Extension of the RADTriage Colorimetric Dosimeter to Low-Dose Gamma-Ray Exposure Using Scanning Densitometry.

ABSTRACT: There is a need for an instantly indicating, easy-to-read, and inexpensive ionizing radiation dosimeter for first responders and members of the general public. One commercially available option is the RADTriage50 TM colorimetric dosimeter. However, existing literature has not adequately addressed the accuracy of RADTriage50 dosimeters at low doses of ionizing radiation (<50 mSv) or the need for methods to quantitatively read the RADTriage50 dosimeters after they are exposed. In this paper, we use digital scanning methods to read the RADTriage50 dosimeters. The performance of the dosimeters was evaluated by irradiation with a gamma irradiator traceable to national standards. Experiments covered a range of deep dose equivalents (50 mSv to 2,000 mSv) within the manufacturer's specified range (50 mSv to 4,000 mSv) and also below 50 mSv to determine if the digital scanning densitometry method allowed for a quantitative readout with a greater dynamic range. We also conducted tests using different gamma energies, 137 Cs (662 keV) and 60 Co (1.17 and 1.33 MeV), and different dose rates to evaluate the dependency of the RADTriage50 dosimeters on these parameters. Modeling of our measurements suggests that the dose-response of the RADTriage50 dosimeter is linear at low doses with strong non-linearity beginning at ~750 mSv and the dosimeter response appearing to plateau at ~2,000 mSv, although additional measurements at doses beyond 2,000 mSv are needed to confirm this finding. We also found that the RadTriage50 dosimeter response varied with gamma energy, but not with dose rate.

Predicting the Public Health Consequences of a Nuclear Terrorism Attack: Drawing on The Experiences of Hiroshima and Fukushima.

The increasing threat of nuclear terrorism warrants consideration of the health consequences of a terrorist incident should preventive measures fail. Although there has not yet been a nuclear terrorist attack of any kind, experiences with the aftermath of the bombing of Hiroshima and the core meltdowns at Fukushima can provide useful insight and allow some inferences to be made regarding the types of casualties that might be sustained and the rescue efforts that might be required. There are many parallels between the events at Hiroshima and what might be expected from an improvised nuclear device, and there are parallels between the radioactivity released to the environment at Fukushima and the aftermath of a radiological dispersal device attack. Nevertheless, there are some unique aspects to a ground-detonated improvised nuclear device that pose health threats beyond those seen at Hiroshima (i.e., fallout). And psychological health may be impacted more than physical health in the case of a radiological dispersal device. Preparedness requires consideration of all of these various health hazards in order to determine how best to mitigate the consequences of a nuclear terrorism attack.

Dose coefficients for ICRP reference pediatric phantoms exposed to idealised external gamma fields.

Organ and effective dose coefficients have been calculated for the International Commission on Radiological Protection (ICRP) reference pediatric phantoms externally exposed to mono-energetic photon radiation (x- and gamma-rays) from 0.01 to 20 MeV. Calculations used Monte Carlo radiation transport techniques. Organ dose coefficients, i.e., organ absorbed dose per unit air kerma (Gy/Gy), were calculated for 28 organs and tissues including the active marrow (or red bone marrow) for 10 phantoms (newborn, 1 year, 5 year, 10 year, and 15 year old male and female). Radiation exposure was simulated for 33 photon mono-energies (0.01-20 MeV) in six irradiation geometries: antero-posterior (AP), postero-anterior, right lateral, left lateral, rotational, and isotropic. Organ dose coefficients for different ages closely agree in AP geometry as illustrated by a small coefficient of variation (COV) (the ratio of the standard deviation to the mean) of 4.4% for the lungs. The small COVs shown for the effective dose and AP irradiation geometry reflect that most of the radiosensitive organs are located in the front part of the human body. In contrast, we observed differences in organ dose coefficients across the ages of the phantoms for lateral irradiation geometries. We also observed variation in dose coefficients across different irradiation geometries, where the COV ranges from 18% (newborn male) to 38% (15 year old male) across idealised whole body irradiation geometries for the major organs (active marrow, colon, lung, stomach wall, and breast) at the energy of 0.1 MeV. Effective dose coefficients were also derived for applicable situations, e.g., radiation protection or risk projection. Our results are the first comprehensive set of organ and effective dose coefficients applicable to children and adolescents based on the newly adopted ICRP pediatric phantom series. Our tabulated organ and effective dose coefficients for these next-generation phantoms should provide more accurate estimates of organ doses in children than earlier dosimetric models allowed.

The New "Normal": Stakeholders and Radiation Protection Limits in a Post-9/11 World.

With the recent upsurge in worldwide terrorism, the prospects for a radiation terrorism event have greatly increased. Current recommendations regarding recovery from such an event specify that decisions about the extent of radiological cleanup will be dependent upon stakeholder acceptance of the risk levels. The case is made here that stakeholders are currently not prepared to make decisions collectively about the acceptability of risk levels and will be even less capable during the aftermath of an attack when a consensus among stakeholders is unlikely to be achieved. In order to better prepare stakeholders to make risk decisions after an attack, there needs to be at least some limited radiation training for people in locations that are likely terrorist targets, and this training is best delivered before a radiological incident has occurred. Additionally, the training should focus on individualized risk assessment based on personal radiation doses and should emphasize that individuals have the ability to control their personal dose by limiting the time that they spend in "zones" that have relatively high contamination levels and restricting their intake of specific contaminated foods. By raising stakeholder consciousness before an incident occurs and reducing decisions about the acceptability of risk to the level of the individual rather than the entire group, individual stakeholders will be empowered to become more fully engaged in the recovery process, more in control of their own lives, and less dependent upon radiation protection professionals to make global decisions about the acceptability of radiation risks on their behalf.

Mitigating the risk of radiation-induced cancers: limitations and paradigms in drug development.

The United States radiation medical countermeasures (MCM) programme for radiological and nuclear incidents has been focusing on developing mitigators for the acute radiation syndrome (ARS) and delayed effects of acute radiation exposure (DEARE), and biodosimetry technologies to provide radiation dose assessments for guiding treatment. Because a nuclear accident or terrorist incident could potentially expose a large number of people to low to moderate doses of ionising radiation, and thus increase their excess lifetime cancer risk, there is an interest in developing mitigators for this purpose. This article discusses the current status, issues, and challenges regarding development of mitigators against radiation-induced cancers. The challenges of developing mitigators for ARS include: the long latency between exposure and cancer manifestation, limitations of animal models, potential side effects of the mitigator itself, potential need for long-term use, the complexity of human trials to demonstrate effectiveness, and statistical power constraints for measuring health risks (and reduction of health risks after mitigation) following relatively low radiation doses (<0.75 Gy). Nevertheless, progress in the understanding of the molecular mechanisms resulting in radiation injury, along with parallel progress in dose assessment technologies, make this an opportune, if not critical, time to invest in research strategies that result in the development of agents to lower the risk of radiation-induced cancers for populations that survive a significant radiation exposure incident.

DNA repair gene variants in relation to overall cancer risk: a population-based study.

The hypothesis that germ-line polymorphisms in DNA repair genes influence cancer risk has previously been tested primarily on a cancer site-specific basis. The purpose of this study was to test the hypothesis that DNA repair gene allelic variants contribute to globally elevated cancer risk by measuring associations with risk of all cancers that occurred within a population-based cohort. In the CLUE II cohort study established in 1989 in Washington County, MD, this study was comprised of all 3619 cancer cases ascertained through 2007 compared with a sample of 2296 with no cancer. Associations were measured between 759 DNA repair gene single nucleotide polymorphisms (SNPs) and risk of all cancers. A SNP in O(6)-methylguanine-DNA methyltransferase, MGMT, (rs2296675) was significantly associated with overall cancer risk [per minor allele odds ratio (OR) 1.30, 95% confidence interval (CI) 1.19-1.43 and P-value: 4.1 × 10(-8)]. The association between rs2296675 and cancer risk was stronger among those aged ≤54 years old than those who were ≥55 years at baseline (P-for-(interaction) = 0.021). OR were in the direction of increased risk for all 15 categories of malignancies studied (P < 0.0001), ranging from 1.22 (P = 0.42) for ovarian cancer to 2.01 (P = 0.008) for urinary tract cancers; the smallest P-value was for breast cancer (OR 1.45, P = 0.0002). The results indicate that the minor allele of MGMT SNP rs2296675, a common genetic marker with 37% carriers, was significantly associated with increased risk of cancer across multiple tissues. Replication is needed to more definitively determine the scientific and public health significance of this observed association.

A population-based study of hedgehog pathway gene variants in relation to the dual risk of basal cell carcinoma plus another cancer.

INTRODUCTION: A personal history of basal cell carcinoma (BCC) is associated with increased risk of other malignancies, but the reason is unknown. The hedgehog pathway is critical to the etiology of BCC, and is also believed to contribute to susceptibility to other cancers. This study tested the hypothesis that hedgehog pathway and pathway-related gene variants contribute to the increased risk of subsequent cancers among those with a history of BCC. METHODS: The study was nested within the ongoing CLUE II cohort study, established in 1989 in Washington County, Maryland, USA. The study consisted of a cancer-free control group (n=2296) compared to three different groups of cancer cases ascertained through 2007, those diagnosed with: (1) Other (non-BCC) cancer only (n=2349); (2) BCC only (n=534); and (3) BCC plus other cancer (n=446). The frequencies of variant alleles were compared among these four groups for 20 single nucleotide polymorphisms (SNPs) in 6 hedgehog pathway genes (SHH, IHH, PTCH2, SMO, GLI1, SUFU), and also 22 SNPs in VDR and 8 SNPs in FAS, which have cross-talk with the hedgehog pathway. RESULTS: Comparing those with both BCC and other cancer versus those with no cancer, no significant associations were observed for any of the hedgehog pathway SNPs, or for the FAS SNPs. One VDR SNP was nominally significantly associated with the BCC cancer-prone phenotype, rs11574085 [per minor allele odds ratio (OR) 1.38, 95% confidence interval (CI) 1.05-1.82; p-value=0.02]. CONCLUSION: The hedgehog pathway gene SNPs studied, along with the VDR and FAS SNPs studied, are not strongly associated with the BCC cancer-prone phenotype.

A population-based study of DNA repair gene variants in relation to non-melanoma skin cancer as a marker of a cancer-prone phenotype.

For unknown reasons, non-melanoma skin cancer (NMSC) is associated with increased risk of other malignancies. Focusing solely on DNA repair or DNA repair-related genes, this study tested the hypothesis that DNA repair gene variants contribute to the increased cancer risk associated with a personal history of NMSC. From the parent CLUE II cohort study, established in 1989 in Washington County, MD, the study consisted of a cancer-free control group (n 5 2296) compared with three mutually exclusive groups of cancer cases ascertained through 2007: (i) Other (non-NMSC) cancer only (n 5 2349); (ii) NMSC only (n 5 694) and (iii) NMSC plus other cancer (n 5 577). The frequency of minor alleles in 759 DNA repair gene single nucleotide polymorphisms (SNPs) was compared in these four groups. Comparing those with both NMSC and other cancer versus those with no cancer, 10 SNPs had allelic trend P-values <0.01. The two top-ranked SNPs were both within the thymine DNA glycosylase gene (TDG). One was a non-synonymous coding SNP (rs2888805) [per allele odds ratio (OR) 1.40, 95% confidence interval (CI) 1.16-1.70; P-value 5 0.0006] and the other was an intronic SNP in high linkage disequilibrium with rs2888805 (rs4135150). None of the associations had a P-value <6.6310(-5), the threshold for statistical significance after correcting for multiple comparisons. The results pinpoint DNA repair genes most likely to contribute to the NMSC cancer-prone phenotype. A promising lead is genetic variants in TDG, important not only in base excision repair but also in regulating the epigenome and gene expression, which may contribute to the NMSC-associated increase in overall cancer risk.

A community-based study of nucleotide excision repair polymorphisms in relation to the risk of non-melanoma skin cancer.

Nucleotide excision repair (NER) is responsible for protecting DNA in skin cells against UVR-induced damage. Using a candidate pathway approach, a matched case-control study nested within a prospective, community-based cohort was carried out to test the hypothesis that single-nucleotide polymorphisms (SNPs) in NER genes are associated with susceptibility to non-melanoma skin cancer (NMSC). Histologically confirmed cases of NMSC (n=900) were matched to controls (n=900) on the basis of age, gender, and skin type. Associations were measured between NMSC and 221 SNPs in 26 NER genes. Using the additive model, two tightly linked functional SNPs in ERCC6 were significantly associated with increased risk of NMSC: rs2228527 (odds ratio (OR) 1.57, 95% confidence interval (CI) 1.20-2.05) and rs2228529 (OR 1.57, 95% CI 1.20-2.05). These associations were confined to basal cell carcinoma (BCC) of the skin (rs2228529, OR 1.78, 95% CI 1.30-2.44; rs2228527, OR 1.78, 95% CI 1.31-2.43). These hypothesis-generating findings suggest that functional variants in ERCC6 may be associated with an increased risk of NMSC that may be specific to BCC.

Elevated Epstein-Barr virus seroreactivity among unaffected members of families with nasopharyngeal carcinoma.

Serum antibodies to Epstein-Barr virus (EBV) antigens can be used to predict the risk of nasopharyngeal carcinoma (NPC). To investigate whether EBV seropositivity rates were higher among healthy family members from multiplex and sporadic families with NPC (i.e., families with multiple or single cases) compared to the general population, a study was conducted on 2,665 unaffected individuals from 140 multiplex and 413 sporadic families. The titers of the IgA antibody to the EBV capsid antigen (VCA-IgA) were compared to those of 904 controls from the general population. The VCA-IgA titer was correlated among sibling pairs to a high significance in both family types (P < 0.0001 and P = 0.0005 for the multiplex and the sporadic families, respectively); parent-offspring pairs also showed significant correlation (P < 0.0001 and P = 0.0002, respectively); and spouse pairs were correlated, but at lower significance levels (P = 0.0790 and P = 0.0040, respectively). When compared to the controls, among first-degree relatives in the multiplex families, the age- and gender-adjusted odds ratio (OR) was 2.06 (95% confidence interval 1.56-2.71), 3.55 (2.24-5.64), and 2.25 (1.57-3.23) for siblings, parents, and children, respectively. In the sporadic families, the adjusted OR was 1.55 (1.21-2.00) and 2.08 (1.51-2.86) for siblings and parents, respectively. The adjusted P-value of spouses lost significance in the multiplex families, but remained significant in the sporadic families (P = 0.0146). In conclusion, EBV seropositivity rates were elevated among unaffected family members in both multiplex and sporadic families with NPC.

Human genetic variants of homologous recombination repair genes first found to be associated with Epstein-Barr virus antibody titers in healthy Cantonese.

Epstein-Barr virus (EBV) infection is a major risk factor for nasopharyngeal carcinoma (NPC). Despite high prevalence of infection among the general population worldwide, only a small proportion of infected individuals presents with seropositivity for EBV-specific IgA antibodies. This seropositive subgroup of EBV carriers has an elevated cumulative risk for NPC during their lifetime. Previous studies reported that the host homologous recombination repair (HRR) system participates in EBV lytic replication, suggesting a potential mechanism to influence EBV reactivation status and thus seropositivity. To investigate whether genetic variants of HRR genes are associated with the serostatus in a healthy population, we investigated the association between seropositivity for anti-VCA-IgA and 156 tagging SNPs in 35 genes connected with HRR in an observational study among 755 healthy Cantonese speakers in southern China. Six variant alleles of MDC1, RAD54L, TP53BP1, RPA1, LIG3 and RFC1 exhibited associations with seropositivity (p(trend) from 0.0085 to 0.00027). Our study provides evidence that genetic variation within the HRR might affect an individual's propensity for EBV seropositive status of anti-VCA IgA antibody.

Phosphorylation of histone H2A.X as an early marker of neuronal endangerment following seizures in the adult rat brain.

The phosphorylated form of histone H2A.X (γ-H2AX) is a well documented early, sensitive, and selective marker of DNA double-strand breaks (DSBs). Previously, we found that excessive glutamatergic activity increased γ-H2AX in neurons in vitro. Here, we evaluated γ-H2AX formation in the adult rat brain following neuronal excitation evoked by seizure activity in vivo. We found that brief, repeated electroconvulsive shock (ECS)-induced seizures (three individual seizures within 60 min) did not trigger an increase γ-H2AX immunostaining. In contrast, a cluster of 5-7 individual seizures evoked by kainic acid (KA) rapidly (within 30 min) induced γ-H2AX in multiple neuronal populations in hippocampus and entorhinal cortex. This duration of seizure activity is well below threshold for induction of neuronal cell death, indicating that the γ-H2AX increase occurs in response to sublethal insults. Moreover, an increase in γ-H2AX was seen in dentate granule cells, which are resistant to cell death caused by KA-evoked seizures. With as little as a 5 min duration of status epilepticus (SE), γ-H2AX increased in CA1, CA3, and entorhinal cortex to a greater extent than that observed after the clusters of individual seizures, with still greater increases after 120 min of SE. Our findings provide the first direct demonstration that DNA DSB damage occurs in vivo in the brain following seizures. Furthermore, we found that the γ-H2AX increase caused by 120 min of SE was prevented by neuroprotective preconditioning with ECS-evoked seizures. This demonstrates that DNA DSB damage is an especially sensitive indicator of neuronal endangerment and that it is responsive to neuroprotective intervention.

Comprehensive pathway-based association study of DNA repair gene variants and the risk of nasopharyngeal carcinoma.

DNA repair plays a central role in protecting against environmental carcinogenesis, and genetic variants of DNA repair genes have been reported to be associated with several human malignancies. To assess whether DNA gene variants were associated with nasopharyngeal carcinoma (NPC) risk, a candidate gene association study was conducted among the Cantonese population within the Guangdong Province, China, the ethnic group with the highest risk for NPC. A 2-stage study design was utilized. In the discovery stage, 676 tagging SNPs covering 88 DNA repair genes were genotyped in a matched case-control study (cases/controls = 755/755). Eleven SNPs with P(trend) < 0.01 were identified. Seven of these SNPs were located within 3 genes, RAD51L1, BRCA2, and TP53BP1. In the validation stage, these 11 SNPs were genotyped in a separate Cantonese population (cases/controls = 1,568/1,297). Two of the SNPs (rs927220 and rs11158728), both in RAD51L1, remained strongly associated with NPC. The SNP rs927220 had a significant P(combined) of 5.55 × 10(-5), with OR = 1.20 (95% CI = 1.10-1.30), Bonferroni corrected P = 0.0381. The other SNP (rs11158728), which is in strong linkage disequilibrium with rs927220 (r(2) = 0.7), had a significant P(combined) of 2.0 × 10(-4), Bonferroni corrected P = 0.1372. Gene-environment interaction analysis suggested that the exposures of salted fish consumption and cigarette smoking had potential interactions with DNA repair gene variations, but need to be further investigated. Our findings support the notion that DNA repair genes, in particular RAD51L1, play a role in NPC etiology and development.

The association between skin characteristics and skin cancer prevention behaviors.

BACKGROUND: Behaviors such as sunscreen use and wearing sun-protective clothing are thought to prevent certain types of skin cancer and precancerous lesions, but few studies have examined differences in these prevention behaviors by skin type. METHODS: We carried out a cross-sectional study (n = 6,858) nested within a community-based prospective cohort in Washington County, Maryland. We measured the associations between skin type, complexion, freckling, and eye color, and sunscreen and sun-protective clothing use. RESULTS: The prevalence of regular sunscreen use was 23% and regular sun-protective clothing use was 21%. There were consistent trends indicating those with the most sun-sensitive skin type were most likely to engage in prevention behaviors. For example, compared with those who tan without burning, those who develop blistering sunburns were more likely to use sunscreen [odds ratio (OR), 6.04; 95% confidence interval (95% CI), 2.82-12.95 men; OR, 4.89; 95% CI, 3.34-7.16 women] and sun-protective clothing (OR, 2.87; 95% CI, 1.71-4.80 men; OR, 4.44; 95% CI, 2.88-6.85 women). Health-related characteristics such as body mass index and cigarette smoking were also significantly inversely associated with prevention behaviors. CONCLUSION: The overall prevalence of prevention behaviors was low. Those with phenotypic risk factors for skin cancer were most likely to use sunscreen and sun-protective clothing. Those with high-risk skin cancer phenotypes may also be those who are most receptive to skin cancer prevention educational interventions.

Hypothesis-driven candidate gene association studies: practical design and analytical considerations.

Candidate gene association studies (CGAS) are a useful epidemiologic approach to drawing inferences about relations between genes and disease, especially when experimental data support the involvement of specific biochemical pathways. The value of CGAS is apparent when allele frequencies are low, effect sizes are small, or the study population is limited or unique. CGAS is also valuable for validating previous reports of genetic associations with disease in different populations. Despite the many advantages, the information generated from CGAS is sometimes compromised because of either inefficient study design or suboptimal analytical approaches. Here the authors discuss issues related to the study design and statistical analyses of CGAS that can help to optimize their usefulness and information content. These issues include judicious hypothesis-driven selection of biochemical pathways, genes, and single nucleotide polymorphisms, as well as appropriate quality control and analytical procedures for measuring main effects and for evaluating environmental exposure modifications and interactions. A study design algorithm using the example of DNA repair genes and cancer is presented for purposes of illustration.

Genome-wide association study reveals multiple nasopharyngeal carcinoma-associated loci within the HLA region at chromosome 6p21.3.

Nasopharyngeal carcinoma (NPC) is a multifactorial malignancy closely associated with genetic factors and Epstein-Barr virus infection. To identify the common genetic variants linked to NPC susceptibility, we conducted a genome-wide association study (GWAS) in 277 NPC patients and 285 healthy controls within the Taiwanese population, analyzing 480,365 single-nucleotide polymorphisms (SNPs). Twelve statistically significant SNPs were identified and mapped to chromosome 6p21.3. Associations were replicated in two independent sets of case-control samples. Two of the most significant SNPs (rs2517713 and rs2975042; p(combined) = 3.9 x 10(-20) and 1.6 x 10(-19), respectively) were located in the HLA-A gene. Moreover, we detected significant associations between NPC and two genes: specifically, gamma aminobutyric acid b receptor 1 (GABBR1) (rs29232; p(combined) = 8.97 x 10(-17)) and HLA-F (rs3129055 and rs9258122; p(combined) = 7.36 x 10(-11) and 3.33 x 10(-10), respectively). Notably, the association of rs29232 remained significant (residual p < 5 x 10(-4)) after adjustment for age, gender, and HLA-related SNPs. Furthermore, higher GABA(B) receptor 1 expression levels can be found in the tumor cells in comparison to the adjacent epithelial cells (p < 0.001) in NPC biopsies, implying a biological role of GABBR1 in NPC carcinogenesis. To our knowledge, it is the first GWAS report of NPC showing that multiple loci (HLA-A, HLA-F, and GABBR1) within chromosome 6p21.3 are associated with NPC. Although some of these relationships may be attributed to linkage disequilibrium between the loci, the findings clearly provide a fresh direction for the study of NPC development.

Binding kinetics and activity of human poly(ADP-ribose) polymerase-1 on oligo-deoxyribonucleotide substrates.

Poly(ADP-ribose) polymerase-1 (PARP-1) is a mammalian enzyme that attaches long branching chains of ADP-ribose to specific nuclear proteins, including itself. Because its activity in vitro is dependent upon interaction with broken DNA, it has been postulated that PARP-1 plays an important role in DNA strand-break repair in vivo. The exact mechanism of binding to DNA and the structural determinants of binding remain to be defined, but regions of transition from single-stranded to double-strandedness may be important recognition sites. Here we employ surface plasmon resonance (SPR) to investigate this hypothesis. Oligodeoxynucleotide (ODN) substrates that mimic DNA with different degrees of single-strandedness were used for measurements of both PARP-1/DNA binding kinetics and PARP-1's enzyme activities. We found that binding correlated with activity, but was unrelated to single-strandedness of the ODN. Instead, PARP-1 binding and activity were highest on ODNs that modeled a DNA double-strand break (DSB). These results provide support for PARP-1 recognizing and binding DSBs in a manner that is independent of single-stranded features, and demonstrate the usefulness of SPR for simultaneously investigating both PARP-1 binding and PARP-1 auto-poly(ADP-ribosyl)ation activities within the same in vitro system.