At a population and individual level , radon exposure arises from a complex convergence of geologic , built environment , demographic , lifestyle , and behavioural factors 19 , 20 , 21 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 . In Canada , evolving building practices over the 20th to 21st century have increasingly and unintentionally captured , contained , and concentrated alpha radiation emitting radionuclides from radon within the residential built environment to unnaturally high and unsafe levels 29 , 31 , 37 . Radiation doses from radon inhalation are also a function of decision making factors and socioeconomics relating to radon awareness , testing , and reduction ( i . e ., how fast an individual is able to understand and reduce radon exposure as a personal risk factor ) 20 , 21 , 30 , 38 , 39 , as well as lifestyle factors such as occupation that dictate activity patterns ( i . e ., the amount of time spent between environments ) 19 , 20 , 21 . Based on current residential radon levels and activity patterns , radiation doses from radon in Canada are estimated to be at historic highs , with radon-vulnerable populations in Canada including younger people with children living at home , who are employed or in education , and / or whose occupations are more amenable to telecommuting 19 . In part , this phenomenon is driven by younger ( those under age 45 ) Canadian adults being more likely to live in newer , more affordable residential buildings that have innately higher radon levels , and / or who are less able to afford radon reduction services due to comparatively lower household incomes 21 .
Socioeconomic disparities in lung cancer risk have been documented previously and are often linked to community types , with people living in more rural area ( i . e . less populated ) communities being more likely to use tobacco , earn less income , be exposed to different and / or higher amounts of environmental lung carcinogens throughout life , and have reduced access to health care and / or higher education 40 , 41 , 42 . In the context of radon exposure , disparities between urban and rural communities are documented and intriguing , but still ambiguous . Certainly , there are many reports of disparate rural versus urban indoor air radon levels across the globe 37 , 43 , 44 , 45 , 46 , 47 , 48 , highlighting a potentially serious issue with an ambiguous origin . One theory has been that domestic water supplies from rural-area groundwater wells often contain higher amounts of dissolved radon relative to ( already de-gassed ) supplies entering houses from urban-area municipal water treatment plants 49 , 50 . However , the contribution of waterborne radon to indoor air radon levels assessed in recent decades has typically been found to be relatively minor (~ 1 – 2 % of total , equating to microsievert ( μSv ) doses ) 51 , 52 , 53 , 54 , 55 , 56 , 57 ; this is most likely because the equilibration ratio of radon from air to water is 1:10,000 , meaning 10,000 Bq / L of radon degassing from water contributes only 1 Bq / m 3 to air 49 . Thus , an important question becomes : if radon being released directly from groundwater to indoor air is not the biggest contributor to the phenomenon of higher rural radon exposure , as current research indicates , then what might it be ?
How ( and to what extent ) radon exposure contributes to elevated lung cancer risks in diverse rural areas currently remains mechanistically unclear . In part , this is because earlier studies documenting radon differences between urban and rural areas were based on ( i ) smaller-scale datasets with limited statistical power ( a few hundred radon readings ), ( ii ) geogenic radon potentials ( i . e ., not empirical measurements of radon in indoor air ), ( iii ) data without matched urban controls from the same region , ( vi ) data that were potentially confounded by