CIH Certified Industrial Hygienist (CIH) MCQ 2 — Questions and Answers
Question 1: Which OSHA standard sets the permissible exposure limit (PEL) for respirable crystalline silica in general industry?
- 29 CFR 1910.1000
- 29 CFR 1910.1053 (Correct answer)
- 29 CFR 1926.1153
- 29 CFR 1910.134
Correct answer: 29 CFR 1910.1053
29 CFR 1910.1053 is the OSHA silica standard for general industry, establishing a PEL of 50 µg/m³ as an 8-hour TWA.
Question 2: A worker is exposed to a noise level of 95 dBA for 4 hours and 90 dBA for 4 hours. What is the total noise dose according to OSHA?
- 75%
- 100%
- 125% (Correct answer)
- 150%
Correct answer: 125%
Using OSHA's formula: D = (4/4 + 4/8) × 100 = (1 + 0.5) × 100 = 150%; the total dose is 150%.
Question 3: Which ventilation parameter is defined as the volume of air supplied to a space divided by the volume of that space per unit time?
- Face velocity
- Capture velocity
- Air changes per hour (ACH) (Correct answer)
- Transport velocity
Correct answer: Air changes per hour (ACH)
Air changes per hour (ACH) quantifies ventilation rate as the number of times the room volume is replaced per hour.
Question 4: The TLV-STEL established by ACGIH represents a concentration that workers should not exceed for more than:
- 15 minutes, with no more than 4 such excursions per day (Correct answer)
- 30 minutes, once per day
- 10 minutes, with no more than 2 such excursions per day
- 20 minutes, with no more than 3 such excursions per day
Correct answer: 15 minutes, with no more than 4 such excursions per day
The TLV-STEL is a 15-minute TWA that should not be exceeded, with no more than 4 excursions per day and at least 60 minutes between them.
Question 5: Which ionizing radiation type has the highest linear energy transfer (LET) and the shortest range in tissue?
- Beta particles
- Gamma rays
- Alpha particles (Correct answer)
- X-rays
Correct answer: Alpha particles
Alpha particles have the highest LET and shortest range in tissue (~40–70 µm), making them the most ionizing but least penetrating.
Question 6: In ergonomics, the NIOSH Lifting Equation calculates a Recommended Weight Limit (RWL). The Load Constant (LC) used in the equation is:
- 23 kg
- 51 lbs
- Both A and B are correct (Correct answer)
- 25 kg
Correct answer: Both A and B are correct
The NIOSH Load Constant is 23 kg (approximately 51 lbs), so both values express the same constant in different units.
Question 7: Which biological monitoring index indicates recent benzene exposure by measuring a urinary metabolite?
- Mandelic acid
- Trans,trans-muconic acid (tt-MA) (Correct answer)
- Hippuric acid
- Methyl hippuric acid
Correct answer: Trans,trans-muconic acid (tt-MA)
Trans,trans-muconic acid (tt-MA) is a specific urinary biomarker for benzene exposure, measured at end of shift.
CIH Certified Industrial Hygienist (CIH) MCQ 2
Which OSHA standard sets the permissible exposure limit (PEL) for respirable crystalline silica in general industry?