Researchers rediscover fast-acting German insecticide lost in the aftermath of WWII

Researchers rediscover fast-acting German insecticide lost in the aftermath of WWII
A monofluoro analog of DDT, as seen through an optical microscope. Solid fluoridated forms of DDT killed insects more quickly than did DDT. Credit: Xiaolong Zhu and Jingxiang Yang, NYU Department of Chemistry

A new study in the Journal of the American Chemical Society explores the chemistry as well as the complicated and alarming history of DFDT, a fast-acting insecticide.

"We set out to study the growth of crystals in a little-known insecticide and uncovered its surprising history, including the impact of World War II on the choice of DDT—and not DFDT—as a primary insecticide in the 20th century," said Bart Kahr, professor of chemistry at New York University and one of the study's senior authors.

Discovering solid forms of DFDT

Kahr and fellow NYU chemistry professor Michael Ward study the growth of crystals, which two years ago led them to discover a new crystal form of the notorious insecticide DDT. DDT is known for its detrimental effect on the environment and wildlife. But the new form developed by Kahr and Ward was found to be more effective against insects—and in smaller amounts, potentially minimizing its environmental impact.

In continuing to explore the crystal structure of insecticides, the research team began studying fluorinated forms of DDT, swapping out chlorine atoms for fluorine. They prepared two solid forms of the compound—a monofluoro and a difluoro analog—and tested them on fruit flies and mosquitoes, including mosquito species that carry malaria, yellow fever, Dengue, and Zika. The solid forms of fluorinated DDT killed insects more quickly than did DDT; the difluoro analog, known as DFDT, killed mosquitoes two to four times faster.

"Speed thwarts the development of resistance," said Ward, a senior author on the study. "Insecticide crystals kill mosquitoes when they are absorbed through the pads of their feet. Effective compounds kill insects quickly, possibly before they are able to reproduce."

The researchers also made a detailed analysis of the relative activities of the solid-state forms of fluorinated DDT, noting that less thermodynamically stable forms—in which the crystals liberate molecules more easily—were more effective at quickly killing insects.

Researchers rediscover fast-acting German insecticide lost in the aftermath of WWII
Allied military officials who interviewed German scientists after World War II dismissed their claims that DFDT (also known as "Gix" or "Fluorgesarol") was faster and less toxic to mammals than DDT, calling their studies “meager” and “inadequate” in military intelligence reports. Image credit: Combined Intelligence Objectives Sub-Committee Report on Insecticides, Insect Repellents, Rodenticides and Fungicides of I.G. Farbenindustrie A.G.,1945 (declassified)

The forgotten history of DFDT

In addition to their chemical analyses, the researchers sought to determine if their creation had a precedent. In doing so, they uncovered a rich and unsettling backstory for DFDT. Through historical documents, they learned that DFDT was created as an insecticide by German scientists during World War II and was used by the German military for insect control in the Soviet Union and North Africa, in parallel with the use of DDT by American armed forces in Europe and the South Pacific.

In the post-war chaos, however, DFDT manufacturing came to an abrupt end. Allied who interviewed Third Reich scientists dismissed the Germans' claims that DFDT was faster and less toxic to mammals than DDT, calling their studies "meager" and "inadequate" in military intelligence reports.

In his 1948 Nobel Prize address for the discovery of the insect-killing capability of DDT, Paul Müller noted that DFDT should be the insecticide of the future, given that it works more quickly than does DDT. Despite this, DFDT has largely been forgotten and was unknown to contemporary entomologists with whom the NYU researchers consulted.

"We were surprised to discover that at the outset DDT had a competitor which lost the race because of geopolitical and economic circumstances, not to mention its connection to the German military, and not necessarily because of scientific considerations. A faster, less persistent insecticide, as is DFDT, might have changed the course of the 20th century; it forces us to imagine counterfactual science histories," said Kahr.

The need for new insecticides

Mosquito-borne diseases such as malaria—which kills a child every two minutes—are major public health concerns, resulting in 200 million illnesses annually. Newer diseases like Zika may pose growing threats to health in the face of a changing climate.

Mosquitoes are increasingly resistant and are failing to respond to the pyrethroid insecticides built into bed nets. Public health officials are concerned and have reconsidered the use of DDT—which has been banned for decades in much of the world with the exception of selective use for malaria control—but its controversial history and environmental impact encourage the need for new insecticides.

"While more research is needed to better understand the safety and environmental impact of DFDT, we, along with the World Health Organization, recognize the urgent need for new, fast insecticides. Not only are fast-acting insecticides critical for fighting the development of resistance, but less can be used, potentially reducing its ," said Ward.


Explore further

Copy-number variants in insecticide resistance in malaria mosquitoes

More information: Xiaolong Zhu et al, Manipulating Solid Forms of Contact Insecticides for Infectious Disease Prevention, Journal of the American Chemical Society (2019). DOI: 10.1021/jacs.9b08125
Citation: Researchers rediscover fast-acting German insecticide lost in the aftermath of WWII (2019, October 11) retrieved 14 October 2019 from https://phys.org/news/2019-10-rediscover-fast-acting-german-insecticide-lost.html
This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.
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Oct 11, 2019
If they're thinking about using DFDT to control mosquitoes, let's have a thorough environmental impact study on the chemical this time. We would know better than to drench farm fields with it like we did DDT...wouldn't we?

Oct 12, 2019
Twentieth century scientists were negligent regarding the wholesale use of DDT. Let us hope that it never happens again with any other insecticide compound.

Oct 12, 2019
Actually, little research was done to determine the toxicity of DDT, particularly among birds. Silent Spring (of which you may have heard) says, paraphrased on Wikipedia:
environmental impacts that coincided with widespread use of DDT in agriculture in the United States, and it questioned the logic of broadcasting potentially dangerous chemicals into the environment with little prior investigation of their environmental and health effects.
I have myself seen a silent spring: in Taiwan in April. Not a bird to be heard or seen. I was glad to be out of there, and worried about what I'd been exposed to.

Oct 12, 2019
If they're thinking about using DFDT to control mosquitoes, let's have a thorough environmental impact study on the chemical this time. We would know better than to drench farm fields with it like we did DDT...wouldn't we?


use ddt as instructed and there are no environment concerns.

Oct 12, 2019
@Shootist.
use ddt as instructed and there are no environment concerns.
It bio-accumulates in animal tissues and affects their hormonal systems. In birds in articular it adversely affects the system for making robust eggshells needed for protecting/incubating the chicks. IT was the thinning and compromising of the eggshells that caused the "Silent Spring" catastrophe mentioned by DS above, where bird populations plummeted, and with that went the birds that ate pest species of insects which would otherwise proliferate uncontrolled and cause disease/losses in agriculture and human health. It's a complex 'web' that makes our world, mate; and everything's connected; so sudden removal of long adapted beneficial species is fraught with danger for humans and the agriculture/environment on which we depend for OUR longterm sustainability/survival. Think more deeply before making hasty decisions about what is or is not 'safe'. Good luck to us all. :)

Oct 12, 2019
So then there's no birds to eat the bugs, so we have to use more insecticide.

Gee, that looks like a positive feedback loop from the point of view of insecticide use. I don't want to eat more insecticide; it just doesn't seem like a good idea. It also looks like a scam by insecticide manufacturers, against the farmers who have to buy the stuff, then deploy it, and then deal with liability for any accidents, all for a service they were getting for free before when the birds ate the bugs.

Oct 12, 2019
So then there's no birds to eat the bugs, so we have to use more insecticide.

Insecticides are responsible for the decline of birds too. Of course this isn't news is it. In 1960 the National Film board of Canada made a film called Poisons, Pests and People; predating Silent Spring, but with the same message, that is still being ignored.

23 hours ago
The replacement for DDT in controlling mosquito populations, so people wouldn't be dying to malaria and dengue in the millions, is spraying ponds and waterways with diesel and kerosene. It's a very popular method in India.

The persistent oil slick drowns the mosquito larvae.

22 hours ago
Yummy, kerosene-flavored fish. :P

21 hours ago
As with many beneficial chemicals banned due to public sentiment stirred up by environmentalists, there was little actual science backing the claims. The studies suggesting egg-shell thinning in birds were poorly designed and more recent studies have found that there are multiple factors in egg-shell thinning having nothing to do with DDT and that thin shells do not correlate to increased mortality. For example:

https://onlinelib....00132.x

DDT is moderately toxic to humans, meaning it's extremely unlikely for someone to be harmed by it. Like glyphosate (Roundup) there are no definitive, replicable studies demonstrating that it is carcinogenic. Studies suggesting other possible adverse effects in humans are weak. Further study is required to establish definitively that there are adverse effects, but so far the benefits of DDT in hundreds of millions of lives saved far outweigh the possible negative impacts.


20 hours ago
there was little actual science backing the claims


But you have to remember, since it is possible that DDT was killing the birds, making the Pascal's Wager was justified. Since it is possible that an environmental catastrophe is happening, it is justified to simply make up your facts, in order to avoid the catastrophe you just made up...

(Compare: Pascal's Wager is a bet about avoiding hell by believing in God, where "hell" is already predicated in your belief in God. I.e. if God exists then hell exists, therefore you must believe in God in order to avoid hell no matter how unlikely it is. The fallacy is in the fact that you first assume hell in order to believe in God, while in reality you cannot assume hell before you assume God - i.e. you can't predict disasters before you identify the causes - otherwise you're just making it up as you go along.)

14 hours ago
use ddt as instructed and there are no environment concerns.


None? Whatsoever? I'd ask for evidence, but given the trollish nature of the post I doubt it's worthwhile. Not to mention the problem of actually enforcing limited use.

13 hours ago
@aksdad.

Because hormone-like effects of some man-made chemicals (ie, "Endocrine Disruptors") produced/used at industrial scales accumulate up the food chain, it is critical to test ALL species for THEIR particular response to such disruption to their WHOLE metabolic processes. Survivability in the LONG term may be different for each species (much the same way some drugs affect different people differently depending on THEIR particular genetic/physiological response to the SAME drug). You need to connect ALL the dots. Egg-shell thinning was merely an INDICATOR (think: "canary in the coal mine") that something was going terribly wrong in the environment. The PROOF was in the BANNING of DDT; egg-shell-thinning abated; bird species/populations rebounded. The MAIN WORRY NOW is the extreme heat (as happening in OZ and other parts of the globe) which result in birds/bats 'dropping out of the skies/trees'; and wild/domesticated LAND ANIMALS dying from heat stroke. Wake up, mate. :)

13 hours ago
They may try to dismiss Rachel Carson's 1970s book "Silent Spring," but the facts are that biodiversity is dwindling, and the long food chain is involved too--what eats mosquitoes such as birds, frogs, and that most aerial spraying ends up in the water somewhere--oceans, rivers, streams, groundwater. At least they admit that it was during WW2 that DFDT/DDT was created. Further, fluoride like ammonia, has been accused of being a nuclear runoff product.

13 hours ago
This comment has been removed by a moderator.

10 hours ago
The cessation of use of DDT cost the lives of about 40 million Africans and Asians. Greece, prior to bans was rendered malaria free, thanks to DDT. Kooks wanting to ban insecticides are putting the world's food supply at great risk and it's because of insect-control (and GMO crops) that it is possible today to have less starvation than 30 years ago.

10 hours ago
@Boy, it's not banned from vector control, only restricted. It's banned from agricultural use, and there are more effective control measures particularly since the insects were becoming immune to it.

So, I'm calling bullshit on your post.

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