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Safety of Pyrethroids for Public Health Use

(WHO Pesticide Evaluation Scheme / WHOPES, 2005)

Full Text
(77 pp, PDF, via WHOPES site)
Preface
1. Introduction
2. Pyrethroids—Structure and insecticidal activity
3. Mechanisms of toxicity
4. Toxicokinetics
5. Toxicity in experimental animals
5.1. Acute toxicity
5.2. Short-term toxicity
5.3. Carcinogenicity
5.4. Genotoxicity
5.5. Reproductive toxicity
5.6. Variation of sensitivity with age
5.7. Neurotoxicity and neurobehavioural effects
5.7.1. Adult animals
5.7.2. Neurodevelopmental effects
5.8. Immunotoxicity
5.9. Endocrine effects
6. Effects on humans
6.1. Acute poisoning
6.2. Paraesthesia
6.3. Allergic reactions
6.4. Carcinogenicity
6.5. Effects observed in public health uses
6.5.1. Bednet impregnation and use
6.5.2. Aircraft disinsection
6.5.3. Indoor residual application
7. Conclusions
8. References

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The purpose of this document is to critically review current knowledge on the safety of pyrethroids and whether existing WHO recommendations for pyrethroid applications should be revised or modified. This review does not consider the use of pyrethroids in space spraying and vapour applications (e.g. in mosquito coils and aerosols). (List of those contributing to the review can be found in the preface.)

Pyrethroids are widely used in public health because of their relative safety for humans, high insecticidal potency at low dosages and rapid knock-down effects. The safety and efficacy of pyrethroids for different applications in vector control, as well as in disinsection of aircrafts, have been assessed by the World Health Organization (WHO). WHO recommendations on the use of pyrethroids include the following compounds:

• Indoor residual spraying: alpha-cypermethrin, bifenthrin, cyfluthrin, deltamethrin, etofenprox and lambda-cyhalothrin.
• Treatment of mosquito nets: alpha-cypermethrin, cyfluthrin, deltamethrin, etofenprox, lambda-cyhalothrin and permethrin.
• Aircraft disinsection: permethrin and D-phenothrin.

The most recent WHO assessments of the safety of these chemicals^* were used as the basis for this review, with additional information that became available afterwards. For this purpose, the following databases were searched: EXTOXNET, EPA, IARC, the International Programme on Chemical Safety (IPCS), Joint FAO/WHO Meeting on Pesticide Residues (JMPR), WHO Pesticide Data Sheets and other relevant WHO publications. A systematic search in the literature database PubMed, with particular attention to papers published after 1990, was also carried out. Furthermore, reports on cases were considered where exposure to pesticides, notably from aircraft disinsection, was alleged to have induced adverse health effects. The available literature is listed at the end of the document.

^* As per Table 1, p. 4: bifenthrin: IPCS, 1993; cyfluthrin: IPCS, 1997b; lamba-cyhalothrin: IPCS, 2000a, 2004a; alpha-cypermethrin: IPCS, 1996, 2004b; deltamethrin: IPCS, 2001; etofenprox: IPCS, 1994; permethrin: IPCS, 2000b; D-phenothrin: IPCS, 1989, 1990e.