Malaria Control Policy Formulation Regarding DDT Use - Essay Example

? DDT (dichlorodiphenyltrichloroethane) is a well-known controversial organo-chlorine insecticide. Originally prepared in 1873, its insecticidal properties were discovered later in 1939. It was used extensively worldwide, for the successful elimination of insect pests in agriculture sector and insect vectors (causing malaria and typhus) in public health sector until a debate on its advantages and disadvantages was initiated. Research proved DDT as a persistent chemical with toxic effects in human beings. It was also found to be responsible for environmental hazards like bio-accumulation and bio-concentration in food chain. Since 1972, most of the developed countries have banned the usage of DDT and a recent Stockholm Convention strictly banned or restricted the use of DDT in around 100 countries. This paper covers the history of DDT, its chemical presentation, current usage, toxic effects on human health and environment, its degradation and its role in control of malaria. This paper reviews malaria control policy formulation regarding DDT use and consequently weighing its detrimental health and environmental effects. Also, it provides a brief description of alternatives to DDT, long term management programs and a pre-requisite organized approach by the concerned authorities to control pests and vectors. Introduction: DDT (dichlorodiphenyltrichloroethane) was first synthesized in 1874 by Zeidler. Its insecticidal properties were later discovered by Paul Mueller in 1939, a chemist researching on development of diverse chemicals to deal with agricultural insects, for a Swiss firm Giegy. He was awarded the Nobel Prize for medicine and physiology in acknowledgment for his remarkable efforts in 1948 (Fiedler, Borja-Aburto, 2003). By the end of World War I, estimated deaths caused by typhus reached more than 5 million. This caused extensive precautionary measures to avoid epidemics during World War II and civilians and allied troops soldiers in Pacific were sprayed with DDT to combat insect vectors (mosquitoes and lice) predominantly malaria and typhus. Eventually after the war in 1945, DDT was employed as an insecticide for public health purposes, among both military and civilian populations to eliminate insect vectors that cause diseases. Also, it was used widely to control insect pests found on agricultural crops (fruits, vegetables and cotton), live stock production, institutions, homes and gardens. DDT quick success as a pesticide led to its extensive use in US and other developed countries a total of approximately 1,350,000,000 pounds of DDT was used domestically. Its popularity was owed to its cost efficiency, control effectiveness, persistence and versatility. History: Initially, DDT was thought to be an ideal insecticide due to its high toxicity to insects/pests and low toxic effects in human beings. Its high persistent rates were considered a further advantage. However, the scientific community soon started to question its credibility and began research on harmful effects of DDT. During the late 1950s and 1960s, the food and environmental regulatory authorities (principally Environmental Defense Fund, the National Audubon Society, the National Wildlife Federation, and the Izaak Walton League) demanded a restriction on use of DDT because of increasing evidence of this pesticide’s declining benefits and toxicological and environmental effects. In particular, Rachel Carson’s book Silent Spring published in 1962, created awareness about environmental problems associated with DDT in general public. In this book, she discussed in detail the decline of American robin in certain regions due to consumption of earthworms laden with DDT to combat Dutch elm disease. Carson’s book initiated concerns in general public about the indiscriminate use of DDT and other pesticides and thus through a series of legal hearings, in 1972 DDT use was banned or restricted in US (EPA, 1975). Most of the developing countries Sweden, Belgium, France etc followed the suit however, in developing countries DDT is still being used in huge amounts particularly in control of malaria carrying mosquitoes. Current status, Production and Usage: Under the United Nations Environmental program, countries have joined together and negotiated a treaty to impose ban and restriction on use of Persistent Organic Pollutants (POPs) worldwide. This is known as Stockholm Convention of POPs which seeks the elimination of 12 pesticides one of which is DDT. In lieu of the fact that DDT is majorly used for prevention of malaria and sudden ban might cause death toll to increase, its restricted use was allowed (UNEP, 2008). For example, in 2006, WHO supported the use of DDT in African countries where malaria is a major health risk causing millions of deaths annually. Several regulatory authorities such as UNEPA, USEPA monitor closely the use of DDT with the aim that it should only be used for integrated vector management programs and not as agricultural insecticide. Presently, DDT is mainly produced in India, China and Democratic People’s Republic of Korea. By far, India is the largest producer of DDT with major amounts being used in disease vector control and for the production of other chemicals. According to UNEP (2008) an estimated amount of 5000 tons of DDT were used for disease vector control in 2005. India is the largest consumer of DDT followed by African countries. Throughout the last decade, a sequence of arguments has taken place in proponents and opponents of DDT. The proponents argue that DDT is effective against eradication of diseases like malaria and typhus and alternatives available are more costly and dangerous. However, the opponents of DDT make a point that DDT is a persistent toxic chemical that accumulates in food chain effecting fish and wild life, therefore creating an unbalanced ecosystem. Exposure For most of the populations, principal means of exposure to DDT is through food in specific the aquatic resources such as fish and sea food. Nonetheless, agricultural products such as cereals and grains may also be an important source. DDT is instantly metabolized into a stable and similarly toxic compound DDE. Both DDT and DDE is lipid soluble and stored in adipose tissue of human beings and animals and primarily secreted by urine and breast milk. Nonetheless, it is an established fact that effects caused by DDT may vary according to animal species, age, gender and the level, degree and duration of exposure. In addition, the abnormal effects of DDT may not be apparent in exposed adult generation and may occur in second or third generation and sometimes may not become evident until the individual reaches sexual and physical maturity. Another significant potential exposure route specifically in areas where DDT is used as vector control is occupational exposure (Han and Stone, 2001). Following are the recent research results that illustrate the harmful effects of DDT on human beings and environment. Effects on Human Beings: 1. DDT and its metabolites are considered as environmental estrogens and can cause reproductive abnormalities in humans and wild life. According to Longnecker, Rogan and Lucier (1997) high level exposure to organo-chlorines appear to cause abnormalities in skin, liver and nervous system; in neonatal, hypotonia or hyporeflexia. 2. Research has indicated that DDT can also act as endocrine disruptor, exerting detrimental effects on major biological mechanisms of body such as development and biochemical pathways (Han and Stone, 2001). 3. DDT can cause multiple effects on immune system such as disturbing the production of antibodies and T-cells thereby manifesting decreased resistance to viral infections, delayed sensitivity to antigen and immunosuppression (Han and Stone, 2001). 4. According to research, reproductive and developmental abilities of and individual are affected by exposure to DDT. It can cause effects like disturbances in reproductive cycles, sex hormone levels, and reduced sperm production. In some cases, low fertility, unexplained infertility, still births, neonatal deaths and in some cases congenital defects are reported in individuals handling this insecticide (UNEP-GPA, 2001). Salazar-Garcia et al., (2004) while researching the reproductive functions of malaria control program workers found an increased risk of birth defects in their off-springs irrespective of level of exposure to DDT. 5. Several epidemiological studies have been reviewed extensively for the association of DDT exposure and increased cancer risk. However, the results investigating breast cancer, uterine cancer, non-Hodgkin lymphoma showed no significant co-relation between adipose tissue concentrations of DDT and cancer (FAO, 2000). Similar results are reported by Longnecker, Rogan and Lucier (1997) suggesting that not a large number of cancers are caused by DDT exposure. However, according to recent studies, apparently DDT exposure promotes the spread of cancer rather than inducing it in the first place. Evidence suggests high incidence of tumors and lesions in individuals exposed to DDT contaminated areas (Han and Stone, 2001). 6. Other reported effects of DDT exposure include disturbed Vitamin A metabolism, disruption in functions of adrenal and thyroid glands. Effects on Environment: 1. Several adverse effects of DDT are witnessed in animals which include reproductive and developmental failure. It is highly toxic to insects, shrimps and fish (UNEP, 2008). In most of the cases, exposure to organo-chlorine insecticide targets nervous and immune system of the animals. In addition, wild bird and animal deaths are recorded after extensive DDT spraying. In laboratory experiments, long exposure to DDT in several species cause neurological, hepatic, renal, immunological impairment and sexual development abnormalities. Many well reported examples of decreased bird population are documented which are caused by decreased/delayed egg production, increased embryo mortality, embryonic abnormalities, egg shell thinning in exposure to DDT (Han and Stone, 2001). Similarly, other studies revealed large residues of DDT in North American peregrines with thinner egg shells and decreased reproductive capabilities. The damage of DDT to predatory birds is largely caused by impairment in reproductive functions. These include a decrease in clutch size, thinner egg shells (which can break under the incubating parent), high death rates of embryos, abnormal parenting behavior while incubating or raising hatchlings (Freedman, 1995) 2. Research has demonstrated that DDT and its metabolites create reservoirs in soil and aquatic (river and lake) sediments thus virtually present at all levels of food chain. Despite a 20 years ban in US it is still persistent in fresh water sediments affecting aquatic vertebrates such as fathead minnow and rainbow trout. 3. Due to its strong affinity for fatty tissues, it travels in the body of a living organism. Due to this ability, a stable molecule of DDT and its metabolites are responsible for environmental phenomenon bio-concentration (a process in which the levels of a harmful substance exceed those of its surrounding environment). Therefore, high levels of bio-concentration are found in aquatic organisms with levels of DDT more concentrated in their bodies than in adjoining water (Faroon, 2010). 4. Environmental phenomenon like bio-magnification caused by DDT occurs when the animals feed on other organisms at each trophic level. Bio-magnification is a cumulative increase in the concentration of persistent contaminant in successive levels of food chain starting at lower trophic levels (algae and zooplanktons) to higher trophic levels (birds and fish). Faroon (2010) demonstrated the bio-magnification of DDT by an increase in concentrations of DDT in organisms present at four trophic levels i.e. planktons, invertebrates, fish and fish eating birds. 5. DDT bio-magnifies and bio-accumulates as it is being transported from one trophic level to the other. The detrimental effects found in association with DDT concentrations in organisms mainly include metabolic processes such as neuro-conduction, osmo-regulation and reproduction (Hummon, 1974). Chemistry and Occurrence DDT‘s chemical formula is represented as [1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane]. It is non-specific pesticide with high solubility in lipids/fats and vast adsorptive qualities. In global environment, most of the DDT and its products have originated from its large scale use in agricultural pest control (UNEP, 2008). DDT possesses very peculiar physical and chemical properties that manipulate the nature of its ecological effects. First, DDT is a persistent molecule in environment and is not easily degraded by biological (microorganisms) or physical (heat, sunlight) factors. Primary product of DDT is DDE that is produced by de-chlorination reactions that occur in alkaline environments or enzymatically in organisms. DDT and its products persist for a very long time in environment and are slowly released with the passage of time. The reported half life of DDT is 2-15 years and that of its metabolic products even longer. Another important characteristic of DDT is its low solubility in water (less than 0.1 ppm) therefore maintains its concentration and in aqueous environment (Freedman, 1995). It can be transported in lower concentrations in water bodies from the point of introduction to distant aquatic bodies and mostly concentrate in the organic and colloidal matter of the sediments. Evidence suggests that DDT enters into the atmosphere through emissions and volatilization from soil and water bodies. As a result, DDT is transported at long distances through a phenomenon known as global distillation (from warm areas to cold areas). Consequently DDT is found in arctic air, snow and sediments and accumulates in animals and human beings (Faroon, 2010). Reducing DDT use and Alternatives available: The decline in DDT use should be achieved due to many reasons i.e. (1) increased insect resistance, (2) detrimental environmental and health effects, (3) government restrictions and ban on its usage, (4) development and successful implementation of other pesticides and evolution of concepts like Integrated pest management. Reduction to DDT exposure for both environment and human beings can be achieved through a series of organized approach with specific focus on eradication of illegal uses of DDT specifically in agricultural sector. Also, a gradual cutback in DDT use for malaria control should be ensured and available alternatives must be explored. Finally, educating and create awareness in general public over the harmful effects of DDT. In this respect, community involvement in reducing the use of DDT and support activities leading towards integrated management (CEC, 1996). Considering the harmful effects of DDT, alternative methods should be developed and adapted in order to decrease human health and environmental risks. In this respect, two approaches are applied i.e. Integrated Vector Management and Integrated Pest management. In vector management, several chemical and non-chemical substitutes can be employed as an alternative to DDT. Most common chemical methods implemented productively in Africa and India includes insecticide treated bed nets and alternative insecticide indoor residual spraying. Most successful alternative to DDT is pytheroids based insecticides which appear to be cost effective and has prolonged residual properties. In addition, use of larvicides in breeding places of disease vectors such as mosquitoes and application of chemical repellents has shown significant results in malaria reduction. Non-chemical methods include habitat manipulation through management of water bodies, intermittent irrigation, flushing of canals, source reduction through drainage or filling and biological control. Also, introduction of genetically modified species and placement of repellent botanical plants may give some local respite from the malaria problem (UNEP, 2008). However, several constraints such as limited chemical product availability, high cost, possible development of vector resistance, lack of awareness and education in non-chemical integrated pest management efforts are present in successful implementation (UNEPA, 2001). In context of integrated pest management, several strategies crop production methods that discourage pest invasion, promoting beneficial predators/parasites and timing of pesticide application etc. have demonstrated promising results for economical and successful pest control. Also, alternative pesticides with less residual properties be developed and employed to reduce the use of DDT (Delaplane, 1996) In conclusion, DDT is a remarkable pesticide with potential results however, with growing environmental and health concerns its use should be substituted and a common solution for DDT issue is to develop and implement long term disease vector control, pest control and management programs keeping in consideration development of new technologies with less reliance on chemical insecticides. References C.E.C. 1997. History of DDT in North America. North American Commission for Environmental Cooperation. Mexican Ministry of health. Delaplane, K. (1996). Pesticide usage in United States: history, benefits, risks and trends. Project of the Southern Extension and Research Activity- Information Exchange Group 1 (Southern Region Pesticide Impact Assessment Program). E.P.A (1975). Excerpt from DDT, A Review of Scientific and Economic Aspects of the Decision To Ban Its Use as a Pesticide, prepared for the Committee on Appropriations of the U.S. House of Representatives by EPA. EPA-540/1-75-022. http://www.epa.gov/history/topics/ddt/02.htm F.A.O (2000). Pesticide residues in food 2000: DDT. Joint Meeting on Pesticide Residues. http://www.inchem.org/documents/jmpr/jmpmono/v00pr03.htm. Faroon, O. (2010). Toxicological profile for DDT/DDD/DDE (update). Diane publishing. 235-236. Fiedler, H. and Borja-Aburto, V. (2003). Persistent organic pollutant. Vol. 3. Springer. 372. Freedman, B. (1995). Environmental Ecology: the ecological effects of pollution, disturbance and other stresses. Academic Press. 229-236. Han, S. and Stone, D. (2001). A case study of POPs concentration in wild life and people relative to effects level. www.chem.unep.ch/POPs/POPs_Inc/proceedings/.../STONE1.html. Hummon, W. (1974). Effect of DDT on longevity and reproductive rate in Lepidodermella squammata (gastrotricha, Chaetonotida). American Midland Naturalist. Vol.92. no. 2. 1-2. Longnecker, M., Rogan, W. and Lucier, G. (1997). The human health effects of DDT (Dichlorodiphenyltrichloroethane) and PCBs (polycarbonated biphenyl) and an overview of organochlorines in public health. Annual review of public health. Vol. 18:211-244. Salazar-Garcia, F., Gallardo-Diaz. E., Ceron-Mireles, P., Loomis, D. and Borja-Aburto, V. (2004). Reproductive effects of occupational DDT exposure among male malaria control workers.Environ Health Perspect. Vol. 112(5): 542–547. U.N.E.P.-W.H.O. (2001). Workshop on sustainable approaches for pest and vector management and opportunities for collaboration in replacing POPs pescticides. 95-139. http://www.chem.unep.ch. U.N.E.P-Global Program Action (2001). Global program action for the protection of marine environment from land based activities: DDT. http://www.chem.unep.ch/gpa_trial/14ddt.htm U.N.E.P. (2008). Global status of DDT and its alternatives for use in vector control to prevent disease. Background document for the preparation of the business plan for a global partnership to develop alternatives to DDT. Stockholm Convention on Persistent Organic Pollutants. Read More