传统农业
“有机农业通常会增加物种丰富度，平均比传统农业系统高出30%。然而，不同研究的结果各不相同，其中16% 的研究实际上表明有机农业对物种丰富度有负面影响。[.
DDT
到目前为止，我们食物中的大多数农药都是植物产生的天然农药。这让我们不得不思考人工化学物质是否对我们更有害。毕竟，并非所有物质都是一样的，有些物质（如 <anchor>DDT</anchor>）在环境中停留的时间更长。同样，有些物质大量喂食给实验室老鼠是有害的，但少量喂食则不会造成太大的危害，甚至不会有益，因为有研究表明，小剂量的毒素实际上对生物体有益，因为它会使生物体对轻微的压力作出反应。[ 需要验证]
Use of DDT in fighting malaria
# Use of DDT in fighting malaria

From Appropedia

(Redirected from DDT)

Malaria affects people in many countries, including many African and Asian countries, and countries of the Americas as far north as Mexico. DDT has been an effective tool in fighting malaria, but at a high cost to the environment and human health.

As mosquitoes have developed resistance to DDT and alternatives have become available, the use of DDT has been greatly restricted. A global ban has not been implemented, however, as its particular properties make it useful in certain very restricted settings where local strains of mosquito are susceptible, and where dispersion in the environment can be minimized. Environmental groups, notably the WWF,W are lobbying for effective alternatives to DDT to be developed and implemented, allowing it to be eventually eliminated.

## Contents

## History[ edit | edit source]

DDT ( d ichloro d iphenyl t richloroethane) is a synthetic pesticide with a controversial history.

DDT's insecticidal properties were discovered in 1939, and it was used in the second half of World War II to control the insect-borne diseases, malaria and typhus. This led to a Nobel Prize in Physiology or MedicineW in 1948.[1] After the war, DDT was used as an agricultural insecticide, and its production and use skyrocketed.[2]

## Bans and restrictions on DDT use[ edit | edit source]

In 1962, Silent Spring by American biologist Rachel Carson was published, describing the environmental impacts of the indiscriminate spraying of DDT in the US and questioned the logic of releasing large amounts of chemicals into the environment without fully understanding their effects on ecology or human health. The book suggested that DDT and other pesticides may cause cancer and that their agricultural use was a threat to wildlife, particularly birds. Its publication was one of the signature events in the birth of the environmental movement, and resulted in a large public outcry that eventually led to DDT being banned in the US in 1972. DDT was subsequently banned for agricultural use worldwide under the Stockholm Convention, but its limited use in disease vector control continues to this day and remains controversial.[3]

Along with the passage of the Endangered Species Act, the US ban on DDT is cited by scientists as a major factor in the comeback of the bald eagle, the national bird of the United States,[4] from near-extinction in the contiguous US.[5]

Rachel Carson endorsed limited use of insecticide when needed - noting that limited rather than wasteful use would reduce problems of resistance.[6]

### Production and use statistics[ edit | edit source]

From 1950 to 1980, when DDT was extensively used in agriculture—more than 40,000 tonnes were used each year worldwide[7]—and it has been estimated that a total of 1.8 million tonnes of DDT have been produced globally since the 1940s.[8]
Today, 4-5,000 tonnes of DDT are used each year for the control of malaria and visceral leishmaniasis, with India being the largest consumer. India, China, and North Korea are the only countries still producing and exporting it, and production is reportedly on the rise.[9]

## The benefits of DDT[ edit | edit source]

There has been lobbying to prevent a global ban on DDT,W largely arguing for the importance of its role in preventing malaria.

DDT is associated in the public mind with harm to ecosystems, and it has mostly been replaced with other pesticides with less persistence in the environment. However it remains effective in specific settings where other pesticides are not.

## Malaria[ edit | edit source]

India, Brazil and Mexico, where 69% of all reported cases of malaria occur (Mosq Control Assoc, 1998). Malaria afflicts hundreds of millions of people and causes millions of human deaths each year. Swiss scientist Paul Muller was awarded the 1948 Nobel Prize in Physiology or Medicine for discovering (1939) DDT's insecticidal properties.

DDT kills mosquitoes. Malaria is transmitted to humans via mosquito bites. According to U.N. estimates, malaria kills one child every 30 seconds and more than a million people each year. [1]

## Appropriate use[ edit | edit source]

DDT is best used on surfaces, especially indoors, as a weapon against the resting mosquito. It is:

- Potent - just two grams of DDT per square meter of wall surface is more than enough to kill a mosquito within its usual one-hour resting period.
- Inexpensive.
- Easily stored and transported[ verification needed]
- Relatively safe for the person doing the spraying.[ verification needed]
- Long lasting - it remains effective for many, many months.[ verification needed]

Inappropriate use includes spraying into the environment, where its long-lasting nature becomes a harmful property.

## The environmental impact[ edit | edit source]

DDT is associated in the public mind with harm to ecosystems, and it has mostly been replaced with other pesticides with less persistence in the environment.

But the environmentalist will have a hard time thinking of the condition of many species if the 1972 U.S. ban of DDT would not have been successful.[10] The most important thing at this point will be an in-depth study on whether it would be beneficial for countries with the malaria epidemic to use DDT as a preventative measure. They will also have to keep in mind how DDT will impact not only the health of humans, but the habitats of animals and other wildlife that may be negatively affected by the insecticide. For species that rely on insects for food, using DDT could ruin a population even if it is benefiting another.

From an environmental standpoint, it would sound absolutely crazy to be using a toxic insecticide to aide in an epidemic like malaria.

## Using DDT to stop malaria in African countries[ edit | edit source]

The African American Environmentalist Association believes that DDT (Dichloro-diphenyl-trichloroethane) insecticide should be used to prevent deaths from malaria in African countries. DDT is an organochlorine pesticide that has been used as an insecticide in agriculture and to combat insect vectors of diseases such as malaria and typhus. Because of its effectiveness at killing insects with few acute effects on humans, DDT had been a mainstay to fight malaria, a parasitic disease that is a growing health threat in Africa and other parts of the world.

## Controversy[ edit | edit source]

Controversy has been fanned by claims of millions of deaths resulting from a ban in the use of DDT. This is a simplistic and inaccurate picture of what has actually happened - for a start, DDT has never been completely banned.

### WWF's call for an eventual ban[ edit | edit source]

WWF initially called for a global phaseout and eventual ban on DDT production and use by the year 2007, together with financial and technical assistance to the developing world. The 2007 deadline was intended as a motivational tool to encourage the necessary financial and technical assistance. The proposal of a 2007 deadline drew considerable public attention to the scope of the world's malaria problem and the need to implement alternatives to DDT.

However, it also raised fears that DDT would be phased out without sufficient guarantees of protection of public health from malaria. To allay these fears, WWF has set aside discussion of the 2007 deadline, while retaining its commitment to eliminating DDT. Both the UNEP and WHO recognize that such elimination can be a "win-win" situation for public health and environmental protection.

DDT is also used in crop growth, and has been linked to the cause of attention deficit hyperactive disorder (ADHD) and also have an affect on the developing stages for children still in the utero. [ verification needed]

### Malaria Foundation International[ edit | edit source]

The Malaria Foundation International [2] expresses fears of a rush to ban DDT before alternatives are in place, noting that in certain situations (giving the examples of KwaZulu-Natal and Ethiopia) there are few effective or affordable alternatives. Their website states:

- Malaria and leishmaniasis are diseases that are in resurgence in many parts of the world. Diminished control efforts are, at least in part, responsible for this resurgence (Roberts et al. 1997, Roberts et al. 2000, Baird 2000).
- The MFI has supported an eventual (not immediate) ban, with the proviso that an effective and affordable replacement is found before DDT is banned.
- DDT is one tool of many in the malaria control worker's toolbox. The reason that it is being discussed at this site is that, unlike other tools, there is an imminent danger of it being taken away. This puts not just health, but lives, at stake. The MFI wants to see all possible tools for malaria control be readily available, because malaria is a serious, resurgent problem with drug resistance and increasing numbers of illnesses and deaths. [3]

## DDT and the POPs Treaty[ edit | edit source]

The Stockholm POPs Convention, a treaty to phase out persistent organic pollutants (POPs), including DDT, is currently open for ratification. WWF welcomes this historic agreement which involved provisions for phasing out DDT, while still allowing for its continued limited use for malaria control.

Evidence continues to accumulate about the dangerous health effects associated with DDT. The treaty provisions appropriately balance the need to reduce these hazards while promoting stronger malaria control programs. The accord states that "with the goal of reducing, and ultimately eliminating the use of DDT," individual countries may continue to use the chemical for controlling malaria. However, these countries will also be encouraged to prepare national implementation plans to reduce their reliance on DDT.

Specifically, the national plans would promote methods for reducing illegal uses of DDT, such as agricultural applications. Countries would also identify steps to implement alternative approaches and promote measures that strengthen health care and reduce the incidence of malaria. The parties to the treaty will periodically review the status of alternative approaches to determine whether DDT is still needed or whether it can be eliminated completely. [4]

## External links[ edit | edit source]

## References[ edit | edit source]

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