Health Hazards and Risk Assessment practice questions

Answer: A) The estimated incremental probability of developing cancer over a lifetime

Excess lifetime cancer risk = lifetime average daily dose × slope factor. Slope factors are used for carcinogens. Noncancer effects are assessed with a reference dose and a hazard quotient (intake ÷ RfD).

• ACorrect. The slope factor is an upper-bound estimate of excess lifetime cancer risk per unit of lifetime average daily dose. Multiplying it by the intake gives a unitless excess lifetime cancer risk for a carcinogen.
• BIncorrect. A hazard quotient is used for noncancer effects. It is the intake divided by the reference dose, not the intake multiplied by a slope factor.
• CIncorrect. That describes a reference dose (a threshold value for noncancer effects). Slope factors assume no threshold for cancer risk.
• DIncorrect. That is a pharmacokinetic elimination rate. It is not the product of intake and a cancer potency value.

Answer: B) No threshold dose (any exposure carries some risk)

• AIncorrect. That's for noncarcinogens.
• BCorrect. Noncarcinogens are assumed to have a threshold.
• CIncorrect. A no-threshold model is assumed.
• DIncorrect. RfDs are for noncancer effects.

Answer: A) 0.1 mg/(kg·day)

• ACorrect. RfD = NOAEL/UF.
• BIncorrect. Divide, don't multiply.
• CIncorrect. Apply the uncertainty factor.
• DIncorrect. Recheck: 10/100.

Answer: B) Choosing a regulatory option after weighing risk estimates against cost and feasibility

Risk assessment covers hazard identification, dose-response, exposure assessment and risk characterization, and its job is to estimate risk. Risk management uses those estimates, together with cost, feasibility and policy, to decide what action to take.

• AIncorrect. Dose-response assessment is one of the four steps of risk assessment.
• BCorrect. Risk management combines the risk-assessment results with other information, such as technical feasibility, cost and statutory policy, to decide whether risk needs to be reduced, how, and by how much.
• CIncorrect. Exposure assessment is a step of risk assessment.
• DIncorrect. Risk characterization is the last step of risk assessment. It produces the estimate that risk managers then act on.

Answer: C) 500 L/kg

The bioconcentration factor is the steady-state concentration in the organism divided by the concentration in water: 5 / 0.01 = 500 L/kg.

• AIncorrect. This is the product of the two concentrations (5 × 0.01). BCF is a ratio, not a product.
• BIncorrect. This is the water concentration divided by the fish concentration, which is the inverse of BCF.
• CCorrect. BCF = C_fish / C_water = (5 mg/kg) / (0.01 mg/L) = 500 L/kg.
• DIncorrect. This is off by a factor of 10, as if the water concentration were 0.1 mg/L. Dividing 5 by 0.01 gives 500.

Answer: C) Ingestion, inhalation and dermal absorption

Exposure routes describe how a contaminant enters the body: ingestion, inhalation and dermal absorption. Media (air, water, soil, food) and transport processes are separate parts of an exposure assessment.

• AIncorrect. These are environmental media that carry contaminants. They are not the routes by which contaminants enter the body.
• BIncorrect. These are elements of a complete exposure pathway. The route of exposure is a separate element of the pathway.
• CCorrect. Contaminants enter the body by being swallowed, breathed in, or absorbed through the skin. Total-exposure assessments consider all three routes.
• DIncorrect. These are fate-and-transport processes that move contaminants between environmental media. They are not routes of entry into the body.

Answer: D) 1.2; a potential concern

• AIncorrect. A value above 1 warrants attention.
• BIncorrect. That's the average.
• CIncorrect. That's the largest value.
• DCorrect. A hazard index above 1 suggests possible adverse effects.

Answer: A) About one extra cancer case over a lifetime among one million similarly exposed people

An excess lifetime cancer risk of 1 × 10⁻⁶ is an incremental lifetime probability: theoretically one extra cancer case per million people exposed in the same way, on top of background risk.

• ACorrect. The value is an incremental (excess) lifetime probability: theoretically one extra cancer case, above background, in a population of one million people exposed in the same way.
• BIncorrect. The value is excess risk from this exposure alone, added on top of background cancer risk. It is not total risk from all causes.
• CIncorrect. Slope-factor risk estimates are lifetime probabilities based on lifetime average daily dose, not yearly incidence rates.
• DIncorrect. Cancer risk assessment assumes no threshold. A risk of 1 × 10⁻⁶ is small but not zero.

Answer: B) Studying the distribution and determinants of disease in human populations

Epidemiology looks at human populations to relate exposures to disease patterns, using designs such as cohort and case-control studies. Toxicology, by contrast, relies on controlled experiments in animals or cells.

• AIncorrect. Controlled animal dosing studies belong to experimental toxicology, not epidemiology.
• BCorrect. CDC defines epidemiology as the study of the distribution and determinants of health-related states or events in specified populations, and of how to use that knowledge to control health problems.
• CIncorrect. Fate-and-transport modeling estimates environmental concentrations. It does not observe health outcomes in people.
• DIncorrect. In vitro cell assays are toxicological screening tools. They do not study disease patterns in populations.

Answer: B) Inhalation

• AIncorrect. That's the RfD.
• BCorrect. The RfD applies to oral exposure.
• CIncorrect. That isn't the RfC.
• DIncorrect. That isn't the RfC.