Units
Picocuries per litre (pCi/L)
The traditional unit for radon concentration used in the United States. One picocurie per litre equals 37 becquerels per cubic metre; the US EPA action level of 4 pCi/L therefore corresponds to about 148 Bq/m³.
Related terms
Becquerel (Bq)The SI unit of radioactivity: one becquerel equals one radioactive disintegration per second. Radon in air is expressed as an activity concentration, in becquerels per cubic metre (Bq/m³).Becquerels per cubic metre (Bq/m³)The standard unit for radon concentration in air in Europe and in WHO guidance: the number of radon disintegrations per second in each cubic metre of air. Reference levels are typically 100–300 Bq/m³. 1 pCi/L = 37 Bq/m³.Sievert (Sv)The SI unit of effective radiation dose, which weights the absorbed energy by radiation type and tissue sensitivity. Radon exposure is often converted to millisieverts per year (mSv/y) to compare it with other radiation sources; in many countries radon is the largest natural contributor to the population dose.Working Level (WL)A historical unit for the concentration of radon decay products in air, originally defined for uranium mines. Cumulative occupational exposure is measured in Working Level Months (WLM), a quantity still used in epidemiological studies of miners.