Quantitative BSE risk assessment: relating exposures to risk

Area of Science:

• Veterinary Epidemiology
• Food Safety
• Risk Assessment

Background:

• Bovine Spongiform Encephalopathy (BSE) transmission routes to humans lack epidemiological evidence.
• Consumption of infected bovine offal before 1989 is the suspected primary source.
• Quantitative risk assessment (QRA) is used to evaluate potential exposure routes.

Purpose of the Study:

• To critically evaluate QRA for BSE transmission risks.
• To compare risks from consuming beef-on-the-bone versus contaminated drinking water.
• To identify limitations in current BSE risk assessment methodologies.

Main Methods:

• Application of quantitative risk assessment methods.
• Analysis of exposure routes: beef-on-the-bone consumption and contaminated water ingestion.
• Comparison of predicted risk levels and underlying assumptions.

Main Results:

• Predicted risks for beef-on-the-bone (10^-9 person^-1 year^-1) are considered realistic.
• Predicted risks for contaminated drinking water (10^-8 person^-1 year^-1) may be overestimated by ~10^20.
• Discrepancies arise from differing exposure doses and lack of consideration for threshold effects in waterborne exposure.

Conclusions:

• Direct comparison of BSE risks across dissimilar exposure routes is cautioned against.
• The existence of a threshold effect for BSE prion infection is critical for environmental risk assessment.
• Further research on threshold effects is more vital than precise species barrier magnitude for environmental BSE risk.