Health Risk Assessment Flashcards

In the classic four-step NRC (1983) risk assessment paradigm, which step comes immediately after hazard identification?

Answer: Dose-response assessment

The NRC Red Book sequence is hazard identification, dose-response assessment, exposure assessment, then risk characterization.

A worker's chronic daily intake of a chemical is 0.006 mg/kg-day and the reference dose (RfD) is 0.003 mg/kg-day. What is the hazard quotient?

Answer: 2.0

HQ = exposure ÷ RfD = 0.006 ÷ 0.003 = 2, indicating potential for non-cancer effects.

Which term describes the highest tested dose at which no statistically or biologically significant adverse effect was observed?

Answer: NOAEL

The No Observed Adverse Effect Level (NOAEL) is the highest dose without observed adverse effects and is often the starting point for an RfD.

When the combined effect of two chemicals is much greater than the sum of their individual effects, the interaction is called:

Answer: Synergistic

Synergism occurs when the combined effect exceeds the sum, such as asbestos exposure combined with smoking.

A cancer slope factor of 0.05 (mg/kg-day)^-1 is applied to a lifetime average daily dose of 0.0002 mg/kg-day. What is the estimated excess lifetime cancer risk?

Answer: 1 × 10^-5

Risk = slope factor × dose = 0.05 × 0.0002 = 0.00001, or 1 in 100,000.

Which route of entry is generally the most significant for occupational exposure to airborne contaminants?

Answer: Inhalation

Inhalation is the primary occupational route because workers continuously breathe air in the work environment.

Why are uncertainty factors applied when deriving a reference dose from animal NOAEL data?

Answer: To account for interspecies and intraspecies variability and data gaps

Uncertainty factors (often 10-fold each) cover animal-to-human extrapolation, sensitive human subgroups, and database limitations.