Which unit is used for lead clearance in dust measurements?

Which unit is used for lead clearance in dust measurements?

• A. micrograms per liter
• B. micrograms per cubic meter
• C. micrograms per square foot
• D. milligrams per liter

Answer: (C)

In lead dust clearance, the measurement focuses on how much lead remains on a surface, not in the air. Dust wipe samples are collected from surfaces and the amount of lead is reported per unit area. That’s why the appropriate unit is micrograms of lead per square foot—the mass of lead divided by the surface area wiped. Units like micrograms per liter or micrograms per cubic meter reflect lead in air or liquids, not surface contamination, so they don’t measure surface clearance. Milligrams per liter is also a liquid concentration and doesn’t describe surface dust loading.

In lead dust clearance, the measurement focuses on how much lead remains on a surface, not in the air. Dust wipe samples are collected from surfaces and the amount of lead is reported per unit area. That’s why the appropriate unit is micrograms of lead per square foot—the mass of lead divided by the surface area wiped.

Units like micrograms per liter or micrograms per cubic meter reflect lead in air or liquids, not surface contamination, so they don’t measure surface clearance. Milligrams per liter is also a liquid concentration and doesn’t describe surface dust loading.