What are the measurement units for radon concentration in the U.S.?

In the United States, the standard measurement unit for radon concentration in air is PicoCuries per liter (pCi/L). This unit specifically quantifies the radioactive decay of radon gas in a given volume of air, making it particularly relevant for assessing radon exposure risks in indoor environments.

PicoCuries measure radioactivity, with one picoCurie representing one trillionth of a Curie, which is a unit that conveys the amount of radioactivity. The use of pCi/L allows homeowners, health agencies, and mitigation professionals to determine safe levels of radon and implement necessary actions for reduction or mitigation when high levels are detected.

While other units provided in the options—such as Bequerels per cubic meter (Bq/m³)—are used internationally and are also valid for measuring radon levels, they are not the predominant unit in the U.S. context. The metric units like milligrams per liter and micrograms per cubic meter are not applicable to radon concentration, as they measure chemical concentrations rather than radioactivity. Thus, the choice of pCi/L is specifically relevant and accurate for the evaluation of radon concentration in the United States.