[pct-l] Mosquitos, Permethrin and leave no trace

[Jim Marco]

Well, That says a lot of how I feel about all chemicals, in general.

The point is, you have to understand and know how to deal with Permethrin.

Yes, it is deadly to aquatic animals. Very few mammals are effected, cats are one. Sprays are typically not that good for the environment. Nor should you ever apply Permethrin directly to your skin. And, you need to wear rubber gloves when handling it. And you need to keep it away from your cats.  

A key point was not mentioned by Mr. Marr, however. This is that Permethrin acts as a sort of dye. Used with natural fibers and nylons, not polyethelene based fabrics or recycled PET like fleeces for example, it attaches loosely with the fabric. After soaking, drying and rinsing, what is left in the fabric will last through up to 30 normal laundry cycles. Like a normal color in most fabrics, it can be considered permanent. It does NOT wash out by tramping through a stream or rinsing with water. Nor does correctly treated and washed clothing leach Permethrin into your skin when you sweat. It stays in the shirt. Spraying on cloths, then using them is not considered safe...for you or the environment. The excess CAN be washed out. Like most dies, it rarely adds .5% to the weight of cloths. This is well below the 2% number that Mr. Marr quoted. 

You should NOT use a washer to launder cloths dipped in Permethrin. They need to be rinsed in a bucket, with a hose, top, down, first. The rinse water should NOT be dumped into the ground. Rather it should be spread out in strong sunlight to allow UV to break it down. Washing into the ground will simply put the chemical into the ground. It is sold as ant or termite killer, too. Treating your house sill, and, foundation is accepted practice. Painting floor joist can make them resistant to termites for many years. Painting sidewalks can leave them ant/bug free around the house. There is a use for the extra from doing cloths, DO NOT SIMPLY DUMP IT DOWN A DRAIN. The sewage plants will NOT break it down and it WILL pollute the water. Again, Sewage Treatment plants do NOT break down Permethrin. Do not spray the excess on your garden. Can you figure out why?   

It is NOT a repellant, except any insects will try to preserve their existence by avoiding it. It is a neurotoxin. Most living things will avoid things that will kill them...I did say most, not people.

Wearing cloths that have been correctly treated and washed poses less of a health risk or about the same, than the risk of contracting diseases/infections carried by insects. As always, you have the choice of determining whether to use Permethrin or not. 

	My thoughts only . . .
			jdm   

-----Original Message-----
From: pct-l-bounces at backcountry.net [mailto:pct-l-bounces at backcountry.net] On Behalf Of Marr, Eli B
Sent: Saturday, April 06, 2013 10:36 AM
To: pct-l at backcountry.net
Subject: [pct-l] Mosquitos, Permethrin and leave no trace

There has been a lot of talk about mosquitoes and using Permethrin as a repellent. Please read this so you can make an informed decisions on whether or not you want to use the chemical in your hike.

First let me say I am a cancer researcher at one of the best Children's Hospital Research centers in the world. I am just a hiker doing my first thru hike on the PCT and am concerned about the environment and all of the great people I'm going to meet on my hike. This being said, here is what I have found about Permethrin:


Colombia gear and several other outfitters are selling anti-bug/insect blocker clothing. This clothing contains the chemical Permethrin as its active ingredient. You can also buy Permethrin at REI or other outfitter stores to treat your clothes, bags and gear with. Permethrin is EXTREMELY toxic to aquatic organisms and invertebrates and is labeled as a carcinogen by the EPA. Columbia states their insect blocker technology is completely safe and registered with the EPA without restriction. Let me give you a few quotes directly from the EPA website about Permethrin:

The Agency classified Permethrin as "Likely to be Carcinogenic to Humans". This classification was based on two reproducible benign tumor types (lung and liver) in the mouse, equivocal evidence of carcinogenicity in Long- Evans rats, and supporting structural activity relationship information.

"The cancer risk estimates for adults exposed to surfaces treated with permethrin from directed surface sprays were above the Agency's LOC." (Level of Concern: This is how the EPA rates products as potentially hazardous to people or the environment. Below LOC=Safe. Above LOC= not so safe)

"Permethrin is highly toxic to both freshwater and estuarine aquatic organisms. Most agricultural, public health, and down-the-drain scenarios modeled resulted in exceedances in the acute risk quotient (RQ) for freshwater and estuarine fish, invertebrates, and sediment organisms."

"All residential/recreational exposures are expected to be short-term in duration. Therefore, no intermediate-term (1-6 months) or long-term (>6 months) aggregate risk was assessed."

Although not on the EPA site Permethrin is highly toxic to some mammals like cats. They used it in flea and tick prevention until cats started getting sick and dying. No more Permethrin allowed on cats.


Though the concentration of Permethrin used by hikers is lower than the EPA's limit keep in mind their limit was set for SHORT TERM use only. They have done no studies whatsoever on how the chemical might effect say... hikers who wear a Permethrin covered shirt for 5 months on the PCT. I don't know about you but that makes me a bit nervous. Permethrin is only absorbed into the skin at about a 2% rate (not that high) and is broken down by the body over time. But it still makes me nervous. I will be using Permethrin on my thru hike. It's effective for repelling bugs and better than getting west nile virus from a mosquito. However I am NOT applying it to anywhere touching my skin. I'm putting it on my pack, parts of my hat and on sections of my tent but it is not touching my clothes.

For anyone following any guidelines for Leave No Trace: DO NOT WASH YOUR PERMETHRIN COVERED CLOTHES IN ANY NATURAL WATER SOURCES!!! It will directly harm the aquatic life. This has been proven through multiple studies conducted by the EPA and other research centers. The EPA has strict regulations on any release of Permethrin near water sources. If you Permethrin your shoes, pants or socks and walk through a stream it puts the Permethrin directly into the ecosystem. Please be respectful of our environment and help keep the PCT clean for future hikers.

Thanks for reading and good luck to everyone! I leave for the trail in a few days.
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