WHO guidance on industrial noise exposure The commonly cited maximum permissible limit for steady industrial noise exposure (8-hour workday) recommended by WHO is approximately:

Introduction / Context:
Industrial hygiene guidelines specify sound level limits to protect workers from hearing loss. While different organisations publish slightly different limits and exchange rates, exam questions often reference a rounded WHO-type guidance value for continuous noise over a standard 8-hour shift.

Given Data / Assumptions:

• Steady, broadband industrial noise exposure.
• 8-hour time-weighted average context.
• Use of a typical reference value rather than a detailed dose-response table.

Concept / Approach:
Values around 75 dB(A) are frequently cited as an upper limit for comfortable speech and acceptable steady exposure in general environments, with occupational action levels often around 85 dB(A) for implementing hearing conservation. In many exam frameworks, 75 dB is presented as a representative “maximum permissible” continuous level in industrial areas for general WHO guidance questions, distinguishing it from higher occupational damage-risk criteria (e.g., 85–90 dB(A)). Thus, among the options, 75 dB is the appropriate selection.

Step-by-Step Solution:

Verification / Alternative check:
Many environmental and occupational references differentiate between community noise goals (≈55–65 dB), comfortable indoor levels, and industrial limits; 75 dB is often used as a boundary for acceptable continuous exposure in older WHO-style summaries.

Why Other Options Are Wrong:

• 35 dB: Far too low for industrial settings.
• 95 or 105 dB: Excessive for 8-hour exposure without significant protection and programme controls.
• 65 dB: Typical of offices or community limits, not the test’s intended industrial reference.

Common Pitfalls:
Confusing hearing conservation action levels (≈85 dB) with “maximum permissible” used in generic environmental engineering questions; always check the exam’s convention.

Final Answer:
75 dB