Levels Of Natural Background Radiation Research Articles

Natural radioactivity and radon exhalation rates in man-made tiles used as building materials in Japan.

Man-made tiles frequently used in Japan were collected, and activity concentrations and radon ((222)Rn) exhalation rates in these tiles were measured. Dose estimations for inhabitants living in houses built using these tiles were also carried out. The activity concentrations of (226)Ra, (228)Ra and (40)K in the man-made tiles were 31-170, 35-110 and 260-980 Bq kg(-1), respectively. The (222)Rn exhalation rates in the tiles were 8.8-21 μBq m(-2) s(-1). The ranges of experimental activity concentrations and (222)Rn exhalation rates were almost identical to those of natural rocks used as typical building materials in Japan. The maximum value of effective dose to inhabitants living in houses built with the man-made tiles was 0.14 mSv y(-1), which is lower than the reference level range (1-20 mSv y(-1)) for abnormally high levels of natural background radiation published in the ICRP Publication 103.

The human cancer in high natural background radiation areas

The studies of health effects in human populations living in places with high levels of natural background radiation are of crucial importance for understanding the impact of low doses of ionising radiation. The paper reviews some exemplary literature that addresses the likelihood of the radiation-induced cancer in aforementioned regions. It is shown that using Bayesian analysis one can arrive at an essentially different conclusion concerning dose-effect dependence from the one which could be guessed from first glance. The general conclusion is that cancers do not correlate with elevated radiation in regions with high natural background radiation.

Effect of high background natural radioactivity on human mitochondrial DNA in Ramsar, the north of Iran

Radioactivity is known to induce tumours, chromosome lesions, and mini-satellite length mutations, but also effects on the DNA sequence. Ramsar region, in the north of Iran with the highest background of natural radiation (226Ra) in the world, with a densely populated area, offers an opportunity to characterise radiation-associated DNA mutations. We sampled 30 individuals from this area and 15 cases from Tehran as controls. We sequenced their mtDNA and found multiple variations in multiple nucleotide positions in Ramsar inhabitants. 16519 and T > C were the most frequent NPS and variables in our study. In this preliminary investigation, we conclude that an elevated level of natural background radiation in Ramsar region had a significant effect on the control region of mtDNA. We think this is the first report from Ramsar in this field. Moreover, using molecular and biological pathways and study of gene expression to understand the cellular and molecular response of human mtDNA to low-dose radiation exposure is recommended.

THE BACKGROUND RADIATION AND EXPOSURE LEVELS AT VARIOUS SOUTH AFRICAN WEST COAST MILITARY UNITS

The West Coast of South Africa between St Helena Bay to the north and Langebaan Lagoon to the south is characterised by numerous granite protrusions. These outcrops are elements of the underlying Cape Granite Suite, which forms the bedrock of a large part of the Western Cape. Granite contains high levels of natural radionuclides, which results in high levels of natural background radiation in the surrounding area. The impacts of these high levels of radiation exposure on military personal are of concern. There are four military units located in this part of the West Coast, namely SAS Saldanha, 4 Special Forces Regiment, Langebaan Road Air Force Base and the Military Academy. Different sites in and around these military units were selected and soil samples were taken. Laboratory gamma ray measurements were done to determine the levels of natural radioactive nuclides in the soil samples. The radioactive nuclide concentrations were interpolated and then mapped with the help of geographic information systems (also known as geospatial information systems or GIS) software. An evaluation of the annual dose rate of military personnel at the units on the West Coast was made and found to range between 0,017 mSv/y and 0,163 mSv/y. These values were mapped and compared to the average global annual dose rate of 0,070 mSv/y. This article reports on an investigation of these results and the overall exposure levels of personnel from the various military units on the West Coast of South Africa.

Evaluation of efficiency for in situ gamma spectrometer based upon cerium-doped lanthanum bromide detector dedicated for environmental radiation monitoring

Nuclear power plants that are planned to be constructed in various countries, including Poland, require to setup an environmental radiation monitoring system. Localization of the installation has to be preceded by the studies determining the level of natural background radiation. Presently the in situ gamma spectrometry is widely used for monitoring the natural as well as artificial radionuclides. An analysis and evaluation of parameters of the spectrometric system equipped with scintillation detector made of cerium-doped lanthanum bromide crystal are both the subject of the paper. The main question of the application of any gamma spectrometry system for the radiation monitoring purpose is how its efficiency looks like. Based on the numerical characteristics of the detector the absolute full energy peak efficiency was calculated. The three dimensions characteristics of gamma ray registration efficiency as the function of its energy and considered contaminated area diameter has been also performed. The study of numerical modeling based on MCNP code was performed by the ISOCS/LabSOCS software tool.

Measurement of activity concentration levels of radionuclides in soil samples collected from Bethlehem Province, West Bank, Palestine

In this study, we report on the activity concentrations of $^{238}$U, $^{232}$Th, $^{40}$K, and $^{137}$Cs in 50 soil samples of Bethlehem Province, West Bank, Palestine. Gamma-ray spectroscopy was employed to perform the measurements using an HPGe detector. On one hand, the activity concentrations of natural radionuclides were found to vary from 12.7 to 122.3 Bq kg$^{-1}$ with an average value of 41.4 Bq kg$^{-1}$ for $^{238}$U, from 2.0 to 32.2 Bq kg$^{-1}$ with an average value of 19.5 Bq kg$^{-1}$ for $^{232}$Th, and from 12.0 to 183.8 Bq kg$^{-1}$ with an average value of 113.3 Bq kg$^{-1}$ for $^{40}$K. On the other hand, the activity concentrations of the artificial $^{137}$Cs radionuclide were found between 1.0 and 12.2 Bq kg$^{-1}$, with an average value of 2.8 Bq kg$^{-1}$. The variations of the assessed radiological hazard parameters indices $Ra_{eq}$, $D_{r}$, $ H_{ex}$, and $I_{\gamma }$ of natural radionuclides were found to be as follows: 16-148, 7-65, 0.04-0.4, and 0.11-1.00, respectively. The results were found to be comparable to or lower than similar reported data worldwide. Accordingly, the investigated soil zones can be considered to have normal levels of natural background radiation.

Assessment of natural and anthropogenic radioactivity levels in soils, rocks and water in the vicinity of Chirano Gold Mine in Ghana

Studies have been carried out within and around the operational area of the Chirano Gold Mine Ltd of Ghana to ascertain the baseline radioactivity levels of naturally occurring radioactive materials as well as artificial radionuclides in the surface and underground mines. The analysis was carried out by using gamma spectrometry to quantify the radionuclides of interest, namely (238)U, (232)Th, (137)Cs and (40)K in soil, ore, waste rock and water samples. The average activity concentrations of (238)U, (232)Th, (40)K and (137)Cs in the soil/rock samples were 9.79±5.39, 9.18±7.06, 237.40±144.34 and 0.64±0.57 Bq kg(-1), respectively. For the water samples, the average activity concentrations were 0.86±0.67, 0.97±1.33 and 9.05±10.45 Bq l(-1) for (226)Ra, (232)Th and (40)K, respectively. The total annual effective dose to the public was estimated to be 0.13 mSv, which is below the International Commission on Radiological Protection recommended level of 1 mSv for public exposure control. The study also assessed the elemental concentrations of U, Th and K in the soil/rock samples from the gold mine and surrounding communities. The average concentrations of the U, Th and K were 0.82±0.48, 2.18±1.77 µg g(-1) and 0.77±0.47 %, respectively. The concentrations of U, Th and K were variable in soil and rock samples taken from different locations in the study area with values varying in the range 0.28-2.21, 0.24-6.50 µg g(-1) and 0.28-1.87 %, respectively. The concentrations of U, Th and K are far lower than the world average values but comparable with the range of similar studies for different countries. The concentration values of gross-alpha and gross-beta for all the water samples were below the Ghana Standards Authority and World Health Organisation recommended guideline values for drinking water quality. The results obtained in this study also show that radiation levels are within the natural background radiation levels found in the literature and compare well with those of similar studies for other countries including Ghana.

Natural and artificial radioactivity distribution in soil, rock and water of the Central Ashanti Gold Mine, Ghana

Direct gamma spectrometry study was carried out within and around the operational area of the Central Ashanti Gold of Ghana to ascertain the baseline radioactivity levels of naturally occurring radioactive materials (NORM), prior to processing of gold ore at the mine. The average activity concentrations of 238U, 232Th, 40K and 137Cs in the soil/rock samples were 64.3, 68.4, 1243.9 and 3.5 Bqkg−1, respectively. For the water samples, the average activity concentrations were 2.5, 2.6, 14.7 and 0.7 BqL−1 for 238U, 232Th, 40K and 137Cs, respectively. The total annual effective dose to the public was estimated to be 0.141 mSv which is below the ICRP recommended level of 1 mSv for public exposure control. The average radium equivalent activity value was 257.8 Bqkg−1 in the range of 72.9–402.3 Bqkg−1. The average values of external and internal indices were 0.7 and 0.8, respectively. The concentrations of U, Th and K were variable in soil and rock samples taken from different locations in the study area with values varying in the range of 0.8–10.9, 2.4–39.4 μg/g and 0.7–6.3 %, respectively. The concentration values of gross-α and gross-β for all the water samples were below the Ghana Standards Board and Who Health Organisation recommended guideline values for drinking water quality. The results obtained in this study shows that radiation levels are within the natural background radiation levels found in literature and compared well with similar studies for other countries.

Determination of environmental radioactivity (238U, 232Th and 40K) and indoor natural background radiation level in Chennai city (Tamilnadu State), India

An extensive study on the determination of the natural radioactivity ((238)U, (232)Th and (40)K) levels in soil samples of Chennai city, India has been undertaken and the results of the same are compared with the levels reported in other Indian cities as well as other parts of the world. The radioactivity content in the soil samples, the absorbed dose rate, annual effective dose equivalent, radium equivalent activity, internal and external hazard indices were calculated and compared with UNSCEAR 2000 recommended values. In addition to the above, mapping of indoor natural background gamma radiation levels has been made using thermo luminescent dosemeters throughout Chennai city and the same are reported.

No evidence of telomere length attrition in newborns from high level natural background radiation areas in Kerala coast, south west India

Purpose: The tandemly repeated hexamers (TTAGGG)n present at the telomeric ends protect the human genome from a variety of environmental exposures including ionizing radiation. In order to find out the effect of chronic low dose radiation exposure, we have determined telomere length among newborns from high level natural radiation areas (HLNRA) of the Kerala coast in South west India.Methodology: Umbilical cord blood samples were collected from 128 newborns from HLNRA and 43 newborns from normal level natural radiation areas (NLNRA) and genomic DNA was isolated using a salt precipitation method. The mean telomere length was determined using SYBR green-based real time quantitative Polymerase chain reaction (qPCR), where telomere gene specific (T) and single copy gene specific (S) primers were used. The average of telomere versus single copy gene (T/S) ratio was calculated which was proportional to telomere length of each individual.Results: The mean relative telomere length was found to be 1.03 ± 0.01 (95% CI, 0.99–1.05) and 1.10 ± 0.03 (95% CI, 1.04–1.17) in HLNRA and NLNRA newborns, respectively (P > 0.05). Based on the level of background radiation dose, samples were divided into four groups, i.e., NLNRA: < 1.50 mGy/year and three HNLRA groups: 1.51–3.00 mGy/year, 3.01–5.00 mGy/year, and > 5.00 mGy/year. The mean relative telomere length in these groups were found to be 1.10 ± 0.03 (95% CI, 1.03–1.17), 0.98 ± 0.01 (95% CI, 0.95–1.01), 1.05 ± 0.02 (95% CI, 1.01–1.10) and 1.07 ± 0.03 (95% CI, 1.04–1.10), respectively. No significant difference was observed between the mean telomere length of male and female newborns.Conclusions: The elevated level of natural chronic background radiation prevailing in Kerala coast did not show any significant effect on telomere length of newborns. To our knowledge, this is the first report on newborn telomere length from a high level natural radiation area.

Environmental radioactivity studies in the proposed Lambapur and Peddagattu uranium mining areas of Andhra Pradesh, India

The present work was aimed at the establishment of baseline radioactive data in the proposed Lambapur and Peddagattu uranium mining areas in the Andhra Pradesh state, India. The background concentrations of naturally occurring radioactivity in the near-surface soils of the study areas were estimated and the results were analysed. The (238)U concentration in the near-surface soil of the study area was found to vary from 100 to 176 Bq kg(-1), with a mean of 138±24 Bq kg(-1). (232)Th in the study area soils was found to vary between 64 and 116 Bq kg(-1), with a mean of 83±15 Bq kg(-1). The (40)K concentration was found to vary between 309 and 373 Bq kg(-1), with a mean of 343±20 Bq kg(-1). The mean natural background radiation levels were also measured with thermoluminescence (TL) dosimetry technique and with a µR-survey meter, in the villages of the study area. Dose rates measured by TL are found to vary from 1287 to 3363 μGy y(-1), with a mean of 2509 ± 424 μGy y(-1). The dose rates measured in the same villages with a μR-survey meter were found to be in the range of 1211-3255 μGy y(-1), with a mean of 2524 ± 395 μGy y(-1). The mean radiation levels in the study area are found to be relatively high when compared with (Indian) national and international averages. Correlations among radon, thoron and gamma dose rates were found to be poor. The pre-operational data produced in this work will be useful for comparison with future radiation levels during the proposed uranium mining operations.

Indoor radon and thoron levels in Neendakara and Chavara regions of Southern Coastal Kerala, India

Some areas of the world, called high background radiation areas (HBRAs), have anomalously high levels of natural background radiation and the population residing in the areas is exposed to higher levels of radiation doses than other parts of the world where the natural radioactivity contents are normal. In the present investigation, levels of radon, thoron and their progeny are studied in 110 houses in the coastal region of the Kollam district in the state of Kerala, India using the multi-detector twin cup dosimeter. Among these, 10 houses were studied in detail with five dosimeters in each house. Radon activity concentrations were found to vary from 7 to 100 Bqm(-3) and that of thoron from 4 to 66 Bqm(-3) in Neendakara panchayat. In Chavara panchayat, the variations of radon concentrations were from 7 to 83 Bqm(-3) and thoron concentrations were varied from 4 to 86 Bqm(-3). The occurrence of radon and thoron concentrations in the dwellings for both study areas shows that in 50% of the dwellings, the concentration of radon is about 25 Bqm(-3) and in 60% of the dwellings thoron concentration is about 15 Bqm(-3). The ratio of thoron-to-radon concentrations in the dwellings showed a mean value 0.55 (GM=0.45) for the region.

Effect of Low and Chronic Radiation Exposure: A Case-Control Study of Mental Retardation and Cleft Lip/Palate in the Monazite-Bearing Coastal Areas of Southern Kerala

A population-based 1:3 age-matched case-control study was conducted during 2006-2009 to assess the role of high-level natural radiation (>1 mSv/year) on congenital mental retardation and cleft lip/palate in the southwest coastal area of Kerala. Dosimetry was carried out in the house where parents resided during conception and the subsequent two trimesters of pregnancy of the study subject. Conditional logistic regression did not suggest any statistically significant association of either mental retardation (n = 445) or cleft lip/palate (n = 116) with high-level natural radiation. The odds of mental retardation and cleft lip/palate among those exposed to high-level natural radiation relative to normal levels of natural background radiation (≤1 mSv/year) were 1.26 (95% CI: 0.91-1.73) and 0.56 (95% CI: 0.31-1.02), respectively, after controlling for gender and maternal age at birth of the study subject. The data did not suggest any dose-related trend in the risk of either mental retardation (P = 0.113) or cleft lip/palate (P = 0.908). Notwithstanding the use of a single dose estimate to reconstruct past radiation exposure and the complex etiology of congenital malformations, it may reasonably be concluded that the prevailing high-level natural radiation in the study area does not appear to increase the risk of either mental retardation or cleft lip/palate among offspring of parents staying in the area.

Radiation and risk: Is it time for a regulatory threshold dose?

This editorial follows somewhat from Madhava Bhat’s guest editorial published in the Sept 2010 issue entitled ‘‘‘‘Fear of radiation’’ is frightening’’ [1]. As Madhava suggests, there is a heightened level of fear in the general community regarding radiation, and this is not just confined to ionising radiation (IR) but also non-ionising radiation (NIR), such as electromagnetic fields and mobile phones. I am not going to discuss NIR here except to say that I believe this area also has some worrying developments from a regulatory perspective, and in particular the use of the precautionary principle where there is a very limited scientific evidence of a biological effect. It is understandable why the general community fears radiation. For instance, you cannot see it or feel it, but due to the sensitivity of detectors we can measure the tiniest amount of it. Over the last 60 years or so, we have been bombarded with images of atomic bombs, people in ‘‘radiation suits’’ and pictures of the known damaging effects of high dose radiation. In addition, images of Homer Simpson ‘‘working’’ in the Springfield nuclear power plant, and the subliminal messages found in many of our comic books suggest that radiation will mutate you into a superhero or villain. Currently, there approximately 221 comic characters who’s powers originated from radiation [2]. As well as the images, there are many conflicting reports or opinions regarding the biological effects of radiation and these are often based on either some ideological or political belief or differences within the scientific and regulatory community itself. This situation is not helped by the current media cycle of unbalanced reporting; often with farleft or far-right political views getting more publicity due to their controversy rather than the facts. As a radiation regulator, I often encounter people who are unaware that they are exposed to background levels of radiation from cosmic, terrestrial and internal (body) radiation sources. Many also don’t know that life has evolved on Earth in which natural background radiation levels some 3.5 billion years ago were about three times higher than they are now [3]. For some reason scientists and regulators have failed to remind the general community, or have been unable to get the message across, about the basics of radiation and that it’s a natural phenomenon. Although the population is ‘‘bathed’’ in background radiation, the fact remains that most will only ever receive a small additional radiation dose from the activities they undertake or the medical procedures they require. The only time a person is likely to be exposed to high or dangerous doses of radiation is when they are undergoing medical treatment e.g. radiotherapy or involved in a radiation incident. However, what is deemed ‘‘dangerous’’ depends on what side of the Linear No Threshold (LNT) fence you sit on! A. M. Hooker (&) Faculty of Health Sciences, School of Medicine, Flinders University, Adelaide, SA 5042, Australia e-mail: tony.hooker@epa.sa.gov.au

Heterogeneity of uranium in water from south peninsular India

The South Peninsular India is known to have very high levels of natural background radiation due to the monazite rich beach sand. Primordial uranium is ubiquitous and the heaviest radio toxic trace element available in all terrestrial substances at varying levels depending on the geology of the region. Uranium series supports several short-lived radioisotopes during its decay including radium. Uranium in drinking water is important in terms of the ingestion dose also. This report depicts the results of uranium analysis of 600 water samples collected from the south coast peninsular region extending parts of Kerala and Tamilnadu states of India through fission track registration technique. Results of the analyses of water samples collected from different sources in the south coast of India show that uranium concentrations vary from 0.82 µg/l to 7.32 µg/l equivalents to the specifi c activity of 10.33 Bq/m 3 and 92.23Bq/m 3 , respectively. Estimated daily intake of uranium through drinking water ranges from 20.22 to 18.58mBq/kg and is lower than the recommended limits of intake. The heterogeneity in distribution of uranium in water bodies is due to the presence of monazite sand deposited in the coast over the years.

Assessment of direct radiological risk and indirect associated toxic risks originated by Coal-Fired Power Plants

Over the past few decades there has been some discussion concerning the increase of the natural background radiation originated by coal-fired power plants, due to the uranium and thorium content present in combustion ashes. The radioactive decay products of uranium and thorium, such as radium, radon, polonium, bismuth and lead, are also released in addition to a significant amount of 40 K.Since the measurement of radioactive elements released by the gaseous emissions of coal power plants is not compulsory, there is a gap of information concerning this situation. Consequently, the prediction of dispersion and mobility of these elements in the environment, after their release, is based on limited data and the radiological impact from the exposure to these radioactive elements is unknown. This paper describes the methodology that is being developed to assess the radiological impact due to the raise in the natural background radiation level originated by the release and dispersion of the emitted radionuclides. The current investigation is part of a research project that is undergoing in the vicinity of Sines coal-fired power plant (south of Portugal) until 2013. Data from preliminary stages are already available and possible of interpretation.

A deviation display method for visualising data in mobile gamma-ray spectrometry

A real time visualisation method, to be used in mobile gamma-spectrometric search operations using standard detector systems is presented. The new method, called deviation display, uses a modified waterfall display to present relative changes in spectral data over energy and time. Using unshielded (137)Cs and (241)Am point sources and different natural background environments, the behaviour of the deviation displays is demonstrated and analysed for two standard detector types (NaI(Tl) and HPGe). The deviation display enhances positive significant changes while suppressing the natural background fluctuations. After an initialization time of about 10min this technique leads to a homogeneous display dominated by the background colour, where even small changes in spectral data are easy to discover. As this paper shows, the deviation display method works well for all tested gamma energies and natural background radiation levels and with both tested detector systems.

Patient dose considerations in computed tomography examinations.

Ionizing radiation is extensively used in medicine and its contribution to both diagnosis and therapy is undisputable. However, the use of ionizing radiation also involves a certain risk since it may cause damage to tissues and organs and trigger carcinogenesis. Computed tomography (CT) is currently one of the major contributors to the collective population radiation dose both because it is a relatively high dose examination and an increasing number of people are subjected to CT examinations many times during their lifetime. The evolution of CT scanner technology has greatly increased the clinical applications of CT and its availability throughout the world and made it a routine rather than a specialized examination. With the modern multislice CT scanners, fast volume scanning of the whole human body within less than 1 min is now feasible. Two dimensional images of superb quality can be reconstructed in every possible plane with respect to the patient axis (e.g. axial, sagital and coronal). Furthermore, three-dimensional images of all anatomic structures and organs can be produced with only minimal additional effort (e.g. skeleton, tracheobronchial tree, gastrointestinal system and cardiovascular system). All these applications, which are diagnostically valuable, also involve a significant radiation risk. Therefore, all medical professionals involved with CT, either as referring or examining medical doctors must be aware of the risks involved before they decide to prescribe or perform CT examinations. Ultimately, the final decision concerning justification for a prescribed CT examination lies upon the radiologist. In this paper, we summarize the basic information concerning the detrimental effects of ionizing radiation, as well as the CT dosimetry background. Furthermore, after a brief summary of the evolution of CT scanning, the current CT scanner technology and its special features with respect to patient doses are given in detail. Some numerical data is also given in order to comprehend the magnitude of the potential radiation risk involved in comparison with risk from exposure to natural background radiation levels.

Telomere length in human adults and high level natural background radiation.

BackgroundTelomere length is considered as a biomarker of aging, stress, cancer. It has been associated with many chronic diseases such as hypertension and diabetes. Although, telomere shortening due to ionizing radiation has been reported in vitro, no in vivo data is available on natural background radiation and its effect on telomere length.Methodology/Principal FindingsThe present investigation is an attempt to determine the telomere length among human adults residing in high level natural radiation areas (HLNRA) and the adjacent normal level radiation areas (NLNRA) of Kerala coast in Southwest India. Genomic DNA was isolated from the peripheral blood mononuclear cells of 310 individuals (HLNRA: N = 233 and NLNRA: N = 77). Telomere length was determined using real time q-PCR. Both telomere (T) and single copy gene (S) specific primers were used to calculate the relative T/S and expressed as the relative telomere length. The telomere length was determined to be 1.22±0.15, 1.12±0.15, 1.08±0.08, 1.12±0.11, respectively, among the four dose groups (≤1.50, 1.51–3.00, 3.01–5.00 and >5.00 mGy per year), which did not show any dose response. The results suggested that the high level natural chronic radiation did not have significant effect on telomere length among young adult population living in HLNRA, which is indicative of better repair of telomeric ends. No significant difference in telomere length was observed between male and female individuals. In the present investigation, although the determination of telomere length was studied among the adults with an age group between 18 to 40 years (mean maternal age: 26.10±4.49), a negative correlation was observed with respect to age. However, inter-individual variation was (0.81–1.68) was clearly observed.Conclusions/SignificanceIn this preliminary investigation, we conclude that elevated level of natural background radiation has no significant effect on telomere length among the adult population residing in HLNRAs of Kerala coast. To our knowledge, this is the first report from HLNRAs of the world where telomere length was determined on human adults. However, more samples from each background dose group and samples from older population need to be studied to derive firm conclusions.

Unique Signatures of Natural Background Radiation on Human Y Chromosomes from Kerala, India

BackgroundThe most frequently observed major consequences of ionizing radiation are chromosomal lesions and cancers, although the entire genome may be affected. Owing to its haploid status and absence of recombination, the human Y chromosome is an ideal candidate to be assessed for possible genetic alterations induced by ionizing radiation. We studied the human Y chromosome in 390 males from the South Indian state of Kerala, where the level of natural background radiation (NBR) is ten-fold higher than the worldwide average, and that from 790 unexposed males as control.ResultsWe observed random microdeletions in the Azoospermia factor (AZF) a, b and c regions in >90%, and tandem duplication and copy number polymorphism (CNP) of 11 different Y-linked genes in about 80% of males exposed to NBR. The autosomal homologues of Y-linked CDY genes largely remained unaffected. Multiple polymorphic copies of the Y-linked genes showing single Y-specific signals suggested their tandem duplication. Some exposed males showed unilocus duplication of DAZ genes resulting in six copies. Notably, in the AZFa region, approximately 25% of exposed males showed deletion of the DBY gene, whereas flanking genes USP9Y and UTY remained unaffected. All these alterations were detected in blood samples but not in the germline (sperm) samples.ConclusionsExposure to high levels of NBR correlated with several interstitial polymorphisms of the human Y chromosome. CNPs and enhanced transcription of the SRY gene after duplication are envisaged to compensate for the loss of Y chromosome in some cells. The aforesaid changes, confined to peripheral blood lymphocytes, suggest a possible innate mechanism protecting the germline DNA from the NBR. Genome analysis of a larger population focusing on greater numbers of genes may provide new insights into the mechanisms and risks of the resultant genetic damages. The present work demonstrates unique signatures of NBR on human Y chromosomes from Kerala, India.