Pesticides used in disease vector control (WHO/PES)
Rolling revision of the WHO Guidelines for Drinking-water Quality
Pesticides used in disease vector control are included in the plan of work of the rolling revision of the WHO Guidelines for Drinking-water Quality.
Various vector-borne diseases, such as malaria and dengue fever, may be strongly associated with the domestic storage of drinking-water. One of the vector control options to address the breeding of vectors in domestic drinking-water storage structures is the application of insecticide substances to drinking-water containers in different formulations (e.g. slow release). The WHO/PES endorses pesticides suitable for this purpose. It relies on WHO/PCS for toxicological assessment and on the Guidelines for Drinking-water Quality for overall assessment of safety in this application. These pesticides are deliberately added where there is a significant risk of disease, so that an overly conservative approach is not appropriate.
There are currently four insecticide compounds and a bacterial larvicide recommended by WHO (under WHO/PES) for addition to drinking-water as larvicides: temephos, methoprene, pyriproxyfen, novaluron and Bacillus thuringiensis israelensis. Of these, only pyriproxyfen has been reviewed to date and is included in the Guidelines for Drinking-water Quality, Third Edition. Temephos (#93), methoprene (#52B), novaluron (#121) and Bti (#52A) are being considered under the rolling revision process. Permethrin (#111) is not recommended for direct addition to drinking-water for public health purposes as part of WHO’s policy to exclude the use of any pyrethroids for larviciding of mosquito vectors of human disease. This policy is based on concern over the possible accelerated development of vector resistance to synthetic pyrethroids, which, in their application to insecticide-treated mosquito nets, are crucial in the current global anti-malaria strategy.
A scoping document on the issue of WHO/PES pesticides was prepared in 2003, which described the technical and assessment issues and approaches for reviewing these pesticides. The Guidelines for Drinking-water Quality Final Task Force meeting (Geneva, 2003) recommended that background documents be prepared on WHO/PES pesticides for which no background documents exist (i.e. temephos, methoprene, novaluron, Bti — see agenda items #93, #52B, #121 and #52A, respectively) and on proposed WHO/PES pesticides (i.e. diflubenzuron and pirimiphos-methyl — see agenda items #52D and #104, respectively). In order to undertake these evaluations, it is first necessary to confirm an overall strategy with WHO/PES, WHO/PCS and JMPR and to develop a plan of work to deal with general (i.e. formulations) and active ingredients.
- New text for Policies and Procedures Manual to explain the relationship between PES, PCS/JMPR and DWQC;
- New text for the Policies and Procedures Manual and the Guidelines for Drinking-water Quality (for second addendum) on the new approach for WHO/PES pesticides;
- Jointly produced summary statements on a group of five or so pesticides for Fourth Edition
Progress to date
The Guidelines for Drinking-water Quality Working Group meeting (Geneva, 2004) agreed to a plan of work. The Guidelines for Drinking-water Quality Working Group meeting (Geneva, 2005) met with the WHO/PES and WHO/PCS groups and agreed to a revised joint plan of work. The path forward was further articulated by the Guidelines for Drinking-water Quality Working Group meeting (Geneva, 2006) following fruitful discussions with representatives of the Vector Ecology and Management Programme at WHO.
The draft text is now available for review. Comments are welcome following the format on the comment sheet, below.
Comments on the draft background documents above should be sent before 15 May 2007 to gdwqWHOPES@who.int.