Insecticides – DDT’s Rise, Fall & Rise Again

DDT is the most famous insecticide, and its story has been one of rise and fall and rise again.

It was first synthesize in 1874, but no one knew the chemical killed insects until 1939 when Swiss chemist Paul Mermann Müller discovered it did just that. That was right before World War II, and with other insecticides in short supply, DDT was credited with halting outbreaks of deadly diseases like typhus and malaria.

After the war, it became a wonder chemical. Between 1940 and 2009, it’s estimated that 1.8 million tons of DDT was produced and used around the world mostly to control insects over huge agricultural fields. The peak year came in 1959 when 36,000 tons were used.

In addition to its use in agriculture, DDT was adopted by the World Health Organization for a program designed to “eradicate” malaria worldwide, beginning in 1955. The WHO sprayed small quantities of DDT inside people’s houses, and the mosquitoes bearing the malarial parasite were either killed or repelled by the chemical. WHO succeeded in essentially wiping out malaria in Taiwan, the Balkans, much of the Caribbean, parts of northern Africa, the northern region of Australia and much of the South Pacific. DDT dramatically reduced the mortality of malaria in Sri Lanka and India. When the campaign started, India was losing 800,000 people every year to malaria. By the late 60s, deaths in India were approaching zero.

Then came Silent Spring. Rachel Carson’s book pointed out how persistent the chemical was in the environment and how it passed from one species to another up the food chain until it was causing thinning in the eggshells of raptors like the bald eagle. The book is credited with fostering the environmental movement and with prompting the U.S. and other governments to ban DDT.

That ban went into effect in the U.S. at the end of 1972, despite the fact that a judge who ran the new EPA’s hearings on DDT concluded that it was not hazardous to humans.

Too often, as the United States go, so goes the world. DDT became “chemical non grata.” International aid organizations stopped funding programs that relied on DDT. Malaria had a resurgence in various countries – Sri Lanka, Madagascar, Swaziland, South Africa and Belize, to name a few. In Mexico, malaria rates rose and fell in direct proportion to the rates of DDT use. The one country in South America that continued to beat the disease was Ecuador, the one country that kept using DDT.

Instead of spraying the pesticide, WHO and other health organizations tried to distribute mosquito nets impregnated with other insecticides. But the nets had to be purchased by individuals and they lost their effectiveness over time. DDT programs, on the other hand, had been organized and paid for by central governments with help from international aid organizations.

As DDT use diminished, malaria kicked back. In 2004, it was estimated that 300 to 500 million people a year got malaria and 2 million people died of the disease. Most were children under the age of five, and 90 percent of those children were born in Africa.

In 2004, the New York Times Magazine published a provocative article titled “What the World Needs Now is DDT.” It went against the bulk of public perception that had held sway for over three decades. The author, Tina Rosenberg, wrote, “DDT killed bald eagles because of its persistence in the environment. Silent Spring is now killing African children because of its persistence in the public mind.”

Finally in 2006, the W.H.O. forcefully endorsed wider use of DDT across Africa. The organization unequivocally stated that DDT posed no health risk to humans because the program would spray small amounts of the insecticide inside the homes of people, rather than spray huge quantities on agricultural fields. They asserted that limited use would diminish the possibility that mosquitoes would develop immunity while effectively protecting entire villages and regions.

Written by Bill Ganzel, the Ganzel Group. First published in 2009. A partial bibliography of sources is here.