Why Some Airlines Spray Pesticide In The Cabin Before Takeoff, And Is It Safe?

Anytime the word "pesticide" comes up in public discourse, it's usually in reference to how ruinous it is to natural ecosystems and public health. There's a reason they've garnered such a negative reputation: Pesticides are poisons. They're designed to kill pests like fungus gnats and mosquitoes, weeds, molds and mildews, and anything else that might harm crop yields. But just as fungi don't welcome pesticides, neither does the human body. So travelers beware: Pesticides are sometimes sprayed on flights, and it might not be good for your health.

There are few places less suited to dangerous chemicals than a flight — a cramped space that can feel cloying and claustrophobic at the best of times. The reason for using onboard pesticides is pretty straightforward: Certain countries require flights to be sprayed with them to kill harmful insect-borne pathogens, like Zika, malaria, and dengue. Some planes are sprayed and wiped down before passengers board — which reportedly kills insects for up to eight weeks — while others are disinfected during the flight. In such cases, the crew (who will at least suggest you cover your eyes) walks along the aisle spraying the pesticide into the air, which must surely be one of the most unusual requirements for being a flight attendant.

Each country sets its own rules, but the likes of Ecuador, India, Seychelles, and Zimbabwe require an aerosolized pesticide to be sprayed on all inbound flights while passengers are on board. Australia, New Zealand, Jamaica, Chile, and other countries allow flights to be disinfected before passengers board the plane. Yet other countries assess the need for pesticides on a case-by-case basis, such as flights to Thailand from areas where yellow fever is present or flights to Egypt from countries dealing with the Zika virus.

Pesticides have been used on airlines since the 1940s for "disinsection," which the Centers for Disease Control and Prevention describes as "the process of applying pesticides to kill insects." The most common chemical used in these pesticides is permethrin, which kills mosquitoes, ticks, and mites — all of which are vectors for pathogens. Dr. Michael Policastro, a Cincinnati-based toxicologist and physician, told USA Today that the goal of permethrin "is to disrupt the nervous system of insects and spare humans the same level of effect." However, Policastro added that there is "a limited amount of literature that looks at long-term exposures in low concentrations to the air flight staff, meaning pilots and flight attendants."

Aircraft pesticides are typically World Health Organization-approved. But they contain a mixture of propellants, solvents, surfactants, and synergists. So, while humans are generally able to metabolize permethrin and avoid its negative effects, the CDC says more research is needed on the effects of long-term exposure to these mixtures. 

It's also already agreed that such pesticides can be an irritant to infants, pregnant mothers, the elderly, asthmatics, and others with underlying health conditions. This is in part why the Environmental Protection Agency forbids their use on commercial aircraft. Add that to the fact that some of the insects the pesticides are designed to kill are resistant to them, and it reinforces the need to explore alternative disinsection methods.

Braving pesticide spray is not something you typically find on a list of tips for surviving ultra-long-haul flights. But there are some things you can do, such as consulting your doctor. It's usually wise to visit a clinic before you travel overseas, but this is especially true if you have a health condition that might flare up on contact with certain pesticides. 

You should also check the pesticide requirements for the flight you're about to take and be sure to avoid skin contact with surfaces that are still wet with the chemical mixtures. If you inform your cabin crew of your concern, they may opt against spraying the pesticide entirely or allow you to stand somewhere on the plane that limits your exposure to the chemicals.

Cabin crew unions are lobbying against the use of pesticides on planes, arguing that mechanical methods should be used instead. At the same time, the CDC and other agencies are skeptical of the use of these chemicals, given the limited amount of research conducted. So, at some point in the future, these potentially harmful sprays may be consigned to aviation's history books.