CIH Toxicology & Health Risk Assessment 1 — Questions and Answers
Question 1: LD50 is defined as the dose that causes death in what percentage of a test population?
- 25%
- 50% (Correct answer)
- 75%
- 100%
Correct answer: 50%
LD50 (Lethal Dose 50) is the dose required to kill 50% of a test population under specified conditions.
Question 2: Which dose-response model assumes there is NO safe threshold for carcinogenic chemicals?
- Hormesis model
- Threshold model
- Linear non-threshold (LNT) model (Correct answer)
- Sigmoid model
Correct answer: Linear non-threshold (LNT) model
The linear non-threshold (LNT) model assumes any dose of a carcinogen carries some risk, with no exposure level being completely safe.
Question 3: What does the term 'carcinogen' specifically describe?
- A substance that causes birth defects
- A substance capable of causing cancer (Correct answer)
- A substance that causes liver damage
- A substance that causes respiratory sensitization
Correct answer: A substance capable of causing cancer
A carcinogen is any substance or agent that can cause or promote the development of cancer in living tissue.
Question 4: OSHA Permissible Exposure Limits (PELs) are based on which exposure duration?
- 15-minute short-term exposure
- 8-hour time-weighted average (TWA) (Correct answer)
- Instantaneous ceiling value
- 24-hour continuous exposure
Correct answer: 8-hour time-weighted average (TWA)
OSHA PELs are primarily established as 8-hour time-weighted averages (TWA) corresponding to a standard workday.
Question 5: Which route of chemical exposure is most common in occupational settings?
- Dermal absorption
- Ingestion
- Inhalation (Correct answer)
- Injection
Correct answer: Inhalation
Inhalation is the most common route of occupational exposure because workers breathe airborne contaminants throughout their work shift.
Question 6: What does IDLH stand for in industrial hygiene?
- Immediately Dangerous to Life or Health (Correct answer)
- Industrial Dose Limit for Hazardous materials
- Integrated Daily Limit for Health
- Instantaneous Detection Level for Hazards
Correct answer: Immediately Dangerous to Life or Health
IDLH stands for Immediately Dangerous to Life or Health and represents the maximum concentration from which a worker could escape within 30 minutes without suffering irreversible health effects.
Question 7: Acute toxicity is best characterized as an adverse effect resulting from:
- Low-level repeated exposure over years
- A single or short-term high-level exposure (Correct answer)
- Cumulative exposure over a lifetime
- Exposure below the NOAEL repeatedly
Correct answer: A single or short-term high-level exposure
Acute toxicity refers to adverse effects occurring from a single or short-duration exposure, typically within 24 hours of contact.
CIH Toxicology & Health Risk Assessment 1
LD50 is defined as the dose that causes death in what percentage of a test population?