In XRF testing of dry surface paint, the lead quantity is expressed in which unit?

In XRF testing of dry surface paint, the lead quantity is expressed in which unit?

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

Answer: (C)

When you use XRF on dry surface paint, you’re measuring how much lead is present on the surface per unit area, not how much lead is mixed into the bulk of the paint or how much is in the air or in blood. This is expressed as mass per area: milligrams of lead per square centimeter of painted surface. This surface loading is the standard metric regulators use to assess exposure risk from painted surfaces, because it reflects how much lead could be transferred through contact with the surface. The other units correspond to different contexts (blood lead levels, bulk concentration in paint, or airborne concentration) and don’t describe the surface exposure the XRF reading is capturing.

When you use XRF on dry surface paint, you’re measuring how much lead is present on the surface per unit area, not how much lead is mixed into the bulk of the paint or how much is in the air or in blood. This is expressed as mass per area: milligrams of lead per square centimeter of painted surface. This surface loading is the standard metric regulators use to assess exposure risk from painted surfaces, because it reflects how much lead could be transferred through contact with the surface. The other units correspond to different contexts (blood lead levels, bulk concentration in paint, or airborne concentration) and don’t describe the surface exposure the XRF reading is capturing.