Risk Assessment (17-18)

Question 1

Risk:

Answer 1

the likelihood of an adverse health effect resulting from exposure to a potential hazard (e.g. a toxic chemical)

Question 2

Hazard:

Answer 2

any source of potential adverse health effects

Question 3

Human Health Risk Assessment:

Answer 3

the process to estimate the nature, probability, and magnitude of adverse health effects in humans who may be exposed to chemicals in contaminated environmental media

Question 4

**The 4 steps of the risk assessment process:

be able to quickly describe each

Answer 4

hazard identification –> dose-response assessment, exposure assessment –> risk characterization

Question 5

4 methods of hazard identification:

Answer 5

1. structure-activity relationships
2. in-vitro and short-term tests
3. animal bioassays
4. epidemiological data

Question 6

NOEL:

Answer 6

no-observed-effect-level; the highest exposure among all the available experimental studies at which no toxic effect was observed

Question 7

NOAEL:

Answer 7

no-observed-adverse-effect-level; the highest exposure at which there is no statistically or biologically significant increase in the frequency of an adverse effect when compared with a control group

Question 8

LOAEL:

Answer 8

lowest-observed-adverse-effect-level

Question 9

**mechanism of action:

Answer 9

a detailed understanding at the molecular level of all the steps involved in the carcinogenic process for a chemical

Question 10

**mode of action:

Answer 10

a general description of the manner in which a chemical might act to produce its effect

Question 11

**weight of evidence evaluation:

Answer 11

comprehensive, integrated judgment of all relevant information supporting conclusions regarding a toxicological effect

Question 12

How would a dose-response curve with no threshold appear?

Answer 12

The line goes straight to the origin (threshold implies that there’s a safe value)

Question 13

With carcinogens, we talk about _____ instead of safe values?

Answer 13

acceptable risk

Question 14

threshold:

Answer 14

the dose below which no additional increase in response is observed

Question 15

**Point of departure (POD):

Answer 15

used to specify the estimated dose near the lower end of the observed dose range, below which extrapolation to lower exposures is necessary

Question 16

RDA

Answer 16

recommended daily allowance

Question 17

ADI

Answer 17

acceptable daily intake

Question 18

**RfD

Answer 18

reference dose

Question 19

**RfC

Answer 19

reference concentration

Question 20

MRL

Answer 20

minimal risk level

Question 21

**Reference dose:

Answer 21

an estimate (with uncertainty spanning perhaps an order of magnitude) of daily exposure to the human population (including sensitive subgroups) that is likely to be without an appreciable risk of deleterious effects during a lifetime

Question 22

**Reference dose formula

Answer 22

RfD = POD/UF (point of departure/uncertainty factors)

Question 23

Uncertainty factors:

Answer 23

necessary reductions in the dose to account for missing data

Question 24

**Cancer slope factor (SF)

Answer 24

derived using the upper bound estimate for risk; true risk to humans is probably unknowable, but is not likely to exceed the upper-bound estimate

Question 25

**Calculation of individual cancer risk:

Answer 25

compare daily exposure with cancer potency factor

Lifetime Risk = Exposure x CPF

Question 26

**Cancer risks of less than… are considered negligible, and greater than…. are considered significant

Answer 26

1/1 million; 1/10,000

Question 27

**Exposure assessment approaches:

Answer 27

direct measurement, exposure scenario modeling, biomonitoring

Question 28

**Risk Assessment:

Answer 28

systematic process of hazard identification, exposure assessments, dose responses, and risk characterization

Question 29

Risk Characterization:

Answer 29

last step of risk assessment; includes not just the number of risks but the characterization of the risk (i.e. uncertainty in values, assumptions)

Question 30

Risk communication:

Answer 30

process of exchanging information and opinion with the public

Question 31

Typical threshold acceptable carcinogenic risk:

Answer 31

10^-6

Question 32

Aggregate exposure:

Answer 32

1 chemical, multiple routes (e.g. blood lead)

Question 33

Cumulative risk:

Answer 33

exposure to single or multiple chemicals and nonchemical stressors

Question 34

**Risk characterization:

Answer 34

integrates components of the risk assessment and synthesizes an overall conclusion about risk that is complete, informative, and useful for decision makers

Question 35

**Risk characterization policy:

Answer 35

a transparent process and products that are clear, consistent, and reasonable

Question 36

**Risk characterization goals

Answer 36

TCCR: transparency, clarity, consistency, and reasonableness

Question 37

**Hazard identification/characterization:

**“appreciate the complexity”

Answer 37

the process of determining whether human exposure to a toxicant could cause an increase in the incidence of an adverse health effect; generally considers toxicity from one route of exposure relevant to other routes; characterizes the nature and strength of the evidence of causation

Question 38

adverse effect:

Answer 38

biochemical damage, functional impairment, or pathologic lesion which impairs performance and reduces the ability of an organism to respond to additional challenges

Question 39

adaptive effect:

Answer 39

enhances an organism’s performance as a whole and/or its ability to withstand a challenge

Question 40

chronic toxicity:

Answer 40

effects that persist over a long period of time whether or not they occur immediately or are delayed

Question 41

critical effect:

Answer 41

the first adverse effects or their known precursors that occur as dose rate increases

Question 42

compensatory effect:

Answer 42

maintains overall function without enhancement or significant cost (e.g. increased respiration due to metabolic acidosis)

Question 43

Frank effect:

Answer 43

the exposure level which produces unmistakable adverse effects, such as reversible or irreversible functional impairment or mortality, at a statistically or biologically significant increase in frequency or severity between an exposed population and its appropriate control

Question 44

severity:

Answer 44

the degree to which an effect changes and impairs the functional capacity of an organ system

Question 45

Uncertainty Factor (UF):

Answer 45

one of several, generally 10-fold, factors used in operationally deriving the RfD from experimental data

Question 46

genotoxic:

Answer 46

does it cause gene mutations?

Question 47

variability:

Answer 47

range of values in quantities related to risk; general sources include exposure, potency, susceptibility

Question 48

possible factors for susceptibility

Answer 48

• fetuses vs. children vs. adolescents vs. elderly
• women vs. men
• race or ethnicity specific factors
• pre-existing health conditions
• nutrition status

Question 49

Unit Cancer Risk:

Answer 49

the estimate of the lifetime risk caused by each unit of exposure in the low exposure region; the upper-bound excess lifetime cancer estimated to result from continuous exposure to an agent at a concentration of 1µg/L in water or 1µg/m^3 in air

Question 50

** Exposure assessment:

Answer 50

Purpose: to calculate the dose that an individual receives

the process of measuring or estimating the magnitude, intensity, frequency, and duration of human exposure to an agent resulting from contact with environmental media

Question 51

**Number of chemicals out there vs. number in IRIS:

Answer 51

80-90,000

<1,000

Question 52

**Four types of studies used to determine hazard:

Answer 52

in vitro and short-term tests, in vivo/animal bioassays, epidemiological data, structure-activity relationships

Question 53

**Best kind of data?

Answer 53

Human epidemiological data

Question 54

**The type of data that we have the most of?

Answer 54

animal bioassays

Question 55

**Why do we have uncertainty in our dose-response curves?

Answer 55

Because they come from animals. Plus, we may not know the chronic effects of exposing animals to these chemicals

Question 56

**Non-threshold approaches:

Answer 56

1. Characterized by a dose-response curve that goes through the origin
2. No “safe dose”
3. Forms the basis of cancer assessments
4. Conservative and Controversial

Question 57

**Threshold approaches:

Answer 57

Defined as the dose below which no additional increase in response is observed.
Implies a “safe dose”
Forms the basis of non-cancer assessments

Question 58

**Dose:

Answer 58

a daily average intake per unit of body weight

Question 59

**Formula for chronic daily intake of the chemical:

Answer 59

CDI = (C•CR•EF•ED) / (BW•AT)

CDI: Chronic daily intake of the chemical (mg/kg-day)
C: concentration of the chemical in an exposure medium
CR: contact rate
EF: exposure frequency (e.g. days/year)
ED: exposure duration (e.g. years)
BW: body weight (kg)
AT: average time (equal to ED x 365 days/year for noncarcinogens and 70 years x 365 days/year for carcinogens)

Question 60

**Formula for cancer risk

definitely know this one

Answer 60

Risk = CDI • CSF

CDI = Chronic daily intake of the chemical (mg/kg-day)
CSF = cancer slope factor for the chemical (mg/kg-day)-1

Question 61

**Formula for noncancer risk:

Answer 61

HQ = CDI / RfD

RfD = reference dose for the chemical for assessing non-cancer health effects (mg/kg-day)

Question 62

**What we call an acceptable risk for cancer:

Answer 62

10^-4