Dr. Lok Pokhrel, an associate professor of environmental health at Temple University’s College of Public Health, is developing a pesticide that uses nano silver to destroy disease-bearing mosquitos – and significantly reduce our chemical footprint. “There are no sustainable pesticides available – they’re all high-dose, high-use, or high-volume – and their footprint is very high – they’re not going anywhere. And their effects are unpredictable.”
[Photo: Dr. Lok Pokhrel]
Dr. Pokhrel has been developing a pesticide made with silver nanoparticles that can destroy disease-bearing mosquitoes without the heavy environmental footprint.
The potential benefits here are twofold. Paramount is the eradication of mosquito-borne diseases including malaria, Zika, Dengue, and Chikungunya – viruses whose debilitating and fatal effects impact millions of people worldwide. (Of the more than 3,500 mosquito species, Aedes aegypti is the one most associated with many of these viruses and the one Pokhrel uses in his research. While not known to carry malaria, it is plausible that the pesticide he’s developing would be effective on Anopheles as well.)
Second is nano silver’s ability to reduce the release of harmful chemicals into the environment. Pokhrel’s new particle combines nano silver with benzoyl urea, the standard chemical used to fight mosquitoes – and to which they are resistant. The current EPA dose of benzoyl urea is up to 845 parts per million — about 845 milligrams per liter of water. Dr. Pokhrel’s nanopesticide would significantly reduce that dosage.
How does it work? “Say you have a normal mosquito egg. When you add water, it will hatch very quickly,” he says, describing the lab simulation of how the eggs are laid and hatched in nature. “When exposed to nano silver that has been modified to make it toxic to the mosquito, the eggshell takes on abnormalities. Something, somehow, is happening inside the egg, and that is exploding the egg.” No more eggs means no more aegypti; no more aegypti means no more Zika, Dengue, or Chikungunya.
When researchers were first adapting materials for nanotechnology, they logically turned to silver. The element is a natural antibacterial and antifungal that has been used in medical treatments for millennia. When silver particles are reduced to the nano level, they acquire a very large relative surface area and start to harm the surrounding cells. Nano silver becomes a kind of super-antibacterial. And it is hydrophilic – so it is an excellent candidate for destroying organisms that lay their eggs in water. Like mosquitoes.
How chemical development will impact the environment is always an educated guess, and nanoparticles are so new that it is not yet known how they will interact with the real world. For the time being, it is generally agreed that the smaller the chemical footprint, the better. Part of Pokhrel’s research includes safety testing on non-target organisms including humans. He argues that the benefits of reducing harmful chemical exposure and eliminating mosquito-borne disease outweigh the risks. “If we eradicate the mosquito for now, the illnesses associated with these problems will be gone, too,” he says.