Transcript Identifying Research Needs for Risk Assessment of US Food Supply Security Bruce Hope

Identifying Research Needs
for Risk Assessment of U.S.
Food Supply Security
Bruce Hope
Oregon Department of Environmental Quality
Portland, Oregon
Society of Toxicology
Risk Assessment Specialty Section (RASS)
Monthly Teleconference
April 13, 2005
Why risk?
 Much is possible, not all is probable.


Hazard is about possibility
Risk is about probability
 Risk is 
Probability that exposure to a pathogen will result in a
negative consequence of some magnitude.
 When probability is ignored…


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High & low priority scenarios may appear equal
Scarce resources may go to low priority scenarios
Confusion over priorities = decision paralysis
Caveat: unconventional  improbable
SOT Telecon (4/05)
A complex human food supply chain…
meat & poultry
dairy
fish & seafood
eggs
R
ANIMAL
PRODUCTION
grain elevators
shippers
feed lots
R
fresh products
prepared products
R
T
R
R
FARM
INPUTS
T
R
T
MULTIPLE FARM
SOURCES
R
R
FARM
PRODUCT
ASSEMBLERS
R
T
R
seed
feed
fertilizer
pesticides
END-PRODUCT
PROCESSORS
CROP
PRODUCTION
grains
oil seeds
fruits
vegetables
MULTIPLE FARM
SOURCES
T
R
R
R
T
INGREDIENT
PROCESSORS
T
milling
slaughtering
crushing
starches
flavorings
R
R
T
T
R
R
T
STORAGE
R
WHOLESALERS
T
Transportation of products between
stages in the system.
R
Potential bioagent
release point.
supermarkets
convenience stores
co-op
restaurants
hotels
schools
hospitals
military bases
vending
farmer’s markets
community feeding
R
R
general home
specialty products
food service
T
RETAILERS
R
CONSUMERS
Is essentially…
PATHOGEN
(source)
EXPOSURE
SCENARIO
(plausible)
TARGET
(susceptible)
 Credibility and urgency of a threat is directly
proportional to the overall probability of this
specific chain of events

Probability of whole process, not just one part, controls
SOT Telecon (4/05)
A context for research needs…
Release
Characterization
PATHOGEN
Dose-Response
Assessment
EXPOSURE
SCENARIO
Hazard
Characterization
TARGET
Exposure
Assessment
SOT Telecon (4/05)
So we need to consider…
 The probability of their being a source and a
target, connected by a plausible chain of events.
 The probabilities associated with the actuality of
source, target, and connecting events.
 The biological, environmental, and cultural
factors which influence these probabilities.
 Research to identify, understand, and quantify,
as well as help alter, these probabilities.
SOT Telecon (4/05)
Risk assessment process
HAZARD
CHARACTERIZATION
PROBLEM
FORMULATION
RISK
MANAGEMENT
ACTION!
RELEASE
CHARACTERIZATION
EXPOSURE-RESPONSE
ASSESSMENT
EXPOSURE
ASSESSMENT
RISK
CHARACTERIZATION
SOT Telecon (4/05)
Hazard characterization
 Factors affecting probability of a pathogen being
chosen as a bioweapon, then obtained, handled,
deployed, and transported successfully.







Virulence and pathogenicity
Pathologic characteristics and diseases caused
Survival and multiplication
Resistance to environmental control measures
Host specificity
Infection mechanism and route; portal of entry
Ecology and natural history; potential for 2° spread
 More attention to non-weaponized agents.
SOT Telecon (4/05)
Hazard characterization (RI 1984)
 Rajneeshee Incident – The Dalles, Oregon – 1984
 Motivation / objectives / needs



Prevent vote for county court hostile to cult
Sicken – dead OK, but no mass casualties
Difficult to detect
 Agent needs v. capabilities - Salmonella



Not highly lethal, common, hard to detect as bioweapon
Not robust, not persistent – affects release mechanism
High probability of obtaining, handling, deploying

Had technically trained personnel & laboratory facilities
SOT Telecon (4/05)
Release characterization
 Factors affecting probability of release for
differing exposure scenario.

Logistical


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Deployment requirements (technical)
Special equipment / handling requirements
Access to desired exposure scenario(s)
Biological (pathogen characteristics)


Environmental requirements (hardiness)
Compatibility with desired exposure scenario(s)
SOT Telecon (4/05)
Release characterization (RI 1984)
 Bioagent characteristics dictated an exposure
scenario with a release point close to target
 Using a technically and logistically undemanding
release mechanism

Cult members placed agent in creamer & salad dressing
at 3 restaurants in county



Several bumbling, abortive attempts in other venues
Easy access, low probability of detection / interdiction
Plausible deniability – “…it’s just food poisoning…”
 Low probability of release failure, yet...
SOT Telecon (4/05)
Exposure assessment
 Factors affecting probability of exposure for
differing exposure scenarios.

Transport & fate characteristics


Pathogen ecology


Environmental reservoirs; amplification, die-off,
persistence
Characteristics of exposed population



Routes of exposure and transmission potential
Demographics (age, immune status, size, etc.)
Feeding behavior (preferences & cultural practices)
Counter-measures

Probability of detection in various media and biological
matrices; detection methods.
SOT Telecon (4/05)
Exposure assessment (RI 1984)
 Transport & fate characteristics



Direct ingestion exposure, limited transport ability
Not persist, no environmental reservoirs
Exposed population assume food is clean, salad is not
processed further
 Counter-measures

Low probability of detection, high probability of
interdiction if detected
 Actual exposure dose impossible to quantify
SOT Telecon (4/05)
Fault Tree Analysis
Estimates probability of
dose (D) of organisms
reaching the target
Probability of
bioagent being
present
AND
Bioagent
not interdicted
in node
Bioagent present
in node
OR
OR
Present from
internal source
Interdiction
Enters from external
environmental source
Enters from
intentional
release in node
Enters from
prior node
AND
Detection
Environmental
conditions
Access
resources
BT has
resources to
access node
BT has technical
dissemination
capabilities
AND
AND
Access
requirements
Dissemination
capabilities
Dissemination
requirements
Exposure – response assessment
 Improved quantification of dose-response for
known pathogens.

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Model fit to data
Applicability of animal models
Assessing multiple exposures
Development of mechanistic (v. empirical) models
Differential response by sensitive sub-populations
 Dose-response studies for new and emerging
pathogens.

Only a few of 150+ enteric viruses studied for doseresponse in human volunteers.
SOT Telecon (4/05)
Exposure-response (RI 1984)




D

Pi  1   1   

  

Risk Assessments of Salmonella in Eggs and Broiler Chickens - 1 - Interpretative Summary.
World Health Organization, Food and Agriculture Organization of the United Nations (2002)
SOT Telecon (4/05)
Risk characterization (RI 1984)
Applied dose not
quantified,
but sufficient to
induce 751
reported
cases of illness.
SOT Telecon (4/05)
Suggestions
 Bioagent of choice need not be:


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
Weaponized
Restricted to a particular pathway (e.g., inhalation)
Harmful to humans or difficult to handle
Hard to obtain
 Food supply as a delivery system

Good for localized impact, poor for mass casualties

Possibly with a “specialized” bioagent?
 Food supply as the target


Loss of system services
Loss of confidence in system

Significant 2° health and economic impacts
SOT Telecon (4/05)