OurBlueSphere.org

Has everyone heard of DDT, once proclaimed as the great boon to the human race?  Used as a garden pesticide and in many households as an insecticide, it was finally brought down by public outrage.  The United States EPA, supposedly saved the environment, and we could breathe again……Or can we?  Surprisingly, DDT is still around.  Maybe in your old barn or greenhouse?  DDT (dichlorodiphenyltrichloroethane) was first synthesized in 1874, but first was used as insecticide in 1939.

In World War II, soldiers and sailors carried small cans of DDT powder to protect themselves against bedbugs, lice and mosquitoes. They came to love the stuff, especially in the tropics.  Millions of DDT aerosol bombs were used to spray the interiors of tents, barracks, and mess halls.  By the end of World War II, DDT had become the most publicized synthetic chemical in the world!

DDT was released for public use in August 1945, just three days before the end of World War II.  When DDT was removed from wartime federal control, the government’s power over its production, distribution, and use was diminished.  There were immediate profits to be made from DDT’s manufacture, distribution and agricultural use.  Because there was a desperate need for all the food and fiber that could be produced, DDT could do more to increase production more than any other insecticide.  Millions of people were saved from starvation because of increased food production made possible by DDT.  The U.S.D.A. has estimated that without chemical pesticides, some 30% of America’s protein supply and 80% of high vitamin crops would be lost to insects – and DDT was by far the most widely and heavily used chemical pesticide throughout the 1950’s.

After World War II, DDT was used extensively as an agricultural insecticide, usually in the form of a spray.  In some cases as much as a ton of DDT was used to treat a single cotton field.  By the 1950’s, in some cases, doses of DDT and other insecticides had to be doubled or tripled as resistant strains developed.  In addition, the evidence began to grow that the chemical became more and more concentrated at higher levels in the food chain. As the stubbornly persistent DDT enters the food chain that begins with plant eaters and runs through small to large and larger meat eaters, including man, the process known as “bioaccumulation” occurs.

Research reports began to note the amazing persistence of DDT, due to its chemical stability and insolubility in water.  Pyrethrum, as then used in ordinary household sprays, was highly poisonous to insects for the first few hours after application,  but gradually lost all its power within a day or two.  But DDT, sprayed upon an interior wall, was fatal to flies and mosquitoes for as long as three months. DDT sprayed on a blanket could be laundered a half dozen times, and still kill every moth that touched it!

In 1962, Rachel Carson’s book Silent Spring was published.  The book argued that pesticides, and especially DDT,  was giving evidence both for and against the use of DDT, where poisoning both wildlife and the environment was happening.  The public reaction to Silent Spring launched the modern environmental movement in the United States, and DDT became a prime target of the growing anti-pesticide movements during the 1960’s.

The EPA held several months of hearings in 1971-72 with scientists giving evidence both for and against the use of DDT.  EPA’s first administrator, William Ruckelshaus, in the summer of 1972, ruled that a ban be placed on the use of DDT in the United States.  The 1970’s ban took place amid a climate of public mistrust of the scientific and industrial community, following such problems as Agent Orange and Love Canal.

DDT continues to be used in other countries (primarily tropical) where mosquito-borne malaria and typhus are greater health problems than DDT’s potential toxicity.  Use of DDT in public health to control mosquitoes is primarily done inside buildings and through household products and selective spraying; this greatly reduces environmental impact compared to the earlier widespread of DDT in agriculture.

The Stockholm Convention in May 2004, called for the elimination of DDT and other persistent organic pollutants. The Convention was signed by 98 countries and is endorsed by most environmental groups.  However, a total elimination of DDT use in many malaria-prone countries is currently unfeasible because of the prohibitive costs of alternative insecticides.

It has recently been estimated that 2,400 tons of DDT has now accumulated in Antarctica’s snow.  Probably from worldwide winds bearing pesticides.  Whatever its ultimate effects may be, the fact is that most of the hundreds of millions of pounds of DDT sprayed over the world during the last quarter century remain in circulation – only a fraction has decayed into harmless substances.

And so the use of DDT continues.  The need for some system of broadly assessing the likely consequences of technological innovations before they are unleashed seems all to apparent. In the case of DDT, we can only hope to live with our mistakes. In the interest of Our Blue Sphere, we must continue to learn and apply that knowledge for now and in the future!