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Wongwiwat TassaneeyakulDepartment of ToxicologyKhon Kaen University
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1) Understand the process of risk assessment.
2) Describe relationship between risk assessment and management.
3) What is the major component in performing risk assessment ?
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the capacity of a substance to cause an adverse effect in a specific organ or organ system
the probability that a hazard will occur under specific exposure conditions
The definition of risk is:
the weighing of policy alternatives and selection of the most appropriate regulatory actions
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RISK DEFINITIONS
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(Morgan 1993).
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How are risks measured and expressed?
Risks are measured by direct observation or by applying
mathematical models and a series of assumptions to animal data to infer risk to humans.
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Actual Number
Scientific Notation
Read As
1/101x10-1
1E-01
One in ten
1/1001x10-2
1E-02
One in a hundred
1/1,0001x10-3
1E-03
One in a thousand
1/10,0001x10-4
1E-04
One in ten thousand
1/100,0001x10-5
1E-05
One in a hundred thousand
1/1,000,000
1x10-6
1E-06
One in a million
1/10,000,000
1x10-7
1E-07
One in ten million
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(NRC, 1983)
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Relationship between risk assessment Relationship between risk assessment and risk managementand risk management
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Step #1Step #1Hazard IdentificationHazard Identification
In this initial step, Information is gathered and analyzed in a weight-of-evidence approach. Data usually consist of:
human epidemiology data
animal bioassay data
supporting data
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Cancer risk assessment
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Step #2 Step #2 Dose-Response Dose-Response AssessmentAssessment "The dose makes the poison."
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Acceptable Daily Intake (ADI)
No observed adverse effect level
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ผลการใช้แบบโมเดลทางคณิ�ตศาสตร�ท��ต�างก�นในการประมาณิข้ามช้�วงมายั�งข้นาดการไดร�บสารพิ�ษ aflatoxin B1 ในข้นาดต&�าๆ ก&าหนดให X = one-hit , M = multistage, W = Weibull, L = logit, G = multi-hit, และ P = probit model ตามล&าด�บ (Lu, 1996).
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Step #3Exposure Assessment
characterization of the exposure setting (e.g., point source, occupational source)
identification of exposure pathways (e.g., groundwater)
quantification of the exposure (e.g., µg/L water)
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ข้นาดการไดร�บตลอดช้�ว�ต หร*อ LADD (Lifetime Average Daily Dose)
LADD = [(conc. ) * contact rate * contact fraction * expos. duration] [(body weight) * (lifetime)]
HEEEs (high-end exposure estimates)
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Step #4Risk Characterization • Review toxicity and exposure
assessment output • Quantify risks • Combine risks across all pathways • Assess & present uncertainties • Consider site-specific human
studies, if available
• Summarize & present baseline riskassessment characterization results
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Risk Communication
(Raafat & Sadhra, 1999).
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Risk cannot be justified save1:1,000 per person/year
1:10,000 per person/year
Tolerable only if risk reduction is impracticable or if its cost is grossly disproportional to the gain
1:1,000,000 per person/year
Unacceptable region
The ALARP (As low as reasonably practicable) or tolerable region
Broadly acceptable region
1:10 million per person/year
Necessary to maintain assurance that risk remains at this level
Risk Communication