Season 4, Episode 6: Race Fever

Mayko and David are called to Québec, where several contestants of a cycling race are coming down with mysterious lung infections. Fearing that they might be dealing with an infectious disease, they try to convince authorities to shut down the race. But while all patients have bacterial infections, the underlying cause for the lung infections appears to be lung damage caused by aluminum particles from a satellite that recently crashed near a section of the race route. Also, Bob continues to have trouble with his memory, and visits a hyperbaric chamber to see if that will reduce the swelling in his brain.

ARE THERE HEALTH RISKS FROM SPACE JUNK OR SATELLITES REENTERING THE ATMOSPHERE?

What is "space junk"?

Millions of pieces from space craft, satellites, launch platforms, or other man-made objects are orbiting the earth and eventually reenter the atmosphere. All pieces larger than 10 cm (about 4 inches), including entire defunct satellites, are tracked to see where they end up. There are about 17,000 of these larger pieces of debris in orbit, and every week a few of them reenter the earth's atmosphere.

Image obtained from the NASA Orbital Debris Program Office website.

Computer generated image of objects in Earth's orbit - 95% of these objects are debris (i.e., not functional satellites).

Why don't we notice all these reentries?

There are a few reasons why we only rarely hear about satellites or space debris falling to Earth. First of all, the majority of the Earth's surface is unpopulated, including oceans and deserts over which most space debris re-enters. Secondly, the smaller debris fragments burn up completely when they reenter the atmosphere so there is nothing left to hit the earth. Even larger pieces of debris, such as entire satellites, can disintegrate entirely. Finally, the pieces that are big enough that they might survive the trip through the atmosphere and hit earth are tracked very closely and often steered in some way to avoid any risk of harming people around where the debris lands.

In February 2008, the US government destroyed a satellite with a missile when they feared that the satellite's fuel tank might survive reentry and contaminate a populated area. By destroying the satellite, only smaller pieces were left, which would all burn up in the atmosphere. Whether the cargo would have been a risk at all is still being debated, but the incident illustrates that satellites are indeed carefully tracked.

Why does space debris disintegrate when it re-enters the atmosphere?

An orbiting satellite has a speed of about 29,000 km/hr and travels in an orbit that is relatively close to Earth. Because the atmosphere doesn't end entirely (i.e. abruptly) before the height at which a satellite travels around the Earth, an orbiting satellite very gradually gets slowed down by the highest regions of the atmosphere. Over time, the loss of speed will allow the Earth's gravity to pull the satellite back towards Earth. As a satellite comes closer to the denser part of the atmosphere, the friction between satellite and atmosphere becomes higher and higher, creating a huge amount of heat.

In this episode, a satellite made of aluminum reenters the atmosphere north of Nitchequon (a ghost town in central Québec) and fully disintegrates on reentry. Aluminum has a relatively low melting temperature, so it's not surprising that this satellite didn't survive the heat of reentry.

Can aluminum chloride from space debris cause lung infections?

In this episode, minute particles of aluminum chloride were found in the air at ground level directly below where the satellite entered the atmosphere, and these particles damaged the athletes' lungs as they cycled through it. Aluminum chloride is produced at very high temperatures in a reaction of aluminum with hydrogen chloride or chlorine gas. It might be a possible by-product of an aluminum satellite burning up on reentry, if there was also a form of chlorine present at the reentry point.

Aluminum chloride can indeed damage lungs, and in general lung damage can make patients more susceptible to bacterial infections (which, in turn, cause more damage). That being said, there are no known cases of anyone inhaling aluminum chloride from space debris and getting a subsequent bacterial infection.

Are there other health risks from space debris?

One of the health concerns surrounding satellite reentries is spread of radioactive materials. In 1978, a satellite launched by the Soviet Union, Cosmos 954, crashed in the Northwest Territories, and spread a radioactive dust cloud over a large area of Canada, extending to parts of Alberta and Saskatchewan. Since that incident, international collaborations and regulations concerning radioactive material in orbit have greatly improved to reduce this risk.

The satellite that was shot down in February 2008 was a possible health risk because it was believed that its fuel tanks might have survived reentry and released a toxic chemical, hydrazine.

So?

There are no known cases of lung infections caused by aluminum chloride clouds from satellite reentries, but there are some other health risks from space debris and satellites reentering the atmosphere, mostly related to toxic materials that may not completely disintegrate on reentry. Fortunately, the reentries of larger objects are carefully monitored, and it's unlikely that even a sparsely populated area like central Québec would not be notified of any possible reentries and related health risks.

DID YOU KNOW?

Bob is trying hyperbaric oxygen therapy: a method where patients spend some time in a chamber breathing 100% oxygen under high pressure. This technique is used, for example, to treat decompression sickness (found in deep sea divers who resurface too fast) or carbon monoxide poisoning, but some medical evidence suggests that other conditions also benefit from hyperbaric chambers.

Image provided courtesy of Shaftesbury Films.

Bob chats with Maya and her mother, Erica, after a session in the hyperbaric chamber.

Bob hopes that the chamber might reduce swelling in his brain. Intracranial abscesses (swelling of the brain) is indeed one of thirteen conditions for which hyperbaric oxygen therapy is supported by medical trials, at least in patients with severe brain injury. The little girl that shares Bob's chamber is getting treatment for cerebral palsy, and for that condition there is no medical evidence that hyperbaric chambers work.

Want to read and learn more?

Visit the website of the NASA Orbital Debris Program Office to learn how they track space debris:
http://orbitaldebris.jsc.nasa.gov/index.html

To learn more about satellite reentry, visit:
http://www.aero.org/capabilities/cords/reentry-overview.html

Read about the 1978 reentry of Cosmos 954:
http://www.hc-sc.gc.ca/ed-ud/fedplan/cosmos_954_e.html

Health Canada has a list of conditions for which hyperbaric chambers are approved or not:
http://www.hc-sc.gc.ca/iyh-vsv/med/hyper_e.html