Which unit is used for measuring lead concentration in paint when using XRF that is a surface measure?

Which unit is used for measuring lead concentration in paint when using XRF that is a surface measure?

• A. Micrograms per cubic meter (ug/m3)
• B. Milligrams per square centimeter (mg/cm2)
• C. Micrograms per gram (ug/g)
• D. Micrograms per deciliter (ug/dL)

Answer: (B)

XRF on a painted surface measures how much lead sits on the surface per unit area, i.e., the surface loading. That makes mass per area the natural way to express the result, so milligrams per square centimeter is the appropriate unit. It reflects how much lead is actually present on the surface you can touch or dust off, which is what matters for exposure from handling or abrasion. The other units don’t fit this context: micrograms per cubic meter is a concentration in air, micrograms per gram would be lead per weight of paint (bulk content, not surface loading), and micrograms per deciliter is a measure of lead in blood.

XRF on a painted surface measures how much lead sits on the surface per unit area, i.e., the surface loading. That makes mass per area the natural way to express the result, so milligrams per square centimeter is the appropriate unit. It reflects how much lead is actually present on the surface you can touch or dust off, which is what matters for exposure from handling or abrasion.

The other units don’t fit this context: micrograms per cubic meter is a concentration in air, micrograms per gram would be lead per weight of paint (bulk content, not surface loading), and micrograms per deciliter is a measure of lead in blood.