When we think of noble gases, we typically think of a relatively benign, inert element that might produce an attractive colour when excited. One noble gas, however, is very far from being benign, and in fact is the direct cause of many thousands of lung cancers per year across the Earth. This is radon gas.
Gaseous radon (222Rn) arises from the radioactive decay of radium, thorium and uranium-containing minerals, which can be very abundant in soils across this planet. It is classified by the International Agency for Research on Cancer (IARC) as a category 1 carcinogen, meaning radon is absolutely known to cause cancer in humans. 222Rn’s cancer-causing properties arise from its ability to emit highly mutagenic (DNA damaging) alpha particle ionizing radiation, the speed at which this occurs (it has only 3.8 day half-life), and the ease by which people are exposed to it (inhalation in any indoor air environment).
Our team specializes in radiation biology and, as alpha particles emitted by radon are the primary mode of ionizing radiation exposure across the average person’s lifetime, the question of how much, how fast and how often people are being exposed to radon is incredibly important to us.
A new and unsettling observation is that North American radon exposure is on the rise. Our recent study, published in Scientific Reports, highlights a growing radon exposure problem across the North American Prairies, with newer residential properties containing higher and higher radon. Worse, radon exposure is becoming more even across the year, meaning that radon exposure relief documented during warmer 20th century months, no longer apply in the 21st century. In most homes we examined, radon exposure was consistent all year, with the rest being split equally between having highest radon in summer or highest radon in winter.
We speculate that changes in our climate and behaviour underlies some of these trends. Over the past few years, poor North American summer air quality due to forest fire smoke has been staggering in its growing frequency and geographic scope. The destructive power of massive, ecology-altering fires has not only caused significant property damage and population displacement, but impacts the way we behave within the built environment. Regional governments, even thousands of kilometers away from fires, are issuing air quality statements, warning people to keep windows and doors closed. And rightly so, as smoke inhalation is a very significant health hazard. In terms of behaviour, it is also a statistical fact that more and more North American homes have air conditioning, and so, even in areas with good outside air quality, more people are sealing up their homes in warm months. As such ‘closed-house’ conditions become the norm throughout the year, we suggest this is leading to higher radon exposure.
Whatever the etiology of this is, it is clear that North American exposure to the noble gas 222Rn (and the particle radiation it emits) is increasing in magnitude and duration. We and others need to continue to study this issue, with radon data collection in real time becoming increasingly important to understanding our rapidly changing world. In doing so, we will learn how to decrease our exposure, and thereby decrease the future burden of radon-attributable lung cancers.
This post was written by Dustin Pearson, MSc, and edited by Aaron Goodarzi, PhD, who are both researchers at the University of Calgary's Charbonneau Cancer Institute at the Cumming School of Medicine in Alberta, Canada. Dr. Goodarzi is also the founder of the Evict Radon non-profit organization that offers non-profit radon testing to the Canadian general public, as part of multiple Research Ethics Board (REB)-approved Canadian University research studies.