It was Jimmy Carter days and the OPEC Oil crisis. Prior to 1973... electricity and heating oil was cheap, there were many single pane windows that didn't seal completely. So the default condition was houses as originally built, cooler temps in Winter and more natural ventilation in houses with corresponding higher energy costs.
In 1973 fears that heating in Winter would get more expensive, saw an increase in home renovation. IR viewers were employed for the first time and IR images showed windows and attic vents as glowing with heat (as they had all along) and it looked like money escaping. Rubber seals on doors and windows. Double pane windows.
This trapped the radon in basements (and for some rising out of the basement onto the first floor) to be breathed by humans and gain higher concentrations for the first time in US history. Homes were hermetically sealed.
Since smokers bore the penance of sin... the rise of the '2nd leading cause' went unrecognized for years.
In 1973 fears that heating in Winter would get more expensive, saw an increase in home renovation. IR viewers were employed for the first time and IR images showed windows and attic vents as glowing with heat (as they had all along) and it looked like money escaping. Rubber seals on doors and windows. Double pane windows.
This trapped the radon in basements (and for some rising out of the basement onto the first floor) to be breathed by humans and gain higher concentrations for the first time in US history. Homes were hermetically sealed.
Since smokers bore the penance of sin... the rise of the '2nd leading cause' went unrecognized for years.