The Chennai Corporation is committed to fighting mosquitoes. Every evening, dark DDT clouds create swirls in the air as diligent corporation workers brave health hazards to protect citizens. While this is commendable, I am sure that I am not the only one asking these questions – is this foul smelling DDT good for me? and if they are so effective, why do mosquitoes keep coming back?
DDT and DEET are the primary chemicals used in the war against mosquitoes.DDT is used by city corporations in India as a mass fumigant to spray over urban settlements and on stagnant water bodies. DEET is used inside homes in synthetic mosquito repellent products like lotions and mats.
DDT
DDT is an insecticide that was first synthesized in 1874 and used to control malaria and typhus during the Second World War. After that, it was re-purposed as a broad-spectrum insecticide to be used in agriculture and mosquito control and its usage skyrocketed.
In 1962, Rachael Carson’s seminal environmental book, “The Silent Spring”, documented evidence against the indiscriminate use of pesticides and due to overwhelming public response, the government banned DDT in 1972.
People in the U.S should still be concerned of DDT as it is a persistent organic pollutant (POP), which means its ill-effects last for several decades after we stop using it. More shockingly, India is the only country in the world that continues to manufacture DDT and is the largest consumer. China stopped in 2007.
When humans eat organisms exposed to DDT or DDT contaminated water (since it makes its way to water bodies from the fields), the pesticide accumulates inside the body and magnifies inside. For example, fish accumulate DDT in their fat and it is passed to humans eating the fish. Evidence of this transfer of DDT up the food chain was found when breast milk samples were found to contain DDT.
Sustained consumption of DDT-exposed food will cause storage or accumulation of DDT in our bodies as it is very slow to metabolize and difficult to excrete. It is a potential carcinogen, can temporarily damage the nerves and reduce reproductive success.
When it was first introduced during World War 2, DDT seemed very effective
against malaria-causing vectors. However, within about 5 -10 years, DDT resistant mosquito strains were observed in Sri Lanka, Pakistan, Turkey, and Central America. In India as well, DDT is mostly ineffective, due to its wide use in agricultural pest control, particularly in mango production.
Today, even WHO acknowledges the growing resistance to DDT, and maintains that DDT should be used only after ensuring that the mosquitoes do not have DDT-resistance. Unfortunately, DDT still continues to the official first line of defence sanctioned by the Indian government.
DEET
DEET, developed by the U.S army, was originally tested as a pesticide on farms and was sanctioned for civilian use in 1957. DEET is the active chemical in mosquito lotions and mats across the world and works as a true repellent (unlike DDT which kills) as mosquitoes intensely dislike the smell of this chemical.
DEET is also bad news for human health, potentially damaging to brain cells. DEET causes brain cell death and behavioural changes in rats after frequent and prolonged use. This exposure causes neurons to die in the regions of the brain that control muscle movement, learning, memory and concentration.
With heavy exposure to DEET, humans may experience memory loss, headaches, weakness, fatigue, muscle and joint pain, tremors and shortness of breath.
Mosquito coils
In India, coils use various active ingredients like pyrethrum, synthetic pyrethrins, allethrin, and others. They burn for upto eight hours, and are cheap. However recent studies show that the smoke generated from coils has a lot of health concerns.
The chemicals we use as a city and as citizens in our war against mosquitoes pose a threat to human life and the environment around us.
