A long time ago there was pretty good data that radon was not in fact bad for you at household levels but actually good for you.  Just to swing the discussion in an unexpected direction I give you ..

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"Approximately 10,000 people occupied these buildings and received an average radiation dose of 0.4 Sv,
unknowingly, during a 9-20 year period. They did not suffer a higher incidence of cancer mortality, as the LNT
theory would predict. On the contrary, the incidence of cancer deaths in this population was greatly reduced – to
about 3 per cent of the incidence of spontaneous cancer death in the general Taiwan public. In addition, the
incidence of congenital malformations was also reduced – to about 7 per cent of the incidence in the general
public. These observations appear to be compatible with the radiation hormesis model."