The LNT model is appropriate for the estimation of risk from low-level (less than 100 mSv/year) radiation, and low levels of radon in homes should be considered harmful to health

The linear no-threshold hypothesis is at the heart of radiation risk calculations, standards setting, and regulatory philosophy. If the LNT "theory" is correct, then any small amount of radiation constitutes a risk to those exposed. On the other hand, if the "theory" is wrong, and risks are much lower than our present regulations are designed to protect against, then we could save considerable time, effort and expense trying to comply with overly restrictive exposure limits. Application of the LNT hypothesis has literally devastated at least one industry in the United States (the nuclear industry) while, at the same time, it has been responsible for spawning others, such as the home radon-proofing industry. It is also responsible for the employment of large numbers of regulators, inspectors and, yes, medical and health physicists. This is clearly an important issue for medical physicists and we are fortunate to have three of the world's foremost experts to debate it in our Point/Counterpoint series.