EarthTalk is a weekly installment from E/The Environmental Magazine.

Dear EarthTalk: Is it true that the DEET used in most mosquito repellents is toxic? If so what problems does it cause? And what are some non-toxic alternatives for keeping mosquitoes at bay?

DEET is commonly known as the king of mosquito repellents, though not everyone is keen to slather it on their skin. A study conducted in the late 1980s on Everglades National Park employees to determine the effects of DEET found that a full one-quarter of the subjects studied experienced negative health effects that they blamed on exposure to the chemical. Effects included rashes, skin irritation, numb or burning lips, nausea, headaches, dizziness and difficulty concentrating.

Duke University pharmacologist Mohamed Abou-Donia, in studies on rats, found that frequent and prolonged DEET exposure led to diffuse brain cell death and behavioral changes, and concluded that humans should stay away from products containing it. But other studies have shown that while a few people have sensitivity to DEET applications, most are unaffected when they use DEET products on a sporadic basis according to the instructions on the label.

The upside of DEET is that it is very effective. A 2002 study published in the New England Journal of Medicine found that DEET-based repellents provided the most complete and longest lasting protection against mosquitoes. Researchers found that a formulation containing 23.8 percent DEET completely protected study participants for upwards of 300 minutes, while a soybean-oil-based product only worked for 95 minutes. The effectiveness of several other botanical-based repellents lasted less than 20 minutes.

But a number of new concentrations of botanical repellents that have hit the market since are reportedly better than ever. In 2005, the U.S. Centers for Disease Control (CDC) granted approval to two healthier alternatives to DEET—picaridin and oil of lemon eucalyptus—for protection from mosquitoes. Picaridin, long used to repel mosquitoes in other parts of the world, is now available in the U.S. under the Cutter Advanced brand name. Oil of lemon eucalyptus, which is derived from eucalyptus leaves and is the only plant-based active ingredient for insect repellents approved by the CDC, is available in several different forms, including Repel Lemon Eucalyptus, OFF! Botanicals, and Fight Bite Plant-Based Insect Repellent.

Some other good choices, according to the nonprofit National Coalition against the Misuse of Pesticides, include products containing geraniol (MosquitoGuard or Bite Stop), citronella (Natrapel), herbal extracts (Beat It Bug Buster) or essential oils (All Terrain). The group also gives high marks to oil of lemon eucalyptus, such as that found in Repel’s Lemon Eucalyptus Insect Repellent.

Another leading nonprofit, Pesticide Action Network North America (PANNA), likes Herbal Armor, Buzz Away and Green Ban, each containing citronella and peppermint as well as various essential oils (cedar wood, lemongrass, etc.). PANNA also lauds Bite Blocker, a blend of soybeans and coconut oils that provides four to eight hours of protection and, unlike many other brands, is safe to use on kids.

CONTACTS: “Comparative Efficacy of Insect Repellents against Mosquito Bites,” http://content.nejm.org/cgi/content/full/347/1/13; National Coalition Against the Misuse of Pesticides (NCAMP), www.beyondpesticides.org; Pesticide Action Network North America, www.panna.org.

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Aside from staying home and drinking tap water out of a washable glass, the best way to be “green” while on the go is choosing your water bottle wisely. From the lowly single-use-only plastic water bottle you can buy at your local gas station to the stainless steel and aluminum options, making the right choice is important in maintaining both your health and the health of the environment!

The worst kind of water bottle is the kind that you only use once - the PET (polyethylene terephthalate) bottle that you find in grocery stores, gas stations, etc, that is used for water, soda and juice. This kind of plastic has been proven to leach DEHP (Bis(2-ethylhexyl)phthalate) after repeated use and is a probable carcinogen. They can also harbor bacterial growth inside any cracks and crevices inside the bottle, which cannot be too good for your health either!

Next to the regular old plastic bottles we see everywhere, probably the most common would be your typical bottle as seen here. These plastic bottles, commonly used by exercise buffs and campers, are made out of thermoplastic polymers that usually goes by the name polycarbonate. However, it’s not just water bottles that are made out of polycarbonate; CD’s, iPods, sunglasses, and computer shells are also made of the material. Thankfully though, we don’t normally chew on CD’s or computers because polycarbonates have been proven to leach BPA, a synthetic hormone that can mimic estrogen and cause prostate cancer. Even scarier is the fact that most baby bottles are made out of polycarbonate, and when you heat up milk in them to feed your baby, the BPA could be leaching in at an even higher rate than normal. Not good at all, if you ask me!

A much better option than either of the above two would be an aluminum water bottle. A big manufacturer of aluminum water bottles is Sigg (which you can get at Reusable Bags, where we got ours), which claims to make environmentally friendly products. They have a lot of information on their site about the safety of aluminum,but one little part concerns me that I didn’t know until just a little while ago - these bottles still have a plastic liner. *Update - The liner inside is made from a water-based resin that is baked into the bottles, according to company representative who just emailed me.

The best way to get your daily dose of water on the go, in my opinion, is a stainless steel reusable container. Kleen Kanteen is a large manufacturer of these type of bottles, and you can get them from Reusable Bags. They are made entirely out of stainless steel, which does not leach, is difficult to break or crack, and does not easily stain or interact with whatever product you are consuming. The water always tastes good out of it (at least ours does, and it is Los Angeles tap water!) and it keeps it reasonably cold for a little while when we go hiking or out in the sun. They don’t recommend using them for hot beverages, which is understandable - that’s what a thermos is for.

Ideally, the best way to drink water on the go would be an aluminum or stainless steel water bottle, as they seem to exhibit the least amount of health concerns out of all the choices. Add in the fact that they can be used over and over again with no degradation and do not need to be recycled each time you use one, they really are the “green” choice. And since upwards of 40% of bottled water is actually just tap water in disguise, buying it seems like not only a health risk due to the plastic leaching possibilities, but also a wallet risk due to wasting money on something you already have at home!