Air Quality

Air Quality Index

The Air Quality Index (AQI) is an air quality indicator. It is used to measure how polluted the air is. Governments use the AQI to correspond air quality levels to the public, which is crucial as it prepares the public, especially those at risk of poor air quality levels.

The AQI scale ranges from 0 to 500. The lower the number, the cleaner the air and the higher the number, the more polluted the air is. There are 6 categories to the AQI, and each category is colour coded. This helps to easily identify the level of air quality at a fast rate. The table below shows the different categories of AQI.¹

Air Quality Testing

The measurement of air quality is crucial in order to gather data on pollution levels. Air quality is measured through a variety of methods depending on the pollution type. As well as general inspections that measure indoor air quality, there are two main air emission monitoring systems the Environment Protection Agency use in the US. These are:

• Ambient Air Quality Monitoring – samples of air pollution are collected and compared to historical data regarding air quality in order to state how clean the air is based upon clean air standards.
• Stationary Source Emission Monitoring – samples collected at locations where high air pollution is likely, such a factories and power plants, to measure the safety of the site.

Ultimately, each method aims to inform the level of air pollution for human safety.

Types of Air Pollution

There are a variety of air pollutants (not to be confused with water and land pollutants) that lessen the quality of air. The table below shows each of these air pollutants.

Causes of Air Pollution in Urban Areas

Air pollution can be caused by many factors. There are both natural and anthropogenic causes of air pollution.

The natural causes of air pollution include:

• Forest Fires
• Volcanic Eruptions

This is because forest fires and volcanic eruptions release gases that contribute to air pollution.

Additionally, there are a higher amount of anthropogenic factors that increase air pollution, these include:

• Transportation
• Industrial Facilities
• Fossil Fuels
• Agriculture

Most of these activities commonly occur in built environments. Therefore, urban areas are more prone to lower air quality than rural areas. But how and why does this occur?

Transportation

There are multiple methods of transportation that occurs in built urban environments such as cities, ranging from cars to trains to planes. Each of these modes of transport contributes to poor air quality by emitting pollutant gases, such as nitrogen oxides, particulate matter, hydrocarbons, carbon dioxide, and carbon monoxide. Since many cities have high amounts of transportation, along with a high density of people, there is often congestion and traffic. This can lead to further air pollution as the transportation emits harmful gases whilst in congested traffic. In fact, transportation contributes to the emission of about 27% of all greenhouse gases in the US.²

Industrial Activity

Industrial activity is another major contributor to pollution. As industrial advancement took place throughout the 20th century, an increase in industrial emissions and pollutants occurred.

Chemical waste, pesticides, radioactive materials, and fossil fuels (as well as many gases) are all pollutants that occur because of industrial activity.

Fossil Fuels

Fossil fuels are major contributors to poor air quality. Coal, oil, and gas are the main fossil fuels that produce pollution. Burning these fossil fuels, which is done to generate energy, releases pollution into the atmosphere. Fossil fuels are used largely in urban environments because buildings and infrastructure require the energy fossil fuels provide in the form of electricity and heating.

Fig 3. Fossil Fuel From Industrial Activity

Agricultural

Although not considered an urban activity, agriculture is an anthropogenic cause of air pollution due to the fact humans partake in agricultural activities that emit air pollutants. Agricultural air pollution mostly includes ammonia, as well as carbon dioxide, methane, nitrogen oxide, and ozone-depleting pollutants, including greenhouse gas emissions. These occur due to equipment used in agriculture that requires the use of fossil fuels, such as tractors and processing equipment.

Air Quality Effects

Low air quality can create several impacts on the environment and society.

Impacts on the Environment

Air pollution can contribute to climate change. This is because the types of air pollution such as greenhouse gases, especially carbon dioxide, methane, and nitrous oxide, can aid in global warming, which ultimately leads to increasing climate change.

Impacts on Society

The main impact of pollution and poor air quality can seriously impact the health and well-being of humans. Vulnerable people, such as young people, elderly people, and people with breathing difficulties such as asthma, are the most likely to be affected by air pollution. However, if the air quality is extremely poor anyone can be impacted. Members of the public can develop respiratory infections and diseases, including asthma, as well as cardiovascular disease and lung cancer or diseases due to bad levels of air quality and pollution.