Photo by James Jordan on Flickr.
In last week’s Sunday Links I posted an article on a new study that has shown there is “evidence for inhibition of cholinesterases in insect and mammalian nervous systems by the insect repellent deet“, or in normal-speak, “DEET is like, uh, bad for you eh”.
The abstract for the study and full 28 page .pdf are available here.
After reading that post @VancityAllie commented:
“Aaah, that’s pretty scary about DEET. I don’t use it very often (I also use a Citronella spray)… but I HATE mosquitoes and use it enough for me to look twice at that article.
Hey I was thinking, maybe you could do an article on safe bug repellent… how to keep the bugs away without poisoning yourself?”
And this is a good point. Aside from being annoying, bugs like ticks and mosquitoes can carry disease, so its not a bad idea to repel them. At the same time, we want to make sure the chemicals we are putting on ourselves are safe and don’t bare any long-term side effects. So lo and behold, I’ve done some research (and as usual, by ‘research’ I mean I hastily Googled some stuff) to get some more information on what options we have to keep those pesky bugs away. Some of the info on DEET was pretty alarming.
You’ll often hear people saying DEET is the best bug repellent, and swear by its effectiveness. So what exactly is DEET? From Wikipedia:
“N,N-Diethyl-meta-toluamide, abbreviated DEET, is a slightly yellow oil. It is the most common active ingredient in insect repellents. It is intended to be applied to the skin or to clothing, and is primarily used to repel mosquitoes. In particular, DEET protects against tick bites (preventing several rickettsioses, tick-borne meningoencephalitis and other tick-borne diseases) and mosquito bites (which can transmit dengue fever, West Nile virus, Eastern Equine Encephalitis, and malaria).”
Effects on health
As a precaution, manufacturers advise that DEET products should not be used under clothing or on damaged skin, and that preparations be washed off after they are no longer needed or between applications. DEET can act as an irritant; in rare cases, it may cause skin reactions.
In the DEET Reregistration Eligibility Decision (RED), the United States Environmental Protection Agency (EPA) reported 14 to 46 cases of potential DEET-associated seizures, including 4 deaths. The EPA states: “… it does appear that some cases are likely related to DEET toxicity,” but observed that with 30% of the US population using DEET, the likely seizure rate is only about one per 100 million users.
The Pesticide Information Project of Cooperative Extension Offices of Cornell University states that “Everglades National Park employees having extensive Deet exposure were more likely to have insomnia, mood disturbances and impaired cognitive function than were lesser exposed co-workers”.
Recently, DEET has been found to inhibit the activity of a central nervous system enzyme, acetylcholinesterase, in both insects and mammals. This enzyme is involved in the hydrolysis of the neurotransmitter acetylcholine, thus playing a role in the function of the neurons which control muscles. Because of this property, many insecticides are used to block acetylcholinesterase, which leads to an excessive accumulation of acetylcholine at the synaptic cleft, causing neuromuscular paralysis and death by asphyxiation. DEET is commonly used in combination with insecticides and has the capacity to strengthen the toxicity of carbamates, a class of insecticides known to block acetylcholinesterase. These findings bring evidence that, besides having known toxic effects on the olfactory system, DEET also acts on the brain of both insects and mammals, and that its toxicity is strengthened in combination with other insecticides.
Effects on materials
DEET is an effective solvent, and may dissolve (part of) some plastics, rayon, spandex, other synthetic fabrics, leather, and painted or varnished surfaces including nailpolish.
Effects on the environment
Although few studies have been conducted to assess possible effects on the environment, DEET is a moderate chemical pesticide and may not be suitable for use in and around water sources.Though DEET is not expected to bioaccumulate, it has been found to have a slight toxicity for coldwater fish such as the rainbow trout and the tilapia, and it has also been shown to be toxic for some species of freshwater zooplankton. DEET has been detected at low concentrations in waterbodies as a result of production and use, such as in the Mississippi River and its tributaries, where a 1991 study detected levels varying from 5 to 201 ng/L.
So while it seems DEET is linked to a lot of health (and environmental) issues, there is a new BBC article I saw in the latest Wanderung newsletter that takes a more balanced stance, saying “the incidence of exposures resulting in neurotoxic effects is very low, when considered in the context of the millions of people around the world who have used insect repellents containing deet”.
So, as usual, it seems to boil down to – There are linkages to health issues, potentially, but we need more research. In the mean time just limit exposure but small doses are fine – But when something can dissolve “(part of) some plastics”, that’s usually when I decide not to put it on my skin. But hey, that’s just me.
So if we don’t want to take the risk, what other options do we have?
Toxicity Category Levels
Category I = very highly or highly toxic
Category II = moderately toxic
Category III = slightly toxic
Category IV = practically non-toxic
(for reference DEET is Category III for eye, dermal and oral)
- Citronella Oil has been used for decades and is non-toxic. A popular alternative, but less effective, and may even attract bears. (Thanks again to Wanderung.ca for that tid-bit).
- Picaridin, a chemical developed by Bayer, is supposedly as effective as DEET, and maybe even more. I wasn’t able to find much on it regarding health issues. A 2005 report by EPA doesn’t show any serious health threats, but I’m sure something will come out in the future once it is studied more. It is Toxicity Category III for acute oral and dermal, and category IV for primary eye and skin.
- Eucalyptus-based repellents are considered effective against mosquitoes. Eucalyptus is an essential oil, but can actually be toxic in large quantities (which made me ask if koalas were aware of this, but apparently they are tolerant to it, phew!). Toxicity Category IV for acute oral, dermal and skin irritation, and Category II for eye irritation.
- Mud bath – Seems to work for elephants, just sayin’.
So I guess there’s a lot more to repelling bugs than I would have ever thought. If only I could repel bugs the same why I repel women, it would all be so simple. In conclusion to my extensive 1 year, er 1 hour, er ok 15 minutes of research, here’s what I would recommend:
Don’t use any repellent containing DEET unless you are going to be in an area with a lot of mosquitoes and/ or ticks. They can carry some nasty things you really don’t want. If you’re out in the backyard having a barbeque, and don’t want a few annoying suckers landing on you, I’d go with one of the plant-based alternatives. I personally would never spray any DEET on kids or pregnant women either (not that I go around randomly spraying insect repellent on people).
Hope that was useful.
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Tags: Bug Repellent,Mosquitos,Ticks
Categories: Safety
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