by Danielle Bongiovanni
On Sept 2, 2021, Bergen County Mosquito Control sent an advisory email to Ramapo College students encouraging them to shut their windows to limit contact with Duet adulticide, an insecticide used to reduce populations of adult mosquitoes and their larvae. This simple alert, sent one day after Hurricane Ida hit New Jersey with torrential rains and flooding, is the outermost layer of the complicated relationship between climate change and insecticides.
An article by Dana Bate for WHYY reported that climate change is indirectly affecting mosquito populations in New Jersey. Increased rainfall has created more available pools of freshwater which many species of mosquitoes use for breeding.
Climate Signals, a nonprofit dedicated to keeping explanations of the impacts of climate change publicly accessible, shared that as the atmosphere warms its average moisture content increases. Extreme precipitation events like Hurricane Ida have more fuel, cause more rain and flooding, and leave more standing freshwater to become mosquito breeding grounds.
Cattail mosquitoes, Coquillettidia perturbans, are one example of a species gaining numbers due to having more places to breed. An annual report from the Metropolitan Mosquito Control District detailed how the catch rate in 2020 was 127.3 cattail mosquitoes per CO2 trap. The report stated that year “Coquillettidia perturbans averages were higher than the 20- year average.”
Asian tiger mosquitoes, Aedes albopictus, are an invasive species that also breed in freshwater and have been observed in increased numbers in New Jersey. Both they and cattail mosquitoes are known vectors for diseases such as West Nile Virus. The Center for Disease Control recorded case numbers jumping from 8 in 2017 to 61 in 2018, then dropping back to 8 in 2019.
Preventing the spread of disease, combating invasive species, and improving citizens’ quality of life are all understandable motivations for Bergen County officials to want to reduce mosquito populations. Whether the consequences of using truck-mounted sprayers and hand spraying insecticides outweigh the benefits, however, is debatable.
Duet adulticide is one of three insecticides used by Bergen County Mosquito Control. Its use was approved by the United States Environmental Protection Agency in 2016. EPA approval does not label a product as harmless. Even when used correctly, the product causes moderate eye irritation in humans, and users are advised to wash their hands and launder and change their clothing after each use. Heavily contaminated materials must be discarded.
The Bergen County Mosquito Control Division has released more extensive fact sheets on the adulticides in its arsenal. Overexposure to Duet can cause symptoms in humans such as “irritation to skin and eyes, respiratory and nasal irritation, irritability to sound or touch, abnormal facial sensation, sensation of prickling, tingling or creeping of skin, numbness, headache, dizziness, nausea, vomiting, diarrhea, excessive salivation, and fatigue,” although the risk of overexposure when the product is properly used is low.
The EPA reports its usage also has environmental repercussions. Duet adulticide is highly toxic to aquatic organisms such as fish and invertebrates, and contaminated runoff is hazardous. The insecticide is also highly toxic to bees that are sprayed or exposed to sprayed plants.
Insecticides are not the only methods of mosquito control used by Bergen County. Maintaining drainage systems and stocking water with fish that prey on mosquitoes reduce the ability of populations to successfully reproduce. However, as climate change creates more available breeding grounds, it follows that Bergen County’s current dependence on insecticides like Duet adulticide will only increase, as will the resultant harm to people and the planet.
At the time of this article’s publication, Bergen County Mosquito Control and Bergen County Department of Public Works did not respond for comment or to answer how the list of overexposure symptoms was acquired.