CIH Hazards & Exposures 3 — Questions and Answers
Question 1: A worker handles crystalline silica dust at a TWA of 0.06 mg/m³ respirable fraction. The current OSHA PEL for respirable crystalline silica is 0.05 mg/m³. Which control action is most immediately required?
- Implement engineering or work practice controls to reduce exposure below 0.05 mg/m³ (Correct answer)
- Provide a NIOSH-approved N95 respirator as the primary control
- Conduct medical surveillance only since exposure is close to the PEL
- Perform additional sampling before taking any action
Correct answer: Implement engineering or work practice controls to reduce exposure below 0.05 mg/m³
Because the TWA exceeds the OSHA PEL of 0.05 mg/m³, engineering or work practice controls must be implemented as the primary corrective measure.
Question 2: What does the term 'skin notation' (SK) next to a chemical's occupational exposure limit signify?
- The substance can be absorbed through the skin and contribute significantly to total body burden (Correct answer)
- The substance causes only contact dermatitis and no systemic effects
- Workers must wear gloves whenever handling any quantity of the substance
- The airborne OEL already accounts for dermal absorption
Correct answer: The substance can be absorbed through the skin and contribute significantly to total body burden
A skin notation warns that dermal absorption can contribute to overall exposure and systemic toxicity, so airborne monitoring alone may underestimate total dose.
Question 3: An industrial hygienist is evaluating ergonomic risk using the NIOSH Lifting Equation. A Recommended Weight Limit (RWL) of 10 kg is calculated and the actual lifted load is 25 kg. What does this indicate?
- A Lifting Index of 2.5, indicating significant musculoskeletal injury risk that requires redesign (Correct answer)
- The lift is acceptable because 25 kg is within general manual handling limits
- A Lifting Index below 1.0, meaning the task is safe
- Only workers with prior back injuries are at risk
Correct answer: A Lifting Index of 2.5, indicating significant musculoskeletal injury risk that requires redesign
The Lifting Index (LI = load/RWL = 25/10 = 2.5) exceeds 1.0, indicating that most workers face elevated risk and the task should be redesigned.
Question 4: Which IDLH value is assigned to carbon monoxide (CO) by NIOSH?
- 1,200 ppm (Correct answer)
- 200 ppm
- 35 ppm
- 50 ppm
Correct answer: 1,200 ppm
NIOSH established an IDLH of 1,200 ppm for CO, representing the concentration that is immediately dangerous to life or health.
Question 5: A worker is exposed to two solvents simultaneously: toluene at 50% of its TLV and xylene at 60% of its TLV. Assuming additive effects, what is the combined exposure ratio and is it acceptable?
- 1.1; exceeds the additive limit and controls are needed (Correct answer)
- 0.55; acceptable because each individual chemical is below its TLV
- 1.1; acceptable because neither individual exposure exceeds its TLV
- 0.5; acceptable with no further action required
Correct answer: 1.1; exceeds the additive limit and controls are needed
For substances with additive effects, the combined ratio = 0.5 + 0.6 = 1.1, which exceeds 1.0 and indicates an overexposure requiring controls.
Question 6: Which type of ionizing radiation has the greatest penetrating power but the lowest ionizing density (LET)?
- Gamma rays (Correct answer)
- Alpha particles
- Beta particles
- Neutrons
Correct answer: Gamma rays
Gamma rays have very high penetrating power and low linear energy transfer (LET), requiring dense shielding such as lead or concrete.
Question 7: A pharmaceutical worker develops asthma symptoms only on workdays, with improvement on weekends. The MOST likely diagnosis is:
- Occupational asthma (OA) (Correct answer)
- Work-aggravated asthma
- Hypersensitivity pneumonitis
- Byssinosis
Correct answer: Occupational asthma (OA)
The classic pattern of symptoms on workdays with weekend improvement is the hallmark of occupational asthma caused by workplace sensitizers or irritants.
CIH Hazards & Exposures 3
A worker handles crystalline silica dust at a TWA of 0.06 mg/m³ respirable fraction.
The current OSHA PEL for respirable crystalline silica is 0.05 mg/m³.
Which control action is most immediately required?