Frequent fogging and insecticide concerns in mosquito control

Straits Times Forum 20 Mar 12;

THE widespread practice of thermal fogging using the insecticide cypermethrin for mosquito control in Singapore is a cause for concern.

In some areas, the residents cannot avoid inhaling the chemical several times a week because of frequent fogging in the neighbourhood. The chemical may also contaminate drain water, a source of Newater.

Cypermethrin is widely used in agriculture in many countries but seldom in densely populated areas.

The National Environment Agency believes cypermethrin is safe. But we really have no knowledge of the long-term effects of repeated exposure to the chemical on people, especially infants and children.

There are no perfectly harmless chemicals and drugs.

When DDT was first introduced in 1939, it was hailed as an ideal insecticide with no harmful effects on higher forms of animals. In 1962, American biologist Rachel Carson found that the chemical could cause cancer and harm animals high up in food chains. And in 1972, DDT was banned in America. Also, aspirin, considered perfectly safe for decades, is now known to have side-effects.

A chemical or drug is used justifiably if its benefits outweigh its harmful effects.

According to a field study carried out in Malaysia and tests published in natural science journal Florida Entomologist, cypermethrin's effectiveness as a larvicide (larvae killer) is doubtful.

When there is an outbreak of a mosquito-related disease, fogging should be an immediate response to kill adult mosquitoes over several hectares at one go, while doubling the efforts to clear the area of stagnant water.

However, it is ludicrous for individual home owners to have thermal fogging carried out routinely in their compounds.

Its efficacy is short-lived and the neighbours' houses can suddenly be shrouded in a chemical fog that is probably harmful to infants and children.

The United States Environmental Protection Agency classifies cypermethrin as a possible human cancer-inducing agent. A recent study has linked pyrethroids, to which cypermethrin belongs, to leukaemia and lymphoma.

Cypermethrin is a neurotoxin that can affect brain tissue and can damage many other organs.

Let us avoid the futile individual thermal fogging, and concentrate our efforts on the key to mosquito control - prevention of stagnant water formation.

Dr Ong Siew Chey