True or False: There exists a known threshold concentration below which radon exposure presents no risk.

The statement is false. Current scientific understanding does not establish a definitive threshold concentration of radon below which radon exposure is considered risk-free. The radon risk assessment is based on the idea that any level of exposure carries some degree of risk for health effects, particularly the risk of lung cancer.

Research indicates that even low concentrations of radon can contribute to cumulative lifetime exposure and therefore potentially increase lung cancer risk. This is pertinent in the context of public health advice, which emphasizes that minimizing radon exposure is beneficial, regardless of the concentration level.

While individual susceptibility to radon may vary based on health and environmental factors, the absence of a known safe threshold means that the best practice is to aim for the lowest possible levels of radon in residential and occupational environments. This understanding underpins efforts in radon measurement and mitigation.