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| Seoul researchers have found that a good way to keep mosquitoes away from humans doesn't involve any chemicals. Gettyimagesbank |
By Ko Dong-hwan
Putting aside nasty pesticides, researchers in Seoul have concluded that one of the most effective ways to keep mosquitoes at bay is simple enough.
The Seoul Institute of Technology said Wednesday that a more effective way to keep the insects ― which mostly live in septic tanks or sewage tunnels in urban environments ― at bay is sealing off any cracks near manhole covers and covering open ventilation shafts connected to the tanks. Blocking these paths worked better than using pesticides against the insects, according to the researchers.
Mosquitoes find their way to the open air through cracks around manhole covers. Researchers have proposed sealing them off with polyurethane-based sealing tape ― such as those that retail as window tape sealing. Holes on manhole covers ― mostly where handles are ― also provide a gateway through which mosquitoes can come and go. The experts suggested covering them with a fiberglass-based fishnet. The same fishnets could also effectively block the opening of ventilation shafts, through which mosquitoes frequently exit the tanks.
The researchers, funded by the Seoul Metropolitan Government, also praised the measures as more cost-effective than using pesticides. Repairing one manhole cover costs just 3,000 won ($2.30). The experts said that given some 2,900 septic tanks with a capacity for use by 200 people or less in the city need their seals repaired, it would cost about 8.7 million won ― 82.6 percent less than what the city previously spent on pesticides.
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| The researchers said sealing off openings at ventilation shafts connected to septic tanks, above, and cracks around manhole covers is more effective in keeping mosquitoes away from humans than spraying harmful pesticides. Courtesy of Seoul Institute of Technology |
To come up with the best methods to stay bite-free, the researchers studied a digital mosquito monitoring system (DMS) installed throughout the city's 25 sub-districts to analyze the changing numbers of mosquitoes in each district per month. It led to a discovery that the city, overall, despite having sprayed pesticides inside septic tanks and sewage tunnels to quell the insects, saw an increasing number of mosquitoes in recent years. The number of mosquitoes recorded in 2021 increased 8 percent compared to 2019.
Mosquitoes were also more frequently spotted around manholes and septic tanks in residential areas concentrated with low-rise dwellings, rather than in high-rise apartment neighborhoods.
The city government said they will advise the 25 sub-districts to employ the newfound methods in low-rise dwelling neighborhoods before monsoon season begins this summer ― the time when mosquito numbers usually spike. The city expects that the new method will cost the city less and reduce the risk of environmental pollution caused by use of pesticides.
Seoul Institute of Technology President Lim Seong-eun said that the latest finding is an outcome of research analysis that led to a more effective alternative solution. "The institute will keep finding innovative solutions for various inconveniences that people of Seoul experience," said the president.
To date, the city government has been using d-Phenothrin mixed with water to control the mosquito population. The institute said the insecticide's relatively low degree of toxicity when breathed in or ingested by humans ― measured by its margin of exposure (MOE) ― has been certified via "Re-registration Eligibility Documents" of the United States' Environmental Protection Agency. The authority has been spraying some 1,600 liters of the pesticide each year, spending 50 million won annually.
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