Radon Exposure and Breast Cancer: A Study Overview
Introduction to Radon and Breast Cancer
Naturally occurring radon can exist at elevated levels in certain homes, raising health concerns. A recent study in the United States aimed to investigate the potential relationship between radon exposure and breast cancer, seeking to answer the question: Does radon cause breast cancer?
Breast cancer is the most prevalent cause of cancer-related fatalities among women globally. Various types of breast tumors exist, categorized by their responsiveness to hormones and the expression of specific proteins. The majority of breast cancers are estrogen-receptor (ER) positive, growing in response to estrogen. Approximately two-thirds are also progesterone-receptor (PR) positive, while around 20% display excessive levels of a protein known as HER2. Additionally, 10-20% of breast cancers are classified as “triple-negative,” indicating a lack of estrogen and progesterone receptors, as well as no HER2 expression. Geographic variations in breast cancer incidence suggest that environmental factors may influence its development.
Radon Levels in Homes
Radon is a naturally occurring radioactive gas found in air, soil, rocks, and water. The primary source of indoor radon is soil gas that infiltrates homes through foundation cracks. Approximately 6% of homes in the United States have radon levels exceeding the recommended limits set by the Environmental Protection Agency (EPA). When inhaled, radon decay products can deliver radiation doses to various organs, including the breast, potentially resulting in DNA damage.
Despite the plausible mechanism by which radon exposure could contribute to the onset of breast cancer, research on this topic has been limited. To address this gap, researchers conducted a study examining the association between environmental radon exposure and breast cancer incidence among women in the U.S. The findings were published in the journal Environmental Health.
Methodology of the Study
The Nurses’ Health Study II (NHSII) is an ongoing investigation involving over 116,000 U.S. female registered nurses who were between 25 and 42 years old when the study commenced in 1989. Participants, residing in all 50 states, complete biennial questionnaires detailing their health status, medical history, diet, lifestyle factors, and health behaviors.
Researchers analyzed data from these questionnaires to identify participants diagnosed with breast cancer. Medical records were subsequently reviewed to confirm diagnoses and to gather information on tumor types. Additionally, the residential addresses of participants were examined, and a National Laboratory computer model was used to estimate each participant’s overall radon exposure.
Findings on Radon Exposure and Breast Cancer Risk
During the study period, nearly 4,000 cases of invasive breast cancer were documented. Detailed statistical analysis revealed that environmental radon exposure was not linked to the overall risk of invasive breast cancer. Furthermore, no association was found between radon exposure and ER-positive or ER/PR-positive breast tumors.
However, a suggestive connection emerged between elevated radon exposure and the risk of ER-negative, ER/PR-negative, and triple-negative tumors. Patients with triple-negative tumors often carry a gene mutation (BRCA1) that hampers DNA repair. The researchers propose that radon exposure may induce similar DNA damage mechanisms.
Conclusion and Future Research Directions
This study represents the first exploration of environmental radon exposure in relation to invasive breast cancer incidence. While no significant association was found between radon exposure and the risk of overall or hormone-receptor-positive breast tumors, a suggestive link was identified concerning hormone-receptor-negative breast tumors. Further research is necessary to clarify this potential association.
Written by: Julie McShane, Medical Writer
Reference: VoPham T, DuPre N, Tamimi RM, et al. Environmental radon exposure and breast cancer risk in the Nurses’ Health Study II. Environmental Health (2017) 16:97. DOI 10.1186/s12940-017-0305-6.