Last week, when North Korea was threatening to send a ballistic missile toward the U.S. territory of Guam, the island's inhabitants were warned that in the case of a nuclear attack, they should not condition their hair.
Hair conditioning might seem like the last thing that would be on a person's mind following a nuclear attack, but this hair care advice has scientific merit: Conditioner can "bind radioactive material to your hair," according to guidelines posted by Guam's Office of Civil Defense Friday (Aug. 11). [Doom and Gloom: Top 10 Post-Apocalyptic Worlds]
It appears that the people of Guam are safe for the moment, however. North Korea has since de-escalated its threat, saying it would "wait a little more" before moving forward with the missile launchings, according to The New York Times.
Even so, the conditioner recommendations stand. During a nuclear attack, a fireball would pulverize everything in its path, launching the resulting vaporized material upward and mixing it with radioactive byproducts from the bomb to create a radioactive dust, according to NPR. This dust is known as nuclear fallout, and it can contaminate everything it falls on, including human hair.
If people survive the blast, they should take off their outer layer of clothing, which can remove up to 90 percent of radioactive material, according to Ready.gov, a U.S. site on disaster preparedness. If water is available for bathing, survivors should also shower with soap and shampoo to wash off any radioactive dust.
But because hair is made of overlapping scales, it's a bad idea to condition it in the aftermath of a nuclear attack.
"[Hair] can come apart during the day like a pinecone," Andrew Karam, a radiation safety expert who consults for government response teams, told NPR. "Radiation contamination particles can get between those scales."
Unlike shampoo, conditioner has certain compounds — mainly cationic surfactants (such as cetrimonium chloride), silicone (like dimethicone) and cationic polymers (such as guar hydroxypropyltrimonium chloride) — that pull down these scales to smooth a person's hair, Perry Romanowski, a cosmetic chemist who hosts The Beauty Brains podcast, told Racked.
If nuclear fallout gets under these scales, when the scales are smoothed down, radioactive particles can be trapped underneath and remain there, Karam told NPR.
In addition, conditioner has sticky, oily compounds that stay in hair, even after it's rinsed. These compounds could make it easier for nuclear fallout to stick to the hair, which could, in turn, increase a person's risk of radioactive exposure, Romanowski told NPR.
In fact, people should avoid applying to their body any oily or sticky cosmetic product, such as skin lotion or color cosmetics, if they're in a nuclear fallout zone, as these products would also amass radioactive dust, Romanowski said.
However, most injuries from a nuclear bomb are caused by pressure from the explosion, as well as fires, collapsed buildings, flying shrapnel and acute radiation poisoning (the kind that happens from the initial explosion rather than long-term exposure like that coming from your hair), Live Science reported previously.
Original article on Live Science.