As a commercial airline pilot, Theresia Eberbach typically weighs several factors when deciding which trips to fly — the dates, destination and how long she’ll be away from home. Unlike most of her peers, Eberbach often has another variable to mull: How much radiation she’s willing to take.
Ionising radiation is a permanent feature of the upper atmosphere, where the protection we take for granted on the surface is significantly thinner. At airlines’ cruising altitude, particles periodically ejected by the sun and cosmic radiation coursing through the universe are 100 times more potent than down below.
Still, the exposure for every extra-long trip across the globe is roughly equivalent to one X-ray. That is, except for two regions: The poles. The planet’s magnetic field helps to minimise radiation for most latitudes, but that shield tends to dissipate at extreme north and south. Airline employees are already the most vulnerable to workplace radiation, but the growing number of polar and long haul routes may make the hazard worse. A flight from Germany to Southeast Asia can be just as long as one to the western US, but the risks can be very different given the latter goes “over the top” of the world.
“If I go to Los Angeles or San Francisco, it’s going to be the highest dosage in our network, whereas when I go to New Delhi or Singapore, it’s about a third of those doses,” said Eberbach, an Airbus A380 first officer for Deutsche Lufthansa AG who also serves as chairman of a radiation protection working group for Vereinigung Cockpit, or VC, the German pilots’ union.
Airline employees face more radiation exposure than radiology workers or nuclear power plant engineers, according to the National Council on Radiation Protection and Measurements. Such exposure is measured using the Sievert. A dose of 4 Sieverts or more at once is often fatal. A CT scan of your head is about 2 milliSieverts (mSv), or two-thousandths of a Sievert, roughly what you’d get going about your daily life for eight months. Generally, a US pilot or flight attendant receives an annual exposure of as much as 5 mSv.
“In our job, we’re going to get this exposure,” said Mike Holland, an American Airlines captain and resident “radiation expert” for the Allied Pilots Association, the union that represents American’s 15,000 pilots. “There’s no way you can be a pilot and not get this exposure.”
Beyond the popularity of polar routes, airlines are also connecting more far-flung cities, with 16-18-hour hauls becoming routine thanks to modern aircraft technology. Singapore Airlines intends to resume its 19-hour non-stop service to New York this year, while Qantas Airways has launched what it calls “Project Sunrise” to connect Sydney with London and New York non-stop by 2022. The effort is aimed at goading Airbus SE and Boeing Co to produce a jet able to fly more than 20 hours, fully loaded. Last month, Norwegian Air Shuttle ASA’s Argentina unit won regulatory approval to begin Boeing 787 flights from Buenos Aires to Perth, Australia, using a flight path near Antarctica.
But these lengthy legs don’t just affect airline employees. Fly frequently for long distances and you, too, may start to consider how much radiation you’re absorbing. In the most extreme examples, planes caught over the poles in a solar storm could see radiation levels spike up to 10 mSv for a single flight. But even advocates for employees say they’re having a hard time being heard by airlines focused on saving time and fuel, and thus money.
“It’s been difficult to get traction” with airlines and regulators, said Judith Anderson, an industrial hygienist for the Association of Flight Attendants-CWA, which represents 50,000 attendants. “The nature of the hazard is invisible, so it’s easier to forget about and get attention for something more pressing.”
Polar routes aren’t new, of course. The Swedish airline SAS AB completed the first trans-Arctic commercial flight in 1952, followed by a regularly scheduled “Polar shortcut” route two years later linking Copenhagen and Los Angeles. More recently, United Airlines inaugurated a Chicago-Hong Kong non-stop polar route in 2001, but only during summer months, when winds were more favourable. Today, its successor, United Continental Holdings Inc, is the US carrier with the most service to Asia, with seven polar routes each day.
Airlines are keen to maximise revenue by using the most direct routes. Flights from the eastern US and Canada to Asian destinations such as Hong Kong, Seoul, Shanghai and Beijing, typically traverse the North Pole — “over the top” in pilots’ parlance — to shave as many as two hours off a typical journey.
Since airlines gained access to Siberian airspace, the number of polar flights has soared, with more than 17,000 trips last year from just a few in 2001, according to data from Nav Canada, the Canadian air traffic services company. These remote regions, and areas just south of the Arctic Circle, are an important path for scores of flights each day, including many of the non-stop routes from India, the Persian Gulf states and Europe to the western US and Canada.
In the far south, Qantas flies from Sydney to Johannesburg and Santiago, Chile, both routes that track below 60 degrees south, near Antarctica. Latam Airlines Group SA and Air New Zealand also occasionally approach the region with their flights between South America and Auckland.
Polar routes, while fiscally desirable, do present airlines with a few technical challenges that require additional instruction for pilots. These regions generally offer fewer diversion options for emergency landings and have a greater potential for communications glitches.
Just as airline meteorologists closely monitor storms and winds, the carriers also keep tabs on space weather. Given the sun’s potential to rapidly fry a vast array of terrestrial communications, the National Oceanic and Atmospheric Administration (NOAA) monitors the sun for coronal mass ejections and other particle events that can increase ionisation near Earth. It sends alerts on solar activity, with a radiation scale of 1-5.
A NOAA weather satellite launched on March 1, GOES-17, is expected to increase the fidelity of space weather forecasts. A sensor developed at the University of New Hampshire is designed to monitor the level of energetic ions, the main source of radiation.