WHO FOOD ADDITIVES SERIES: 53

First draft prepared by

Professor L. Ritter
Canadian Network of Toxicology Centres, Department of Environmental Biology, University of Guelph, Ontario, Canada; and

and

Dr K. Greenlees
Division of Human Food Safety, Office of New Animal Drug Evaluation, Center for Veterinary Medicine, Food and Drug Administration, Rockville, Maryland, USA

Cypermethrin and alpha-cypermethrin are highly active pyrethroid insecticides, which are effective in public health and animal husbandry, and target a wide range of pests in agriculture. Cypermethrin has been widely used throughout the world since the late 1970s, while alpha-cypermethrin has been available commercially since the mid 1980s. The present Committee responded to a request from the Codex Committee on Residues of Veterinary Drugs in Foods (CCRVDF) at its Fourteenth Session (Codex Alimentarius Commission, 2003) to consider the establishment of a common ADI and common MRLs, for both cypermethrin and alpha-cypermethrin.

At its forty-seventh meeting (Annex 1, reference 125), the Committee evaluated cypermethrin and alpha-cypermethrin and established an ADI of 0-0.05 mg/kg bw for cypermethrin and of 0-0.02 mg/kg bw for alpha-cypermethrin. The Joint FAO/WHO Meeting on Pesticide Residues (JMPR) had also evaluated cypermethrin and established an ADI of 0-0.05 mg/kg bw (JMPR, 1980, 1982).

Cypermethrin typically contains 20-40% alpha-cypermethrin. The Committee noted that alpha-cypermethrin comprises the two most toxicologically active isomers of cypermethrin. As the ratio of isomers in commercial cypermethrin products is variable, the toxicity of these products also varies. The NOEL for alpha-cypermethrin alone was lower than that for cypermethrin. However, the observed toxicity was qualitatively similar. The Committee also noted that the metabolism of alpha-cypermethrin and of cypermethrin is similar, although not identical.

At its present meeting, the Committee received only new data on analytical methods.

The Committee concluded that as alpha-cypermethrin alone and cypermethrin are qualitatively similar in their toxicity and metabolism, and in view of the fact that cypermethrin includes a substantial proportion of alpha-cypermethrin, the ADI previously established for alpha-cypermethrin could apply for both substances. alpha-Cypermethrin is more toxic than cypermethrin, and the proportion of alpha-cypermethrin in cypermethrin may depend on the commercial source. The Committee reconfirmed the NOEL for alpha-cypermethrin of 1.5 mg/kg bw per day on the basis of a 52-week study in dogs fed with alpha-cypermethrin, as identified at the forty-seventh meeting.

The Committee established a group ADI of 0-0.02 mg/kg bw for cypermethrin and alpha-cypermethrin, using a safety factor of 100 and by rounding up.

Codex Alimentarius Commission (2003) Report of the Fourteenth Session of the Codex Committee on Residues of Veterinary Drugs in Foods, Arlington VA, USA. 4-7 March 2003. Rome, Food and Agriculture Organization of the United Nations (unpublished document ALINORM O3/31A).

European Agency for the Evaluation of Medicinal Products in 1998 (EMEA, 1998).

JMPR (1980) Pesticide residues in food—1979. Report of the Joint Meeting of the FAO Panel of Experts on Pesticide Residues in Food and the Environment and the WHO Expert Group on Pesticide Residues. Rome: Food and Agriculture Organization of the United Nations (FAO Plant Production and Protection Paper, No. 26).

JMPR (1982) Pesticide residues in food—1981. Report of the Joint Meeting of the FAO Panel of Experts on Pesticide Residues in Food and the Environment and the WHO Expert Group on Pesticide Residues. Rome: Food and Agriculture Organization of the United Nations (FAO Plant Production and Protection Paper, No. 37).

    See Also:
       Toxicological Abbreviations
       Cypermethrin and alpha-cypermethrin (WHO Food Additives Series 38)