[BSE: milk and risk potential?].

A potential BSE risk for milk and milk products has to be evaluated by means of risk analysis, especially risk assessment. The 3rd element of risk assessment--hazard exposition--is of decisive significance. In 1997, the Scientific Steering Committee of the European Commission has categorized risk materials in 4 classes. Colostrum, milk and tissues of the mammary gland have been classified in category 4, i.e. "infectivity not detected". A secondary contamination of the milk can be excluded (living animals). However, the term "not detected" refers also to the low sensitivity of the mouse test, which has to be taken into consideration. Therefore, in 2000 investigations started in Great Britain to test milk fractions, especially the fraction of somatic cells, for the possible occurrence of prions, using newly developed and highly sensitive methods. Results can not be expected before 2003 at the earliest. In case prions would be detected, their biological activity has to be demonstrated in order to develop an appropriate risk assessment for the consumer. Investigations in Great Britain in the early nineties of the last century with suckling cows under practical conditions have shown no indications of a BSE transfer via the milk to the calves. Therefore, the statement of national and international organizations is still valid, that milk can be regarded safe according to the present state of scientific knowledge.