In the 1940s a group of competent toxicologists led by William B. Deichmann conducted a number of thorough studies using state-of-the-art methods to conclude that the active ingredient dichloro-diphenyl-trichloroethane, or DDT, could be safely released to the environment for its use as insecticide. DDT was one of the first wide spread synthetic pesticides, and its widespread use led to resistance in many insect species.
As can be seen in the pictures, DDT was promoted to be used as insect repellent directly on human skin, to treat food products, or to impregnate the wall paper of your children’s room, so they won’t be bothered by mosquitoes. Tender images, such as a mother feeding a baby were used in commercial campaigns to basically sell poison. (*)
In the early 1970s, a scientific article authored by Deichmann (1972) himself and other studies provided enough evidence for the US Environmental Protection Agency to finally forbid the use of DDT as it became known to be toxic to humans, persistent in the environment, travel long distances in the upper atmosphere, and accumulate in fatty tissues of living organisms.
What did actually happen between the 1940s and the 1970s? Why was DDT first considered innocuous or degradable and 30 years later banned and labelled as poisonous for humans, wildlife and the environment?There are several possible answers to these questions.
In the fist place, the ecotoxicity of certain chemicals when applied in small doses may only appear through cumulative effects (cf. http://www.efsa.europa.eu/fr/node/872721). Time is needed for problems to arise, or to become evident.
Second, and most importantly, the capacity of science to detect the adverse effects of a certain molecule released to the environment can progress substantially in 30 years.Problems that were overlooked or remained undetected in the past could be later on well understood and documented. (And the amount of scientific evidence that needs to be accumulated to be able to bend the arm of the chemical industry in court cases is not a minor detail).
The most skeptical opinions, in the third place, would argue that DDT was banned once the patent for exclusive production expired, and /or when the industry was ready to release a new product on the market. But these are just speculations.
What’s important to take home is that examples such as this one should teach us about the long-term risk (uncertainty) associated with the widespread release of toxins into the environment, either as synthetic molecules or through toxin-producing plants (e.g., Cheeke et al., 2012). Alarming ideas such as the commercial release of genetically engineered microorganisms for soil amendment have been underway for a while (e.g. Viebahn et al., 2009), with unknown consequences for soils and the environment.
When it comes to releasing new technologies for food and agricultural production, I’d say it makes sense to follow precautionary principles. Releasing toxins into the environment: another case of organised irresponsibility…
(*) I believe that, nowadays, the baby in the early campaigns of DDT has been replaced by the term ‘sustainability’, which is also used in commercials and websites that advertise poison or toxin-producing plants.
Cheeke, T.E., Todd N. Rosenstiel, and Mitchell B. Cruzan. 2012. Evidence of reduced arbuscular mycorrhizal fungal colonization in multiple lines of Bt maize. American Journal of Botany 99, 700-707. DOI: 10.3732/ajb.1100529
Deichman, W.B., 1972. The debate on DDT. Arch. Toxikol. 29 (Springer), 1 – 27.
Viebahn, M., Smit, E., Glandorf, D.C.M., Wernars, K., Bakker, P.A.H.M., 2009. Effect of genetically modified bacteria on ecosystems and their potential benefits for bioremediation and biocontrol of plant diseases – a review. E. Lichtfouse (ed.) Sustainable Agriculture Reviews 2, Springer, p.45. doi 10.1007/978-90-481-2716-0_4.