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The story behind DDT: Why did it become a star in killing mosquitoes?
Mosquito-borne diseases such as dengue fever and malaria have a huge impact on global health. According to the World Health Organization (WHO), indoor residual spraying (IRS) is considered an important strategy for controlling these diseases. Of these sprays, DDT was undoubtedly a star because of its long history and effectiveness in combating mosquitoes. However, with the improvement of environmental awareness, the use of DDT has also encountered challenges. What is the story behind this?
Indoor Residual Spray (IRS) Practices
IRS is a spraying technique used indoors to kill mosquitoes that transmit malaria. This method is mainly suitable for walls made of earth or wood, while plastic or plaster walls may not be able to achieve the spray effect effectively. Such sprays not only kill mosquitoes, but also effectively prevent the spread of diseases. According to the latest data, in 2008, 44 countries had implemented IRS as a malaria control strategy, demonstrating its importance.
The World Health Organization lists IRS as one of the three main malaria control methods, the other two being the use of mosquito nets (ITNs) and timely treatment of confirmed cases.
WHO recommendations and the use of DDT
In WHO recommendations, the use of IRS is not limited to areas with sporadic malaria. Since 2006, WHO has begun to recommend the use of this strategy in areas of stable transmission as well. WHO emphasizes that for the effective implementation of IRS, the country's public health system needs to have adequate management capacity and financial support, including appropriate selection of insecticides and maintaining high coverage.
Economic Benefit and Effectiveness Analysis
According to a 2010 Cochrane review, IRS are considered an effective strategy for reducing malaria incidence. When compared to mosquito nets, both are almost equally effective. Although DDT is considered the most cost-effective option economically, its advantages are decreasing over time. UNEP stated in 2008 that while DDT remains affordable and effective in many circumstances, the external costs of using DDT need to be carefully assessed.
"IRS use of DDT remains affordable and effective in many situations, but we need to reconsider its advantages over other pesticides."
Residents’ opposition
For IRS to be effective, at least 80% of the area needs to be sprayed. However, many residents expressed opposition to certain pesticides such as DDT, primarily due to their odor and the stains they left behind. While this stain serves as a marker for where spraying has taken place, it has led some residents to refuse to have their homes sprayed. In contrast, other pesticides that do not leave residues are favored by residents, which may affect the overall control program.
Balance between environmental protection and public health
With the changes in society, many traditional houses have been gradually replaced by Western-style houses, which makes the use of DDT more and more limited. Therefore, how to effectively use DDT and strike a balance between alternative pesticides has become a new challenge for public health managers. Many experts believe that improving understanding and acceptance of pesticides while facing opposition from residents will be a key focus for future work.
Conclusion: The future of DDT
DDT was once a star in killing mosquitoes, but with the emergence of environmental problems and residents' aversion to it, the status of this "star" is being shaken. However, DDT still demonstrates its irreplaceable effectiveness and value in certain circumstances. In the future, we should think about how to find the best balance between public health and environmental protection to cope with the ever-changing epidemiological challenges?
