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Resurrection of DDT: need for caution.

Sir,

Apropos the editorial on resurrection of DDT by Dash et al (1). The authors have highlighted the desirable attributes and unquestionable utility of DDT in vector-borne disease control, particularly against malaria which is emerging and resurging in different parts of the world including India. The unwarranted misuse and overuse of DDT in agriculture and public health during the DDT era and detection of residue of DDT in human breast milk, plants and animals had made the world look at DDT with fear (2-6). This fear was further aggravated by environmentalists who agitated against DDT altogether. Further, the Environmental Protection Agency (EPA) has listed DDT as a "probable human carcinogen" (7).

The editorial falls short of the reasons for such a resurrection of DDT. It seems to imply either most of the malaria vectors have developed resistance to all the insecticides currently used in public health or none of the insecticides in use today is as potential as DDT. This resurrection might be due to its affordable cost and appreciable efficacy over other insecticides used in public health at present (2). Though a maximum of 10, 000 metric tones of DDT per annum for the control of malaria and kala-azar is permitted in India (8), there have been very few evidences of the dramatic decline of malaria cases. Further, it has been reported that malaria vectors are still resistant to DDT in certain places/States in India (8-10). The authors have not made any suggestions on what India should do under such circumstances.

The emergence of resistance by many malaria vectors against most of the insecticides including the synthetic pyrethroids used in public health and their alarming cost have made the entomologists and the public health specialists to reconsider the use of DDT but with care. The inevitable role of DDT to bring down malaria cases in South African countries is unquestionable (11). But DDT is a chemical tool to control vector borne diseases in general and malaria in particular. DDT also needs to be used with caution, it may cause harm to human health rather than protecting them from malaria and other vector borne diseases. High incidence of undescended testes, poor sperm quality, miscarriage, reduced breast milk production, neurological effects, elevated risk of breast cancer, other types of cancer and undesirable impacts on the nervous system and liver have been reported (12,13). So, it would be desirable if the use is confined only to public health particularly for indoor residual spray (IRS) especially during rotation of insecticides and management of resistance in vector borne disease control programmes. Further, DDT is not the only insecticide used for IRS and so, alternative insecticides may also be considered for use as and when required (14). Unilateral reliance of DDT in malaria vector control in the long run may lead to greater danger of human exposure and hastening the development of resistant mosquito population. Even in many malaria endemic African countries, there are several instances that certain social and cultural factors hinder the effectiveness of DDT sprayed indoors (15). Preventive measures to watch out the leakage of DDT into the environment or agriculture should also be strengthened. More effective and safer alternative approaches for malaria control should be envisaged as also bioenvironmental control measures through multi-sectoral collaboration and community participation.

N. Sivagnaname

Division of Applied Field Research

Vector Control Research Centre (ICMR)

Puducherry 605006, India

email: sivagnaname777@yahoo.com

References

(1.) Dash AP, Raghavendra K, Pillai MKK. Resurrection of DDT : A critical appraisal. Indian J Med Res 2007; 126 : 1-3.

(2.) WHO backs DDT for malaria control? Available from: http:/ /news.bbc.co.uk//2/hi/science/nature/5350068.stm, accessed on October 22, 2007.

(3.) Garabrant DH, Held J, Langholz B, Peters JM, Mack TM. DTT and related compounds and risk of pancreatic cancer. J Natl Cancer Inst 1992, 84 :764-71.

(4.) Wolff MS, Toniolo PG, Lee EW, Rivera M, Dubin N. Blood levels of organochlorine residues and risk of breast cancer. J Natl Cancer Inst 1993, 85 :648-52.

(5.) Bouwman H, Schutte CH. Levels of DDT and metabolites in breast milk from Kwa-Zulu mothers after DDT application for malaria control. Bull World Health Organ 1990, 68:761-8.

(6.) Curtis CE Control of malaria vectors in Africa and Asia. In: Radcliffe RB, Hutchison, WD editors. Radcliffe's IPM world textbook, St. Paul, MN: University of Minnesota; 1996. Available from: http://ipmworld.umn.edu, accessed on October 22, 2007.

(7.) DDT ban takes effect. Available from: http://www.epa.gov/ history/topics/ddt/01.htm, accessed on October 23, 2007.

(8.) DDT-the age of old mosquito control. P-Posted by Dr D. Raghunatha Rao on September 18, 2006. Available from: http://www.medicalnewstoday.com/your opinions php? opinionid=11543, accessed on October 22, 2007.

(9.) Bioenvironmental Strategy for Malaria Control. Studies on the reliance of DDT, HCH and malathion in Vector Control Programme. Available from: http://www.mrcindia.org/ MRC_Profile/alternate_strategy/insecticide_VCP.pdf, accessed on October 22, 2007.

(10.) The World Bank and DDT use in India. Available from: http:/ /lnweb18.worldbank.org/ESSD/envext.nsf/50ByDocName, accessed on October 24, 2007.

(11.) To control malaria, We need DDT. 21st Century Science and Technology. Available from: http://www. 21stcenturysciencetech.com/articles/fall02/DDT.html, accessed on October 23, 2007.

(12.) Mosquito Control and Environment. Available from: http:// www.the conscientioushome.net/articles.php?con_id=169, accessed on October 23, 2007.

(13.) DDT. Available from: http://www.pan-UK.org/pestnews/ actives/ddt.htm, accessed on October 27, 2007.

(14.) Frequently asked questions on DDT use for disease vector control. Available from: http://www.who.int/malaria/docs/ FAQonDDT.pdf, accessed on October 23, 2007.

(15.) DDT's resurrection. Available from: http://pubs.acs.org/ subscribe/journals/esthag-w/2007/aug/science/nl_ddt.html, accessed on October 27, 2007.

Authors' Response

Sir,

N. Sivagnaname (1) is probably unable to understand the genesis of our editorial (2) due to his lack of expertise and familiarity of the enormous volume of scientific data available on global malaria control and well structured malaria control strategies successfully practised in India.

Resurrection of DDT was not our decision and it was done by the WHO as it lifted the ban of DDT deployment in malaria control, a consequence of the failure of its Roll Back Malaria (RBM) initiative primarily focused to control malaria in Africa. We have elucidated the multifarious reasons in explicit manner which prompted this bold pragmatic decision. The failure of RBM was essentially due to development of resistance by malaria vectors in Africa to synthetic pyrethroids. In that scenario reintroduction of DDT was indeed a great success in countries in South African region. Similar success stories happened in South American countries also. This turn of events, however, was not appreciated by donor agencies from European Union and United States till WHO lifted the ban. DDT deployment was not promoted due to its low cost as presumed by the author (1). DDT is currently costlier in the global market compared to synthetic pyrethorids. The author further questions the wisdom of deployment of DDT in North Eastern States in India and he claims malaria incidence is increasing in those States. This erroneous statement reflects his ignorance of the fact that malaria vectors in this region are still susceptible to DDT and the recent malaria outbreak in Assam was effectively controlled by its use. It is also incorrect to say that malaria is resurging in India. The author is probably ignorant of the epidemiological reports of National Vector Borne Disease Control Programme which clearly indicate that malaria incidence in India has been stable for last many years and deaths due to malaria is declining. This has been internationally recognized as in a recent publication citing India as a winner along with Brazil, Eritrea and Vietnam in effectively controlling malaria when globally other malarious countries have failed (3).

The author's contention that continued use of DDT would harm the human race has not been substantiated by the scientific data available so far. WHO decided to lift the ban on DDT in September 2006 after a thorough and careful consideration of whole gamut of scientific data generated till that date on health hazards and environment impact of DDT. This decision has been welcomed by many international agencies, WWF and environmentalists who support malaria control in Africa and in other countries. In our editorial we tried to elucidate scientific facts supporting this pragmatic decision of WHO. The author seems to have no comprehension of enormous quantities of DDT that was indiscriminately used both in developed and developing countries from the period of World War II since early 1940s till 1972 when US banned DDT. However, this large scale use of DDT did not cause any catastrophic effects or any epidemiological mass effect on human race as evidenced and should clearly dispel the unwarranted alarming fear. Since DDT is restricted mainly for malaria vector control the envisaged impact on human health and environment would be further reduced. The sermonizing statement that DDT should not be used in agriculture is redundant as DDT ban in agriculture is implemented in most countries including in India. Our editorial has not mentioned anything about ban of DDT in agriculture. Use of DDT in malaria control strictly adhering to WHO protocols and guidelines hopefully will mitigate people from the scourge of malaria in Africa and other malarious countries.

A.P. Dash ([dagger]), K. Raghavendra & M.K.K. Pillai *

National Institute of Malaria Research (ICMR) 22, Sham Nath Marg, Delhi 110054

* 37, Saakshara Apartments, A-3, Paschim Vihar New Delhi 110063, India

([dagger]) For correspondence: apdash2@rediffmail.com

References

(1.) Siragnaname N. Resurrection of DDT: need for caution. Indian J Med Res 2007; 126: 584-5.

(2.) Dash AP, Raghavendra K, Pillai MKK Resurrection of DDT--A critical appraisal. Indian J Med Res 2007; 126 : 1-3.

(3.) Barat, L M. Four malaria success stories: How malaria burden was successfully reduced in Brazil, Eritrea, India, and Vietnam. Am J Med Hyg 2006; 74 : 12-6.
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Article Details
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Title Annotation:Correspondence; Dichloro-Diphenyl-Trichloroethane
Author:Sivagnaname, N.; Dash, A.P.; Raghavendra, K.; Pillai, M.K.K.
Publication:Indian Journal of Medical Research
Article Type:Letter to the editor
Geographic Code:9INDI
Date:Dec 1, 2007
Words:1662
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