The modes of action of DDT

Last year, the World Health Organisation reversed a 25-year-old policy and recommended using the pesticide DDT to fight malaria in the Developing World. A new study published in the public health journal, PLoS ONE, provides more evidence that the decision was long overdue, says the Wall Street Journal.

The United States and Europe solved their malaria problem a half-century ago by employing DDT, but the mosquito-borne disease remains endemic to the lowland tropics of South America, Asia and Africa, where each year a half-billion people are infected and more than a million die. Despite those staggering numbers, radical environmental groups like the Pesticide Action Network continue to oppose use of the insecticide. One of their favourite arguments is that DDT is ineffective because mosquitoes can build resistance to the chemical's toxic properties.

According to the new study, however, that concern is misplaced.

DDT continues to work as a repellent and irritant long after it is no longer killing mosquitoes on contact.

The researchers found that three out of five DDT-resistant mosquitoes avoided homes sprayed with the insecticide and reduced the risk of disease transmission by 73 per cent.

Repeated studies have shown DDT to be safe for people and nature when sprayed indoors, yet other supposedly greener pesticides like alphacypermethrin have been touted as viable alternatives. Nevertheless, the latest research shows that DDT continues to be the most effective tool we have, as well as among the cheapest. "To date," conclude the authors, "a truly efficacious DDT replacement has not been found." Opponents of DDT are only ensuring more misery and death, says the Journal.

Source: Editorial, The Uses of DDT, Wall Street Journal, August 16, 2007.

For text: http://online.wsj.com/article/SB118722940723299229.html

For more on Environment Issues: http://www.ncpa.org/sub/dpd/index.php?Article_Category=31

FMF Policy Bulletin/ 21 August 2007