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ENVS 4113 > Module 2 > Flashcards

Module 2 Flashcards

ENVS 4113 Midterm

1
Q

What is the Risk formula?

A

Risk = Hazard x Exposure

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2
Q

What is Hazard in relation to Chemical Risk Assessment?

A

Built-in property of chemical’s potential to cause adverse effects to an organism, system or population when exposed to it

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3
Q

What is Risk in relation to Chemical Risk Assessment?

A

The probability of occurrence of the adverse effect.

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4
Q

What is Exposure in relation to Chemical Risk Assessment?

A

How much chemical is present

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5
Q

Is the following True or False? A hazardous chemical substance poses no risk if there is no exposure

A

True

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6
Q

What is the goal of Chemical Risk Assessment?

A

To have a full understanding of the nature, magnitude, and probability of a potential adverse health or environmental effect of a chemical.

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7
Q

What does Chemical Risk Assessment take into account?

A

Both the hazard and exposure

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8
Q

What is Risk Assessment?

A

Forms the foundation of regulatory decisions for industrial chemicals, pesticides, pharmaceuticals, cosmetics, food additives, and food contact substances in developed countries today.

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9
Q

What is Hazard Characterization?

A

The dose-response determination (LD50/LC50, NOAEL, T25, EC50, NOEC, etc.) determines the relationship between the magnitude of exposure to a hazard with the probability and severity of adverse effects.

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10
Q

What are the three steps in Chemical Risk Assessment?

A

1) Hazard Characterization, 2) Exposure Assessment, 3) Risk Characterization.

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11
Q

What is Exposure Assessment?

A

Identifying the extent to which an exposure actually occurs. Exposure levels are usually estimated or measured.

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12
Q

What is Risk Characterization?

A

Combining the information from the hazard characterization and the exposure assessment in order to form a conclusion about the nature and magnitude of risk, and, if indicated, implement additional risk management measures.

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13
Q

What is the procedure for following the Chemical Risk Assessment?

A

Step 1) Gather info and Evaluate, Step 2) Hazard Characterization, Step 3) Exposure Assessment, Step 4) Risk Characterization (RCR = Exposure/No-Effect level)

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14
Q

What does RCR stand for?

A

Risk Characterization Ratio

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15
Q

What is the formula for Risk Characterization Ratio?

A

RCR = Exposure Estimate / Derived No-Effect Level (DNEL)

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16
Q

What does an RCR<1 mean?

A

Means the Chemical Risk Assessment determined the chemical was an acceptable risk.

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17
Q

What does RCR>1 mean?

A

Means the Chemical Risk Assessment determined the chemical was an unacceptable risk.

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18
Q

What does GHS mean and what’s GHS Classification Criteria?

A

GHS = Global Harmonization System. It’s used to determine the nature and relative severity of the hazard of a chemical substance or mixture.

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19
Q

What does the term degradation mean?

A

Is the process by which a chemical substance is broken down to smaller molecules by biotic (biodegradability) or abiotic means (hydrolysis, photolysis, or oxidization).

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20
Q

What does persistence mean in the context of Chemical Risk Assessment?

A

Persistence, also known as Half-Life DT50, is defined as the time it takes for an amount of a compound to be broken down by half.

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21
Q

What is Abiotic Degradation?

A

Includes both hydrolysis and photolysis. Hydrolysis in water is often dependent on pH.

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22
Q

What does PNEC stand for and definition?

A

Predicted No-Effect Concentration – the concentration of a substance in any environment below which adverse effects will most likely occur during long-term or short-term exposure. If PEC/PNEC is < 1 – risk is acceptable.

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23
Q

What is does LOC stand for and how is it used in Environmental Risk Assessment?

A

LOC = Level of Concern. It is a pre-set number that is used by EPA to represent toxicology or ecotoxicology Effect Endpoint value in a calculated risk quotient (RQ) in risk assessment. LOC represents the hazard in a risk equation.

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24
Q

What does RQ stand for and what is the formula?

A

RQ = Risk Quotient = Estimated Environmental Concentration (EEC) / Effect Endpoint (LC50, EC50, NOAEC).

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24
Q

What is the LOC in a Risk Quotient Equation?

A

The Effect Endpoint

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25
Q

What does EEC stand for and what does it mean?

A

EEC = Estimated Environmental Concentration. Is the estimated exposure concentration or mass of a chemical in the environment and represents the “Exposure” in the risk equation.

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26
Q

What is the Effect Endpoint?

A

Also known as LOC, it represents the hazard portion within the risk equation. It is determined by toxicological studies and usually associated with the lowest chemical mass or concentration that has a measured adverse effect in lab studies.

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27
Q

What is Toxicology?

A

Defined as the study of the adverse effects of chemicals or physical agents on living organisms. Toxicology studies are used for hazard assessment.

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28
Q

What are types of toxicological studies?

A

o Acute toxicity (oral, inhalation, dermal)
o Skin and eye irritation
o Sensitization (skin, respiratory)
o Repeated dose toxicity (28d, 90d and chronic)
o Mutagenicity and genotoxicity
o Reproductive and developmental toxicity
o Carcinogenicity
o Toxicokinetics

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29
Q

What is Ecotoxicology?

A

The study of the effects of toxic chemicals on biological organisms, especially at the population, community, ecosystem, and biosphere levels. The goal is to reveal and predict effects of pollution in the environment.

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30
Q

Does Ecotoxicology differ from environmental toxicology?

A

Yes, ecotoxicology integrates the effects of stressors across all levels of biological organization and environmental toxicology focuses upon effects at the level of the individual and below.

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31
Q

What does the term Dose Descriptor mean and where is it used?

A

It is used to identify the relationship between a specific effect of a chemical substance and the does at which it takes place. It’s determined in toxicological studies and expressed as LC50, LD50, NOAEL, T25, BMD, EC50, NOEC, etc.

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32
Q

Is dose descriptors used in hazard classification but not risk assessment?

A

No, it is used in both.

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33
Q

What is Acute Toxicity?

A

Describes the adverse effects of a substance that result either from a single exposure or from multiple exposures in a short period of time (usually less than 24 hours).

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34
Q

Acute Toxicity Studies include 3 routes: What are they?

A

Oral, Inhalation, Dermal

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35
Q

What is the dose descriptor for acute toxicity?

A

LD50, LC50

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36
Q

What does LD50 stand for and mean?

A

Lethal Dose 50% - dose at which 50% of biological life will be expected to die (mg/kg)

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37
Q

What does LC50 stand for and mean?

A

Lethal Concentration 50% - concentration at which 50% of biological life will be expected to die. Used in air concentrations, ppm.

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38
Q

Is the following true? A lower LD50 or LC50 value indicates a higher acute toxicity.

A

Yes

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39
Q

What does EC50 stand for and mean?

A

Median Effective Concentration. Used in ecotoxicology – the concentration that results in 50% reduction in either algae growth (EbC50) or algae growth rate (ErC50). Mg/L

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40
Q

Where are EC50 values usually obtained?

A

From acute toxicity studies and calculation of predicted non-effect concentration.

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41
Q

What does PNEC stand for?

A

Predicted Non-Effect Concentration

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42
Q

Define Chronic Toxicity

A

Studies conducted for >90 days – estimates the effects from long-term exposure to a substance.

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43
Q

What is Repeated Dose Toxicity and what’s the goal?

A

Estimates the chronic exposure effects from long-term exposure to a substance.

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43
Q

What is essential for the quantitative risk assessment of chemical substances?

A

Repeated Dose Toxicity Studies

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44
Q

What types of dose descriptors can be obtained from repeated dose toxicity studies?

A

NOAEL or LOAEL

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45
Q

What does LOAEL stand for and mean?

A

LOAEL = Lowest Observed Adverse Effect Level – the lowest exposure where there’s adverse effects between exposed population and control.

45
Q

What does NOAEL stand for and mean?

A

NOAEL = No Observed Adverse Effect Level – highest exposure where there’s no adverse effects between exposed population and control

46
Q

What is the average duration of NOAEL studies?

A

28 day, 90 day, or chronic toxicity study

47
Q

NOAELs are used to derive threshold safety exposure dose to humans such as:

A

Derived No-Effect Level (DNEL), Occupational Exposure Limit (OEL), and Acceptable Daily Intake (ADI).

48
Q

What is the inhalation route for determining NOAEL?

A

NOAEC

49
Q

Does High or Low NOAEL values indicate lower systemic toxicity or lower chronic toxicity?

A

Higher

50
Q

What does NOEC stand for and mean?

A

NOEC = No Observed Effect Concentration – the concentration in water, soil, etc which below an unacceptable effect is unlikely to be observed.

51
Q

What type of studies is NOEC derived from?

A

Chronic aquatic toxicity studies and terrestrial studies

52
Q

What does PNEC stand for and what value is used to calculate?

A

PNEC = Predicted Non-Effect Concentration – the NOEC values used to calculate PNEC.

53
Q

What is a carcinogen?

A

A chemical substance or a mixture of chemical substances that induces cancer or increases its incidence.

54
Q

True/False? Chemicals that have induced cancer in experimental animal studies are presumed carcinogenic in humans unless there is strong evidence tumor formation not relevant in humans.

A

True

55
Q

What is a tumor (neoplasm)?

A

Uncontrolled growth of cells. Benign tumors do not invade adjacent cells and are treatable. Malignant tumors invade adjacent cells, difficult to treat, and often lead to death.

56
Q
  • What are two dose descriptors when dealing with human carcinogen toxicity?
A

o T25 and BMD10

57
Q

What does DMEL stand for and what does it mean?

A

DMEL = Derived Minimum Effect Level – reference risk level when dealing with T25 of BMD10 in carcinogen studies.

58
Q

If exposure is below the DMEL, what does that mean?

A

Exposure risk level below the derived minimum effect level is seen as tolerable.

59
Q

What does T25 stand for?

A

The chronic dose rate that will give 25% of the animals’ tumors within lifetime of that species.

60
Q

What does BMD10 stand for?

A

Is the derived benchmark dose assumed to give 10% of the animals’ tumors within lifetime of that species.

61
Q

What is used to calculate DMEL?

A

T25 and BMD10

62
Q

What does DNEL stand for and what does it mean?

A

DNEL = Derived No-Effect Level – level of exposure above which humans should not be exposed.

63
Q

What does a DNEL<1 mean?

A

Exposure is tolerable for humans

64
Q

What does MOE stand for and mean?

A

MOE = Margin of Exposure – the ratio of the NOAEL to the estimated/predicted human exposure level or dose. MOE = NOAEL / Estimated Exposure Dose

65
Q

What is one example where MOE in human health assessment is used?

A

Assessing safety of cosmetic ingredients or food impurity.

66
Q

A higher MOE than 100 is needed when?

A

the NOAEL is not obtained from chronic toxicity studies while exposure is chronic
o only a LOAEL but not a NOAEL was identified.
o there are uncertainties regarding the quality of the available data
o there is a probability for underestimation of exposure
o there is a need to protect a sensitive group of people

67
Q

What does an MOE >= 100 mean?

A

Considered to be protective (if not carcinogenic or genotoxic)

68
Q

What MOE value is needed for carcinogenic or genotoxic compounds?

A

MOE >= 10,000

69
Q

There are 3 definitions for Margin of Safety (MOS) that is often used. Name the formulas for each.

A

o MOS = LD1 / ED99
o MOS = NOAEL / Estimated Exposure Dose
o MOS = Derived Refence Dose / Estimated Exposure Dose

70
Q

What does POD stand for and what does it mean?

A

POD = Point of Departure - Defined as the point on a toxicological dose-response curve (established from experimental data or observational data) that generally corresponds to an estimated low-effect level or no-effect level.

71
Q

What does POD mark the beginning of?

A

Estimating a toxicological reference dose (RfD) or reference concentration (RfC)

72
Q

What does RfD stand for and mean?

A

RfD = Reference Dose – An estimate of a daily oral or dermal exposure to the human population that is likely to be without an appreciable risk of deleterious effects during a lifetime. Unit is in ppm.

73
Q

What does RfC stand for and mean?

A

RfC = Reference Concentration – An estimate of a continuous inhalation exposure to the human population that is likely to be without an appreciable risk of deleterious effects during a lifetime. Unit is in ppm.

74
Q

What are the most common PODs used to derive an RfD?

A

NOAEL, LOAEL, BMD

75
Q

What is one rule when calculating POD?

A

When there are multiple NOAELs or LOAELs use the lowest for your calculation.

76
Q

What is the formula for RfD or RfC?

A

POD / Uncertainty Factors (UF1)(UF2), etc

77
Q

What is the EPAs preferred POD measurement to derive an RfD in the USA?

A

The BMD approach is now EPAs preferred approach and is fast becoming the worlds standard for dose-response analysis.

78
Q

What are the advantages when using BMD over NOAEL?

A

The modeled benchmark dose (BMD05 or BMD10) reflects the shape of the dose-response curve and is less affected by the choice of experimental concentrations. However, BMD requires a robust data set and additional knowledge of statistical modeling.

79
Q

What’s used by regulatory authorities such as the US EPA to describe the risk category of a chemical substance?

A

Hazard Quotient (HQ) and Risk Quotient (RQ)

80
Q

What does HQ stand for and mean?

A

HQ = Hazard Quotient – is the ratio of potential exposure to a substance and the level at which no adverse effects are expected.

81
Q

HQ <= 1 means what?

A

Adverse effects not likely to occur

82
Q

What is HQ usually used to assess?

A

Health risks from air toxins

83
Q

HQ >=1 means what?

A

Doesn’t exactly mean there’s adverse effects. Need to determine whether an exposure concentration exceeds the RfC.

84
Q

What does HI stand for and mean?

A

HI = Hazard Index – is the sum of the hazard quotients for substances that affect the same target organ or organ system.

85
Q

What is the formula for HQ?

A

HQ = Exposure concentration / Reference Concentration (RfC)

86
Q

What does RQ stand for and mean?

A

RQ = Risk Quotient – ratio of estimated exposure and an estimate of effects. It’s primarily used by the US EPA to assess ecological risk of pesticides.

87
Q

What is the formula for RQ?

A

RQ = EEC / (lowest LC50 or EC50)

88
Q

What is RQ usually used to assess?

A

Ecological risk of pesticides

89
Q

The US EPA has replaced ADI and TDI with the single term_____?

A

Reference Dose (RfD)

90
Q

What dose BMD stand for and mean?

A

BMD = Benchmark Dose – a dose or concentration that produces a predetermined change in the response rate of an adverse effect. This predetermined change is called benchmark response (BMR).

91
Q

What is the default % change in benchmark response (BMR) and which is continuous (in individual animals) or quantal (in a species population)?

A

BMR is 5% for continuous and 10% for quantal

92
Q

Which benchmark dose is often used to calculate human health guidance value because it is more conservative?

A

BMDL = Benchmark Dose (lower confidence limit)

93
Q

What criteria is needed to determine if BMD modeling is suitable for use?

A

o Reported response data must be either quantal data or continuous data.
o There is a clear dose-response trend.
o There are sufficient dose groups (minimum 3 dosing groups + 1 control group).
o Datasets in which response is only observed at the high dose are usually not suitable for BMD modeling

94
Q

True / False? Has NOAEL been the standard method for deriving a POD for decades?

A

Yes

95
Q

What is the common UF safety factor used when determining the RfD or ADI?

A

UF = 100. The 100-fold safety factor is based on the need to take into account both the differences in species and differences in toxicokinetics and toxicodynamics.

95
Q

True / False? Is BMD modeling easy to use, quick to model and not as complicated as other modeling software?

A

No, it’s time consuming and more complicated decision-making process

96
Q

What does ADI stand for and mean?

A

ADI = Acceptable Daily Intake – defined as the maximum amount of a chemical that can be ingested daily over a lifetime with no health risk.

97
Q

What does DT50 stand for and mean?

A

DT50 = Half-life - time it takes for an amount of a compound to be reduced by half through degradation in an environmental compartment (water, soil, air, etc).

97
Q

If you had determined the RfD or ADI to be 0.1 mg/kg/bw/d and you were asked to determine how much of that chemical a 60kg person could intake per day, how would you solve the problem?

A

You would use multiplication (60 x 0.1 = 6mg daily intake per day).

98
Q

What is the unit for DT50?

A

Day

99
Q

Define Aquatic Toxicity?

A

study of the effects of a chemical substance on aquatic species.

100
Q

What are the three trophic levels used in studying aquatic toxicity?

A

o Vertebrates (fish)
o Invertebrates (crustaceans such as Daphnia)
o Plants (algae)

101
Q

What does numerical analysis mean?

A

The branch of mathematics concerned with obtaining numerical answers by approximation rather than by analytic solution (i.e. can’t be solved by pen and paper)

102
Q

True / False? Are solutions approximate answers to limit equations?

A

Yes

103
Q

If these conditions are not met, each successive iteration produces a result that progressively moves away from the true solution. This is known as _______?

A

Divergence

104
Q

For any iterative numerical technique, each successive iteration results in a solution that moves progressively closer to the true solution. This is known as ______?

A

Convergence

105
Q

________ is the difference between the result produced by a given algorithm using exact arithmetic and the result produced by the same algorithm using finite-precision, rounded arithmetic.

A

Round-Off Error

106
Q

When using approximation equations or algorithms, especially when using finitely many digits to represent real numbers (which in theory have infinitely many digits), one of the goals of numerical analysis is to estimate ________?

A

Computation Errors or Numerical Errors – which include both round-off and truncation errors.

107
Q

What are two major facets of round-off errors?

A

Computers have magnitude and precision limits and certain numerical manipulations are highly sensitive to round-off errors

108
Q

The discretization of a partial differential equation (PDE) should become exact as the mesh size tends to zero (i.e., truncation error should vanish).

A

Consistency

109
Q

Numerical errors which are generated during the solution of discretized equations should not be magnified.

A

Stability

110
Q

The numerical solution should approach the exact solution of the partial differential equation (PDE) and converge to it as the mesh size tends to zero.

A

Convergence

111
Q

Underlying conservation laws should be respected at the discrete level (i.e., artificial sources/sinks are to be avoided).

A

Conservation

112
Q

Quantities like densities, temperatures, concentrations should remain free of spurious wiggles and stay within their respective real-world bounds. These properties must be verified for each (component of the) numerical scheme.

A

Boundedness

ENVS 4113 (6 decks)

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