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Science Policy and Risk Forums

The ORACBA Risk Forums provide an opportunity for discussion of a broad range of policy-related scientific, and methodological issues concerning risk assessment. Forums are open to all public and private risk assessors.

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Optimal Food Safety Sampling Under a Budget Constraint

September 18, 2013
10:00 a.m. - 11:30 a.m.
USDA South Building, Rm. 4433
Mark Powell, ORACBA Risk Scientist
Much of the literature regarding food safety sampling plans implicitly assumes that all lots entering commerce are tested. In practice, however, only a fraction of lots may be tested due to a budget constraint. In such a case, there is a tradeoff between the number of lots tested and the number of samples per lot. To illustrate this tradeoff, a simple model is presented in which the optimal number of samples per lot depends on the prevalence of sample units that do not conform to microbiological specifications and the relative costs of sampling a lot and of drawing and testing a sample unit from a lot. The assumed objective is to maximize the number of nonconforming lots that are rejected subject to a food safety sampling budget constraint. If the ratio of the cost per lot to the cost per sample unit is substantial, the optimal number of samples per lot increases as prevalence decreases. However, if the ratio of the cost per lot to the cost per sample unit is sufficiently small, the optimal number of samples per lot reduces to one (i.e., simple random sampling), regardless of prevalence. In practice, the cost per sample unit may be large relative to the cost per lot due to the expense of laboratory testing and other factors. Designing effective compliance assurance measures depends on economic, legal, and other factors in addition to microbiology and statistics.

Government employees, please bring your government ID. If you are not a government employee, please call (202-720-8022) or e-mail Jennifer Lohr ( or Linda Abbott ( to register. You will need to bring a picture ID and be escorted to Room 4433.  Enter the South Building at the Wing 1 entrance at 12th and Independence (next to the entrance for the Smithsonian Metro station using the “Independence Ave” exit).  Room 4433 is on the 4th floor, 4th wing. If you would like to attend via webinar, please contact Jennifer Lohr at 202-720-8024 or by COB Sept. 17th.

This paper is currently available in the early view on-line version of Risk Analysis (DOI: 10.1111/risa.12054)

Risk Analysis: Advancing Analysis Workshop - Presentations

Mini-2013 SRA
June 18th, 2013
Washington, DC

Analysis to Support Regulations and Metrics Development

Lettuce, enterohemorrhagic E. coli and irrigation water: Application of FDA's iRISK rool for rapid risk assessment to support proposed produce regulation
Yuhuan Chen, Division of Risk Assessment, Office ofAnalytics and Outreach, CFSAN/FDA

Interagency Risk Assessment for L. monocytogenes in Retail Delis
Janell Kause, Scientific Advisor for Risk Assessment, Office of Public Health Science, FSIS, USDA

Quantitative Assessment of the Risk of Listeriosis from Soft-ripened Cheese consumption in the United States and Canada
Régis Pouillot, Division of Risk Assessment, Office of Analytics and Outreach, CFSAN/FDA

Methods for Risk Informed Decision Making

Addressing Chemical Contaminants Without Established Regulatory Limits in Meat, Poultry and Egg Products: the De Minimis Level Approach  
Alexander Domesle, Risk Analyst, Office of Public Health Science, FSIS, USDA

How do you model a "negligible" probability under the WTO Sanitary and Phytosanitary Agreement?
Mark Powell, Risk Acientist, Office of Risk Assessment and Cost-Benefit Analysis, OCE,USDA

Revising Analytical Methods in Response to New Data or Information

Using a systems approach to retrospective regulatory review: quantifying economic impact and potential risk reduction due to cumulative regulatory actions in an agricultural watershed in Washington
Linda Abbott, Director, Office of Risk Assessment and Cost-Benefit Analysis, OCE, USDA

EPA Dietary Exposure Assessment of Pesticides:  Overview and Evaluation of Updated Consumption Data on Commodity Intake and Exposure
Aaron Niman, LT, U.S. Public Health Service, Office of Pesticide Programs, HED, EPA

2012 Risk Forums

05/04/2013 Procedures for the Pesticide evaluation-assessment in the EU, role of EFSA, Dr. Jordi Serratosa, European Food Safety Authority (EFSA)

Science, Policy and Risk Forum, Estimation of cancer risks and benefits associated with a potential increased consumption of fruits and vegetables, Rick Reiss, Principal Scientist, Exponent


Risk versus Hazard – Lessons from Europe, Ragnar Löfstedt, of King’s College of London