We joined about 12 other passengers waiting at Air Botswana’s bright and airy gate for Maun. The doors were open and a warm breeze filled the space. The chairs were a mix of new and extremely worn. There was a nice bathroom nearby and a coke machine that took rand, which sadly I did not have. Our water bottles were empty and I wondered how long it would be before we could ask for a sprite on the plane.
Shortly, we boarded an airport bus for a 5 minute drive across the steamy tarmac. The land around Johannesburg airport is remarkably flat. For some reason, I didn’t expect that. There were very few parked planes, and they were spaced far apart, giving a snap-shot-in-time impression that the airport is far bigger than necessary. Perhaps it is busier at other times. It was New Year’s Day after all.
I was starting to notice the heat. Now I generally like hot weather as long as I can be in the shade and preferably by a pool. I had also just come from the northern hemisphere where winter is in full swing. Only yesterday, I was wearing a down coat in the London rain. Luckily the coat was still in London because it would have seemed absurd to carry it here.
We boarded with our usual 8 pieces of hand luggage. There are four of us, but the kids are not reliable about keeping track of their stuff and they get tired of carrying it. So it’s more like I have 6 pieces of hand luggage and a great luggage allowance.
Before take-off, a member of the crew walked through the cabin spraying an aerosol insecticide that smelled like a mix of baby powder and, well, insecticide. We were assured in a placating tone by the crew that the insecticide is completely non-toxic but we were invited to cover our mouths and noses if it made us feel better. Naturally I looked it up, given that I study how insecticides and other manmade chemicals affect animals (and of course people are in the Kingdom Animalia, along with most other creatures).
According to recommendations by the World Health Organization, we were most likely receiving a big whiff of permethrin, along with the poorly chosen baby powder smell (perhaps with its own toxicity issues). Permethrin is a synthetic insecticide in the pyrethroid family (natural versions of pyrethroids are found in chrysanthemums, which use pyrethroids to defend against insect pests).
Permethrin is a neurotoxin, meaning that it negatively affects nerve function by prolonging sodium channel activation. My cell biology students should be able to explain that keeping sodium channels open can cause muscle tremors and paralysis. Permethrin kills insects on contact by paralyzing their nervous systems. It also acts as a “stomach poison” to insects that eat the insecticide. Permethrin is used heavily to kill insects in agriculture. It’s also used on mosquito nets and the U.S. and British militaries are now treating all uniforms with permethrin to save soldiers from the annoyance of biting insects.
Permethrin is sprayed in airplanes coming from tropical areas to reduce the potential for malaria-carrying mosquitoes and other disease vectors from hitching rides to other countries. Interestingly, there are stories of travelers catching malaria from a hitch-hiking mosquito while on a plane.
Before we talk about human toxicity concerns, I think a more pressing issue is that permethrin kills bees on contact, along with all sorts of other beneficial insects. This is a serious repercussion of permethrin use. I have no interest in catching malaria, but I also enjoy the 35% or so of my diet that relies on bee pollination. In my case it’s probably more than 35% because I eat of lot of fruit and nuts. Take almonds for example. They need bees to pollinate them. Imagine the cost of almonds if we had to hire people to pollinate almond flowers by hand, using a Q-tip! I guess the Q-tip people would be happy.
Okay, so what about toxicity of permethrin to people? Is that sickly airplane spray bad for me and my kids?
An excellent citizen’s guide to permethrin toxicity was prepared by a TEDX, a leading organization in the review of endocrine disruption research. In short, permethrin is most toxic when breathed into the lungs (like we did while on the airplane). It is not absorbed through the skin especially well unless you are a young child. Children do absorb permethrin through their skin and there is evidence that they accumulate the insecticide in their bodies. Apparently it takes about a week to excrete 90% of the permethrin absorbed –mostly in urine. So we were still peeing out permethrin a 7 days after we arrived in Botswana.
Exposure to high doses of permethrin can cause dizziness, headache, and nausea for several hours. Larger amounts might cause muscle twitching, reduced energy, and changes in awareness. Even larger amounts could cause convulsions and loss of consciousness that could last for several days.
I didn’t feel any of these things, so probably that single exposure to permethrin on the plane was fine. A bigger issue might be the ongoing exposure to small doses – first on the airplane, then from my mosquito nets, then from the food I ate for dinner, etc. The TEDX review shows that over time, continued exposure to low doses of permethrins can impair reproduction, immune function, and social behavior – certainly in lab animals, and possibly in people.
So use of permethrins is not without risk. My airplane encounter with the pesticide is just part of an ongoing cocktail of chemicals my body sees every day. Whether this will impact my disease risk or lifespan – who knows. And even if I die before my time – would I be able to blame permethrins? Buried within the complexity of my life exposures, blaming a single pesticide would not stand up in a court of law. Pesticide companies continue to benefit from this reality. Given the choice, I would rather not be exposed and I certainly want to protect my children. So next time we board a plane in Botswana, it will be with a handkerchief in hand.