Use of malathion for vector control
Report of a WHO meeting, Geneva, 16–17 May 2016
The World Health Organization (WHO) convened a group of experts to review the risk of malathion used in public health and discuss the implications of WHO’s recommendations on the use of malathion in vector control following the evaluation of malathion as “probably carcinogenic to humans” by the International Agency for Research on Cancer (IARC). A particular concern was the potential implication of the availability or non-availability of malathion for vector control in the context of Zika virus disease.
The IARC monograph concluded that there was “limited evidence” in humans for carcinogenicity, based on observations of positive associations with the incidence of non- Hodgkin lymphoma and aggressive cancer of the prostate. It also concluded that there was “sufficient evidence” for carcinogenicity in experimental animals, and mechanistic and other relevant data supported the classification of malathion in Group 2A (“probably carcinogenic to humans”).
In consideration of the IARC’s classification and the availability of a significant number of new studies, an extraordinary Joint FAO/WHO Meeting on Pesticide Residues (JMPR) was held on 9–13 May 2016 at WHO headquarters in Geneva, Switzerland. The outcome of this meeting, at which the risk to consumers from exposure to malathion via residues in food following its agricultural use was assessed, informed the assessment by the experts of the risk from its vector control uses.
The meeting of experts was opened by Dr Dirk Engels, Director, WHO Department of Control of Neglected Tropical Diseases. He welcomed participants and recalled that the extraordinary meeting of the JMPR (Geneva, 9–13 May 2016) had re-assessed the risk of malathion, as well as of glyphosate and diazinon, and that the conclusions from that meeting would be discussed in this specific meeting. He noted that IARC’s classification of malathion as probably carcinogenic could have some implications on continuing the use of malathion for vector control, especially in the control of Aedes spp. in the context of the Zika virus outbreak. WHO is committed to recommending the use of low-risk pesticide products for public health and vector control, and Dr Engels hoped that the advice given to WHO would help the Organization in making an evidence-informed decision to advise Member States on the use of malathion.