� Housing Stock Changes: over time, older homes are often destroyed or remodeled, thus radon measurements will be non-existent or highly varied; a home ' s radon level may change, higher or lower, over time if new ventilation systems are installed, the occupancy patterns are substantially different, or the home ' s foundation shifts or cracks appear.
� Inaccurate Histories: often a majority of the lung cancer cases( individuals) being studied are deceased or too sick to be interviewed by researchers. This requires reliance on second-hand information which may not be as accurate. These inaccuracies primarily affect: o Residence History: a child or other relative may not be aware of all residences occupied by the patient- particularly if the occupancy is distant in time or of relatively short duration. Even if the surrogate respondent is aware of a residence they may not have enough additional information to allow researchers to locate the home.
o Smoking History: smoking history historically has reliability problems. Individuals may under-estimate the amount they smoke. Conversely, relatives or friends may over-estimate smoking history.
o Other: complicating factors other than variations in smoking habits include an individual ' s: genetics, lifestyle, exposure to other carcinogens, and home heating, venting and air conditioning preferences.
Visit our Radon website to learn more about Radon. Source: https:// www. epa. gov / radon / describe‐radon‐epidemiological‐studies