1. Quantitative Risk Assessment
Don Schaffner, Ph.D.
Rutgers, The State University of NJ
Food Safety Microbiology - February, 2005

2. Food Safety Microbiology - February, 2005
Overview
How does risk analysis relate to risk assessment?
How is risk assessment applied to food microbiology?
A very simple example of a quantitative risk assessment
Web links and more information
Food Safety Microbiology - February, 2005

3. Risk Analysis Components
(Quantitative) Risk Assessment
How big is the risk, what factors control the risk?
Scientific process
Risk Communication
How can we talk about the risk with affected individuals?
Social and psychological process
Risk Management
What can we do about the risk?
Political process
Food Safety Microbiology - February, 2005

4. Food Safety Microbiology - February, 2005
Cartoon
Food Safety Microbiology - February, 2005

5. Step in Risk Assessment
Hazard Identification
What microbe, food(s) and people are involved?
Exposure Analysis
What is the chance of exposure?
How many cells?
Dose-Response Analysis
What is the human health effect of the exposure?
Risk Characterization
Complete picture of the assessed risk
Food Safety Microbiology - February, 2005

6. Hazard Identification
Epidemiological data linking
Foods
Pathogens
Human illness
Special considerations
Disease complications
Acute vs. chronic disease
Specific sensitive consumer populations
Characteristics of the organism
Organisms mode of action
Food Safety Microbiology - February, 2005

7. Food Safety Microbiology - February, 2005
Exposure Analysis
Estimate
likelihood of consumption
likely number (dose) of the pathogen
If “quantitative” assessment
Modeling
Simulation
Food Safety Microbiology - February, 2005

8. Exposure - Simple Example
Initial number of organisms follows a Poisson distribution
Growth rate is normally distributed
Product composition and storage temperature are fixed
The product becomes unsafe when it contains 100,000 organisms/gram
Food Safety Microbiology - February, 2005

9. Initial number - Poisson
Food Safety Microbiology - February, 2005

10. Food Safety Microbiology - February, 2005
Growth rate is normal
Food Safety Microbiology - February, 2005

11. Food Safety Microbiology - February, 2005
Simulation Results
Food Safety Microbiology - February, 2005

12. Dose-Response Analysis
Translates exposure analysis output in to a measure of human health
If “quantitative”
Use dose-response curve
Estimate probability of infection and illness from dose
Food Safety Microbiology - February, 2005

13. Food Safety Microbiology - February, 2005
Dose response curve
Cassin et al. Quantitative risk assessment for Escherichia coli O157:H7 in ground beef hamburgers. Int.J.Food Micro. 41 (1):21-44, 1998.
Food Safety Microbiology - February, 2005

14. Dose-Response factors
Statistical model(s) to analyze or quantify dose- response relationships
Threshold vs. non-threshold models
Dose response data
Human
Animal
Outbreak or intervention data
Food Safety Microbiology - February, 2005

15. Dose-Response factors
Source and preparation of challenge material or inoculum
Organism type and strain
Virulence factors or other measures of pathogenicity
Characteristics of the exposed population
Age, immune status, etc.
Food Safety Microbiology - February, 2005

16. Risk Characterization
Final task in risk assessment
Combines the information from
Hazard identification
Exposure analysis
Dose-response analysis
Produces a complete picture of the assessed risk
Food Safety Microbiology - February, 2005

17. A good risk assessment…
Transparent
Iterative
Includes…
Variability and uncertainty
Management input into problem formulation
Food Safety Microbiology - February, 2005

18. A hot-air balloon floats overhead…
RM: I’m lost, can you tell me where I am?
RA: Sure, you are 30 feet off the ground
RM: Aha, you must be a risk assessor
RA: Why yes, how did you know?
RM: Because what you told me was technically correct, but of absolutely no use.
Food Safety Microbiology - February, 2005

19. A hot-air balloon floats overhead…
RA: Aha, you must be a risk manager?
RM: Why yes, how do you know?
RA: That’s easy, you don’t know where you are, what you want or where you are going… and you are in the same position now as you were before you asked for my help, but now it’s my fault!
Food Safety Microbiology - February, 2005

20. Importance of risk assessment
Teaching
Students can see “what if...”
Research
Pinpointing uncertainties or knowledge gaps
Industry
Optimizing safety while retaining quality
Government
Designing regulations for the greatest benefit
Food Safety Microbiology - February, 2005

21. Food Safety Microbiology - February, 2005
For more information
Annotated bibliography on Food Safety Risk Assessment, Management and Communication
Food Safety Risk Analysis Clearinghouse
Food Safety Microbiology - February, 2005

22. Food Safety Microbiology - February, 2005
For more information
Revised Framework for Microbial Risk Assessment – ILSI
WHO/FAO microbial risk analysis page
Food Safety Microbiology - February, 2005

23. Food Safety Microbiology - February, 2005
Software
USDA Pathogen Modeling
@risk
Crystal ball
Analytica
Food Safety Microbiology - February, 2005

24. Food Safety Microbiology - February, 2005
Books
T. A. McMeekin, et al. Predictive microbiology: Theory and application, Somerset, England:Research Studies Press Ltd., 1993.
C.H. Haas, et al. Quantitative microbial risk assessment, Ny, NY: John Wiley & Sons, 1999.
D. Vose. Risk Analysis: A Quantitative Guide, Chichester:John Wiley & Sons, 2000.
Food Safety Microbiology - February, 2005

25. Published risk assessments
S. enteritidis in eggs
Listeria in RTE foods
Fluoroquinolone Resistant Campylobacter in Chicken
Food Safety Microbiology - February, 2005

26. Published risk assessments
Vibrio in shellfish
E.coli O157:H7 in ground beef
Campylobacter in chicken
Food Safety Microbiology - February, 2005

27. Food Safety Microbiology - February, 2005
Cartoon
Food Safety Microbiology - February, 2005