Certified Industrial Hygienist (CIH) MCQ Flashcards

Which OSHA standard sets the permissible exposure limit (PEL) for respirable crystalline silica in general industry?

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.

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?

Answer: 125%

Using OSHA's formula: D = (4/4 + 4/8) × 100 = (1 + 0.5) × 100 = 150%; the total dose is 150%.

Which ventilation parameter is defined as the volume of air supplied to a space divided by the volume of that space per unit time?

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.

The TLV-STEL established by ACGIH represents a concentration that workers should not exceed for more than:

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.

Which ionizing radiation type has the highest linear energy transfer (LET) and the shortest range in tissue?

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.

In ergonomics, the NIOSH Lifting Equation calculates a Recommended Weight Limit (RWL). The Load Constant (LC) used in the equation is:

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.

Which biological monitoring index indicates recent benzene exposure by measuring a urinary metabolite?

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.