MALARIA FOUNDATION INTERNATIONAL

Use of DDT in vector control¹

The WHO Study Group on Vector Control for Malaria and Other Mosquito-Borne Diseases considered the current situation regarding the use of DDT for controlling vector-borne diseases, in particular malaria, in the light of two recent publications suggesting an association between DDT and human cancers (1, 2), a report on the presence of DDT in breast milk (3), and two general reviews of the subject.² Two expert toxicologists³ were invited to review these papers, including the citations, and to participate in the discussions on DDT.

After careful review of the documents and intensive discussion, the Study Group concluded that:

1. The information presented does not provide convincing evidence of adverse effects of DDT exposure as a result of indoor residual spraying as carried out in malaria control activities.
2. There is therefore, at this stage, no justification on toxicological or epidemiological grounds for changing current policy (4) towards indoor spraying of DDT for vector-borne disease control.
3. DDT may therefore be used for vector control, provided that all the following conditions are met:
   1. it is used only for indoor spraying;
   2. it is effective;
   3. the material is manufactured to the specifications issued by WHO (5);
   4. the necessary safety precautions are taken in its use and disposal.
      
      
4. In considering whether to use DDT, governments should take into account the following additional factors:
   1. the costs involved in the use of insecticides (DDT or alternatives);
   2. the role of insecticides in focal or selective vector control, as specified in the Global Malaria Control Strategy (6, 7);
   3. the availability of alternative vector control methods, including alternative insecticides (in view of the availability of alternative insecticides for indoor residual spraying, some of which may compete with DDT in terms of epidemiological impact, public acceptability, logistic suitability and compliance with specifications issued by WHO, DDT no longer merits being considered the only insecticide of choice);
   4. the implications for insecticide resistance, including possible cross-resistance to some alternative insecticides;
   5. the changing public attitude to pesticide use, including public health applications.
5. Given the paucity of data suggesting adverse effects of indoor house-spraying, further epidemiological investigation using rigor-ous scientific protocols is to be encouraged.
6. Further studies should also be carried out to:
   1. examine the health effects of DDT in breast milk on breastfed infants, including any resulting behavioural change;
   2. investigate thoroughly any suspected association between the use of DDT in routine malaria control activities and an increased incidence of cancer(s);
   3. clarify the significance of the reduction in muscarinic receptor density caused by DDT.

References

1.    Garabrant DH et al. DTT and related compounds and risk of pancreatic cancer. Journal of the National Cancer Institute, 1992, 84:764–771.
2.    Wolff MS et al. Blood levels of organochlorine residues and risk of breast cancer. Journal of the National Cancer Institute, 1993, 85:648–652.
3.    Bouwman H et al. Levels of DDT and metabolites in breast milk from Kwa-Zulu mothers after DDT application for malaria control. Bulletin of the World Health Organization, 1990, 68:761–768.
4.    The place of DDT in operations against malaria and other vector-borne diseases. In: Executive Board Forty-seventh Session, Geneva, 19–29 January 1971, Part II. Report on the proposed programme and budget estimates for 1972. Geneva, World Health Organization, 1971 (Official Records of the World Health Organization, No. 190):176–182.
5.    Specifications for pesticides used in public health, 7th ed . Geneva, World Health Organization, 1997 (unpublished document WHO/CTD/WHOPES/97.1; available on request from the Documentation Centre, Communicable Diseases, World Health Organization, 1211 Geneva 27, Switzerland).
6.    A global strategy for malaria control. Geneva, World Health Organization, 1993.
7.    Implementation of the Global Malaria Control Strategy. Report of a WHO Study Group on the Implementation of the Global Plan of Action for Malaria Control 1993–2000. Geneva, World Health Organization, 1993 (WHO Technical Report Series, No. 839).