NOx is a toxic, acidic gas, produced in the heat of the combustion engine, which can be transported over many hundreds of miles and deposited as acid rain. It is described as a local pollutant, a precursor of photochemical ozone formation, playing a major role in the atmospheric reactions that produce smog. NOx reacts with ammonia, moisture, and other compounds to form nitric acid, toxic organic nitrates and other particulate material. This particulate matter can penetrate into sensitive parts of the lungs and cause or worsen respiratory diseases such as emphysema and bronchitis. It can also aggravate existing heart conditions and lead to premature death.

Global NOx emissions from shipping are expected to continue to increase if no measures are implemented. By 2020 the NOx emissions from international shipping around Europe alone are expected to reach 5,000 tonnes annually, costing the society around 50 billion euro a year, or roughly 10,000 euro per tonne of emitted NOx. This only demonstrates the severity of the problem and the urgency for action.


What is Nitrogen Oxide?

NOx is a generic term for the mono-nitrogen oxides NO and NO2 (nitric oxide and nitrogen dioxide). NOx should not be confused with nitrous oxide (N2O), which is a greenhouse gas and has many uses as an oxidizer, an anaesthetic and a food additive.


How are Nitrogen Oxides formed?

NOx is formed from the endothermic reaction of nitrogen and oxygen gases in the air during combustion, especially at high temperatures, during the combustion of oil, coal or gas.


What are the main sources of Nitrogen Oxide?

All combustion in air produces oxides of nitrogen. Key sources include non-road mobile sources (e.g. marine, railroads, diesel equipment) and on-road mobile sources (e.g. trucks, cars and motorcycles); power plants; cement and concrete installations; other industrial processes.


What are the environmental impacts of Nitrogen Oxide?

When NOx and volatile organic compounds (VOCs) react in the presence of sunlight, they form photochemical smog, a significant form of air pollution, especially in the summer. They are also involved in tropospheric production of ozone.
Nitrogen oxides form nitric acid when dissolved in atmospheric moisture, forming a component of acid rain. This contributes to the acidification of aquatic and terrestrial ecosystems. In addition, excess nitrogen inputs from the atmosphere promote increased growth of phytoplankton and other marine plants which, in turn, may cause more frequent harmful algal blooms and eutrophication (the creation of oxygen-depleted “dead zones”) in some parts of the ocean.


What are the health impacts of Nitrogen Oxide?

Short-term NOx exposures, ranging from 30 minutes to 24 hours are linked with adverse respiratory effects, including airway inflammation in healthy people and increased respiratory symptoms in people with asthma.
NOx reacts with ammonia, moisture, and other compounds to form small particles. These can cause or worsen respiratory disease, such as emphysema and bronchitis, and can aggravate existing heart disease, leading to increased hospital admissions and premature death.
Children, the elderly, people with lung diseases such as asthma, and people who work or exercise outside are at risk for adverse effects from ozone, formed from NOx. These include reduction in lung function, increased respiratory symptoms and possibly premature deaths.