Which measurement method is used to determine the threshold of 1.0 mg/cm2 for lead content?

• A. XRF
• B. Lab methods
• C. Visual inspection
• D. Dust wipe testing

Answer: (A)

Measuring lead content per unit area on a painted surface is most directly determined with X-ray fluorescence (XRF). XRF instruments scan the surface and report the amount of lead as milligrams of lead per square centimeter (mg/cm2), which is exactly the units used for the 1.0 mg/cm2 threshold. This allows inspectors to quickly and non-destructively decide in the field whether a surface exceeds the threshold and requires action. Lab methods, by contrast, require sampling and destroying paint chips and then reporting lead content as mg/kg or ppm, which doesn’t give a surface mg/cm2 value and is not as practical for rapid threshold determination. Visual inspection cannot quantify lead content, and dust wipe testing measures lead in dust rather than the paint coating itself. So the method that directly determines whether the surface reaches or exceeds the 1.0 mg/cm2 threshold is XRF.