DDT disrupts the working of a cell and affects the plasma membrane of the cell, which in this case are the mosquitoes. The job of the plasma membrane is to separate the inside of the cell from the outside and to allow substances to enter and leave the cell, and is made of lipids (fats). DDT is fat soluble so it dissolves into the plasma membrane resulting in the opening of the membrane causing the cell to leak. Potassium and sodium ions slip through the membrane. Potassium and sodium ions help determine when the cell to fire its signals in a nerve cell. Nerve impulses tell the muscles when to contract and relax. However with DDT present, nerve impulses do not fire when they are supposing to.
DDT results in the organism’s death through random uncontrolled contractions of the muscles of by complete loss of muscle control.
Data gathered shows how effective using DDT to decrease malaria cases was. In Sri Lanka, the program reduced cases from about 3 million per year before spraying to 29 in 1964. After 1964, the use of DDT was halted to save money, and malaria increased to 600,000 cases in 1968 and 1969.
South Africa is one country that continues to use DDT under WHO guidelines. In 1996, the country switched to alternative insecticides and malaria incidence increased dramatically. Returning to DDT and introducing new drugs brought malaria back under control. According to DDT advocate “Donald Roberts”, malaria cases increased in after countries in that continent stopped using DDT..Research data shows a significantly strong negative relationship between DDT residual house sprayings and malaria rates. In a research from 1993 to 1995, Ecuador increased its use of DDT and resulted in a 61% reduction in malaria rates, while each of the other countries that gradually decreased its DDT use had large increase in malaria rates. (DDT Wikipedia) [7] Wikipedia can be unreliable as people can add their own information, but I have checked with other sources to confirm the data found in Wikipedia.
Figure 2 below, shows there is a link between the use of DDT and malaria cases. The graph shows that as countries discontinued their house spraying programs, the malaria cases increased. Countries that reported low or reduced HRS also reported in the increase of malaria. Only Ecuador reported a decrease in malaria cases due to the increased use of DDT after 1993. In 1993 malaria cases decreased to -60% after they increased using the DDT spray. Countries such as Peru and Paraguay had an increase of 90% of malaria cases after they stopped using the DDT spray after 1993. Overall the graph shows a real life example supporting the evidence that DDT was an effective solution to Malaria, as countries that used DDT, cases of Malaria were low compared to countries that didn’t use DDT which showed a high number of Malaria cases reported.
Ethical, Economic and Environmental issues
DDT is now banned in Britain due to the many disadvantages that are resulted from the use of it. The economic side was affected because as the pesticide, DDT was used a lot; the mosquitoes became resistant to it. Mosquitoes that were not affected by DDT were the ones that survived and passed on their resistance to their offspring. Where DDT was used a great deal, most of the mosquitoes are now resistant to it. (Guardian newspaper) [8] That was a waste of money as the testing of DDT was costly so when mosquitoes became resistant to it, it was costly. And in the end it was harmful to us and the insects were breeding generations that were immune to the effect of DDT.
Environmental issues:
The use of DDT also has an impact on the environment because it flows into rivers from the soil which indirectly leads to the accumulation of the DDT along food chains. (Marinebio) [9] As the DDT breaks down in the environment, it damages it. DDT is persistent in the environment because it is not degraded by sunlight or heat; however it is broken down by the product DDE which is produced by enzymatic metabolism in organisms. (Science environmental effects of DDT) [10] They also get into the water supplies when there is heavy rainfall, which is dangerous for humans. They get washed into the soil and spread throughout the waterways. DDT is insoluble it water which means it cannot be diluted so it is an abundant chemical in the Earth’s environment and in organisms. This chemical pollution may kill many organisms some distance from the crop. DDT was even found in the penguins in the Antarctic. Presumably it had been in the fish they had eaten. (DDT factsheet) [11]
Benefits and risks of DDT spray
The only advantage of using DDT was to humans. As the DDT is very strong, only a tiny amount needs to be used and so it is a cheap and effective way of preventing malaria, which devastates a huge number of people every year. (DDT: Sniffing out excellent white powder, Roberts D) [12]
There were many disadvantages of using the DDT on humans, other organisms and the environment. DDT spray was so good and effective in killing insects so large quantities of it was used which increased the amount of the chemical in the world. As a lot of DDT was used, the risks which resulted from the DDT increased which is spoken more about below.
Other organisms and animals were affected as DDT was sprayed on the crops to kill the insects. However, it was not realised at the time that DDT was a very long lasting chemical. It stayed in the soil which was sprayed on for up to ten years and plants grow in the soil absorbed the DDT. When humans ate these crops, the DDT was not excreted and remained in their lipid tissues. This did not directly harm the humans who had DDT in their lipid tissues, but it did harm to animals. DDT appeared in the lipid of animals throughout all the food webs where primary consumers fed on sprayed crops and where DDT drained from crops into waterways so the DDT is passed on as predators eat preys with DDT in them which can cause their death. (“Human Detoxification from the Effects of Living in Our Polluted Environment”)
An alternative solution - Antimalarial tablets
The use of anti-malarial drugs before entering a malaria prone area, is advisable, and the use of Chloroquine, which interferes with the development of the parasite by reaching high concentrations in the vacuoles of the parasite, which due to its alkaline structure raises the internal pH. By raising the pH levels in the parasite vacuole, toxic chemicals are released, thus poisoning the parasite through excess levels of toxicity. (Wikipedia – Antimalarial medication) No antimalarial medicine is totally effective, but your risk of malaria will be greatly reduced if you take the right medicine for your destination. (Travel Doctor, Malaria information page) [13]
Chloroquine helps to prevent malaria developing if you take it properly. If you have diarrhoea or vomiting it may be less effective. Chloroquine was used in the past, but in most parts of the world malaria has become resistant to it. This means that it will not protect you from malaria in most regions. If a malaria-carrying mosquito bites you then you could still contract malaria. It can be used on its own or in combination with other antimalarials to increase its effectiveness. It can also be used to treat some forms of malaria. (NHS Malaria) [14] I think this source is reliable because it’s a national service which people use daily to diagnose all types off illness’s and treatments.
All medicine has side effects and the side effects of chloroquine are: feeling or being sick, diarrhoea which can be overcome by drinking plenty of water and replacing any lost fluids. Headaches will occur, your skin may become more sensitive to sunlight and loss of hair, changes to skin colour, skin rash and mood changes will happen. (Patient UK, Chloroquine) [15]
The advantage of Chloroquine is that it’s the least expensive, best tested and safest drug of all available drugs.
An alternative solution - Insecticide-treated mosquito nets
Mosquito nets help keep mosquitoes away from people and greatly reduce the infection and transmission of malaria however even small holes in the nets will allow mosquitoes to enter so the nets are not a perfect barrier and they are now treated with an insecticide designed to kill the mosquito before it has time to search for a way past the net. Insecticide-treated nets (ITNs) are estimated to be twice as effective as untreated nets and offer greater than 70% protection compared with no net. (Malaria, Wikipedia) [16] The female Anopheles mosquito, which spreads malaria by transmitting the Plasmodium parasite to humans, is nocturnal. She only bites at night. Therefore, an insecticide-treated bed net can be an extremely effective tool in the prevention of malaria. A mosquito net is hung up over the middle of a bed so that it completely covers one or more sleeping persons. Mosquito nets not only create a barrier to mosquitoes, but the insecticide kills mosquitoes on contact as well, creating limited protection even for family members sleeping outside the net. (FAQ malaria campaign) [17] Although ITNs are proven to be very effective against malaria, less than 2% of children in urban areas in Sub-Saharan Africa are protected by ITNs. (East African Community Health) [18] The net should be small-meshed, with no holes, and tucked in under the bottom sheet. When sleeping outdoors or in an unscreened room, have an insecticide-treated mosquito net around your bed.
During the day, it should be rolled up, so mosquitoes and other insects can't get inside while it's not in use. (“Jon. N, 2002, ‘Taming the mosquito’, New Scientist, Volume, May 25th, pg 8) [19] this is a reliable source because the book is very scientific and has all the information about malaria with prevention methods. Information which I picked out from the book, I confirmed it with sources from the internet. Also it being unbiased makes it reliable.
The graph below shows the total number (in millions) of insecticide-treated nets produced by UNICEF between 2000-2006. It increased from 1 million in 2000 to 25 million in 2006.
An alternative solution – Pyrethroid (Alternative of DDT)
There are 9 other insecticide which can be used other than the DDT. Pyrethroid is an insecticide which can be used to prevent the spreading of malaria as it does the same job as DDT, by killing the mosquitoes when they get into the house. The insecticide pyrethroid does not have any issues connected with it; the only disadvantage of it compared to DDT is that it’s very costly. Advantages of using pyerthroid follow from: Low in toxicity to mammals, fast acting and require low doses to kill insects. [U.S National library of medicine, 2000 December] [20] I think this is a reliable source because it’s from a web based library and is not biased as there is lots of information available on the DDT.
Conclusion
In conclusion the most reasonable ways to tackle the malaria problem and to prevent the spreading of the disease is to educate and inform the people travelling abroad, mainly to Africa. This can be done through the use of creating TV advertisements, posters and leaflets. The best prevention method seems to be the Insecticide-treated mosquito nets because there are no social, enviromental and economic impacts. However ITN are good in the short run because the effect is immediate but as said above, the mosiqitoes may become resistant to it and will not be effective.
The use of DDT spray is to be said the most effective method but because the cons overcomes the pros, I think that solution is not good, mainly due to the environmental and economic impacts.
Three sources that I have used are: , which is a scientific malaria information page, a bit like a journal where I gained most of the information on malaria. I think this source is reliable because it is unbiased, as it talks about everything about the disease and also it is published by doctors. The fact that all the information about malaria on the website is backed up by figures, makes it very reliable, for example “Malaria occurs in over 100 countries and more than 40% of the people in the world are at risk”. I have checked this statement from the “traveldoctor” website with other websites and they show similar data. Also as the website is made by doctors, it has been peer reviewed and has gone through the stages of ensuring the data is valid, making the source reliable.
My second source was a book which was non web-based, “Jon. N, 2002, ‘Taming the mosquito’, NewScientist, Volume, May 25th, pg 8. This Book being unbiased and not one sided makes is reliable as it gave all the information about the disease and scientific books such as this one are mostly always reliable.
The final source I used was another web based website, . The reason why I used this source was because I needed to confirm my data which I found from my other sources. All the information is detailed which makes the source reliable.
Data such as “The female Anopheles mosquito, which spreads malaria by transmitting the Plasmodium parasite to humans, is nocturnal. She only bites at night. Therefore, an insecticide-treated bed net can be an extremely effective tool in the prevention of malaria” is from a website which can be seen as unreliable and inaccurate as the website was a question and answer where people answer peoples questions. However I found this piece of information from the website and checked it with other sources and found it was correct. I also checked that piece of data with a non web based source and found the same information so I used it. As people are answering questions on the website, “ “, it can be incorrect.
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