Paul Müller and the Doubtful Qualities of DDT

Paul Müller (1899 - 1965)

Paul Müller (1899 – 1965)

On January 12, 1899, Swiss chemist and Nobel Laureate Paul Hermann Müller was born. Müller received the 1948 Nobel Prize in Physiology or Medicine for his 1939 discovery of insecticidal qualities and use of DDT in the control of vector diseases such as malaria and yellow fever.

“We have discovered many preventives against tropical diseases, and often against the onslaught of insects of all kinds, from lice to mosquitoes and back again. The excellent DDT powder which had been fully experimented with and found to yield astonishing results will henceforth be used on a great scale by the British forces in Burma and by the American and Australian forces in the Pacific and India in all theatres.”
— Winston Churchill, September 24, 1944 [6]

Paul Müller – Youth and Education

Paul Hermann Müller’s father was employed as a businessman by Swiss Rail. He spent his early childhood in Lenzburg (Canton Aargau) before his family moved to Basel. Here Paul Hermann Müller attended the Freie Evangelische Volksschule, later the Untere and the Obere Realschule.. Already during his later school years Paul Müller had a small laboratory where he was able to develop photographic plates or build radio equipment. Because of bad grades he left the Obere Realschule in 1916 to work as a laboratory assistant at Dreyfus and Company. He became assistant chemist in the Scientific-Industrial Laboratory of the electrical plant of Lonza A.G one year later. After returning to his formal education, Paul Müller earned his high school diploma by 1919 and entered Basel University in the same year. There he studied chemistry with a minor in botany and physics. He also studied inorganic chemistry under professor Friedrich Fichter. In 1922, Müller continued his studies in the organic chemistry lab of Hans Rupe. Paul Müller received his PhD on Die chemische und elektrochemische Oxidation des as. m-Xylidins und seines Mono- und Di-Methylderivates (The Chemical and Electrochemical Oxidation of Asymmetrical m-Xylidene and its Mono- and Di-methyl Derivatives) in 1925 under the supervision of Fichter.

Seed Disinfectants

During the same year Paul Müller began working as a research chemist for the dye division of J. R. Geigy AG in Basel. When Geigy started researching moth- and plant-protection agents, Müller was especially enthusiastic for plant protection, intending to start synthesizing chemical plant protection agents himself. Müller was able to patent a technique for synthesizing novel rhodanide- and cyanate-based compounds which showed bactericide and insecticide activity and developed the seed disinfectant Graminone, which is still used as a herbicide today.

Synthetic Contact Insecticides

Since 1935 Müller was systematically working in the field of synthetic contact insecticides. He first formulated requirements for an optimal effect of these substances, developed numerous animal experimental techniques for the quantitative determination of the effect and then synthesized several hundred substances whose effects he tested. While working on the topic, Müller found out that insects absorbed chemicals differently than mammals, which led him to the assumption that there must be chemicals toxic exclusively to insects.

The Development of DDT

While attempting to create an insecticide that was long-lasting and cheap to produce, Müller was motivated by a food shortage in Switzerland and a typhus epidemic in Russia. After 349 attempts, Paul Müller finally found the compounds he was looking for. The compound he had placed in the cage was dichlorodiphenyltrichloroethane (DDT), which he had produced by condensation of chloral with chlorobenzene. Müller quickly realized that DDT was the chemical he had been searching for. Tests of DDT by the Swiss government and the U.S. Department of Agriculture confirmed its effectiveness against the Colorado potato beetle. In 1942 the first preparations based on DDT, “Gesarol” and “Neocid” appeared on the market. Through the use of DDT, a series of epidemics in which insects act as vectors (typhoid fever, cholera, spotted fever) could be contained during the Second World War.[4] Further tests demonstrated its astonishing effectiveness against a wide range of pests, including the mosquito, louse, flea, and sandfly, which, respectively, spread malaria, typhus, the plague, and various tropical diseases.

Nobel Prize and Side Effects

It later became apparent that the substance had already been shown in 1872 by Othmar Zeidler in the laboratory of Adolf v. Baeyers in Strasbourg. However, Müller was the first to recognize the insecticidal effect of this compound, which proved to be far superior to all previously known insecticides.[4] He synthesized a large number of homologous compounds, the testing of which provided valuable information on the relationships between the structure and mechanisms of action of this substance class, but which all lagged behind DDT in their effect. For a long time, the test methods developed by Müller formed the most important basis for all developments in the field of insecticides.[4] In 1948 Müller was awarded the Nobel Prize for Medicine “for discovering the strong effect of DDT as a contact poison against several arthropods“.[1] It was the first time that this prize was awarded to a non-physician.

DDT was later used to combat malaria, sleeping sickness and some livestock diseases in tropical countries. The extermination of the Anopheles mosquito, the carrier of the malaria virus, saved millions of lives. DDT is only slightly toxic for humans. Since about 1970, however, it has been recognized that it can only be degraded very slowly in the biosphere and accumulates in the organisms of the food chain, which leads to extreme stresses on ecosystems.

Müller worked for Geigy until his retirement in 1961, from 1946 as Deputy Director, from 1959 as Deputy Director. He died in the early morning of October 13, 1965 in Basel after a short illness .

Do we really need pesticides? – Fernan Pérez-Gálvez, [9]

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