Air Quality: What Doesn't Pollute The Air?

Air pollution is the release of various gases, finely divided solids, or finely dispersed liquid aerosols into the atmosphere at rates that exceed the environment's capacity to dilute or absorb them. These substances can cause harmful health effects, economic damage, or undesirable aesthetic changes. Six major air pollutants have been designated by the US, including sulfur dioxide, nitrogen dioxide, and carbon monoxide, which are emitted directly from burning fossil fuels. However, what about the substances that are not considered air pollutants? Understanding what does not contribute to air pollution is crucial for comprehending the complex dynamics of atmospheric chemistry and the delicate balance of our ecosystem.

Nitrogen

In indoor environments, tobacco smoke and the burning of fossil fuels in appliances like stoves, ovens, heaters, and fireplaces are significant sources of NO2. Outdoor sources of NO2 are predominantly related to road traffic, with vehicles emitting nitrogen oxides that contribute to air pollution.

While nitric oxide (NO) is also considered a pollutant, it is less stable and rapidly oxidizes in ambient conditions to form nitrogen dioxide (NO2). Therefore, NO2 is typically considered the primary pollutant when discussing nitrogen oxides.

It is important to distinguish between nitrogen, an essential and abundant component of the Earth's atmosphere, and specific nitrogen compounds like nitrogen dioxide and nitric oxide, which are harmful air pollutants with significant impacts on human health and the environment. Regulatory bodies like the Environmental Protection Agency (EPA) and the World Health Organization (WHO) have established guidelines and standards, such as the National Ambient Air Quality Standards (NAAQS), to monitor and limit the presence of these nitrogen oxide pollutants in the air we breathe.

Oxygen

Air is a mixture of gases, some of which are naturally occurring, and some of which are human-made pollutants. The six most common air pollutants, known as "criteria air pollutants", are regulated by the US Environmental Protection Agency (EPA) as they can harm human health, the environment, and cause property damage. These pollutants include particle pollution and ground-level ozone, as well as toxic air pollutants, or hazardous air pollutants (HAPs), which are known or suspected to cause cancer and other serious health and environmental issues. Examples of HAPs include benzene, perchloroethylene, and methylene chloride.

In contrast, human-made chemicals can negatively impact human health and the environment. For example, vehicle exhaust contains nitrogen dioxide and other polluting chemicals such as carbon monoxide and sulfur dioxide. The manufacturing processes and the widespread use of combustion engines have also increased the number of aerosols in the atmosphere, which affect the climate by influencing cloud formation and scattering or absorbing sunlight.

Therefore, while oxygen is a critical component of the air we breathe and is not considered a pollutant, human activities can introduce harmful pollutants into the atmosphere, negatively impacting human health and the environment.

Argon

While Argon is not considered an air pollutant, it is important to note that its presence in the atmosphere has been slowly increasing since the Earth's formation. This gradual increase in atmospheric Argon is a natural process and is not typically considered a significant environmental concern.

Carbon dioxide

The increase in CO2 emissions contributes to global warming and climate change. It is one of the primary drivers of rising global temperatures, leading to extreme weather shifts, rising sea levels, and changes in wildlife populations and habitats. However, some argue that the increase in atmospheric CO2 may not be a cause for alarm and could even have positive effects. They attribute climate change to natural causes rather than industrial activity.

CO2 emissions result from various human activities, such as cement production, which releases CO2 when fossil fuels are used to fire the base materials in a kiln. Deforestation also plays a role, releasing stored carbon into the atmosphere. On the other hand, growing forests through sequestration can help store surplus carbon, mitigating the increase in CO2 levels.

While CO2 itself is not classified as an air pollutant, it contributes to the greenhouse effect, which has detrimental consequences for the planet. The complex chain of events triggered by the greenhouse effect leads to global climate change, encompassing not just rising temperatures but also shifts in weather patterns and the Earth's climate.

Monitoring and managing local air pollution levels are crucial steps in addressing global warming. While CO2 may not be categorized as an air pollutant, its role in climate change underscores the importance of reducing emissions and transitioning to low-carbon energy alternatives.

Water vapour

The increase in water vapour in the atmosphere is largely attributed to a feedback process rather than human-generated activities. As the climate warms, air temperatures rise, leading to more evaporation from water sources and land. This, in turn, increases the moisture content in the atmosphere. The feedback process involving water vapour is believed to be responsible for intensifying the greenhouse effect, contributing to global warming.

Although water vapour is not classified as a pollutant, it plays a crucial role in the global warming process. As the climate warms, more water vapour is evaporated into the atmosphere, enhancing the greenhouse effect and leading to further warming. This positive feedback loop has a significant impact on the Earth's climate system.

It is worth noting that while water vapour itself is not considered a pollutant, it can, under certain conditions, contribute to the formation of air pollutants. For example, water vapour can react with other substances in the atmosphere to form secondary pollutants, such as fine particulate matter. However, this does not negate the fact that water vapour, in its pure form, is not classified as an air pollutant.

Frequently asked questions