Monday, December 2, 2019

Radon Exposure and Cancer Risk: Warranted Caution or Unnecessary Hype?

Concern for a multitude of chemicals, environmental elements and toxic substances has been on the increase in recent years. Clearly, being surrounded by such influential components is not preferable, yet it remains to be proven that they are the primary cause of ill-health in our world. With that being said, there can be benefit to investigating the true effects of assumed toxins to determine whether or not they pose negative implications to health. 
Radon, a naturally-occurring radioactive gas found typically in rocks and soil, is produced when thorium and uranium radioactively decay.1 It is an odorless, colorless, inactive gas that does not chemically bond with other substances.1 With a half-life as long as 3.8 days, it has the potential of remaining in the air for an extended time.2  Radon has been the culprit of multiple claims suggesting its link to cancer, particularly for those exposed to it via occupational means (mining). As mentioned previously, however, it is important to review the evidence behind such hypotheses before engaging in great measures to eliminate exposure. Further, for the purposes of this analysis, focus will be given solely to indoor radon exposure rather than outdoor exposure experienced in situations such as underground mining.
In a nested case-control study, researchers in Finland examined the effect of indoor radon exposure and lung cancer risk, due to the conflicting outcomes observed in other studies.3 Study participants consisted of 517 case-control pairs in the matched analysis, and 1055 case subjects and 1544 control subjects  in the unmatched analysis.3 All participants lived within radon-exposed homes over a period of multiple years.3  Outcomes demonstrated that the odds ratio of lung cancer in the matched and unmatched analyses displayed no statistically significant indications for a heightened risk of lung cancer in relation to indoor radon concentration.3 Subsequently, researchers concluded that radon exposure did not appear to pose a causal threat to the incidence of lung cancer.3
In a French hospital-based case-control study, researchers looked at the connection between radon exposure and cancer risk.4 Four hundred eighty-six cases and 984 controls with radon measures in at least one dwelling were examined.4 Following adjustments for age, sex, region, cigarette smoking and occupational exposure, lung cancer risk was studied in relation to indoor radon exposure.4 Researchers concluded that a minimal increased lung cancer risk existed in relation to indoor radon exposure.4
A meta-analysis of 17 case-controlled studies was performed to determine the relationship between residential radon exposure and risk of lung cancer, based upon the exposure rate of 150 Bq/m3.5 Adjusted odds ratios with 95% confidence intervals (CI) in regard to lung cancer risk and concentration of radon exposure were extracted and quality of studies was examined.5 Authors noted that it was difficult to draw definitive conclusions based upon confounding variables, while also mentioning the caution that was taken to eliminate as many of these as possible to display accurate results.5 Further, authors stated that despite the inability to fully predict or assume direct association between residential radon exposure and lung cancer risk, a dose-response relationship was demonstrated in the review.5 Authors concluded that enough evidence was displayed to suggest the importance of developing strategies to reduce human exposure to radon.5
Researchers  in Germany performed two case-control studies during 1990-1997 and analyzed data from 2,963 lung cancer patients and 4,232 controls.6 Results demonstrated a linear dose-response relationship between the level of radon exposure and lung cancer in all subjects (smokers and never-smokers alike).6 Incidence of lung cancer among smokers with radon exposure showed even higher rates of lung cancer incidence.6 Researchers concluded that the risk for developing cancer as a result of radon exposure was significant.6
A New Jersey study was conducted amongst 433 female lung cancer cases compared to 402 control cases.7 After controlling for smoking and occupational histories, results showed a notable trend of increased risk of lung cancer in those exposed to residential radon.7 Though researchers acknowledged study limitations such as differences in housing construction and ventilation, age and socioeconomic status of participants and diet and lifestyle choices of those included, evidence remained that radon exposure posed a threat for many people in regard to cancer risk.7 Researchers concluded that though the study resulted in a positive correlation, limitations of the study should prompt further research, taking into account such variables before drawing firm conclusions.7
Based upon the preponderance of the evidence presented here, it appears that the risk associated with radon exposure is significant enough to pay attention to. Though future research is warranted in regard to confounding variables and study design, recommendations to limit radon exposure seem wise.

1. Yoon JY, Lee JD, Joo SW, Kang DR. Indoor radon exposure and lung cancer: a review of ecological studies. Annals of Occupational and  Environmental Medicine. 2016;28:15. doi:10.1186/s40557-016-0098-z.
2. International Commission on Radiological Protection (ICRP) Protection against radon-222 at home and at work. A report of a task group of the International Commission on Radiological Protection. Ann ICRP. 1993;23(2):1–45. doi: 10.1016/0146-6453(93)90002-P.
3. Auvinen A, Mäkeläinen I, Hakama M, et al. Indoor radon exposure and risk of lung cancer: a nested case-control study in Finland. Journal of the National Cancer Institute. 1996;17;88(14):966-72.
4. Baysson H, Tirmarche M, Tymen G. Indoor radon and lung cancer in France. Epidemiology. 2004 Nov;15(6):709-16.
5. Pavia M, Bianco A, Pileggi C, Angelillo IF. Meta-analysis of residential exposure to radon gas and lung cancer. Bull World Health Organization. 2003;81(10):732–738.
6. Wichmann HE, Rosario AS, Heid IM, Kreuzer M, Heinrich J, Kreienbrock L. Increased lung cancer risk due to residential radon in a pooled and extended analysis of studies in Germany. Health Physics.  2005;88(1):71-9.
7. Schoenberg JB, Klotz JB, Wilcox HB, et al. Case-control study of residential radon and lung cancer among New Jersey women. Cancer Research. 1990; 50(20):6520-4.