Final answer:
The annual effective dose from radon progeny, as part of the worldwide average natural radiation exposure, is typically about 3 mSv.
Step-by-step explanation:
The annual effective dose from natural sources worldwide, including radon progeny, is typically about 3 mSV. This estimation is a part of understanding radiation exposure and its potential biological effects. Doses are categorized as low (0.1 Sv or less), moderate (0.1 to 1 Sv), and high (over 1 Sv) with corresponding risks and long-term effects such as cancer and genetic defects. To calculate the dose received in mSv, the relative biological effectiveness (RBE) of the specific type of radiation needs to be taken into account as per the relationship 1 mSv = 1 mGy x RBE.