Particulate matter (PM) emissions during metalworking During which of the following metalworking operations is atmospheric pollution by airborne particulate matter least likely to occur under normal shop conditions?

Introduction / Context:
Airborne particulate matter (PM) from metalworking is a key occupational and environmental concern. Different unit operations release very different particle size distributions and mass emissions. Understanding which common operations generate respirable dust vs. larger chips helps in selecting controls such as local exhaust ventilation, enclosures, mist collectors, and housekeeping protocols.

Given Data / Assumptions:

• Grinding and polishing abrade surfaces and commonly create fine particulates and metallic fines that become airborne.
• Cutting may generate some fines but tends to produce larger chips or swarf that fall rapidly.
• Conventional machining (e.g., turning, milling, drilling) with proper feeds/coolant mainly yields chips rather than respirable dust.
• Normal, well-maintained shop conditions are assumed (not dry abrasive blasting).

Concept / Approach:
The likelihood of atmospheric PM pollution correlates strongly with whether the operation fractures material into sub-100 micrometer particles. Abrasive processes (grinding, polishing) are high-risk for PM. Chip-forming processes (machining, sawing/cutting) chiefly generate coarse chips that are not easily airborne. Hence, among the options, machining is least associated with PM emissions to the surrounding air.

Step-by-Step Solution:

Verification / Alternative check:
Industrial hygiene measurements show highest respirable PM near abrasive wheels and polishing stations, while lathe or mill areas primarily contend with oil mist and chip handling rather than dust.

Why Other Options Are Wrong:

Common Pitfalls:
Confusing oil mist (from machining coolants) with metallic PM; both are hazards, but respirable dust risk is higher in abrasive finishing.

Final Answer:
machining