DDT: The Chemical Revolution Stumbles into Health and Environmental Issues
Lessons Learned: Looking Back to Go Forward
A series of articles exploring historical events that provide an important lesson for ensuring a more sustainable and healthy environment. Originally published as a bulletin feature for the newsletter of CHE-WA (Collaborative on Health and the Environment, Washington State chapter); produced by Steven G. Gilbert.
"We are rightly appalled by the genetic effects of radiation; how then, can we be indifferent to the same effect in chemicals we disseminate widely in our environment?" - Rachel Louise Carson, from Silent Spring
Dichlorodiphenyltrichloroethane, or DDT, was first synthesized by Othmar Zeidler (1859 - 1911), an Austrian chemist, in 1874. In 1939, Paul Hermann Müller (January 12, 1899 - October 12, 1965), a Swiss scientist, resynthesized DDT and recognized its insecticidal properties. In 1948 Müller received the Nobel Prize in Physiology or Medicine for this discovery and for the use of DDT in the control of vector diseases such as malaria and yellow fever. This organochlorine compound was both cheaper (as low as $0.25 per pound in the 40s) and less hazardous than the lead- and arsenic-based insecticides it rapidly replaced. It was hailed as "the wonder insecticide of World War II" for its seemingly low human toxicity but its deadly effects on insects, particularly disease-carrying mosquitoes. It was quickly adopted by the military and was promoted for a range of uses, including wallpaper, and touted as safe for all.
In the 1960s, 400,000 tons were applied annually worldwide, largely for agricultural use, and DDT is credited with eradicating malaria in the southern US. DDT is a neurotoxicant that kills insects by opening neurons’ sodium ion channels, causing the neurons to fire spontaneously and cause spasms and eventual death. Some insects naturally adapted due to mutations in their sodium channel gene, resulting in resistances to DDT and similar insecticides.
DDT is nearly insoluble in water but highly soluble in fats. Like other organochlorine insecticides, it is very persistent, biodegrades slowly, and builds up in the food chain (bioaccumulates). It can be passed to the next generation through breast milk, has long-term health effects, and is often referred to as a PBT: a persistent, bioaccumulative, and toxic compound. It has a disastrous effect on a variety of animals and causes the thinning of eggshells in birds, especially eagles and hawks, resulting in dramatic population declines. In humans, DDT is linked with cancer, endocrine disruption, and reproductive and developmental effects. Sweden banned DDT in 1970 and the U.S. banned it in 1972, after months of hearings, because of environmental concerns.
DDT’s other distinction is its role in giving birth to the modern environmental movement. Rachel Carson dramatically highlighted the environmental health hazards of DDT in her book Silent Spring. This book documented that even a very effective chemical can have extremely serious hazardous properties that must be studied and considered before wide environmental distribution. Today, over forty years after it was banned, DDT and its metabolites are still regularly detected in women’s breast milk and the fat of wildlife.
The story of DDT illustrates the importance of scientific research to evaluate the potential hazardous properties of a chemical and then to take a precautionary approach to manage its use. Only in this way can we benefit from useful chemicals while ensuring that all creatures develop in an environment in which they can reach and maintain their full potential.
