Mosquitoes

Permethrin

Does your city “fog” for mosquitoes?

The active ingredient in the fog is “permethrin” which is neurotoxic. The mechanism of action is to interfere with the transport of sodium across neuronal membranes.

Permethrin is very toxic to arthropods. So it’s great to kill insects, but also is toxic to lobsters and crabs (as well as other sea life). Of course, this not only includes mosquitoes but also insects such as bees which are very important for pollination.

From a human perspective, the benefit probably outweighs the harm. After all, those darn mosquitoes sure are annoying! So hey, what’s a little toxic burden if we can avoid those itchy mosquito bites? As an alternative, we might want to consider the benefits of natural predators of mosquitoes such as bats!

We are told that permethrin is safe for humans. Safe is of course a relative term. In humans, P450 enzymes metabolize and detoxify permethrin. Thus how toxic it is to any particular individual depends on your individual P450 enzymes metabolism and overall toxic burden. Some people have genetic traits which impair their ability to detoxify such substances. We also have to consider other toxins (like most pharmaceutical drugs) that are also detoxified by the P450 pathway. Note: usually rare genetic traits are called genetic defects but they really are more trade-offs of being better at one thing and worse at another.

P450 enzymes are responsible for detoxifying a number of carcinogens. I3C (Indole-3-carbinol) found in cruciferous vegetables like cabbage, helps boost P450 detoxification. Hypericum (St. John’s wort) also boosts P450, this is a reason industrial medicine doesn’t like St. John’s wort, it makes their drugs less effective by helping your body detoxify them! Note: this includes oral contraceptives! One of my points here is that the number of interactions between these substances is bewildering, thus when industrial medicine studies something in isolation and declares it “safe” they are making a very crude simplification.

If you are taking pharmaceutical drugs, use extra caution when being exposed to permethrin. Supplement users may also want to take note as polyphenols in particular interact with P450 detoxification (some boost it, others inhibit P450).

Also note that caffeine is metabolized by P450, so breathing in mosquito fog may impact the effect that drinking coffee has on you!

Permethrin is also used in flea collars. Cats are far more sensitive to permethrin than dogs are. Cats are very slow to breakdown permethrin. So if you live in a city that fogs for mosquitoes and you also have a cat, you want to be extra careful of the exposure of your cat to the fog.

Permethrin will stick to plants and may stay on leaves for one to three weeks. Trace amounts of permethrin have been found in the edible parts of plants such as bananas, squash and watermelon. If you have a garden in such a city, you may want to cover your plants prior to each time they fog for mosquitoes. Also keep in mind that breathing permethrin is different from eating it. When you breath it in, you bypass liver detoxification, when you eat permethrin your liver is going to detoxify it (assuming you haven’t overburdened your P450 enzymes).

Permethrin’s lethal oral dose in humans is between 1 and 2 grams per kg of body weight (you’d have to consume a substantial amount to kill yourself quickly).

My recommendation is that if you live in such a city, sign up to be notified of when they will be spraying (usually in the evening / night) and make sure you close your windows when they will be spraying.