We used to consider radon as the second leading cause of lung cancer. This has been proved by means of many studies and research projects. However, radon can be used as a tracer too. One example is an investigation carried out in Antarctica to look into how the relationship between pollutants reaching Antarctica and global climate models. What stands out from this study in terms of radon metrology is the device developed by Australian Nuclear Science and Technology Organisation (ANSTO). Have a look at the published paper to observe the very low values this instrument is able to measure. It can measure mBq m-3. For further information check the article published on phys.org.