As the weather continues to increase in warmth and humidity, our former Great Black Swamp experiences the buzz of mosquitoes. Recent academic research into mosquito control led me to investigate the chemicals we use here in Lucas County and what we know about their safety. Do the benefits outweigh the risks? Turns out, the answer isn’t very clear. I researched what was in each of the chemicals used in mosquito sprays in Lucas County.
The two main active ingredients are various forms of what are known as Pyrethroids and Piperonyl Butoxide, or BPO. While pyrethroids seem fairly safe for humans, studies show they are incredibly toxic to fish and spraying near any freshwater sources should be avoided (Prusty et al., 2015). Pyrethroids are also highly toxic to aquatic insects if the spray drifts or if chemicals runoff into nearby water sources, which affects the whole food web (a system of interdependent food chains) since many creatures depend on aquatic insects as a food source (Antwi et al, 2015; Wurzel et al, 2020). For example, fish and birds both consume them to survive. When it comes to BPO, there isn’t a lot of research that can provide a clear answer on its risk to wildlife, but perhaps the most concerning aspect is its effect on humans. Research on a group of 36-month-old children in New York City found that while they seemed to be unaffected by pyrethroids, the BPO they were exposed to in utero caused significant developmental impacts, such as delays in cognitive development (Horton et al., 2011).
In a surprise twist, my research revealed that the active ingredients in these sprays may not be what we should be most concerned about. Inactive ingredients are considered trade secrets by chemical companies, have very little regulation, and few studies have been conducted about their safety. You may assume, like I did initially, that because they are “inactive” ingredients, they are safe, as simple and pure as water. Unfortunately, this is not the case.
The kicker?
Some of the spray compounds are made up of as much as 87 percent of these inactive ingredients. Most of the inert chemicals in mosquito spray are something called “petroleum distillate.” These are basically petroleum byproducts from crude oil. We don’t have long-term studies that show effects on humans, wildlife, or the environment. All we know is when researchers used a technique called mass spectrometry to investigate pesticide petroleum, they found that 11 of the petroleum formulations alone were more than 50 times higher than toxicity standards, and three of them were over the recommended standards by over 1,000 times (Jungers et al., 2022). Epidemiological studies on petroleum distillates found that both children and adults on farms were more likely to have issues with wheezing (Mesnage et al., 2018).
Mosquitoes can carry deadly diseases and the task of controlling their populations is critical. However, we must ensure that we aren’t repeating our past mistakes. I can’t help but to think of the warnings Rachel Carson made in Silent Spring when she attempted for years to get people to heed the dangers of chemicals like DDT, despite companies and the government assuring everyone that it was perfectly safe (Carson, R., 1962). Most of the existing studies have an overlying theme, which I wholeheartedly agree with; more research is needed. Research on low-dose, long-term exposure for all species is crucial to understanding the effect on human life and the tiniest arthropods that make up part of our diverse ecosystems.
In addition to calling on our local mosquito control task force to further investigate the impact of all chemicals, including those considered “inert,” I also ask that community members living near our precious local freshwater sources consider the option to opt out of spraying in their area, which can be done easily through the TASD website. Protecting the fish and invertebrates in these sources is critical to our local biodiversity. (Plus, fishing is a huge part of our local economy!)
Finally, exploring alternative mosquito control solutions must continue.
Perhaps depending more on controlled larvicide in certain standing water environments is part of the answer. Ecological solutions such as supporting habitats for dragonflies, bats, and birds like purple martins (all mosquito-eaters) could help. Maybe one of the genetically altered methods being tested elsewhere that naturally cut down on the population is worth investigating. At the least, it is worth carefully considering multifactor, safer solutions in our own swampy ecosystem, a prime mosquito habitat.
Ms. Frank is a freelance environmental journalist in West Toledo.
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