Nitrogen dioxide and its relevance to health and air quality

Nitrogen dioxide (NO2) is a harmful gas whose presence in the atmosphere is mainly due to the use of fossil fuels in combustion vehicles and industrial activities. This chemical compound, formed by the combination of nitrogen and oxygen, can have serious consequences for human health, causing lung diseases such as asthma, bronchitis and pulmonary oedema. It also contributes to an increase in respiratory infections, particularly in children.

In nature, nitrogen dioxide can cause serious environmental damage by reacting with compounds in the air to form nitric acid. Catalysed by sunlight, nitric acid is the main cause of acid rain and tropospheric ozone. Both have a direct impact on climate change. It also contributes to the formation of smog in urban areas.

Nitrogen is a key element in the Earth’s atmosphere and is particularly abundant in ambient air. It is also an essential chemical element in the formation of the stratospheric ozone layer, which protects the biosphere.

It is an essential element for life as it is part of proteins and nucleic acids, the main components of living cells.  

Nitrogen dioxide, made up of one atom of nitrogen and two atoms of oxygen, is a gas that occurs both naturally and as a result of human activity. It can occur in a gaseous state or be converted into liquid nitrogen

In its gaseous state, however, nitrogen is inert, meaning that it does not react easily with other elements. In order for plants and other organisms to use it, it must be converted into a more reactive form, such as nitrogen dioxide. This process, known as nitrogen fixation, occurs naturally in the soil and is essential to the nitrogen cycle in nature.

Sources and health effects of nitrogen dioxide - Kunak

Sources and health effects of nitrogen dioxide (Source: EPA Victoria)

While nitrogen is an essential element for life, its transformation in the air into oxides such as nitrogen dioxide can be harmful. It is therefore essential to monitor and control the levels of this gas in the air, both indoors and outdoors. 

A number of strategies need to be developed to achieve this:

  • Improving pollution control technologies in urban areas and industrial plants.
  • Implementing regulatory measures for mobility and industry.
  • Reducing the use of private cars and promoting sustainable mobility.
  • Promoting the use of cleaner and more efficient energy sources.
  • Demanding public policies and, if necessary, resorting to environmental justice, that promote the reduction of these oxides and improve air quality.

Ensuring that our air is clean and safe to breathe should be a priority for everyone, both indoors and outdoors, and we should take steps to minimise our exposure to pollutants such as nitrogen dioxide. To achieve this, it is a shared responsibility to keep informed about the levels of nitrogen dioxide in the air and to take steps to protect ourselves when levels are high.

Emission sources and formation of nitrogen dioxide

The main sources of nitrogen dioxide emissions are high-temperature combustion processes, such as by-products from internal combustion engines in vehicles, the combustion of oil, coal and natural gas, and industrial activities. In these processes, nitrogen naturally present in the air combines with oxygen to form nitrogen oxides (NOx), including harmful nitrogen dioxide (NO2).

In addition to anthropogenic sources, nitrogen dioxide can also have a natural origin. Lightning during thunderstorms can combine nitrogen and oxygen in the fresh air to form nitrogen dioxide. It is also produced in high concentrations during forest fires and volcanic eruptions.

Nitrogen dioxide can also be formed from liquid nitrogen, which is widely used in a variety of industrial applications. Although less common outdoors, liquid nitrogen has industrial uses that can increase nitrogen dioxide levels. For example, in industrial manufacturing, liquid nitrogen is used to maintain the low temperature conditions required for certain chemical processes.

Nitrogen dioxide pollution-WHO-Kunak

Effects of nitrogen oxide on human health

Prolonged exposure to nitrogen dioxide can cause serious respiratory problems. When inhaled, nitrogen dioxide irritates the eyes, nose and throat and can cause shortness of breath and long-term respiratory problems due to reduced lung capacity. For people with pre-existing respiratory conditions such as asthma, exposure to nitrogen dioxide can aggravate symptoms and trigger asthma attacks.

In addition, exposure to high levels of nitrogen dioxide has been shown to increase the risk of developing chronic respiratory diseases such as bronchitis and chronic obstructive pulmonary disease (COPD).

It should be noted that nitrogen dioxide can be more concentrated in indoor air due to human activities such as heating and cooking, which are sources of nitrogen dioxide emissions. In addition, if the indoor air is poorly ventilated, the gas can build up indoors, causing very harmful effects to people who spend time indoors on a daily basis.

Effects of nitrogen dioxide in the environment

The presence of nitrogen dioxide causes a number of problems in ecosystems. For example, it can contribute to the acidification of soil and water, which alters aquatic flora and life. In addition, high levels of nitrogen dioxide in the air can cause oxidative stress in plants, directly affecting their growth and proper vegetative development.

The presence of high levels of nitrogen dioxide in the atmosphere can alter the chemical balance of the air and thus affect the global climate.

Nitrogen dioxide can also react with other air pollutants to form harmful particulate matter. It also reacts with ozone to form photochemical smog. This smog is not only harmful to human health, but can also have a negative impact on ecosystems by reducing visibility and damaging vegetation.

In short, nitrogen dioxide can have a significant impact on ecosystems and it is important to take action to reduce its presence in our air to protect our health and the health of our planet.

Global data nitrogen dioxide and PM2.5 - Kunak

Global data nitrogen dioxide and PM2.5

The impact of nitrogen dioxide on air quality

When we breathe fresh air, we expect it to be free of harmful pollutants. Although nitrogen is an abundant and essential element for life on Earth (it is present in 78% of the air we breathe), its form, nitrogen dioxide, can have detrimental effects on human health and the environment as it is one of the most harmful nitrogen oxides in existence.

The relationship between nitrogen in its liquid and gaseous states is essential to understanding how nitrogen dioxide can affect air quality.

In its gaseous form, nitrogen dioxide is a brownish-red gas with a strong, unpleasant odour. In its liquid form, it is a yellowish liquid that freezes to form white crystals. However, it is in its gaseous form that it poses the greatest risk to human health and the environment. In this state, it can contribute to the formation of smog, which is dangerous for air quality. In addition, the presence of high levels of nitrogen dioxide in the air can cause health problems, so it is vital to work to reduce its presence in the air we breathe.

High levels of nitrogen dioxide are mainly found in urban areas with heavy traffic and high industrial activity.

It is important to understand that it is crucial to monitor and take measures to reduce nitrogen dioxide emissions, both in indoor and outdoor air. Although we cannot control natural sources, we can regulate anthropogenic sources of emissions through sustainable transport policies and the use of clean and renewable energy. 

Regulations and guidelines to reduce nitrogen dioxide

While nitrogen is an essential chemical element for life on Earth, in its liquid state it is widely used in various industries. However, when it is converted into nitrogen dioxide, it has harmful effects on life in general. Especially when it reaches high levels in the air we breathe. For this reason, there are strict regulations and guidelines to control and manage nitrogen dioxide to ensure a safe and healthy environment.

These regulations apply not only to industries that emit the nitrogen group of gases, of which nitrogen dioxide is a member, but also to individuals, as our daily actions can contribute to the accumulation of these gases in the air. These nitrogen gases are made up of various nitrogen oxides present in the atmosphere, known as NOx, as they are all a mixture of nitrogen and oxygen.

According to the US Environmental Protection Agency (EPA), there are standard reference levels based on primary standards or those that protect public health, including the health of ‘sensitive’ populations such as asthmatics, children and the elderly. Secondary standards protect public welfare, including protection against impairment of visibility and damage to animals and crops,vegetation and buildings.

To ensure healthy air for people and the environment, the EPA sets an hourly exposure to nitrogen dioxide of 100 ppb (parts per billion) for the primary standard and 53 ppb per year, which applies to both the primary and secondary standards.

By 2021, more than 90% of the EU’s urban population was exposed to harmful levels of nitrogen dioxide. European Environment Agency (EEA).

The European regulation of nitrogen dioxide levels sets limits of 200 µg/m3 (micrograms per cubic metre) per hour and a maximum of 40 µg/m3 per year.