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.


Risk Assessment

• Risk Assessment in daily life !!

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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


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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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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2

3

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)


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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Thank you

Date post:	29-Nov-2014
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Human health risk assessment

Education