RADON, DNA and CANCER

Radon, the environmental carcinogen is ubiquitous. The EPA estimates levels of 4 PcI/L (4-Picocuries/liter) or more are hazardous to health. By hazardous to health they mean cancer inducing.

Uranium238 with a 4.1 billion years of half life and the only naturally occurring fissile isotope, decays to Thorium232 and that decays to Radium226 ultimately yielding Radon222. Radon emits alpha particles into the air. Humans breathing a high concentrations of these Radon particles into their lungs can develop Lung Cancer.

                                           

In 1898 from a Uranium ore, Marie Curie (Maria Sklodowska 1867-1934) discovered radioactivity after grinding, dissolving, filtering, precipitating, collecting, redissolving, crystallising and recrystallizing the uranium ore into tiny parts of Radium (she is the only woman to have received a Nobel Prize in Physics and Chemistry). Thus began the journey of radioactivity that cost her, her life to Aplastic Anemia and her daughter’s life to Leukemia while studying the properties of Uranium and its decay products. Both illnesses a consequence of the radioisotope exposure!

"Nothing in life is to be feared; it is only to be understood."  - Marie Curie

15,000 to 22,000 cases of Lung Cancer are estimated as consequence of Radon exposure from over 200,000 cases of Lung cancer a year in the United States. The Radon gas is emitted from the soil and is based on the Uranium/Thorium concentrates within the soil. The highest concentrations within homes appear in the unventilated basements located over Uranium/Thorium rich-soils. Radon emits high energy He2+ ions as Linear Energy Transfers or LET.

                                            

The alpha particle is helium nuclei, composed of two protons and two neutrons. Because the nuclei have no electrons, they have a +2 charge. Because of its mass, alpha radiation does not penetrate healthy skin. However, entry of alpha radiation via the mouth or nose, may cause cancers in lungs. These emissions breathed into the lungs disrupt the alveolar/bronchial cell DNA Mutations, Single and Double stranded Breakage due to disrupted phosphate bonds, Single Nucleotide Polymorphisms, Cell Cycle disruptions, Mismatch DNA Repair ( NER -Nucleotide Excision Repair, BER -Base Excision Repair, MMR -Mismatch Repair))mechanism function (cells have the ability to repair the damage done to DNA by radiation, chemicals, or physical trauma. The effectiveness of these cellular repair mechanisms depends on the kind of cell, the type and dose of radiation, the individual and other biological factors), over expressions of oncogenes or suppression of tumor suppressor genes and even successful apoptosis if the p53 gene is fully functional and not overwhelmed or any combination of above can start the nidus of the cancer within the lung. Since alpha particles are massive and highly charged, they are extremely damaging to living tissue. Alpha particle emissions from decay of radon progeny in the lungs cannot reach cells in any other organs, except breathed into the lungs. Even with a fully functional DNA Repair mechanism intact, a single genetic aberration passed down to the cellular progeny can play havoc and create the malignancy. Additionally the active Alpha Particles also inexact with whole cells and their mitochondria releasing Oxygen Reactive Species and creating oxidative stresses thru direct cell damage leading to molecular disturbances within the genome and thus propagation. Thus lungs are the main target of developing cancers.

Recent data from Scandinavia seems to suggest that there is a slightly higher incidence of “blood cancers” (Leukemia, Lymphoma and other Bone Marrow Disorders) in women. The authors did a meta-analysis and discovered a 60% increase of such cancers in women that showed a dose response curve to the Radon exposure. The Author of the study, Dr. Teras stated, “The overall lifetime risk of hematological cancers in the United States is about 2%, so even a 60% relative increase would still mean a relatively small absolute risk.” The data came from an analysis including 140,652 participants among whom there were 3,019 hematologic cancers during 19 years of follow-up. The entry of the alpha particles via the pulmonary vasculature and into the bone marrow may if proven in future studies turn out to be the proposed mechanism.

The logical question that follows is what if anything that can be done about risk mitigation strategies to limit Radon exposure:

1. Have surrounding soil samples checked for Uranium/Thorium levels.

2.Vacuum the dust over a period of 30-90 days in the home’s basement and using a Geiger counter determine the extent of the exposure. A crude but reasonable estimate can be made. Nowadays Test Kits are sold in various stores. The reliability is never completely guaranteed. 

3. Ventilate the basement and the first floors periodically with fresh air. For more information review the website provided below.

https://www.health.ny.gov/environmental/radiological/radon/mitigation/what_is_mitigation.htm

Can we eliminate all risks? Probably not. But mitigate a percentage of the risk? Probably so.

References:

Darby S, Hill D, Deo H, et al. Residential radon and lung cancer: Scandinavian Journal of Work, Environment and Health 2006; 32(Suppl 1):1–83. Erratum in Scandinavian Journal of Work, Environment and Health 2007; 33(1):80.

Field RW. A review of residential radon case-control epidemiologic studies performed in the United States. Reviews on Environmental Health 2001; 16(3):151–167.

Harley NH, Robbins ES. Radon and leukemia in the Danish study: another source of dose. Health Physics 2009; 97(4):343–347.

Möhner M, Gellissen J, Marsh JW, Gregoratto D. Occupational and diagnostic exposure to ionizing radiation and leukemia risk among German uranium miners. Health Physics 2010; 99(3):314–321.

Lauren R. Teras et al, Residential radon exposure and risk of incident hematologic malignancies in the Cancer Prevention Study-II Nutrition Cohort, Environmental Research (2016)DOI: 10.1016/j.envres.2016.03.002