Younger North Americans are exposed to more radon gas due to occupancy biases within the residential built environment

Abstract

Residential buildings can concentrate radioactive radon gas, exposing occupants to particle radiation that increases lung cancer risk. This has worsened over time in North America, with newer residences containing greater radon. Using data from 18,971 Canadian households, we calculated annual particle radiation dose rates due to long term residential radon exposure, and examined this as a function of occupant demographics. The current particle radiation dose rate to lungs from residential radon in Canada is 4.08 mSv/y from 108.2 Bq/m³, with 23.4% receiving 100-2655 mSv doses that are known to elevate human cancer risk. Notably, residences built in the twenty-first century are occupied by significantly younger people experiencing greater radiation dose rates from radon (mean age of 46 at 5.01 mSv/y), relative to older groups more likely to occupy twentieth century-built properties (mean age of 53 at 3.45-4.22 mSv/y). Newer, higher radon-containing properties are also more likely to have minors, pregnant women and an overall higher number of occupants living there full time. As younger age-of-exposure to radon equates to greater lifetime lung cancer risk, these data reveal a worst case scenario of exposure bias. This is of concern as, if it continues, it forecasts serious future increases in radon-induced lung cancer in younger people.

Figure 1

Residential occupancy status, age and employment status of the radon-tested cohort. (A) The measured long term residential radon level for the entire Canadian study cohort (grey: n = 18,971) was compared to the sub-study (red: n = 3,518), i.e. participants who also provided demographic data. The radon test outcomes for the sub-study reflected the entire cohort, with no significant difference in the geometric mean radon (black lines ± geometric standard deviation) or data distribution between sets. All remaining data refers to the sub-study cohort unless otherwise indicated. (B) The amount of time each participant indicated they had lived in the radon-tested property at the time of testing. (C) The total number of occupants living full time in the radon-tested property, with yellow indicating properties where there are pregnant occupants or minors (ages 0–17) living or visiting regularly, and grey sections indicating homes where all occupants are 18 or more years of age. (D) Reported gender balance by age group of the cohort. (E) The reported employment status of the cohort. The inset pie chart shows the percentage of those in full or part time work who indicate working from home either part or all of the time. (F) The geometric mean of the amount of time each participant reported spending per year in the primary residence, as a function of reported occupation status, showing 2-way ANOVA analysis of indicated pairwise comparisons. ****p < 0.0001.

Figure 2

Yearly and cumulative particle radiation exposure from radon inhalation. (A). Rubric delineating residential radon exposure (high exposure =  ≥ 100 Bq/m³) as a function of the amount of time a participant reports living in that property (long exposure =  ≥ 10 y). (B) Residential radon exposure as a function of years lived in that environment, with red and yellow lines demarcating exposure brackets outlined in (A). (C) Using the indicated formula from ICRP (see methods), Bq/m³ radon levels were combined with exposure durations to derive mSv/y particle radiation dose rates, expressed as a function of participant age. The geometric mean dose rate and the percent of the cohort experiencing < 5, ≥ 5, ≥ 10, ≥ 20, or ≥ 40 mSv/y are indicated. (D) The particle radiation dose rate (mSv/y) was broken down by exposure brackets outlined in (A), additionally indicating the geometric mean of participant ages and the time they reported spending in their primary residence per year. (E) The estimated cumulative particle radiation exposure for all primary respondents (in mSv) was expressed as a function of the number of occupants for that specific property. (F) The particle radiation dose rate (mSv/y) for the larger cohort of radon tested, properties (n = 18,971) was estimated using the geometric mean amount of time each participant reported spending per year in the primary residence (5549 h/y). The geometric mean annual particle dose rate and the percent of the cohort experiencing < 5, ≥ 5, ≥ 10, ≥ 20, or ≥ 40 mSv/y are indicated.

Figure 3

Canadian radon exposure as a function of residence age, occupant age, number of occupants and presence of minors and pregnant occupants. (A) Long term radon-test outcomes (grey bars, right y-axis) and geometric mean age of primary homeowner/renter (grey circles, line overlaid with red dashed polynomial trendline, left y-axis) for Canadian residences grouped into 5 year bracket (x-axis). (B) Long term radon-test outcomes (grey bars, right y-axis) and geometric mean age of the number of full time occupants (grey diamonds, line overlaid with orange dashed polynomial trendline, left y-axis) for Canadian residences grouped into 5 year bracket (x-axis). (C) Scatter plot of occupant age data from (A) by property construction period, showing 2-way ANOVA analysis of properties from 2020–2006 pairwise compared to all other period brackets. ****p < 0.0001. (D) Line graph of the geometric mean occupants per property (from B), showing 2-way ANOVA analysis of all comparisons. ****p < 0.0001. (E) The percent distribution of responses for reported number of minors (or pregnant women) living full time within the property, grouped by period of property construction.