Risk assessment of BSE infectivity in the environment from rendering of over thirty month scheme cattle

Abstract

One of the measures put in place by the UK government following the emergence of new variant CJD and the likely link to BSE in cattle was the exclusion of older cattle from food for human consumption, the so called Over Thirty Month Scheme. Cattle slaughteredunder this scheme are rendered to produce Meat and Bone Meal and tallow for subsequent disposal. Concern was expressed about the liquid waste effluent from one rendering plant, which was being discharged to a soakaway over an aquifer used for public drinking water supply. This risk assessment was carried out for the UK Environment Agency to assess whether the public drinking water supply was safe, and to evaluate alternative options. The study considered both normal effluent and accidental spills, and evaluated the various barriers that affect the amount of infectivity getting into the drinking water supply. The study was able to demonstrate that the risks to people drinking the water are extremely low, and thus provide a useful input to decision making even with the high levels of uncertainty about many of the input parameters.