4) Departure: It's not my fault I'm gassy

Ever wondered why it’s so noisy when you board the plane?

The APU's exhaust is at my rear, just below my enormous tail

Well, I’m running my auxiliary power unit (APU), which powers the aircraft before the engines are started. We’re eventually pushed backwards by the tow vehicle, I start my engines and begin taxiing us to the runway. But we keep stopping every few minutes. When we finally make it to the runway, my engines roar and before you know it, we’re airborne.

A BA A380 approaching Los Angeles International airport over a thick layer of photochemical smog. Although this smog is directly attributable to road traffic emissions, it presents a very visible display of local pollution

But what am I overlooking? At every single phase of departure, I’m releasing ‘local’ pollutants such as nitrogen oxides (NOx), carbon monoxide (CO) and particulate matter (PM). Whilst most of my emissions are when I’m at full thrust during take-off, running the APU, taxiing and idling all produce emissions that have adverse effects on the health of workers and residents around the airport. In fact, long-term exposure to NOx is linked to higher incidences of respiratory diseases, CO to pulmonary heart disease and PM to lung disease (predominantly for ground staff working near the engines). Just 10 minutes with my engines running at idle power as I await a take-off clearance produces as much sulphur dioxide as 500,000 cars operating over the same time period!

But there’s more. As a result of larger aircraft operating at Heathrow (which require more time to get passengers onboard and therefore run their APU for longer), NOx emissions rose by 5.7% in 2016 alone. Furthermore, research has shown that it’s not simply my exhaust gases that contribute to local air pollution but those from the ground vehicles working at airports. Remember the baggage carts, the fuel trucks and the tug that pushed us back from the gate; these contribute significantly to local pollution, with a study at Zurich airport suggesting that ground vehicles were in fact the primary source of pollutants like NOx. Although the same may not be true for other airports around the world, it still highlights the importance of looking beyond aircraft like me when assessing air quality around airports. There remains, however, an absence of research into the the impact of passengers travelling by car to/from the airport as well as the network of surface transportation associated with air cargo operations.

London's annual NOx concentrations in 2016, with Heathrow's two runways and terminals clearly identifiable as the hotspot in West London (Source: London Atmospheric Emissions Inventory 2016)

Source: International Air Transportation Association

So how does all of this play out in terms of local pollution? Let's take a look at NOx concentrations in London; you can see I contribute significantly to pollution around Heathrow (the hotspot in West London). However, you can also see there are much higher concentrations along roads and in Central London, highlighting road traffic as the main source of local pollutants. Coupled with the fact that my local emissions are small relative to other transport modes (see the table opposite), it’s clear that my impact is limited to the immediate vicinity of airports.

Join me next week as I take a more global perspective to my emissions.