Lead concentration in air is expressed in which unit?

Lead concentration in air is expressed in which unit?

• A. Micrograms per liter (ug/L)
• B. Micrograms per cubic meter (ug/m3)
• C. Micrograms per gram (ug/g)
• D. Micrograms per square meter (ug/m2)

Answer: (B)

Lead concentration in air is a measure of how much lead mass is present in a given volume of air, so the unit must be mass per volume. In environmental and occupational practice, this is expressed as micrograms per cubic meter (μg/m3). Using a volume like a cubic meter reflects the way air samples are collected and compared to exposure guidelines, which are specified per volume of air. Other units describe different things: micrograms per liter would be for liquids or solutions, micrograms per gram would be a mass fraction within a solid or mixture, and micrograms per square meter would describe deposition on a surface, not concentration in air.

Lead concentration in air is a measure of how much lead mass is present in a given volume of air, so the unit must be mass per volume. In environmental and occupational practice, this is expressed as micrograms per cubic meter (μg/m3). Using a volume like a cubic meter reflects the way air samples are collected and compared to exposure guidelines, which are specified per volume of air. Other units describe different things: micrograms per liter would be for liquids or solutions, micrograms per gram would be a mass fraction within a solid or mixture, and micrograms per square meter would describe deposition on a surface, not concentration in air.