Innovative Modeling Approaches Applicable to Risk Assessments Thomas P. Oscar, PhD USDA, ARS Princess Anne, MD, USA

Risk Assessment  Hazard Identification  Hazard Characterization  Exposure Assessment  Risk Characterization Predictive Microbiology Food Safety Information

What came first?  Risk Assessment Model  Predictive Model I say, I say, son… its easier to fit round pegs into round holes

Hazards  Chemical  Physical  Microbial

Hazard Events  Rare  Random  Variable  Uncertain growth death survival removal contamination

Rare Events Modeling Iteration : 100 Discrete 1 0 : 0 Pert (0,1,4) : 2.2 Power : 0 Round 63 0 : 0 =RiskDiscrete({90,10},{0,1}) =RiskPert(0,1,4) =Power(10,Pert) =Round(IF(Discrete=0,0,Pert),0)

20% J. Food Safety (1998) 18: Unit Operation Hazard Event IncidentExtentPackaging Initial Contamination 20% 1 (0 – 3) log/bird DistributionGrowth20% 0.5 ( ) logs RAREEVENTSMODELINGRAREEVENTSMODELING RISKASSESSMENTRISKASSESSMENT

0.9% J. Food Safety (1998) 18: Unit Operation Hazard Event IncidentExtentCookingSurvival20% -1.5 (-2 to -1) logs

7.0% J. Food Safety (1998) 18: Unit Operation Hazard Event IncidentExtentServingCross-contamination25% 2 (1 to 5)% transfer No correlation!

J. Food Safety (1998) 18: Normal Risk High Risk Unit Operation Hazard Event IncidentExtentConsumption Normal Risk 80% 750 ( ) cells High Risk 20% 200 (50 to 350) cells Healthy Old Anti-microbials High Fat Probiotic Clinical isolate

Relative risk of salmonellosis = (Dose Consumed ÷ Infection Dose) * 100 J. Food Safety (1998) 18: Higher risk!

Hazard Identification  Cornerstone  Expensive  Number and Subtype  Packaging

Microbial Ecology  Minority  Unattached  Attached  Entrapped

Standard incubation conditions Rare Events Model (Initial Contamination) Detection limit = 10 2 cells/ml Target pathogen (< 1/ml) Detection Time J. Food Prot. (2004) 67(6):

Sample Control Time, h Qualicon BAX™ PCR System for Salmonella spp. PCR Score = 12 None = 0 Faint = 1 <Full = 2 Full = 3 J. Food Prot. (2004) 67(6): >10 4 <10 2

Final Standard Curve 95% Prediction Interval J. Food Prot. (2004) 67(6):

Predictive Model J. Food Prot. (2004) 67(6): Rare Events Model

Exposure Assessment Develop predictive models for hazard events from hazard identification to consumption GrowthSurvival Cross-contamination Physical Removal

Real Food + Microbial Competition + Low Dose  MPN  CFU J. Food Prot. (2006) 69(9): J. Food Prot. (2008) 71(6): J. Food Prot. (2009) 72(2): J. Food Prot. (2009) In press

General Regression Neural Network (GRNN) Model Rare Events Model J. Food Prot. (2009) in press

Hazard and Risk Characterization Severity of Illness Infected Mild Illness Doctor Severe Illness Hospital Chronic Disability Death

Hazard Characterization Uniform Pathogen Food Host Human feeding trials are no longer ethical!

Risk Anal. (2004) 24(1): Rare Events Model

Risk Anal. (2004) 24(1):41-49.

Disease Triangle Modeling Hazard Host Food -1 log -2 log -0.5 log Very young Very old Cancer Diabetes HIV Pregnant : Top clinical isolate Acid resistant : High fat Anti-acid : Oscar, book chapter, in press High Risk

Disease Triangle Model Rare Events Model

Relative versus Absolute Risk 0% Absolute 100% Absolute Human feeding trials are not ethical! 100% Relative 0% Relative

Scenario Analysis  Plant A  Plant B Oscar, book chapter, in press

Risk Pathway Packaging (Contamination) Distribution (Growth) Washing (Removal) Cooking (Survival) Serving (Contamination) Consumption (Dose-response) I see only one risk pathway

Module A90%10%Plant B Oscar, book chapter, in press Rare Events Model

Module B Oscar, book chapter, in press Rare Events Model

Risk Assessment Results Your fired! n = 200 replicate simulations per scenario

I see two risk pathways I see data gaps! Hazard strain Time & Temp Predictive Models Consumer Surveys Packaging (Contamination) Distribution (Growth) Washing (Removal) Cooking (Survival) Serving (Contamination) Consumption (Dose-response)

Research Results Plant A Plant B Initial Contamination 25%10% Temperature Abuse 20%40% Washing15%30% Proper Cooking 90%90% Cross-contamination15%30% High Risk Food 10%10% High Risk Pathogen 20%60% High Risk Host 20%30%

Filtered Results

Exposure Assessment Oscar, book chapter, in press

Hazard Characterization Oscar, book chapter, in press

Risk Characterization  Single Risk Pathway  Multiple Risk Pathways

Unsafe Safe Single Risk Pathway

Multiple Risk Pathways Unsafe Safe

The End Thank you for your attention! I will be glad to answer your questions