One pesticide that most people can name is DDT. In fact, DDT is so common to the point that it often features in crossword puzzles in newspapers and magazines with clues like ‘banned insecticide’ or ‘banned pesticide’. So, it is probably safe to assume that many people know that DDT is banned. However, would they know why DDT was banned or whether it is still being used today despite its banning?
Dichloro-diphenyl-trichloroethane (DDT) is an organochlorine insecticide that was first synthesized in 1874 and later became widely used for insect control in the 1940s. DDT became a popular insecticide in the United States and was used widely in agriculture and generally around people. In 1962, Rachel Carson wrote a book titled ‘Silver Spring’ that brought to light the devastating effect that DDT had on the environment. One of the detrimental effects pointed out by Carson was how DDT contamination was responsible for the near-extinction of the bald eagle, the national symbol of the United States of America. Thereafter, the United States Environmental Protection Agency (USEPA) was established in 1970 and DDT was banned in 1972.
DDT was one of the most widely used pesticides following World War II and was promoted as having insect-killing powers that would make homes healthier and comfortable. At the same time, evidence was mounting on how DDT could persist in the environment and bioaccumulate as it moved up the food chain. Bioaccumulation occurs when an organism absorbs a substance, such as a chemical or pesticide, at a faster rate than it can metabolize or excrete it. The substance can then become highly concentrated in an organism and cause problems.
Thus, because of DDT bioaccumulation, the compound became particularly deleterious to birds by making the shells of fertilized eggs so brittle that they cracked under their parents’ weight. The most threatened birds included peregrine falcons, ospreys, brown pelicans, and bald eagles, all of which were brought to the brink of extinction.
By the time DDT was banned in the US it had already contaminated nearly everything that Americans ate. Several years thereafter, DDT and its carcinogenic metabolite dichloro-diphenydichloro-ethylene (DDE), were still being detected in US food.
The story of DDT does not end with its banning by the USEPA. Elsewhere it is still in use in countries that continuously battle malaria until suitable alternatives for the control of mosquitoes can be found. How those countries are being affected by the continued use of DDT is largely unknown because there seemingly are no ‘Rachel Carsons’ to study the effects on the environment so as to alert society. I doubt that many know the reasons why DDT was banned in the first place and use it because it is moderately toxic and relatively safe when handled.
When growing up in Kenya, I applied DDT by hand to control corn borers without using personal protective equipment. It never even crossed my mind that there was any problem with the chemical and it is only later when I had the opportunity to study pest management that I learned the reality. I wonder how many Africans are even remotely aware of the dangers posed by the continuous use of DDT?
SUPESTA (www.supesta.com) confronts the challenge of pesticide use in Africa. We:
work with smallholder farmers, agro-dealers, extension personnel and others who routinely apply pesticide and help them build a knowledge base in pesticide use and safety,
promote alternative approaches to total reliance on pesticides, such as integrated pest management, and
help develop easily accessible tools that provide information on pesticide handling.
Ultimately, less harm will come to humans and the environment when pesticides are used by knowledgeable people.