravate respiratory diseases such as asthma, emphysema and bronchitis.

Main Digest

Nitrogen dioxide is a bad-smelling gas. Some nitrogen dioxide is formed naturally in the atmosphere by lightning and some is produced by soil, water and plants. Only around 1% of the total amount of nitrogen dioxide found in the air of cities; however, is formed in this manner. Nitrogen dioxide is an important air pollutant because it contributes to the formation of photochemical smog, something which may have a notable impact on human health.

Nitrogen dioxide (NO2) is a reddish-brown gas with a pungent and irritating odour. It transforms in the air to form gaseous nitric acid and toxic organic nitrates. NO2 also plays a major role in atmospheric reactions that produce ground-level ozone, a major component of smog. It is also a precursor to nitrates, which contribute to increased respirable particle levels in the atmosphere. Nitrogen dioxide is toxic to humans when inhaled. The compound is acrid and easily detectable by smell at low concentrations. However, low concentrations (4 ppm) will anesthetize the nose, thus creating a potential for overexposure.

The major source of nitrogen dioxide in the nation of Australia; for example, is the burning of fossil fuels such as oil, gas and coal. Most of the nitrogen dioxide in cities comes from motor vehicle exhaust, approximately 80%. Additional sources of nitrogen dioxide are gasoline and metal refining, electricity generation from coal-fired power stations, other manufacturing industries and food processing. Un-flued gas cookers and heaters are the major sources of nitrogen dioxide in homes in Australia.

Nitrogen Dioxide and Human Health

Current scientific evidence links short-term nitrogen dioxide (NO2) exposures, ranging from thirty minutes to twenty-four hours, with undesired respiratory effects including airway inflammation in otherwise healthy people and increased respiratory symptoms in people who experience asthma. Studies also show a connection between breathing elevated short-term NO2 concentrations and increased visits to emergency room departments, as well as hospital admissions for respiratory issues - particularly asthma.

Nitrogen dioxide (NO2) concentrations in vehicles and near roadways are notably higher than those measured at monitors in the current network. In fact, in-vehicle concentrations may be two to three times higher than measured at nearby area-wide monitors. Near-roadway, or within approximately fifty meters, concentrations of NO2 have been measured to be around thirty to one-hundred times higher than concentrations away from the roads.

People who spend time on or near major roads may experience short-term NO2 exposures considerably higher than measured by the current network. Around 16% of the housing units in America are located within three-hundred feet of a major roadway, airport, or railroad - around forty-eight million people. The people in this population likely includes a higher proportion of non-white and economically-disadvantaged people. Nitrogen dioxide exposure concentrations close to roads are of particular concern for people who are susceptible, to include people with asthma, seniors and children.

The sum of nitric oxide (NO) and NO2 is commonly called, 'nitrogen oxides.' Other oxides of nitrogen including nitrous acid and nitric acid are part of the nitrogen oxide family. While the Environmental Protection Agency's (EPA) National Ambient Air Quality Standard (NAAQS) covers the entire family, NO2 is the component of greatest interest and the indicator for the larger group of nitrogen oxides.

NOX reacts with moisture, ammonia and other compounds to form small particles. The small particles penetrate deeply into sensitive portions of a person's lungs and might cause or worsen respiratory disease such as emphysema and bronchitis and may aggravate existing heart disease leading to increased hospitalizations and premature death.

Ozone is formed when NOX and volatile organic compounds react in the presence of sunlight and heat. Children, seniors, people with lung diseases such as asthma and people who exercise or work outside are at risk for negative effects from ozone. The risks include a reduction in lung function and an increased risk of respiratory symptoms, as well as respiratory-related emergency room visits, hospital admissions and the potential for premature death.

Emissions that lead to the formation of NO2 usually also lead to the formation of other NOX. Emissions control measures leading to reductions in NO2 can generally be expected to reduce population exposures to all gaseous NOX. Emissions control measures may have the important co-benefit of reducing the formation of ozone and fine particles, both of which present significant public health threats.

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