As climate change creates new habitat for mosquitoes, it’s time to protect yourself and your furry friends
It’s another stifling summer day in Boulder, Colorado, winding down into a still, humid evening. During my daily evening walk with my dog, we turn toward a wooded bike path, hoping the shade will offer some relief. My rough collie, with his thick double coat, is as grateful as I am to get out of the sun. A friend’s Labrador likes to take a swim in a nearby shallow canal.
Photo by ASCOM Prefeitura de Votuporanga
As we get closer to the canal, the onslaught begins — mosquitoes. They have everything they need right here: plenty of water, heavy undergrowth, and a steady stream of runners, bikers, and dog-walkers. This is the perfect habitat for them, and they seem to be making the most of it. Even through the fabric of my t-shirt, I can feel the bites. The bugs quickly home in on the dog’s head and snout. My friend’s black lab fares even worse, thanks to his short, dark fur.
According to the City of Boulder, 2018 has been an exceptional year for mosquito activity. Though mosquitoes are usually just a mild annoyance in our high, dry climate, so far the city has recorded almost twice the numbers seen in 2017, and three times the average.
Across the US, however, 2018 hasn’t been an anomalous mosquito year, but even under normal conditions, skeeters can be one of summer’s most annoying features. They can also be dangerous. Mosquitos carry a range of diseases in the US, including West Nile Virus, and less commonly, malaria, dengue, and Zika. And they are likely to become even more annoying across much of the country. Research shows that climate change is allowing mosquitoes — as well as other disease-bearers like ticks — to spread to new regions as they warm. The risk of disease transmission from mosquitoes also increases in warmer temperatures, specifically, when temperatures are between 61 and 93 degrees Fahrenheit. As you may have guessed, the number of so called “danger days” where temperatures fall within this range are also increasing in the US.
“Spending plenty of time outside, whether in your backyard, on the beach or on a family camping trip, is important,” David Andrews, senior scientist with the Environmental Working Group, said in a statement. “By taking a few simple steps, you can spend more time enjoying the outdoors and less time worrying about bug bites.”
So what can you do if you find yourself swatting more than usual this summer?
The first obvious answer is bug sprays. A few squirts of DEET, and you’re good to go, right? DEET is regarded as the most effective option, and is the world’s most widely used repellent. DEET, or N,N-diethyl-3-methylbenzamide, is effective against mosquitoes, chiggers, fleas, ticks, and biting flies. Yet, many people are wary of using it because of its potential toxic impact on both our health and the environment.
The main concern regarding DEET is that, when used in heavy concentrations, it can be neurotoxic. It is most toxic if ingested, but is also absorbed through the skin. According to the Environmental Health Association of Nova Scotia, lab tests showed a potential for neurological damage in animals that absorb DEET in high doses. Mosquitoes also develop resistance to pesticides and other chemicals over time, and some say this means that the chemical is now progressively getting less effective. There is also concern about neurological damage to young children, especially with sprays that have a high DEET concentration.
But overall, most experts agree that there is very little chance of harm from the low concentrations of DEET found in commercial products, if used correctly. Correct use, the Centers for Disease Control and Prevention (CDC) states, includes not applying it to any cuts or abrasions, and keeping it off of children’s hands to avoid accidental ingestion. The CDC recommends washing it off your skin after coming indoors, and washing any clothing that has DEET on it before wearing it again. In 2002, Health Canada began phasing out products that contained more than 30 percent DEET, though they maintain that the product is safe for public use. (The US does not have similar regulations on the concentration of DEET products.)
DEET use does also raise some possible concerns about ecosystem impacts. It makes its way into sewage systems and ultimately into waterways when it is washed off the skin, and is the most commonly detected chemical contaminant in US water, and in fact in water around much of the world. The US Environmental Protection Agency has said it is “slightly toxic” to birds, fish, and aquatic invertebrates, but there’s not a whole lot of research on the environmental impacts of DEET pollution. EPA tests throughout 30 US states found that by 2007, “DEET was detected at low levels in 75 percent of streams sampled in the US, but implications of this finding are not known.”
As for now, even the most pesticide-wary environmental groups agree that it’s OK to use this bug spray, especially in regions where people are at risk of serious mosquito-borne diseases, as long as usage guidelines are followed stringently. “In situations of high vector borne disease rates DEET is probably a safer alternative than using highly hazardous pesticides for vector control,” says Medha Chandra, campaigns coordinator with Pesticide Action Network North America (PANNA).
Another repellent option highly recommended by experts is picaridin (known as icaridin outside of the US), a synthetic compound derived from plants in the pepper family. Products with a 20 percent picaridin concentration rated higher than 25 percent DEET products for repellant effectiveness in a 2016 Consumer Reports study. The Food and Drug Administration (FDA) previously recommended that neither DEET nor picaridin be used on children younger than three years old. However, they have changed that recommendation to say use is all right on babies older than two months. (For babies under six months, the Environmental Working Group and PANNA advise using fine netting over baby carriages and strollers instead of repellent sprays.)
But if you’d rather try natural mosquito repellents, the most effective is oil of lemon eucalyptus, which has been verified by the CDC as having repellent qualities similar to DEET. It is available in several products, including Repel Lemon Eucalyptus, which also rated higher than DEET in Consumer Reports’ results. The FDA recently advised that oil of lemon eucalyptus should not be used on children under three years old.
There are many essential oils that are said to have repellent effects, but some are ineffective at repelling insects and others can be harmful if misused.
For example, Joseph Conlon from the American Mosquito Control Association says that clove oil has repellent qualities, but only in concentrations that would damage the skin. Also, before you mix up a concoction of your own, make sure you use oils from the right plant species. While lemon and red eucalyptus, as well as western red cedar, are repellent to mosquitoes, blue eucalyptus and deodar cedar are not. Be aware too that lemon eucalyptus oil is not the same as oil of lemon eucalyptus. Steam-distilled lemon eucalyptus essential oil has very low concentrations of PMD, the compound that repels insects. It has to be further refined into oil of lemon eucalyptus before it is highly effective.
If you want to upgrade your yard to a mosquito-free haven, there are several things you can do while avoiding chemicals. If you have an outside electrical outlet or extension cord, using one or more electric fans is an easy, non-toxic option. The forced air movement both disrupts the insects’ flight and dispels the tell-tale signs of a potential host, like carbon dioxide and body heat.
Joseph Conlon, technical adviser with the AMCA, recommends keeping outside areas free of trash and other items, such as old tires, that may hold water, and changing the water in birdbaths or emptying drip pans at least once a week. Keeping grass and shrubbery well-trimmed will reduce hiding places for adult mosquitoes, and allowing proper drainage of rainwater reduces puddles where they breed. He also recommends using yellow lights on porches and decks, such as GE “Bug Lights,” which do not attract mosquitoes like white incandescents do. Wearing light-colored, loose clothing with a tight weave is another easy way to ward off bug bites.
Chandra of PANNA adds that using physical barriers against bugs such as bed nets, long sleeved shirts and full pants, screens on house windows and doors are important components of an overall approach to avoiding bites and reducing vector borne disease rate.
If you have a pooch, you’ve probably noticed that bugs harass them at least as much as you, particularly around the face. Bugs also have the potential to spread harmful diseases to your pets, like heartworm parasites, which are life-threatening to dogs if infected.
Dr. Jason Nicholas, from The Preventive Vet, says you should never use DEET on your dogs. Picaridin seems to be safe for dogs, though there are currently no commercially made products specifically made for them. Many of the same essential oils recommended for human topical use, including oil of lemon eucalyptus, can also be applied topically to dogs, or to a bandana that the dog wears around his neck. However, since the dog may lick off the mixture at some point, it’s important that both the repellent and the carrier oils or sprays are safe and are very diluted. Also, be aware of which essential oils, like wintergreen, clove, and pine, are toxic for animals.
For more information, both the EPA and CDC register mosquito repellents that have been tested for safety and effectiveness. Oregon State University operates a website that lists products by name, by manufacturer, by ingredients, or by the insects they work effectively against. For further information about insect repellents and children, the Environmental Working Group provides a helpful list.