Risk Assessment. Risk Assessment Topics What is Risk? Risk, Hazard and Exposure How is Risk...

Risk Assessment

Risk Assessment Topics

What is Risk? Risk, Hazard and Exposure How is Risk Expressed? Risk Categories What is Risk Assessment? Risk Assessment Applications

What is Risk?

Risk is the probability or likelihood of an adverse effect due to some hazardous situation

Safety is the complement of risk, or the probability that an adverse effect will not occur

Risk = f ( Hazard, Exposure)

Magnitude or severity of risk are a function of the type of harm i.e. Hazard and the extent or likelihood of Exposure

Leaking Pipe

Risk and Hazard Determination

Leaking Pipe

Leaking Pipe

Hazard : Potential for creating undesired adverse consequences.In this case it remains same as chemical flowing through pipe is same.

Leaking Pipe

Exposure : Vulnerability to hazardPipe 2 poses greatest risk of exposure due to leakage.

How is risk expressed?

Probability of adverse effects associated with a particular activity

Unitless From 0-1E.g. 1x10-1 - One in 101x10-2 - One in 100

Factors in Risk Acceptability Voluntary

– Smoking– Bungee Jumping– Diet

Nonvoluntary– Risk resulting from uncontrollable actions of others (Occupational

exposure, pesticide residues)– Natural disasters

Degree of control Magnitude of the outcome Awareness Catastrophic Potential Group involvement Cost of alternatives

Activity Annual RiskSmoking 10 cigarettes/day 1 x 10-3

Motor vehicle accidents 2 x 10-4

Manufacturing work accident 8 x 10-5

Pedestrian hit by automobiles 4 x 10-5

Drinking two beers/day 4 x 10-5

Person in a room with a smoker 1 x 10-5

Peanut butter (4 teaspoons/d) 8 x 10-6

Drinking water with EPA limit of Trichloroethene 2 x 10-9

Risk Values

What is Risk Assessment?

Analytical tool for studying situations that could result in adverse consequences

Qualitative and quantitative assessment of environmental status

Process to identify and quantify the risk and select necessary action

Risk Assessment Applications

Identification of any ecological risk

Identification of the need for additional data collection

Site remediation alternative selection

Establishment of cleanup standards

Remediation Options?

No Action

Excavation, Incineration/re-

landfilling

In place containment, groundwater pumping

and retreatment alternative

No Action

No capital cost Groundwater contamination is definite

In place containment, groundwater pumping

and retreatment alternative

Creating a barrier to prevent or extend the

groundwater contamination around the site

Construction of containment

facility

Air Stripping

Volatilization and Particulate migration

Volatilization

Excavation Incineration/

Re-Landfilling

Vehicular transport to incinerator

Stockpiling at

incinerator Incinerator

Re- Landfilling

Particulate migration /

Volatilization

Flue Gas Emissions

Process

H a z a r d

D a t a

I d e n t i f i c a t io n

D o s e - R e s p o n s e

R is k M a n a g e m e n t

W h a t a g e n t s a r e p o t e n t i a l l y h a r m f u l ?

W h o w i l l b e e x p o s e d t ow h a t a n d f o r h o w lo n g ?

H o w i s in t a k e o r d o s er e la t e d t o a d v e r s e e f f e c t s ?

W h a t e f f e c t s a r e l ik e l y o n h u m a n h e a l th a n d e n v i r o n m e n t?

Exposure

Assessment

Risk

Assessment

Characteristics

Risk Assessment ProcessHazard

Identification

Dose Response

Exposure Assessment

Risk characterizatio

n

Hazard Identification

Toxicity assessment determines whether exposure to a chemical, physical, or biological agent can cause an increase in the incidence of an adverse effect.

Necessary condition for a health or safety risk Physical, metabolic, and chemical properties

of the agent; Potential routes of exposure; toxicological

effects; results of animal studies (dose-response); and site characteristics

Hazard Identification – Toxicity ScoreRanking of chemicals from contaminated

sites depending upon their toxicity scoresHelp in identifying contaminants with a

significant impact at the site Need data from the contaminated site

Hazard Identification – Toxicity Score – Non=carcinogensToxicity score (TS) = Cmax / RfD

Cmax = Maximum Concentration

RfD = Chronic Reference Dose i.e. acceptable daily intake

TS = Toxicity score

Hazard Identification – Toxicity Score - Carcinogens

Toxicity score (TS) = Cmax * CSF

Cmax = Maximum Concentration

CSF = Cancer Slope factor

TS = Toxicity score

Hazard Identification – Toxicity Score – Example Landfill ABC

Chemicals Air (mg/m3) Groundwater (mg/L)

Soil (mg/kg)

Mean Max Mean Max Mean Max

Chlorobenzene (NC)

4.09E-08

8.09E-08 2.5E-04

1.10E-02

1.39E+00

6.40E+00

Chloroform (C, NC)

1.12E-12

3.12E-12 3.3E-04

7.60E-03

1.12E+00

4.10E+00

1,2-Dichloroethan

e (NC)

1.12E-08

2.40E-08 2.1E-04

2.00E-03

ND ND

BEHP (C, NC) 3.29E-07

8.29E-07 ND ND 1.03E+02

2.30E+02

ND – Not Detected; C= Carcinogenic, NC = Non-carcinogenic

Hazard Identification – Toxicity Score

Chemicals RfD ( mg/kg-day)

Soil (mg/kg)

Mean Cmax

Chlorobenzene 2.00E-02 1.39E+00 6.40E+00

Chloroform 1.00E-02 1.12E+00 4.10E+00

1,2-Dichloroethane

NA ND ND

BEHP 2.00E-02 1.03E+02 2.30E+02

ND – Not Detected; NA-Not Applicable

Rank the non-carcinogenic chemicals for soil

Hazard Identification – Toxicity Score

Chemicals RfD ( mg/kg-

day)

Soil (mg/kg) TS = Cmax/RfD

Rank

Mean Cmax

Chlorobenzene 2.00E-02 1.39E+00

6.40E+00 320 3

Chloroform 1.00E-02 1.12E+00

4.10E+00 410 2

1,2-Dichloroethane

NA ND ND NA

BEHP 2.00E-02 1.03E+02

2.30E+02 11,500 1

ND – Not Detected; NA-Not Applicable

BEHP poses the greatest risk for the given site followed by chloroform and Chlorobenzene.

Hazard Identification – Toxicity Score

Selection of chemicals by TS method is followed by further evaluation which deals with other properties of that contaminant like mobility, persistence in environment, treatability etc. depending on the purpose of assessment.

Hazard Identification – Toxicity Score

Now try the same problems for carcinogens.

Also find RfD for the same contaminants in groundwater and air, on web and perform TS calculations

Risk Assessment ProcessHazard

Identification

Dose Response

Exposure Assessment

Risk Characterizati

on

Risk Assessment Process

Dose Response

How large a dose causes what magnitude of

effect?

Dose-Response AssessmentDose-response assessment is the process

of characterizing the relation between the dose of target contaminant administered or received, and the incidence of an adverse health effect in exposed populations, and estimating the incidence of the effect as a function of human exposure to the agent.

Represents variations in response of receptor at different contaminant levels

Generally, increasing the dose of contaminant will result in a proportional increase in both the incidence of an adverse effect as well as the severity of the effect.

Quantitative relationship between exposure and toxic effects

Enables risk assessor to estimate a safe dose Actual dose is compared with safe dose in risk

assessment process

Dose-Response Curve

Dose-Response CurveD

ose

Response

XX

XX

XRfD

NOAEL Threshold

Dose: mg chemical/kg of body weight

Response: % population affected by dose.

Curvature of dose response curve illustrates varying sensitivity of exposed population.

No-Observed-Adverse-Effect-Level (NOAL)

– the greatest test dose level at which no adverse effect is noted

Lowest-Observed-Adverse-Effect-Level (LOAEL)

– Lowest level at which an adverse effect is detected

Cancer Response-Dose Curve

Dose: mg chemical/kg of body weight

Response: % population cancer

Extrapolate to low dose/risk

Response

Dose

X

X

X X

No Threshold, Linearat Low Doses

Slope = Cancer Slope Factor

Reference Dose

RfD: An estimate of daily exposure to the human population that is likely to be without appreciable risk of deleterious effects during a lifetime

Expressed as mg pollutant / kg body weight/day

Also expressed as Reference Concentration (RfC), mg/m3

Reference Dose

RfD = NOAEL /(FAFHFSFLFD)Where:

NOAEL: No-Observed-Adverse-Effect-Level

FA: An adjustment factor to extrapolate from animal to human population

FH: Adjustment factor for differences in human susceptibility

FL: An adjustment factor applied when LOAEL is used instead of NOAEL

FS: An adjustment factor applied when data set is dubious or incomplete

Reference Dose - Problem

In a three month subchronic study in mice, the NOAEL for tris-(1,3-dichloro-2-propyl) phosphate was 15.3 mg/kg body weight per day; the LOAEL was 62 mg/kg at which dose abnormal liver effects were noted. If each of the adjustment factor is equal to 10, calculate the reference dose for chemical.

Reference Dose - Problem

Given: NOAEL = 15.3 mg/kg body weight per dayLOAEL = 62 mg/kg (no need here as NOAEL is

given)Calculate RfD using NOAEL and LOAEL

RfD = NOAEL / (FA FH FS FLFD)

Adjustment factors applicable for this problem are: FA, FH, Fs

RfD = 15.3/(10*10*10) = 0.015 mg/kg-day

Reference Dose - Problem

Using LOAEL :

RfD = LOAEL/(FA FH FS FLFD)Adjustment factors applicable are : FA, FH, Fs

and FL

RfD = 62/(10*10*10*10) = 0.0062 mg/kg-day

Reference Dose - Problem

RfD = 0.015 mg/kg-day (Using NOAEL)

RfD = 0.0062 mg/kg-day (using LOAEL)

The lowest of two values will be the reference dose for tris-phosphate i.e. 0.0062 mg/kg-day

Reference Dose - Problem

Repeat the RfD calculations for tris-phosphate for which NOAEL was determined to be 22mg/kg-day and the LOAEL was found to be 44 mg/kg-day for increased weight of liver and kidneys in rat.

Risk Assessment ProcessHazard

Identification

Dose Response

Exposure Assessment

Risk characterizatio

n

Exposure Assessment

Exposure Assessment

Deals with various exposure pathways for released contaminant

Exposure Assessment - PathwaysSource (e.g. landfill, lagoon)Chemical release mechanism (e.g.

leaching)Transport mechanism (e.g. groundwater)Transfer mechanism (e.g. sorption)Transformation mechanism (e.g.

biodegradation)Exposure point (e.g. residential well)Receptor Exposure route ( e.g ingestion, inhale)

Means of Exposure

Occupational Exposure, i.e. exposure at workplace

Community Exposure, i.e. exposure at workplace

Exposure Assessment

Exposure Assessment

Lungs Exposure(Inhalatio

n)

Routes of Exposure

Dermal Exposure

(Skin) Ingestion

Exposure Assessment

Process

Air

Inhalation Ingestion

Work Surface

Skin

Dermal Absorptio

n

Exposure

Duration (Time)

Severity (mass/time)

Breathing/Ingestion

Rate (volume/tim

e)

Env. concentratio

n (mass/volum

e) Period (time/exposure)

Frequency (no. exposures)

Inhalation/Ingestion Exposure Framework

Exposure (mass)

Severity (mass/time)

Absorption (mass/area/inciden

t)

Surface (area skin exposed)

Frequency (no. incidents)

Dermal Exposure Framework

NSP: Nanoscale particles

( C x CR x EF x ED)

I = --------------------------

(BW x AT)I = Intake (mg/kg of body weight per day)

C = Concentration at exposure point (e.g. mg/L in water or mg/m3 in air)

CR = Contact Rate ( e.g L/day or m3/day)

EF = Frequency (day/year)

ED = Exposure Duration (yr)

BW = Body weight (kg)

AT = Averaging Time (days)

Calculation

Standard Parameters for Calculating Exposure and Intake

Parameter Adults Child Age (6-12) Child Age ( 2-6)

Average Body Weight (kg)

70 29 16

Skin surface are (cm2) 18,150 10470 6980

Water Ingested (L/day) 2 2 1

Air breathed (m3/hour) 0.83 0.46 0.25

Retention rate (inhaled air)

100% 100% 100%

Absorption rate (inhaled air)

100% 100% 100%

Soil ingested (mg/day) 100 100 200

Bathing duration (minutes)

30 30 30

Exposure frequency (days)

365 365 365

Exposure duration (years)

30 6 4

Intake Rate Calculation

Determine the chronic daily inhalation intake, by adults, of a non-carcinogenic chemical as a function of concentration in fugitive dust at a landfill ABC.

Intake Rate Calculation

( C x CR x EF x Ed x RR x ABS)I = -----------------------------------------

(BW x AT)Air breathing rate for adults = 0.83 m3/hrCR = 0.83 x 24 = 19.92 m3/dayEF = 365 days ED = 30 years ( For chronic exposure, non-carcinogen)RR = 1, ABS = 1 ( Assumption in the absence of any

data)AT = 365 days x 30 years

Intake Rate Calculation

I = (C x 19.92 x (365 x 30) x 1x1)/ (70 x (365x60))

I = 0.285 m3/kg-day x C

C = Exposure point concentration (mg/m3)

Risk Assessment ProcessHazard

Identification

Dose Response

Exposure Assessment

Risk characterizatio

n

Risk Characterization

Final step of risk assessment process

Integration of hazard identification, dose response assessment and exposure assessment.

Risk Characterization

Carcinogenic RiskNon-carcinogenic

Risk

Risk Characterization

Risk Characterization - Carcinogens

Risk = CDI x SF

Where:

CDI = Chronic daily intake (mg/kg-day) hazard assessment

SF = carcinogenic slope factor (kg-day/mg)

Risk Characterization - CarcinogenicCalculate the average carcinogenic risk from chloroform due

to dermal contact of soil by workers at the landfill ABC.

From TS calculation table: C = 1.12 mg/kg

From carcinogenic dose intake calculations I = 2.9 x 10-9 x C = 3.26 x 10-9 mg/kg-daySF for Chloroform = 6.1 x 10-3

Risk = 6.1 x 10-3 x 3.26 x 10-9 mg/kg-day

Risk= 1.99 x 10-11

Risk Characterization: Non-carcinogenicNormally characterized in terms of

hazard index (HI) HI = (CDI/RfD) where

• CDI = Chronic daily intake (mg/kg-day)• RfD = Reference dose (mg/kg-day)• HI = Hazard Index (Unitless)

HI < 1.0 is acceptable

Risk Characterization: Non -carcinogenic

Calculate the hazard index for chlorobenzene, based on intake calculated for landfill ABC.

Solution:

HI = CDI/RfD

RfD = 2 x 10-2 ; CDI = 2.82 x 10-7

HI = 1.41 x 10-5 < 1 OK

Risk Management

Regulatory actionDecision to mitigate riskAction level

Uncertainty

The risk assessment process is extremely conservative in nature and utilizes measurements which are uncertain.

Insufficient data or information gaps often exist in characterizing the potential risk of an agent, necessitating the need for assumptions or educated guesses.

Uncertainty

Use computational tools from the field of decision analysis to account for the uncertainties in the process

These tools allow risk to be expressed as a probability distribution rather than a single number which can then be used to make a more informed decision during risk management

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Last updated October 2008 by Dr. Reinhart