Air pollution defines the presence of harmful substances within the Earth’s atmosphere. The substances are often pollutants emitted by day-to-day human activities or natural processes. Air pollution impacts all living organisms and the environment, from health effects to climate change.
Origins of Pollutants
There are many forms of pollutants which contribute towards air pollution: gases (such as sulphur dioxide, carbon dioxide etc), organic and inorganic particles; and biological molecules. The pollutants are classified into two categories; primary and secondary.
Primary pollutants can have a natural (from earth's physical processes) or anthropogenic (man-made) origin, such as ash clouds from volcanic eruptions or exhaust emission from cars. Secondary pollutants are not directly emitted into the atmosphere, rather they are a blend of primary pollutants that react with air, such as ground level ozone.
Pollutants are emitted in various ways, man-made and natural. Human sources of air pollutants include motor vehicle operations, diesel locomotives, aircraft, control burn practices within agriculture, and the use of fossil fuels in factories and waste incinerators. Natural sources of pollutants range from dust storms in areas where there is little to no vegetation, to output of methane from cattle, radioactive decay and volcanic activity.
There are many incentives and policies in place globally aimed at reducing the emissions of pollutants within the earth's atmosphere, as well as reducing the risk imposed on human health and the effects on the environment. The list of pollutants is not exhaustive; below we describe three most prominent naturally and anthropogenically occurring pollutants.
Carbon dioxide (CO2)
One of the greenhouse gases, which is a prominent pollutant - often considered the worst. Carbon dioxide is naturally present within the air, being essential for flora and a by-product of the human respiratory system. However, it is the increase of CO2 emissions within the atmosphere that is concerning.
Levels of CO2 in the air have drastically increased over time, equating to 410ppm in comparison to 280ppm during pre-industrial times. A major contributor of CO2 emissions has been the combustion of fossil fuels and carbon rich sources.
Sulphur oxides (SOx)
Chemical compounds that are generated by volcanic activity or through industrial processes. The combustion of coal and petroleum-based fuels release sulphur oxide particles. Sulphur particles can go onto producing acid rain, which heightens the environmental concerns associated with pollution.
Particulate matter (PM)
Small particles of liquids and solids subtended in the atmosphere. Some particles can occur from natural processes, such as volcanic activity, dust and forests; whereas, others will come from human activity through the combustion of fossil fuels in motor vehicles and industrial power plants.
It is said that anthropogenic aerosol particles (man-made particles combined with gas) account for 10% of the world's atmosphere. The two most concerning particles are PM10 and PM2.5 due to their effects on human health.
Impact on air quality and human health
Air pollution not only affects the environment by accelerating climate change, but also poses an impact on air quality and its subsequent effect on human health. The increase in pollutants within the air decreases its breathable quality.
It has been found that the majority of the world's population residing within urban regions are subjected to the poorest air qualities. The continuously growing road emissions and industrial practices increase the number of pollutants within a region. This begins to gravely impact the surroundings. World’s cities are at the worst of it in comparison to its rural counterparts.
As a result, poor air quality affects human health, with the potential risk of exposure changing from person to person. The World Health Organisation has set up guidelines for the allowable exposure limits. The exposure limits take into consideration the different ages and the demographics of an area, such as infants, children, pregnant women and other sensitive populations.
The health effects of air quality range from respiratory infections, coronary diseases, lung diseases and cancers, chronic obstructive pulmonary diseases, as well as effects to the central auditory system and neuro deficits. The air pollution worsens pre-existing health conditions such as respiratory and cardiac conditions. PM10 and PM2.5 exposure especially can impact health due to the small particles’ size, which are able to penetrate the airway, causing further discomfort to those suffering from asthma and other respiratory infections.
Air pollution in the context of Urban Air Mobility (UAM)
It has been a conscious effort for many industries to reduce the level of emissions and pollutants subjected to the atmosphere. To achieve this, initiatives range from the ban on diesel cars in London, to the adoption of electric vehicles, as well as developments in fuel technology, airframe design and material selection to reduce overall aircraft emissions.
As a newly emerging industry, Urban Air Mobility (UAM) vehicles and infrastructure can carry sustainability values at the core of development, to offer a pollutant-free means of mobility. From its implementation, the UAM ecosystem should consider the possible impacts of its operations and plan ahead to provide a sustainable, affordable and accessible means of alternative aerial mobility.
The vehicles are being designed to operate as electric or hybrid electric, therefore expected to project zero emissions directly into the earth atmosphere. The UAM ecosystem can adopt the developing advancements in sustainability research and technology, which allows continuous enhancements of UAM without the need for drastic changes. Therefore, UAM operations will not introduce any new pollutants or have extra detriment to the air quality.
Sources and suggested reading :
Air pollution - WHO
What Causes Air Pollution? - NASA, Climate Kids
Air Pollution - Our World in Data
Clean Air Strategy 2019 - Department for Environment, Food & Rural Affairs