Previously, in 2009, she collaborated with other researchers to analyze DDT and other pesticides in water where low levels of DDT metabolites were detected. Illegal diversion to agriculture is also a concern, as it is difficult to prevent and its subsequent use on crops is not controlled. For example, the use of DDT is widespread in Indian agriculture,[135] particularly in mango production,[136] and is reportedly used by librarians to protect books. [137] Other examples include Ethiopia, where DDT is reportedly used in coffee production to combat malaria,[138] and Ghana, where it is used for fishing. [139] [140] Residues in crops that are not acceptable for export have been an important factor in bans in several tropical countries. [125] In addition, there is a shortage of skilled workers and managers. [131] Although the pesticide was banned in many countries, some countries in Africa, Asia, and South America needed the mosquito repellent pesticide to reduce the risk of malaria. In 2006, WHO supported the use of DDT indoors in African countries where malaria remains a major challenge. The organization said the benefits of pesticides for African countries outweigh the negative impact on the environment. India and North Korea have continued to use pesticides for agricultural purposes despite the ban.
Approximately 4,000 tonnes of DDT are produced annually for the vector control programme. It is legal to manufacture DDT in the United States, although it can only be exported for overseas use. DDT can only be used in the United States for public health emergencies, such as the control of vector-borne diseases. Today, DDT is produced in North Korea, India and China. India remains the largest consumer of this product for vector control and agriculture. China produces 4,500 tons of this product, of which 80 to 90% is used to produce Dicofol, an acaricide. African countries do not use the product for agricultural purposes, but countries such as Ethiopia, South Africa, Swaziland and Uganda use it to fight malaria. DDT is a persistent organic pollutant that adsorbs easily to soils and sediments and can serve as both sinks and sources of long-term exposure for organisms. [14] Depending on environmental conditions, soil half-life can range from 22 days to 30 years.
Pathways of loss and degradation include runoff, volatilization, photolysis, and aerobic and anaerobic biodegradation. Due to its hydrophobic properties, DDT and its metabolites are absorbed by aquatic organisms in aquatic ecosystems and adsorbed to suspended particles, leaving little DDT dissolved in water (however, its half-life in aquatic environments is given by the National Pesticide Information Center at 150 years[69]). Its degradation products and metabolites, DDE and DDD, are also persistent and have similar chemical and physical properties. [1] DDT and its degradation products are transported from warmer areas to the Arctic by global distillation, where they then accumulate in the region`s food web. [70] In September 2006, the World Health Organization (WHO) declared its support for the use of DDT in African countries where malaria remains a major health problem, stressing that the benefits of the pesticide outweigh the health and environmental risks. WHO`s position is consistent with the Stockholm Convention on POPs, which bans DDT for all uses except malaria control. The relative cost-effectiveness of IRS and ITNs has been studied several times. Both have been considered attractive interventions in terms of disability-adjusted life-cycle cost (Goodman et al.
2000), but their relative effectiveness depends on vector behaviour and human sleep patterns in a given environment. ITNs tend to be less expensive in highly endemic environments (Yukich et al. 2008), while IRS operations can respond more quickly to epidemic situations (Curtis and Mnzava 2000). IRS with insecticides is an effective method of malaria control. Its strength lies in its effect on shortening the lifespan of adult mosquitoes near their human targets, which has a crucial impact on malaria transmission (MacDonald 1957). However, there is little information on the effectiveness and operational feasibility of IRS in African countries where malaria is highly endemic, some of which have recently reintroduced IRS or are planning to do so. Twelve insecticides belonging to four chemical classes are recommended for IRS in vector control, which together treat only three types of toxic effects (Nauen 2007). Pyrethroids are the most cost-effective alternatives to DDT in malaria control, except in cases of pyrethroid resistance (Walker 2000).
There are several barriers to implementing alternatives to DDT. Vector resistance to insecticides poses a direct threat to the durability of insecticide-treated nets and IRS. Resistance to pyrethroids has been reported in malaria vectors in West, East and South Africa (ANVR 2005; Coleman et al., 2007). In particular, kdr-like cross-resistance between pyrethroids and DDT strongly limits the choice of insecticide. South Africa was forced to reintroduce DDT after the failure of pyrethroids, as one of the locally extinct vectors had returned and developed resistance to pyrethroids (non-KDR type) elsewhere (Hargreaves et al. 2000). The only remaining legal use of DDT is to control mosquitoes that transmit malaria. As a devastating disease, malaria kills more than 800,000 people each year, the highest number of child deaths in sub-Saharan Africa. Indoor DDT spraying is one of many tools used around the world to fight malaria. Only in rare cases is it the most effective choice.
PAN works with international allies, governments and grassroots groups in Africa to mobilize resources and political will to fight malaria, and remains active in international legal processes to support the global elimination of DDT and promote the safest and most effective malaria control solutions. WHO`s malaria campaign in the 1950s and 1960s relied heavily on DDT, and the results were promising, albeit temporarily in developing countries. Experts link the resurgence of malaria to several factors, including the lack of leadership, management and funding of malaria control programmes; Poverty; Agitation; and increased irrigation. The development of resistance to first-generation drugs (e.g. chloroquine) and insecticides has aggravated the situation. [20] [114] Resistance has been largely fueled by unrestricted agricultural use. Resistance and damage to humans and the environment have led many governments to restrict the use of DDT in vector control and agriculture. [41] In 2006, WHO reversed a long-standing policy against DDT by recommending the use of DDT as an indoor pesticide in areas where malaria is a major problem. [115] China, Solomon Islands, and Vietnam have largely replaced their IRS programs with ITNs in recent decades (Najera and Zaim, 2001). Conversely, the use of IRS is increasing in Africa, where aspects of vector biology and disease epidemiology make malaria control more difficult.
In South Asia, indoor spraying of DDT and alternative insecticides continues on a large scale, but the quality of the intervention is a critical issue (JMM 2007). The use of chemical insecticides as larvicides to control mosquito reproduction can play an important role in malaria control when appropriate and feasible, particularly in urban environments, but the large-scale effects of most chemicals are of concern to the integrity of aquatic ecosystems. In addition, chemical repellents may play a useful complementary role in vector control (Rowland et al. 2004). Groundbreaking work is underway on the attractiveness of human odour to malaria vectors, with potential applications such as attractants and mosquito repellents for use in traps and personal protection (Zwiebel and Takken 2004). Most studies on the effects of DDT on human health have been conducted in developed countries where DDT is not used and exposure is relatively low. [42] [73] [134] Prof. Mbongwe conducted an extensive study of DDT in Botswana in 2000 and measured its concentrations and metabolites in water, plants, invertebrates and fish in some lagoons of the Greater Okavango Delta, where DDT has been used for about 50 years to control malaria and treat African sleeping sickness. Studies of malaria-carrying mosquitoes in South Africa`s KwaZulu-Natal province found a 4% susceptibility of DDT (WHO susceptibility standard) in 63% of samples, compared to an average of 87% in the same species caught outdoors. The authors concluded that “DDT resistance in the An.
arabiensis, near the area where we previously reported resistance to pyrethroids in the An vector. Giles highlights the urgent need to develop an insecticide resistance management strategy for malaria control programmes in southern Africa. [129] Both the effectiveness and cost of DDT depend on local circumstances and merit careful consideration with respect to alternative products or methods. DDT is known as the only insecticide that can be used in a single application in areas where the transmission season is > 6 months. However, there is a lack of information on the potential variability of residual action of insecticides, including DDT (e.g. due to sprayable surface, climatic conditions, social factors). Despite the global ban, agricultural use continued in India,[65] North Korea, and possibly elsewhere. [20] In 2013, an estimated 3,000-4,000 tonnes of DDT were produced for disease vector control, including 2,786 tonnes in India.
[66] DDT is applied to the interior walls of homes to kill or repel mosquitoes. This procedure, called indoor residual spraying (IRS), significantly reduces environmental damage.