Human health risk assessment
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Transcript of Human health risk assessment
National University of Malaysia
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Human Health Risk Assessment
28-Jan-14
Wan Zuhairi Wan Yaacob (Assoc. Prof, PhD) Faculty of Science and Technology
National University of Malaysia 43600 Bangi, Selangor, MALAYSIA.
National University of Malaysia
Risk Assessment
• Risk Assessment in daily life !!
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National University of Malaysia
2 types of Risk Assessment
1. QRA – Quantitative Risk Assessment – Risk = Likelihood x consequences
2. ERA – Environmental Risk Assessment a) Human Health Risk Assessment (HRA)
• Health related risk
• Risk = hazard x exposure
• (i) carcinogenic (ii) non-carcinogenic chemicals
b) Ecological Risk Assessment (ERA) • Ecological risk at sites
• Risk = hazard x exposure
Fukushima Daiichi nuclear disaster
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Quantitative Risk
• Hazard
• Probability
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RISK in Oil and Gas Industry
National University of Malaysia
Risk Assessment
• Risk of particular event =
probability of that event to occur x consequence of the event
• Consequence = damage to people, property, economic activity, public service, etc)
• Large earthquake: low probability but high consequence
• Acceptable risk
– Minimum risk that people can accept
– Eg. Driving a Car
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National University of Malaysia
Risk Assessment & Risk Management?
RISK PERCEPTION
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RISK ASSESSMENT
RISK MANAGEMENT
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Risk Assessment (Risk Matrix)
E = Extreme risk; H = High Risk; M = Medium Risk; L = Low Risk
Example: • Risk of travelling by car in Malaysia? • Risk of travelling with an aeroplane
nowadays?
Example • Risk of volcanic eruption in Malaysia? • Risk of earthquake in Japan?
National University of Malaysia Concept of Human Health Risk (1)
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Risk = hazard x exposure
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National University of Malaysia Concept of Human Health Risk (2)
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RISK : Source ------ Pathways ------ Receptors 10 28-Jan-14
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Concept of Source – Pathways - Receptors
SOURCE PATHWAYS RECEPTORS RISK
YES
NO
NO
NO
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Human Health Risk Assessment (HRA)
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Oil Well Pump
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• Quantify contaminant intake at the point of exposure
• Intake = I
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Exposure Assessment
(Intake)
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Exposure Assessment
The General Equation for chemical intake is:--
• I = intake (mgkg-1d-1)
– Mg/kg body weight per day
• Chemical related variable, C
– Chemical concentration; the average concentration contacted over the exposure period (eg, mg/L water or mg/kg soil or PPM)
• Variables that describe the exposed population
– CR = contact rate; the amount of contaminated medium contacted per unit time or event (eg. Litres/day)
– EFD = exposure frequency and duration, describes how often and how long exposure occurs. Often calculated using two terms (EF & ED)
– EF = exposure frequency (days/year)
– ED = exposure duration (years)
– BW = body weight; the average body weight over the exposure period (kg) – 70kg (Adult 70kg ; infant (5 kg) ; children (10kg)
I = C x CR x EFD -------------- BW x AT
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• Assessment-determined variable
– AT = averaging time OR total exposure time; period over which exposure is averaged (days)
– (1) For evaluation of carcinogenic effects, AT = life expectancy for population of concern (70 years in US) x 365 days/year
– (2) For evaluation of non-carcinogenic effects, AT = ED x 365 days/year
Exposure Assessment
I = C x CR x EFD -------------- BW x AT
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Toxicity values
• Animal studies
Rats Uncertainty factor(UF) or safety factor (SF)
Toxicity value for human
Cancer slope factor (SF) Reference dose (RfD)
Feeding, inhalation testing
Uncertainty factor(UF) or safety factor (SF)
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Toxicity values for Carcinogens
• Use slope factor (y = mx)
• There is no threshold
because exposure to any
level of a carcinogenic
chemical poses a probability,
however small, of generating
carcinogenic response.
• The curve passes through
the origin
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(mg/kg/day)-1
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No Observed Adverse Effect Level (NOAEL)
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RISK CHARACTERIZATION
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Determination of non-carcinogenic risk
• Represented by Hazard Quotient (HQ); the ration of chronic daily intake to RfD:
HQ = I / RfD
• HQ = hazard index (dimensionless) • I = the intake (TDI, mgkg-1d-1) • RfD = reference dose (mgkg-1d-1)
• HQ <1.0 = acceptable risk for all contaminants and routes of exposure
• HQ>1.0 = the receptors are exposed to the contaminant
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• Acceptable Non-Cancer Hazard Quotient (or Hazard Index)
– US Superfund NCP codified acceptable HQ of 1
– DOE Malaysia (2009); HQ = 1
– US Clean air Act; HQ =1
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; DOE = CLMCG No 2
Determination of non-carcinogenic risk
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Determination of carcinogenic risk
• Carcinogenic risk is a function of the chronic daily intake (CDI – chemical intake) and the slope factor (SF):
US: RISK = CDI x SF
• Risk is the probability of carcinogenic risks (fractions); unitless; IELCR = incremental Excess Lifetime Cancer Risk
• CDI or lifetime average daily dose= daily intake (CDI, mgkg-1d-1) -- exposure
• SF = carcinogenic slope factor (mgkg-1d -1) -1
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Acceptable cancer risk levels
• US State RBCA Target Risk Policies: 10-5 to 10-4 for development of risk based soil and groundwater cleanup standards.
• US Clean Air Act : risk 10-4
• Malaysia (DOE, 2009) : 1/10000 to 1/1,000,000 @ 10-4 to 10-6
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Summary (1)
RISK OF CHEMICAL OF CONCERN
EXPOSURE TO HUMAN
• Inhalation
• Ingestion
• Contact
TOXICITY OF CHEMICAL
• Carcinogenic • Non-Carcinogenic
• Use slope factor • Use NOAEL
Calculate Risk for Carcinogenic
Calculate Risk for Non-Carcinogenic
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Summary (2)
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Conclusions - Risk is always present - Risk can be assessed (calculated) - Risk can also be managed properly to avoid any health effect / accidents
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Computer Software
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National University of Malaysia
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Thank you