Following a request from the European Commission, the Panel on Contaminants in the Food Chain was asked to deliver a scientific opinion on cross-contamination of non-target feedingstuffs by narasin authorised for use as a feed additive. Narasin is a polyether carboxylic ionophore agent that is authorised according to Commission Regulation No (EC) 1464/2004 as a coccidiostat for use in chickens for fattening with a maximum content of the active substance in feed of 70 mg/kg and a withdrawal period of one day. Despite the requirements set for feed business operators in Regulation No (EC) 183/2005, it is generally acknowledged that under practical conditions during the production of mixed feeds, a certain percentage of a feed batch remains in the production circuit and these residual amounts can contaminate the subsequent feed batches. This cross-contamination may result in the exposure of non-target animal species, and hence the potential health risks for non-target animal species as well as potential residues in foods derived from these non-target animal species have been evaluated. Signs of intoxication, including anorexia, dyspnoea, lung oedema, liver cell necrosis and muscle fibre damage have been reported to occur in various non-target animal species. These signs of toxicity are consistent with the mode of action of polyether ionophores. Particularly sensitive are dogs, horses, cattle and probably turkeys and rabbits. Toxicity occurred in turkeys and rabbits at feed concentrations lower than the maximum level authorised for chickens for fattening. This reflects the considerable species differences in sensitivity and the small margin of safety between the effective dose of narasin as a coccidiostat and the dose that causes toxicity. The Panel concluded that in sensitive non-target animal species adverse effects may occur at feed concentrations below the maximum level authorised for use in chickens for fattening. In contrast, it is expected that no toxicological or pharmacological effects will occur in non-target animals given feed containing narasin at the dietary levels resulting from cross-contamination up to 10 % of the maximum amount permitted in the feed of target animals. This expectation is based on a comparison of the level of exposure of non-target animal species to narasin via contaminated feed batches with the no-observed-adverse-effect-level (NOAEL) derived from toxicological and pharmacological studies. In dogs, the most sensitive laboratory animal species, a NOAEL of 0.5 mg/kg b. w. was identified, based on the induction of neurotoxicity in a one-year feeding trial. Assuming a feed intake of approximately 50 g/kg b.w. per day, which is applicable to most monogastric food-producing animals and levels of cross contamination of 2, 5 and 10 %, this would result in levels of exposure of 0.07, 0.17 and 0.35 mg/kg b. w. per day, respectively, which are all below the NOAEL. Kinetic studies in various animal species showed that narasin does not accumulate in edible animal tissues. When given to laying hens it can be found in eggs. The highest levels of narasin residues found in edible tissues of non-target animals in kinetic studies (pig liver and chicken eggs) were used to calculate a worst-case estimate of consumer exposure to narasin. No data on possible carryover into milk are available. These calculations indicated that human exposure estimated to result from consumption of food products from non-target animal species exposed to feed cross-contaminated up to a level of 10 %, would be well below the acceptable daily intake (ADI) of 5 ae g/kg b. w. as established by the EFSA Panel on Additives and Products or Substances used in Animal Feed (FEEDAP Panel). Therefore, the Panel concluded that there is negligible risk to consumers' health from ingestion of narasin residues in tissues of animals exposed to feed cross-contaminated up to a level of 10 %.
