In 2010, the eruption of the Eyjafjallajokull volcano affected many Easter holidays. The closure of European airspace left many people stranded but millions enjoyed a break from aircraft noise and could look up at brilliant blue skies, free from contrails. Switching off airports allowed scientists to show that Heathrow and Gatwick were affecting local air pollution. Nitrogen dioxide decreased by nearly 30% around some parts of Heathrow and by more than 10% near Gatwick. At the time we thought it was a unique experiment that would never be repeated.
Roll forward a decade and Covid has also had major impacts on aviation. UK passenger numbers have been down by about 90%. This year, nitrogen dioxide near Heathrow and Gatwick has been half pre-pandemic levels, making them amongst the most improved locations in and around London.
A recent study has revealed more detail of air pollution beneath flight paths. Pre-Covid, researchers from Tufts University in Massachusetts, US, parked their mobile laboratory in the driveway of a house near Logan international airport in Boston. The colonial-style wood-frame house dated from the 1920s when the airport was a muddy military airfield. Located on a peninsular with no through roads, the area was quiet in traffic terms and air pollution was very low when the winds blew from the sea.
But pre-pandemic, the airport had more than 1,000 flights per day, many passing above the rooftop. When wind blew from the airport, 1.3km away, nitrogen dioxide was greater than that measured next to busy roads in the Boston area. As the planes passed overhead the amount of ultra-fine particles, smaller than the wavelength of visible light, increased by nearly five times. Being indoors offered little protection; it only reduced concentrations by about 20%. Ultra-fine particles inside the house still were greater than concentrations measured close to busy roads. Oddly, landing aircraft had a greater impact than those taking off. This may have been due to the low approach heights and vortices that form under aircraft wings swirling pollution to the ground.
The economic impacts of aviation shutdowns are being felt in many communities, but pre-Covid more than 1 million people in the UK were regularly affected by aircraft noise and air pollution from airports could be measured tens of kilometres away. A return to aviation as before will bring about serious deteriorations in noise and air pollution for many millions of people.