For dust sampling on floors, which unit is used to express lead quantity?

For dust sampling on floors, which unit is used to express lead quantity?

• A. Microgram per gram (ug/g)
• B. Microgram per square foot (ug/ft2)
• C. Milligrams per square centimeter (mg/cm2)
• D. Microgram per cubic meter (ug/m3)

Answer: (B)

Lead on floor dust is reported as a loading: how much lead is present per unit area of the floor. Reporting this as micrograms of lead per square foot (µg/ft^2) directly reflects the surface amount that people touch and could transfer, which is why it’s the standard unit used for floor dust lead loading and related hazard standards. Other units don’t fit this context: micrograms per gram would measure lead relative to the mass of dust, not the surface area, which doesn’t capture surface contamination relevant to exposure. Milligrams per square centimeter is a mass-per-area unit too, but the established practice in housing lead standards uses micrograms per square foot, and the magnitude differs in a way that could mislead interpretation. Micrograms per cubic meter measures lead in the air, not on the floor surface, so it reflects airborne concentration rather than surface loading.

Lead on floor dust is reported as a loading: how much lead is present per unit area of the floor. Reporting this as micrograms of lead per square foot (µg/ft^2) directly reflects the surface amount that people touch and could transfer, which is why it’s the standard unit used for floor dust lead loading and related hazard standards.

Other units don’t fit this context: micrograms per gram would measure lead relative to the mass of dust, not the surface area, which doesn’t capture surface contamination relevant to exposure. Milligrams per square centimeter is a mass-per-area unit too, but the established practice in housing lead standards uses micrograms per square foot, and the magnitude differs in a way that could mislead interpretation. Micrograms per cubic meter measures lead in the air, not on the floor surface, so it reflects airborne concentration rather than surface loading.