Some practical problems arising from use of the gamma multihit model for risk estimation.

The Scientific Committee of the Food Safety Council recently recommended use of the gamma multihit model for risk assessment. Some practical problems arising from the use of this model are presented. In some instances the model produces what appear to be unreasonably high "safe dose" estimates. In other instances the estimates appear unrealistically low. Neither the original "standard" nor the "conservative" confidence limits seem adequate for practical application. The assumptions leading to the use of Abbott's correction are difficult to verify, but have a great effect on safe dose estimates. Indeed, the introduction of as little as 1% additive background into the gamma multihit model leads to safe dose estimates closer to those produced by the Armitage-Doll model than to those of the pure gamma multihit model.