Background
The volume of commercial air traffic has increased exponentially in recent decades, leading to airports which are always busy and often overcrowded. But modern airports no longer serve only as places to catch flights; they have evolved into destinations for shopping excursions, fine dining, and entertainment. Changi Airport of Singapore and Dubai International Airport, as just two examples, are marketed as tourist attractions rather than merely airports. This evolution has not only resulted in a greater number of passengers, but also airline staff, airport administrators, security personnel, baggage handlers, caretakers, maintenance crew, air traffic controllers, shopkeepers, and ground transportation staff (e.g., taxi and bus drivers). The rapidly growing post-pandemic market demand ensures that this expansion of the aviation sector will continue into the foreseeable future.
Research in recent years has revealed that those living and working in and around airport terminals are exposed to air pollutants on a near-continuous basis. Effective measures are therefore needed to reduce this exposure and protect the health and safety of passengers and airport staff.
Air Pollution In and Around Airports
The construction of an airport is a mega-project that requires not only the construction of terminal buildings and runways, but also major road and rail infrastructure. Residents around the construction site are therefore exposed to high concentrations of particulates and vehicular pollutants long before the airport is fully functional. This exposure continues upon project completion in the form of aviation-related pollutants; despite the vast open spaces, a significant proportion of this contaminated air disperses to nearby residential areas and into the terminal buildings.
Primary aviation air pollutants include oxides of nitrogen (NOx), volatile organic compounds (VOCs), carbon monoxide (CO), and fine particulate matter (PM2.5), with trace amounts of sulfur dioxide (SO2). Primary pollutants NOx and VOCs also interact with each other in the presence of sunlight to produce secondary pollutants like ozone (O3); this then combines with primary pollutants like PM2.5 to produce smog which can dramatically reduce visibility. Combustion of jet fuel is also a significant source of CO2 emissions, which, though not an immediate health threat, is a greenhouse gas of great concern. The cavernous interior spaces of airport buildings often necessitate dedicated onsite heating and/or cooling plants to fulfill their enormous requirements for climate control, and these plants themselves are also large emitters of air pollutants.
Aviation Air Pollutants – Sources & Health and Environment Impacts
NOX: It is estimated that every aircraft produces 8–50 kg of NOX during each take-off/landing cycle, depending on its size. This amounts to a substantial fraction of global NOX emissions when the combined total air traffic typically handled by busy airports around the world is considered.
PM: Combustion within aircraft jet engines generates considerable amounts of PM2.5, which is combined with the dust that gets dispersed due to the air currents from their movement. Large plumes comprised of all particle size fractions are thus produced during each take-off/landing sequence which travels to adjacent residential areas and permeates into terminal buildings. Smaller particles are especially problematic as they can reach the alveoli within the lungs and may even permeate into the bloodstream. High levels of particulates are known to adversely affect cardiovascular health.
VOC: Jet fuel is highly volatile, and thus fugitive emissions of VOC occur while it is transported to and within the airport and while filling the aircraft. This combines with VOC emissions from incomplete combustion in jet engines to produce substantial concentrations of VOC in and around airport buildings. Some common VOCs, such as benzene and formaldehyde, are known human carcinogens.
CO: This is typically generated because of partial or high-temperature combustion of fossil fuels. An aircraft jet engine involves high-temperature combustion, and thus elevated levels of CO are typical near airport runways.
O3: The primary pollutants NOX and VOC react with each other in presence of UV light (sunlight) to produce O3. Because of the dependence on sunlight, O3 levels tend to be highest in the summer months. High O3 levels are worrisome since they may aggravate diseases such as asthma, chronic bronchitis, and emphysema.
Smog: Accumulation of PM2.5, O3, and NO2 leads to the formation of smog, which is characterized by a grey or yellow-brown haze that hovers over an affected area. It is worsened by low wind conditions and meteorological inversions and may result in poor visibility.
CO2: Combustion of any hydrocarbon, e.g., jet fuel, generates CO2. Though the fuel efficiency of aircraft jet engines has increased significantly, the increase in air traffic has more than offset these improvements. CO2 from the aviation industry is, therefore, a major contributor to the total global CO2 emissions and climate change.
Noise: Noise from aircraft and vehicular traffic is probably the airline industry’s most obvious environmental nuisance because it is easily noticeable and disruptive. Aircraft noise is generated by both the engine and the airframe and is most evident during landing and take-off, especially around busy airports. Other significant sources of noise pollution include noise generated from taxiing aircraft, the application of reverse thrust (an optional braking aid on landing), and engine tests. Exposure to aircraft noise is associated with an increased risk of health problems such as high blood pressure, in addition to being simply disruptive to those living nearby.
Cleaner Airports
It is critical to monitor air pollution around airports as it affects both nearby residents as well as the travelers and workers inside the airport buildings. Modern airports are a world of their own as there are people active inside them 24/7 all year round. Air travelers are the least exposed to aviation-related air pollutants as they remain in terminals for relatively short periods of time. Those who work in and around the airport, on the other hand, are continuously exposed to these pollutants as they infiltrate indoors via the ventilation system or boarding gates. This problem gets much more aggravated when airports are not equipped with proper air filtration and air conditioning systems, especially during heavy rush hours. The air inside airports is technically referred to as “indoor” air but considering the amount of air interchange and the enormous interior size of terminals, it should properly be treated as ambient air and therefore continuously monitored according to stringent regulations.
Data indicate that emissions from most heavy air polluting sectors are declining due to the implementation of tighter controls, but this is not the case for the aviation industry. The exponential growth in air travel and the continued lack of government control programs for aircraft engines in most countries effectively negate the impacts of the pollution control measures that do exist. This has the effect of preventing countries from lowering their overall air emissions targets and meeting their air quality and public health goals. The lack of proper pollution mitigation programs compared to other industry sectors is remarkable considering that the aviation industry reported 40.2 million flight operations in 2019. International bodies like the International Civil Aviation Organization acknowledge that airport-related emission sources can contribute to deteriorating air quality in surrounding communities. National and international air quality programs and standards are therefore continually instructing airport authorities and government bodies to address air quality issues in the vicinity of airports; however, more stringent policies are required to adequately address this issue.
Airport and/or regulatory authorities can start collecting air pollution data in and around airports by installing a network of real-time monitoring stations. The airport authorities can utilize this data to create air pollution reduction programs and carry out their implementation. The data will help determine the relative impacts of aircraft emissions on those present in and around the airports like air travelers, airline staff, vendors, baggage handlers, etc., while also helping to identify carbon footprints and ensure that pollution levels are within permissible limits. One of the most feasible ways to achieve this is through the use of continuous ambient air quality micro-monitoring stations (CAAQMMS). Micro air monitoring stations installed around airport fence lines will provide valuable data on air pollutants escaping to adjacent residential areas, while stations installed inside the terminals will provide real-time indoor air pollution levels to facilitate the improvement of public health and safety.
A.U.G. Signals Ltd. has developed an “Advanced, Accurate and Affordable” CAAQMMS called AirSENCE which provides real-time measurements of aviation pollutants including PM10, PM2.5, PM1, NOX, CO, O3, CO2 and VOCs along with weather/environment parameters like temperature, humidity, noise, rainfall, and wind speed and direction. AirSENCE is not an air monitoring system but a complete air monitoring micro station that offers complete flexibility to be installed anywhere in and around an airport’s vicinity. AirSENCE is a compact and lightweight plug and play system with very low power consumption and completely autonomous operation, making it ideally suited for application in airport environments. Its data storage on a secure cloud server and URL-based dashboard allows authorities to access, view, and download air quality data even from their smartphones, empowering them to make timely and well-informed decisions that affect the livelihoods of travelers and airport workers alike.