Miao Lei
As a pesticide, DDT is considered as a harmless, efficient and cheap product. With the endorsement of the Nobel Prize, DDT was put on the altar in 1950s. In the fields where DDT was used, there was a bumper harvest of grain, and American farmers even sprayed DDT on each other and cheered and celebrated. After being widely used around the world, scientists discovered a chilling thing: DDT is actually harmful to people and animals!
Spray DDT to celebrate
The whole story began in the 1930s. Before the invention of DDT, most countries were faced with food crisis. Miao Lei's native country, Switzerland, often suffers from locusts, which leads to food loss of crops and people.
locust
What is even more frightening is that harmful insects such as body lice, fleas and mosquitoes can be used as vectors of infectious diseases. During World War II, epidemic typhus took countless lives. This infectious disease caused by rickettsia microorganisms will invade the human body by arthropods such as lice and fleas. The culprit is mosquitoes and pests in farmland. But in fact, there were many kinds of pesticides at that time, but they were either expensive, or their efficacy was not long-lasting, or they easily made pests resistant to drugs, and the effect was average. Effective pesticides are harmful to human beings, such as arsenic arsenide. Miao Lei's childhood friend died of eating fruits and vegetables sprayed with arsenic by mistake.
Wouldn't it be perfect if there was a pesticide that was harmless to human body and environment, deadly to pests and cheap and affordable for African people? Whenever I think of people living in dire straits, Miao Lei, a doctor of chemistry, decides to regain his childhood dream and invent an efficient pesticide. From 65438 to 0935, Miao Lei began a systematic study of pests, and he found that insects and mammals absorbed chemicals in different ways. Following this clue, it took four years and failed 349 times. 1September, 939, Miao Lei found his ideal insecticide-1,1- trichloro-2,2-bis (4- chlorophenyl) ethane, which is DDT.
DDT
But the scientist who synthesized DDT for the first time was not Miao Lei. 1874 records that osma, a Viennese medical scientist, was the first person to synthesize DDT, but at that time he did not investigate the chemical properties of this substance, nor did he understand its function and value. The toxic mechanism of DDT is that chitin penetrates the insect body wall and enters the insect body, which inhibits the transmission of nerve signals, makes the insect muscle spasm or overexcitation, and finally dies of paralysis, similar to snake neurotoxin. DDT has little effect on mammals and is considered harmless.
1940, DDT was patented in Switzerland for the first time, and the Swiss government confirmed its effectiveness against potato beetles and other insects. Subsequently, DDT applied for a patent in other countries and mass-produced it. The invention of DDT is tantamount to dropping a bombshell on pests.
According to the data of the World Health Organization, in Sri Lanka, there are about 1948 new malaria patients 1 10,000 each year, and the number of new malaria patients is 1963. The effect can be described as shock. 1954 The unit yield of farmland in the United States was 60% higher than that in 1943 without DDT. Because DDT is cheap, it is fatal to pests and harmless to human body, and the total usage in the world exceeds 6,543,800 tons.
When the grain harvest is good, American farmers use DDT instead of champagne to spray revelry.
You can also spray DDT when swimming, which will reduce the mosquito repellent effect.
Apply some DDT to the forest to kill pests.
Even the models in fashion magazines use DDT as the surrounding background, which proves that it is safe and harmless to human body. At that time, it seemed that the first life was given by parents, and the second life was given by DDT, because the problems of illness and food were solved. This fanatical pursuit wave successfully sent DDT to the hall of Nobel Prize in 1948. When people were immersed in the joy of DDT, the situation changed 180 degrees.
1962, some scholars found that after using DDT, birds near their homes died one after another, which was thought to be caused by DDT, and called on the masses to stop using DDT as soon as possible. After several months of investigation, it is found that DDT can enter the human body through bioaccumulation, which is harmful to the human body!
Biological enrichment
Due to the stable chemical properties of DDT, it is difficult to decompose in nature, and its concentration will increase along the food chain. After testing, the concentration of DDT in the lake water was 0.000003ppm, which reached 25pm in birds through the food chain, an increase of 8.33 million times! The circulation of nature has also brought DDT to every corner of the world, and even DDT can be detected in the blood of Antarctic penguins and the snow water of Mount Everest.
Eggshell thinning
High concentration of DDT will interfere with the calcium metabolism of birds, make eggshells thinner, and few of them can hatch smoothly, which will seriously affect the reproductive function and bird life span. DDT is a lipophilic and hydrophobic organic substance. For humans, it will be stored in fat cells, which will affect the secretion of human hormones and have a spermicidal effect. In addition, medical research also found that DDT has an impact on liver function, which is potentially threatening and may even cause cancer. DDT has been widely used in the United States, and the damage to the ecological environment and human health is immeasurable. The American people set off a protest movement, demanding a total ban on DDT. Some scientists believe that the use of DDT should be strictly controlled, not banned, because it is very effective in anti-malaria. However, considering the high anti-DDT sentiment of the people, Kennedy, the then American leader, deliberately courted the people for his support rate in the next election, and only publicized the negative effects of the DDT survey results, ignoring the positive effects. Sure enough, Kennedy's approval rating rose.
Nixon
Later, President Nixon used the same method, announcing that the production and use of DDT would be completely stopped and calling on other countries to ban it. From 65438 to 0972, under the leadership of the United States, many countries in the world began to ban the use of DDT, even African countries suffering from malaria. In this way, DDT won the Nobel Prize from 1948 and was banned by many countries in the world from 1972. It only took 25 years. It's really "thirty years in Hedong, thirty years in Hexi".
However, is it really the best choice to disable DDT? After DDT was banned, malaria in Africa revived, and the number of malaria patients in a province in South Africa soared from 8,000 to 40,000. After stopping DDT in Sri Lanka, the number of malaria patients increased by 500,000 within one year. In decades, tens of millions of people died because of banning DDT, more than Hitler killed. Some scientists point out that DDT can be used as an insect repellent to drive mosquitoes out of their homes and avoid the spread of diseases. If the concentration and application range of DDT are limited and only a small amount is used indoors, the incidence of malaria can be reduced by 90%. If used properly, it will not pollute the environment and will not cause harm to the human body.
Malaria patients
By the end of the 20th century, people began to reflect on the benefits of DDT. In 2000, there were 300 million malaria patients in the world, and the number of people who died of malaria every year exceeded 1 10,000, most of whom were Africans. In 2003, South Africa re-used DDT, which directly reduced the number of malaria deaths by 50% within one year. Since then, under the advocacy of the World Health Organization, more countries in Africa have re-used DDT to fight malaria.
The above figure shows the incidence of malaria in Africa without DDT in 2000. The picture below shows the incidence of malaria in Africa in 20 12 years, and the effect is obvious.
From the cheers when DDT was invented, to the protests when the harm was discovered, and then to the reflection when DDT saved malaria patients. It is a poison that poisons the environment and animals, and also an antidote to save malaria patients. In the final analysis, it is not DDT that is wrong, but who uses it and how to use it.