Residential radon and brain tumour incidence in a Danish cohort

The connection between six common air pollution particles and adult brain tumors: a meta-analysis of 26,217,930 individuals

Environmental air pollutants (black carbon (BC), nitrogen oxides (NOx), particulate matter with diameter < 2.5 μm (PM2.5), nitrogen dioxide (NO2), particulate matter with diameter <10 μm (PM10), and ozone (O3)) are one of the major menaces to mankind's health globally. This analysis reviews the association between exposure to these air pollutants and the chance of developing brain tumors in adults (total brain tumors, malignant brain tumors, and benign brain tumors). Studies published by April 2022 were searched. Raw effect sizes were converted to standardized effect sizes per 10 μg/m3 increase. Random effect models were applied to calculate combined effect size and 95% confidence intervals (CIs) were computed. A total of 8 articles were included for meta-analysis. The pooled effect size (ES) for per 10 μg/m3 BC intake was 1.67 (95% CI: 1.25, 2.22), P = 0.449. For every 10 μg/m3 rise in NO2 concentration, ES was 1.03 (95% CI: 1.01, 1.05), P = 0.319. Meanwhile, there was a boundary association between NOx and adult brain tumors (ES and 95% CI: 1.01; 1.00, 1.01/10 μg/m3; P = 0.716). While there was no conjunction between PM2.5, PM10, O3 (PM2.5: ES and 95% CI: 1.04; 0.99, 1.08/10 μg/m3; P = 0.834; PM10: ES and 95% CI: 1.01; 0.97, 1.04/10 μg/m3; P = 0.627; O3: ES and 95% CI: 0.97; 0.94, 1.00/10 μg/m3; P = 0.253). This research shows testimony of a significant link between air pollutants and brain tumors in adults, especially when exposed to BC, NO2, and NOx. This evidence emphasizes the importance of improving air quality as part of a comprehensive approach to prevent the occurrence and deterioration of brain tumors.

Exposure to radon and heavy particulate pollution and incidence of brain tumors

BACKGROUND

Global incidence for brain tumors varies substantially without explanation. Studies correlating radon exposure and incidence are inconclusive. Particulate pollution has been linked to increased tumor incidence. Particulates may disrupt the blood-brain barrier allowing intracranial exposure to oncogenic radon. We investigated the relationship between exposure to residential radon, particulate pollution, and brain tumor incidence in the United States (US).

METHODS

County-level median radon testing results and annual air quality index values were obtained and divided into tertiles. Counties without both values were excluded. Four groups of counties were generated: high particulate/high radon (high/high), high/low, low/high, and low/low. Using incidence data from the Central Brain Tumor Registry of the US (provided by CDC's National Program of Cancer Registries and NCI's SEER), annual age-adjusted incidence rates (AAAIRs) by group were generated by behavior. Incidence rate ratios were calculated to examine for significant differences (α = .05). Poisson regression accounting for possible confounders was conducted.

RESULTS

Counties with available data included 83% of the US population. High/high exposure was significantly associated with increased AAAIR of all non-malignant tumors (up to 26% higher, including most meningiomas) even after accounting for potential confounders. An increased AAAIR was noted for all malignant tumors (up to 10% higher), including glioblastoma, but was negated after accounting for demographic/socioeconomic differences.

CONCLUSIONS

We present the first report suggesting increased non-malignant brain tumor incidence in regions with high particulate and radon exposure. These findings provide insight into unexplained variation in tumor incidence. Future studies are needed to validate these findings in other populations.

Ionizing radiation exposure during adulthood and risk of developing central nervous system tumors: systematic review and meta-analysis

Many studies on ionizing radiation (IR) exposure during childhood have shown deleterious effects on the central nervous system (CNS), however results regarding adult exposure are inconsistent, and no systematic reviews have been performed. The objectives are to synthesize the findings and draw evidence-based conclusions from epidemiological studies on the risk of benign and malignant brain and CNS tumors in humans exposed to low-to-moderate doses (< 0.5 Gy) of IR during adulthood/young adulthood. A systematic literature search of four electronic databases, supplemented by a hand search, was performed to retrieve relevant epidemiological studies published from 2000 to 2022. Pooled excess relative risk (ERR_pooled) was estimated using a random effect model. Eighteen publications were included in the systematic review and twelve out of them were included in a meta-analysis. The following IR sources were considered: atomic bombs, occupational, and environmental exposures. No significant dose-risk association was found for brain/CNS tumors (ERR_pooled at 100 mGy = − 0.01; 95% CI: − 0.05, 0.04). Our systematic review and meta-analysis did not show any association between exposure to low-to-moderate doses of IR and risk of CNS tumors. Further studies with histological information and precise dose assessment are needed.

A systematic review on groundwater radon distribution with human health consequences and probable mitigation strategy

Groundwater radon contamination is a serious global concern for its eco-toxicological effects. The major health hazard occurs due to toxic indoor air inhalation and consumption of contaminated drinking water supplied from different distribution systems, especially groundwater. There are fragmented reports on the measurement of radon contamination and their health consequences with physical radon removal strategies as well as characterization of inhabitant microbial communities. As it concerned with human health, collective information is much essential on their groundwater distribution, their physicochemical properties and possible mitigation strategies, not done so far. In such prospect, this review summarizes the physicochemical properties of radon, their sources, global as well as Indian groundwater radon contamination scenario, health effects and inhabitant microbes along with their survival strategies. It also summarizes the physical radon removal techniques and especially emphasizes the microbes based bioremediation process as well as a combination of both as a future effective radon remediation process.

Environmental/Occupational Exposure to Radon and Non-Pulmonary Neoplasm Risk: A Review of Epidemiologic Evidence

Although Radon (Rn) is a known agent for lung cancer, the link between Rn exposure and other non-pulmonary neoplasms remains unclear. The aim of this review is to investigate the role of Rn in the development of tumors other than lung cancer in both occupational and environmental exposure. Particularly, our attention has been focused on leukemia and tumors related to brain and central nervous system (CNS), skin, stomach, kidney, and breast. The epidemiologic literature has been systematically reviewed focusing on workers, general population, and pediatric population. A weak increase in leukemia risk due to Rn exposure was found, but bias and confounding factors cannot be ruled out. The results of studies conducted on stomach cancer are mixed, although with some prevalence for a positive association with Rn exposure. In the case of brain and CNS cancer and skin cancer, results are inconclusive, while no association was found for breast and kidney cancers. Overall, the available evidence does not support a conclusion that a causal association has been established between Rn exposure and the risk of other non-pulmonary neoplasms mainly due to the limited number and heterogeneity of existing studies. To confirm this result, a statistical analysis should be necessary, even if it is now not applicable for the few studies available.

Brain cancer incidence rates and the presence of nuclear reactors in US states: a hypothesis-generating study

BACKGROUND

The etiology of brain cancer is poorly understood. The only confirmed environmental risk factor is exposure to ionizing radiation. Because nuclear reactors emit ionizing radiation, we examined brain cancer incidence rates in the USA in relation to the presence of nuclear reactors per state.

METHODS

Data on brain cancer incidence rates per state for Whites by sex for three age groups (all ages, 50 and older, and under 50) were obtained from cancer registries. The location, number, and type of nuclear reactor, i.e., power or research reactor, was obtained from public sources. We examined the association between these variables using multivariate linear regression and ANOVA.

RESULTS

Brain cancer incidence rates were not associated with the number of nuclear power reactors. Conversely, incidence rates per state increased with the number of nuclear research reactors. This was significant for both sexes combined and for males in the 'all ages' category (β = 0.08, p = 0.0319 and β = 0.12, p = 0.0277, respectively), and for both sexes combined in the'50 and older' category (β = 0.18, p = 0.0163). Brain cancer incidence rates for counties with research reactors were significantly higher than the corresponding rates for their states overall (p = 0.0140). These findings were not explicable by known confounders.

CONCLUSIONS

Brain cancer incidence rates are positively associated with the number of nuclear research reactors per state. These findings merit further exploration and suggest new opportunities for research in brain cancer epidemiology.

Reactive astrogliosis in the dentate gyrus of mice exposed to active volcanic environments

Air pollution has been associated with neuroinflammatory processes and is considered a risk factor for the development of neurodegenerative diseases. Volcanic environments are considered a natural source of air pollution. However, the effects of natural source air pollution on the central nervous system (CNS) have not been reported, despite the fact that up to 10% of the world's population lives near a historically active volcano. In order to assess the response of the CNS to such exposure, our study was conducted in the island of Sao Miguel (Azores, Portugal) in two different areas: Furnas, which is volcanically active one, and compared to Rabo de Peixe, a reference site without manifestations of active volcanism using Mus musculus as a bioindicator species. To evaluate the state of the astroglial population in the dentate gyrus in both samples, the number of astrocytes was determined using immunofluorescence methods (anti-GFAP and anti-GS). In addition, the astrocytic branches in that hippocampal area were examined. Our results showed an increase in GFAP+ astrocytes and a reduction in GS+ astrocytes in Furnas-exposed mice compared to animals from Rabo de Peixe. In addition, astrocytes in the dentate gyrus of chronically exposed animals exhibited longer branches compared to those residing at the reference site. Thus, reactive astrogliosis and astrocyte dysfunction are found in mice living in an active volcanic environment.

Radon-The Element of Risk. The Impact of Radon Exposure on Human Health

Lung cancer is a heterogeneous group of diseases with multifactorial aetiology. Smoking has been undeniably recognized as the main aetiological factor in lung cancer, but it should be emphasized that it is not the only factor. It is worth noting that a number of nonsmokers also develop this disease. Radon exposure is the second greatest risk factor for lung cancer among smokers-after smoking-and the first one for nonsmokers. The knowledge about this element amongst specialist oncologists and pulmonologists seems to be very superficial. We discuss the impact of radon on human health, with particular emphasis on respiratory diseases, including lung cancer. A better understanding of the problem will increase the chance of reducing the impact of radon exposure on public health and may contribute to more effective prevention of a number of lung diseases.

Radon Exposure and Neurodegenerative Disease

Background: To carry out a systematic review of scientific literature about the association between radon exposure and neurodegenerative diseases. Methods: We performed a bibliographic search in the following databases: Pub med (Medline), Cochrane, BioMed Central and Web of Science. We collected the data by following a predetermined search strategy in which several terms werecombined. After an initial search, 77 articles were obtained.10 of which fulfilled the inclusion criteria. Five of these 10 studies were related to multiple sclerosis (MS), 2 were about motor neuron diseases (MND), in particular amyotrophic lateral sclerosis (ALS) and 3 were related to both Alzheimer's disease (AD) and Parkinson's disease (PD). Results: The majority of the included articles, suggested a possible association between radon exposure and a subsequent development of neurodegenerative diseases. Some of the studies that obtained statistically significant resultsrevealed a possible association between radon exposure and an increase in MS prevalence. Furthermore, it was also suggested that radon exposure increases MND and AD mortality. Regarding AD and PD, it was observed that certainde cay products of radon-222 (²²²Rn), specifically polonium-210 (²¹⁰Po) and bismuth-210 (²¹⁰Bi), present a characteristic distributionpattern within the brain anatomy. However, the study with the highest scientific evidence included in this review, which investigated a possible association between the concentration of residential radon gas and the MS incidence, revealed no significant results. Conclusions: It cannot be concluded, although it is observed, that there is a possible causal association between radon exposure and neurodegenerative diseases. Most of the available studies are ecological so, studies of higher statistical evidence are needed to establish a causal relationship. Further research is needed on this topic.

Tidal variations of background ionizing radiation and circadian timing of the suprachiasmatic nucleus clock

Recently, correlations of different physiological processes in humans with variations in the local lunisolar gravitational tide force have been observed under highly controlled laboratory conditions. Understanding of the physical nature of this phenomenon needs a comprehensive study of its possible molecular mechanisms. One of the possible timing cues is the strong periodic variation of the emanation fields of radon-222 and its progeny produced by tidal deformations of geological environment. In the present work, we argue that this variation could induce temporal modulation of radiation-induced bystander signaling pathways associated with fundamental regulators of gene expression in the suprachiasmatic nucleus clock.

Incidence of brain and spinal cord cancer and county-level radon levels in New Jersey, Wisconsin, Minnesota, Pennsylvania, and Iowa, USA

Ionizing radiation at diagnostic and therapeutic doses is a known contributor to the development of brain and spinal cord (CNS) cancer. However, little is known about risk from exposure to radon, a natural radiation source which the general population is exposed to residentially and environmentally. This study investigated correlations between mean county radon levels and CNS cancer incidence in five highly populated and radon-enriched US states (Minnesota, mean radon level 4.6 pCi/L; Wisconsin, 5.7 pCi/L; Pennsylvania, 8.6 pCi/L; Iowa, 6.1 pCi/L; and New Jersey, 4.4 pCi/L). Mean radon levels per county were accessed through AirChek, which provides publicly available radon data measured in residences and workplaces. CNS cancer incidence data were accessed through the states' health department websites and span differing amounts of time due to the publicly accessible nature of the data, though all time spans were over 10 years. Negative binomial regressions were run to assess correlations between mean radon and CNS cancer incidence per county. Quantile maps were constructed and Moran's I was calculated to assess spatial autocorrelation in residuals; no spatial autocorrelation was evident. Iowa was the only state with a significant positive association between radon and CNS incidence; no associations were detected in other states, and a negative association was observed in the 5 states combined. This study does not provide evidence that radon is a risk factor for CNS cancer; however, the possibility of an association cannot be ruled out due to limitations of the study, principally its ecologic nature and lack of individual-level exposure data.

Glioblastoma Cellular Origin and the Firework Pattern of Cancer Genesis from the Subventricular Zone

Glioblastoma (GBM) is a disease without any definite cure. Numerous approaches have been tested in efforts to conquer this brain disease, but patients invariably experience recurrence or develop resistance to treatment. New surgical tools, carefully chosen samples, and experimental methods are enabling discoveries at single-cell resolution. The present article reviews the cell-of-origin of isocitrate dehydrogenase (IDH)-wildtype GBM, beginning with the historical background for focusing on cellular origin and introducing the cancer genesis patterned on firework. The authors also review mutations associated with the senescence process in cells of the subventricular zone (SVZ), and biological validation of somatic mutations in a mouse SVZ model. Understanding GBM would facilitate research on the origin of other cancers and may catalyze the development of new management approaches or treatments against IDH-wildtype GBM.

Radiation in different types of building, human health

Radon is a radioactive gas permanently produced in rocks, soils, building materials as an indirect decay product of uranium and thorium. According to EPA, radon is the second most frequent cause of lung cancer, after cigarette smoking. The aim of survey was to measure radon levels and ambient gamma dose rates in dwellings in various types of buildings situated on various ground and to evaluate health parameters depended on indoor radiation such as lung cancer risk and total annual effective dose rate. Moreover, we wanted to verify the possibility to predict indoor radon concentration in specific dwelling knowing types of soil, building construction, building materials and floor number. The measurements of radon concentrations were carried out using SSNTDs Kodak LR-115 which were exchanged seasonally. The ambient gamma dose rates were measured using Geiger counter. Radon concentrations in all dwellings were lower than 300 Bq m^-3 (recommended by EU action level). In some dwellings during some seasons radon concentrations were above 100 Bq m^-3. Prolonged exposure to indoor radon at the levels of 100 Bq m^-3 causes statistically significant increase of lung cancer. The average indoor radon concentration in Wroclaw's dwellings was 46 Bq m^-3. The annual risk of lung cancer was lower than 0.0005%. The total annual effective dose rates ranged from 1.36 mSv y^-1 to 3.3 mSv y^-1. We observed seasonal, vertical, spatial variations of radon concentrations. We did not notice significant drop of ambient gamma dose rates between the ground floor and floors 2nd to 5th as we did for radon concentrations. We noticed that indoor radon concentrations differed 4 to 6 times even among dwellings located in these same types of buildings, on these same soil types or these same floors.

Long-Term Exposure to Air Pollutants and Cancer Mortality: A Meta-Analysis of Cohort Studies

The aim of this study was to examine the relationship between main air pollutants and all cancer mortality by performing a meta-analysis. We searched PubMed, EMBASE (a biomedical and pharmacological bibliographic database of published literature produced by Elsevier), and the reference lists of other reviews until April 2018. A random-effects model was employed to analyze the meta-estimates of each pollutant. A total of 30 cohort studies were included in the final analysis. Overall risk estimates of cancer mortality for 10 µg/m³ per increase of particulate matter (PM)2.5, PM10, and NO₂ were 1.17 (95% confidence interval (CI): 1.11⁻1.24), 1.09 (95% CI: 1.04⁻1.14), and 1.06 (95% CI: 1.02⁻1.10), respectively. With respect to the type of cancer, significant hazardous influences of PM2.5 were noticed for lung cancer mortality and non-lung cancer mortality including liver cancer, colorectal cancer, bladder cancer, and kidney cancer, respectively, while PM10 had harmful effects on mortality from lung cancer, pancreas cancer, and larynx cancer. Our meta-analysis of cohort studies indicates that exposure to the main air pollutants is associated with increased mortality from all cancers.

Association of Radon Background and Total Background Ionizing Radiation with Alzheimer's Disease Deaths in U.S. States

BACKGROUND

Exposure of the brain to ionizing radiation might promote the development of Alzheimer's disease (AD).

OBJECTIVE

Analysis of AD death rates versus radon background radiation and total background radiation in U.S. states.

METHODS

Total background, radon background, cosmic and terrestrial background radiation measurements are from Assessment of Variations in Radiation Exposure in the United States and Report No. 160 - Ionizing Radiation Exposure of the Population of the United States. 2013 AD death rates by U.S. state are from the Alzheimer's Association.

RESULTS

Radon background ionizing radiation was significantly correlated with AD death rate in 50 states and the District of Columbia (r = 0.467, p = 0.001). Total background ionizing radiation was also significantly correlated with AD death rate in 50 states and the District of Columbia (r = 0.452, p = 0.001). Multivariate linear regression weighted by state population demonstrated that AD death rate was significantly correlated with radon background (β= 0.169, p < 0.001), age (β= 0.231, p < 0.001), hypertension (β= 0.155, p < 0.001), and diabetes (β= 0.353, p < 0.001).

CONCLUSION

Our findings, like other studies, suggest that ionizing radiation is a risk factor for AD. Intranasal inhalation of radon gas could subject the rhinencephalon and hippocampus to damaging radiation that initiates AD. The damage would accumulate over time, causing age to be a powerful risk factor.

High Radon Areas and lung cancer prevalence: Evidence from Ireland

This paper examined the relationship between radon risk and lung cancer prevalence using a novel dataset combining spatially-coded survey data with a radon risk map. A logit model was employed to test for significant associations between a high risk of indoor radon and lung cancer prevalence using data on 5590 people aged 50+ from The Irish Longitudinal Study on Ageing (TILDA) and radon risk data from Ireland's Environmental Protection Agency (EPA). The use of data at the individual level allowed a wide range of potentially confounding factors (such as smoking) to be included. Results indicate that those who lived in an area in which 10%-20% of households were above the national reference level (200 Bq/m³) were 2.9-3.1 times more likely to report a lung cancer diagnosis relative to those who lived in areas in which less than 1% of households were above the national reference level.

Residential radon and cancer mortality in Galicia, Spain

Residential radon exposure is a serious public health concern, and as such appears in the recommendations of European Code Against Cancer. The objective of this study was to assess the association between residential radon levels and mortality due to different types of cancer, using misaligned data analysis techniques. Mortality data (observed cases) for each of the 313 Galician municipalities were drawn from the records of the National Statistics Institute for the study period (1999-2008). Expected cases were computed using Galician mortality rates for 14 types of malignant tumors as reference, with a total of 56,385 deaths due to the tumors analyzed. The effect estimates of indoor radon (3371 sampling points) were adjusted for sociodemographic variables, altitude, and arsenic topsoil levels (1069 sampling points), using spatial/geostatistical models fitted with stochastic partial differential equations and integrated nested Laplace approximations. These models are capable of processing misaligned data. The results showed a statistical association between indoor radon and lung, stomach and brain cancer in women in Galicia. Apart from lung cancer (relative risk (RR)=1.09), in which a twofold increase in radon exposure led to a 9% rise in mortality, the association was particularly relevant in stomach (RR=1.17) and brain cancer (RR=1.28). Further analytical epidemiologic studies are needed to confirm these results, and an assessment should be made of the advisability of implementing interventions targeting such exposure in higher-risk areas.

Residential radon exposure and brain cancer: an ecological study in a radon prone area (Galicia, Spain)

We aimed to know if radon concentration is associated with municipal mortality due to brain cancer in Galicia, Spain. We designed an ecological study taking as study unit Galician municipalities. To be included, municipalities had to have at least three radon measurements. We correlated radon concentrations with municipal mortality due to these malignant tumors during the period 1999-2008. We calculated the relative risk of dying of brain cancers for each municipality and correlated this value with municipal radon concentration using Spearman's Rho. 251 municipalities were included, with close to 3,500 radon measurements and an average of 14 radon measurements at each municipality. We observed a significant correlation between residential radon with brain cancer mortality for males and females and the intensity of the correlation was higher for females. These results were reinforced when the analysis was restricted to municipalities with more than 5 radon measurements: Spearman's Rho 0.286 (p-value < 0.001) and Spearman's Rho 0.509 (p-value < 0.001) for males and females, respectively. These results suggest an association between residential radon and brain cancer mortality. More research using more robust epidemiological designs is needed to confirm these findings.

Variation with socioeconomic status of indoor radon levels in Great Britain: The less affluent have less radon

We demonstrate a strong correlation between domestic radon levels and socio-economic status (SES) in Great Britain, so that radon levels in homes of people with lower SES are, on average, only about two thirds of those of the more affluent. This trend is apparent using small area measures of SES and also using individual social classes. The reasons for these differences are not known with certainty, but may be connected with greater underpressure in warmer and better-sealed dwellings. There is also a variation of indoor radon levels with the design of the house (detached, terraced, etc.). In part this is probably an effect of SES, but it appears to have other causes as well. Data from other countries are also reviewed, and broadly similar effects seen in the United States for SES, and in other European countries for detached vs other types of housing. Because of correlations with smoking, this tendency for the lower SES groups to experience lower radon levels may underlie the negative association between radon levels and lung cancer rates in a well-known ecological study based on US Counties. Those conducting epidemiological studies of radon should be alert for this effect and control adequately for SES.

Possible scenarios of the influence of low-dose ionizing radiation on neural functioning

Possible scenarios of the influence of ionizing radiation on neural functioning and the CNS are suggested. We argue that the radiation-induced bystander mechanisms associated with Ca(2+) flows, reactive nitrogen and oxygen species, and cytokines might lead to modulation of certain neuronal signaling pathways. The considered scenarios of conjugation of the bystander signaling and the neuronal signaling might result in modulation of certain synaptic receptors, neurogenesis, neurotransmission, channel conductance, synaptic signaling, different forms of neural plasticity, memory formation and storage, and learning. On this basis, corresponding new possible strategies for treating neurodegenerative deceases and mental disorders are proposed. The mechanisms considered might also be associated with neuronal survival and relevant to the treatment for brain injuries. At the same time, these mechanisms might be associated with detrimental effects and might facilitate the development of some neurological and psychiatric disorders.

Residential Radon Exposure and Incidence of Childhood Lymphoma in Texas, 1995-2011

There is warranted interest in assessing the association between residential radon exposure and the risk of childhood cancer. We sought to evaluate the association between residential radon exposure and the incidence of childhood lymphoma in Texas. The Texas Cancer Registry (n = 2147) provided case information for the period 1995–2011. Denominator data were obtained from the United States Census. Regional arithmetic mean radon concentrations were obtained from the Texas Indoor Radon Survey and linked to residence at diagnosis. Exposure was assessed categorically: ≤25th percentile (reference), >25th to ≤50th percentile, >50th to ≤75th percentile, and >75th percentile. Negative binomial regression generated adjusted incidence rate ratios (aIRR) and 95% confidence intervals (CI). We evaluated lymphoma overall and by subtype: Hodgkin (HL; n = 1248), Non-Hodgkin excluding Burkitt (non-BL NHL; n = 658), Burkitt (BL; n = 241), and Diffuse Large B-cell (DLBCL; n = 315). There was no evidence that residential radon exposure was positively associated with lymphoma overall, HL, or BL. Areas with radon concentrations >75th percentile had a marginal increase in DLBCL incidence (aIRR = 1.73, 95% CI: 1.03–2.91). In one of the largest studies of residential radon exposure and the incidence of childhood lymphoma, we found little evidence to suggest a positive or negative association; an observation consistent with previous studies.

Residential Radon Exposure and Skin Cancer Incidence in a Prospective Danish Cohort

Background

Although exposure to UV radiation is the major risk factor for skin cancer, theoretical models suggest that radon exposure can contribute to risk, and this is supported by ecological studies. We sought to confirm or refute an association between long-term exposure to residential radon and the risk for malignant melanoma (MM) and non-melanoma skin cancer (NMSC) using a prospective cohort design and long-term residential radon exposure.

Methods

During 1993–1997, we recruited 57,053 Danish persons and collected baseline information. We traced and geocoded all residential addresses of the cohort members and calculated radon concentrations at each address lived in from 1 January 1971 until censor date. Cox proportional hazards models were used to estimate incidence rate-ratios (IRR) and confidence intervals (CI) for the risk associated with radon exposure for NMSC and MM, and effect modification was assessed.

Results

Over a mean follow-up of 13.6 years of 51,445 subjects, there were 3,243 cases of basal cell carcinoma (BCC), 317 cases of squamous cell carcinoma (SCC) and 329 cases of MM. The adjusted IRRs per 100 Bq/m³ increase in residential radon levels for BCC, SCC and MM were 1.14 (95% CI: 1.03, 1.27), 0.90 (95% CI: 0.70, 1.37) and 1.08 (95% CI: 0.77, 1.50), respectively. The association between radon exposure and BCC was stronger among those with higher socio-economic status and those living in apartments at enrollment.

Conclusion and Impact

Long-term residential radon exposure may contribute to development of basal cell carcinoma of the skin. We cannot exclude confounding from sunlight and cannot conclude on causality, as the relationship was stronger amongst persons living in apartments and non-existent amongst those living in single detached homes.

Mutations of the human interferon alpha-2b (hIFNα-2b) gene in low-dose natural terrestrial ionizing radiation exposed dwellers

Natural terrestrial ionizing radiations emerge from uranium deposits and can impact human tissues by affecting DNA bases which constitute genes. Human interferon alpha-2b (hIFNα-2b) gene synthesizes a protein which exhibits anticancerous, immunomodulatory, anti-proliferative and antiviral properties. This research aimed to find out hIFNα-2b gene mutations for those residents who were chronically exposed to low-dose natural terrestrial ionizing radiations. The gene amplifications was done through PCR technique and gene mutations were identified by bioinformatics in order to conclude as to how mutations identified in hIFNα-2b gene sequences will lead to alterations in the hIFNα-2b protein in radiation exposed residents. The range of radiation dose exposure was 0.4383-4.55832 (mSv/y) for the selected radiation exposed locations which were having uranium mineralization. Mutations (24%) in hIFNα-2b gene shows that some of the radiation exposed inhabitants were having a modulated immune response. The CBC (Complete Blood Count) parameters: WBC (White Blood Cells), MCH (Mean Corpuscular Hemoglobin), MCHC (MCH Concentration) and PLT (Platelets) on average were below the normal range in 24% radiation exposed subjects who were having hIFNα-2b gene mutations. Immunomodulation is observed by the mixed trend of either lymphocytosis or lymphopenia and neutropenia or neutrophilia in the exposed population. Thus, a radioactive exposure from uranium can affect the immune system and can induce mutations.

Distance to high-voltage power lines and risk of childhood leukemia--an analysis of confounding by and interaction with other potential risk factors

We investigated whether there is an interaction between distance from residence at birth to nearest power line and domestic radon and traffic-related air pollution, respectively, in relation to childhood leukemia risk. Further, we investigated whether adjusting for potential confounders alters the association between distance to nearest power line and childhood leukemia. We included 1024 cases aged <15, diagnosed with leukemia during 1968-1991, from the Danish Cancer Registry and 2048 controls randomly selected from the Danish childhood population and individually matched by gender and year of birth. We used geographical information systems to determine the distance between residence at birth and the nearest 132-400 kV overhead power line. Concentrations of domestic radon and traffic-related air pollution (NOx at the front door) were estimated using validated models. We found a statistically significant interaction between distance to nearest power line and domestic radon regarding risk of childhood leukemia (p = 0.01) when using the median radon level as cut-off point but not when using the 75th percentile (p = 0.90). We found no evidence of an interaction between distance to nearest power line and traffic-related air pollution (p = 0.73). We found almost no change in the estimated association between distance to power line and risk of childhood leukemia when adjusting for socioeconomic status of the municipality, urbanization, maternal age, birth order, domestic radon and traffic-related air pollution. The statistically significant interaction between distance to nearest power line and domestic radon was based on few exposed cases and controls and sensitive to the choice of exposure categorization and might, therefore, be due to chance.