Japanese Legacy Cohorts: Six-Prefecture Cohort Study (Hirayama Cohort Study).

Late Dr Takeshi Hirayama and his colleagues conducted a mortality follow-up of a large-scale cohort in six prefectures in Japan. This study is called the six-prefecture cohort study or Hirayama Cohort Study. The study subjects were residents aged 40 years or older at the baseline survey in 1965, which covered 94.8% of residents identified in the study area by the National Census conducted on October 1, 1965. The mortality of 264,118 cohort members was followed until the end of 1982. One of the most important findings made by this study was an association between second-hand smoke exposure and lung cancer. This finding is the origin of the worldwide spread of smoking ban in indoor public venues and workplaces. Other major findings obtained from the study are also briefly described in this article.

Radiation-induced Epstein-Barr virus reactivation in gastric cancer cells with latent EBV infection.

Epstein-Barr virus, a ubiquitous human herpes virus with oncogenic activity, can be found in 6%-16% of gastric carcinomas worldwide. In Epstein-Barr virus-associated gastric carcinoma, only a few latent genes of the virus are expressed. Ionizing irradiation was shown to induce lytic Epstein-Barr virus infection in lymphoblastoid cell lines with latent Epstein-Barr virus infection. In this study, we examined the effect of ionizing radiation on the Epstein-Barr virus reactivation in a gastric epithelial cancer cell line (SNU-719, an Epstein-Barr virus-associated gastric carcinoma cell line). Irradiation with X-ray (dose = 5 and 10 Gy; dose rate = 0.5398 Gy/min) killed approximately 25% and 50% of cultured SNU-719 cells, respectively, in 48 h. Ionizing radiation increased the messenger RNA expression of immediate early Epstein-Barr virus lytic genes (BZLF1 and BRLF1), determined by real-time reverse transcription polymerase chain reaction, in a dose-dependent manner at 48 h and, to a slightly lesser extent, at 72 h after irradiation. Similar findings were observed for other Epstein-Barr virus lytic genes (BMRF1, BLLF1, and BcLF1). After radiation, the expression of transforming growth factor beta 1 messenger RNA increased and reached a peak in 12-24 h, and the high-level expression of the Epstein-Barr virus immediate early genes can convert latent Epstein-Barr virus infection into the lytic form and result in the release of infectious Epstein-Barr virus. To conclude, Ionizing radiation activates lytic Epstein-Barr virus gene expression in the SNU-719 cell line mainly through nuclear factor kappaB activation. We made a brief review of literature to explore underlying mechanism involved in transforming growth factor beta-induced Epstein-Barr virus reactivation. A possible involvement of nuclear factor kappaB was hypothesized.

The association between high birth weight and the risks of childhood CNS tumors and leukemia: an analysis of a US case-control study in an epidemiological database.

BACKGROUND: High birth weight (BW), 4000 g or larger, is an established risk factor for childhood leukemia. However, its association with central nervous system (CNS) tumor risk is yet unclear. The present study examined it, analyzing data obtained from a case-control study conducted among three states from the US. The association with childhood leukemia risk was also further examined. METHODS: In this study, a data set provided by the Comprehensive Epidemiologic Data Resource was analyzed with an official permission. The original case-control study was conducted to examine the association between paternal preconception exposure to ionizing radiation and childhood cancer risk. Cases with childhood cancer were mainly ascertained from local hospitals, and controls were selected, matched with birth year (1-year category), county of residence, sex, ethnicity and maternal age (+/-2 years). Since the ID numbers were unavailable, conventional logistic analyses were conducted adjusting for those matching variables except for the county of residence. In addition to those variables, gestational age, age at diagnosis and study sites as covariables were included in the logistic models. RESULTS: Analyzed subjects were 72 CNS tumor cases, 124 leukemia cases and 822 controls born from 1945 to 1989. The odds ratios (ORs) of CNS tumor risk for children with low BWs (<2500 g) and high BWs (>4000 g) were 2.0 (95% confidence interval [CI]) = 0.7, 5.9) and 2.5 (95%CI = 1.2, 5.2)], respectively. When high-BW children were restricted to those who were large for gestational age (LGA), the OR for high-BW children remained similar (OR = 2.7; 95%CI = 1.1, 6.2). On the other hand, the ORs of leukemia risk for children with low and high BWs were 0.8 (95%CI = 0.2, 3.0) and 1.4 (95%CI = 0.7, 2.6), respectively. In the normal range of BW (2500-4000 g), higher BW was positively associated with CNS tumor risk (beta = 0.0011, p for trend = 0.012). However, the association with leukemia risk was not significant (beta = -0.0002, p for trend = 0.475). CONCLUSION: High-BW and LGA children had an elevated childhood CNS tumor risk. In the normal BW range, the BW itself was positively related to CNS tumor risk. No significant association between BW and childhood leukemia risk was observed in this study.

Radiation dose due to radon and thoron progeny inhalation in high-level natural radiation areas of Kerala, India.

In order to evaluate internal exposure to radon and thoron, concentrations for radon, thoron, and thoron progeny were measured for 259 dwellings located in high background radiation areas (HBRAs, outdoor external dose: 3-5 mGy y-1) and low background radiation areas (control areas, outdoor external dose: 1 mGy y-1) in Karunagappally Taluk, Kerala, India. The measurements were conducted using passive-type radon-thoron detectors and thoron progeny detectors over two six-month measurement periods from June 2010 to June 2011. The results showed no major differences in radon and thoron progeny concentrations between the HBRAs and the control areas. The geometric mean of the annual effective dose due to radon and thoron was calculated as 0.10 and 0.44 mSv, respectively. The doses were small, but not negligible compared with the external dose in the two areas.

Long-term effects of radiation exposure on health.

Late-onset effects of exposure to ionising radiation on the human body have been identified by long-term, large-scale epidemiological studies. The cohort study of Japanese survivors of the atomic bombings of Hiroshima and Nagasaki (the Life Span Study) is thought to be the most reliable source of information about these health effects because of the size of the cohort, the exposure of a general population of both sexes and all ages, and the wide range of individually assessed doses. For this reason, the Life Span Study has become fundamental to risk assessment in the radiation protection system of the International Commission on Radiological Protection and other authorities. Radiation exposure increases the risk of cancer throughout life, so continued follow-up of survivors is essential. Overall, survivors have a clear radiation-related excess risk of cancer, and people exposed as children have a higher risk of radiation-induced cancer than those exposed at older ages. At high doses, and possibly at low doses, radiation might increase the risk of cardiovascular disease and some other non-cancer diseases. Hereditary effects in the children of atomic bomb survivors have not been detected. The dose-response relation for cancer at low doses is assumed, for purposes of radiological protection, to be linear without a threshold, but has not been shown definitively. This outstanding issue is not only a problem when dealing appropriately with potential health effects of nuclear accidents, such as at Fukushima and Chernobyl, but is of growing concern in occupational and medical exposure. Therefore, the appropriate dose-response relation for effects of low doses of radiation needs to be established.

Dose and dose-rate effects of ionizing radiation: a discussion in the light of radiological protection.

The biological effects on humans of low-dose and low-dose-rate exposures to ionizing radiation have always been of major interest. The most recent concept as suggested by the International Commission on Radiological Protection (ICRP) is to extrapolate existing epidemiological data at high doses and dose rates down to low doses and low dose rates relevant to radiological protection, using the so-called dose and dose-rate effectiveness factor (DDREF). The present paper summarizes what was presented and discussed by experts from ICRP and Japan at a dedicated workshop on this topic held in May 2015 in Kyoto, Japan. This paper describes the historical development of the DDREF concept in light of emerging scientific evidence on dose and dose-rate effects, summarizes the conclusions recently drawn by a number of international organizations (e.g., BEIR VII, ICRP, SSK, UNSCEAR, and WHO), mentions current scientific efforts to obtain more data on low-dose and low-dose-rate effects at molecular, cellular, animal and human levels, and discusses future options that could be useful to improve and optimize the DDREF concept for the purpose of radiological protection.

Improved survival of gastric cancer with tumour Epstein-Barr virus positivity: an international pooled analysis.

BACKGROUND AND OBJECTIVE: About 9% of gastric carcinomas have Epstein-Barr virus (EBV) in the tumour cells, but it is unclear whether viral presence influences clinical progression. We therefore examined a large multicentre case series for the association of tumour EBV status with survival after gastric cancer diagnosis, accounting for surgical stage and other prognostic factors. METHODS: We combined individual-level data on 4599 gastric cancer patients diagnosed between 1976 and 2010 from 13 studies in Asia (n=8), Europe (n=3), and Latin America (n=2). EBV positivity of tumours was assessed by in situ hybridisation. Mortality HRs for EBV positivity were estimated by Cox regression models stratified by study, adjusted for distributions of sex (71% male), age (mean 58 years), stage (52% tumour-node-metastasis stages III or IV), tumour histology (49% poorly differentiated, 57% Lauren intestinal-type), anatomic subsite (70% non-cardia) and year of diagnosis. Variations by study and continent were assessed using study-specific HRs for EBV positivity. RESULTS: During median 3.0 years follow-up, 49% of patients died. Stage was strongly predictive of mortality, with unadjusted HRs (vs stage I) of 3.1 for stage II, 8.1 for stage III and 13.2 for stage IV. Tumour EBV positivity was 8.2% overall and inversely associated with stage (adjusted OR: 0.79 per unit change). Adjusted for stage and other confounders, EBV positivity was associated with lower mortality (HR, 0.72; 95% CI 0.61 to 0.86), with low heterogeneity among the study populations (p=0.2). The association did not significantly vary across patient or tumour characteristics. There was no significant variation among the three continent-specific HRs (p=0.4). CONCLUSIONS: Our findings suggest that tumour EBV positivity is an additional prognostic indicator in gastric cancer. Further studies are warranted to identify the mechanisms underlying this protective association.

HPV-associated lung cancers: an international pooled analysis.

Human papillomavirus (HPV) is the etiologic risk factor for cervical cancer. Some studies have suggested an association with a subset of lung tumors, but the etiologic link has not been firmly established. We performed an international pooled analysis of cross-sectional studies (27 datasets, n = 3249 patients) to evaluate HPV DNA prevalence in lung cancer and to investigate viral presence according to clinical and demographic characteristics. HPV16/18 were the most commonly detected, but with substantial variation in viral prevalence between geographic regions. The highest prevalence of HPV16/18 was observed in South and Central America, followed by Asia, North America and Europe (adjusted prevalence rates = 22, 5, 4 and 3%, respectively). Higher HPV16 prevalence was noted in each geographic region compared with HPV18, except in North America. HPV16/18-positive lung cancer was less likely observed among White race (adjusted odds ratio [OR] = 0.33, 95% confidence interval [CI] = 0.12-0.90), whereas no associations were observed with gender, smoking history, age, histology or stage. Comparisons between tumor and normal lung tissue show that HPV was more likely to be present in lung cancer rather than normal lung tissues (OR = 3.86, 95% CI = 2.87-5.19). Among a subset of patients with HPV16-positive tumors, integration was primarily among female patients (93%, 13/14), while the physical status in male cases (N = 14) was inconsistent. Our findings confirm that HPV DNA is present in a small fraction of lung tumors, with large geographic variations. Further comprehensive analysis is needed to assess whether this association reflects a causal relationship.

Case-case comparison of smoking and alcohol risk associations with Epstein-Barr virus-positive gastric cancer.

Helicobacter pylori is the primary cause of gastric cancer. However, monoclonal Epstein-Barr virus (EBV) nucleic acid is also present in up to 10% of these tumors worldwide. EBV prevalence is increased with male sex, nonantral localization and surgically disrupted anatomy. To further examine associations between EBV and gastric cancer, we organized an international consortium of 11 studies with tumor EBV status assessed by in situ hybridization. We pooled individual-level data on 2,648 gastric cancer patients, including 184 (7%) with EBV-positive cancers; all studies had information on cigarette use (64% smokers) and nine had data on alcohol (57% drinkers). We compared patients with EBV-positive and EBV-negative tumors to evaluate smoking and alcohol interactions with EBV status. To account for within-population clustering, multilevel logistic regression models were used to estimate interaction odds ratios (OR) adjusted for distributions of sex (72% male), age (mean 59 years), tumor histology (56% Lauren intestinal-type), anatomic subsite (61% noncardia) and year of diagnosis (1983-2012). In unadjusted analyses, the OR of EBV positivity with smoking was 2.2 [95% confidence interval (CI) 1.6-3.2]. The OR was attenuated to 1.5 (95% CI 1.01-2.3) by adjustment for the possible confounders. There was no significant interaction of EBV status with alcohol drinking (crude OR 1.4; adjusted OR 1.0). Our data indicate the smoking association with gastric cancer is stronger for EBV-positive than EBV-negative tumors. Conversely, the null association with alcohol does not vary by EBV status. Distinct epidemiologic characteristics of EBV-positive cancer further implicate the virus as a cofactor in gastric carcinogenesis.

Epidemiological studies of Fukushima residents exposed to ionising radiation from the Fukushima Daiichi Nuclear Power Plant prefecture--a preliminary review of current plans.

It is now more than six months since the beginning of the accident on 11 March 2011 at the Fukushima Daiichi Nuclear Power Plant in Japan. The Japanese government and local health authorities have started to collect the information necessary to estimate radiation doses received by those living in the area around the plant, drafted plans for the health care of residents, and started to implement some of them. This paper reviews and discusses the studies necessary for risk evaluation of cancer and non-cancer diseases, including those already planned, mainly from the view point of evaluating health risk using epidemiological approaches. In the long run, it is important to establish a cohort with a control group. Even if the cumulative doses are estimated to be so low that it is difficult to evaluate the risk of cancer and non-cancer diseases, it is necessary to conduct such a study to reassure residents. The health care programme of the Fukushima Prefecture government, including health check-ups of residents, will help to assess indirect effects of radiation exposure, including psychological problems. The success of any studies of radiation epidemiology depends on the collection of accurate information on radiation doses received by the study subjects. However, some of the dosimetry surveys were not conducted in a timely manner. (It should be recognised, though, that such a problem might have been inevitable, considering the chaotic condition after the nuclear accident.) Accurate estimation of the radiation dose received by each resident is not only important for scientific risk evaluation but also to inform each resident about his or her potential risk. Otherwise, residents will bear an undue psychological burden from uncertainties regarding their radiation exposure and its health consequences. One of other important tasks in Fukushima is the improvement of the quality of the regional cancer registry in this prefecture. It is also important to start thyroid cancer screening in a year or two since the expected minimum latent period among those exposed in early childhood is about 4 years. Recently, local health authorities decided to start a thyroid screening programme for those aged 18 years or younger. Any scientific efforts in Fukushima, which need to gain the trust of study subjects about the objectivity of research, may suffer from the fact that residents in Fukushima Prefecture have begun to suspect that the Japanese government and local authorities are keeping important information from them. It seems necessary to make more effort to reflect the opinions of residents when planning health care programmes and to gain the understanding of the public for the programme. In summary, there are many problems that make the evaluation of cancer and non-cancer disease risk in Fukushima difficult. The help of international colleagues will be invaluable for overcoming those problems. In this paper, these efforts are briefly summarised and some comments are made.

The third analysis of cancer mortality among Japanese nuclear workers, 1991-2002: estimation of excess relative risk per radiation dose.

The present study estimated excess relative risk per sievert (ERR/Sv) of cancer mortality among the cohort of 200 583 male Japanese nuclear workers, with an average individual cumulative dose of 12.2 mSv (<10 mSv, 75.4%; 100 + mSv, 2.6%), conducting Poisson regression using dose category specific observed and expected numbers of deaths, and average doses obtained from the official report of the Radiation Effects Association (REA) on the analysis of mortality of Japanese nuclear industry workers for 1991-2002, which reported the estimates of ERR/Sv for leukaemia but not for all cancers or any other cancer site. The possible confounding biases from drinking alcohol and smoking tobacco were evaluated by examining the association of cumulative radiation dose with the mortality of cancers related to drinking or smoking. For leukaemia (80 deaths), the estimate of ERR/Sv was - 1.93 (95% confidence interval (CI) = - 6.12, 8.57). For all cancers excluding leukaemia (2636 deaths), while the ERR/Sv was estimated to be 1.26 (95%CI = - 0.27, 3.00), confounding by alcohol consumption was suspected since the ERR/Sv estimate of alcohol-related cancers was 4.64 (95%CI = 1.13, 8.91) and the ERR/Sv estimate of all cancers excluding leukaemia and alcohol-related cancers was 0.20 (95%CI = - 1.42, 2.09). In conclusion, confounding by important lifestyle factors related to cancer risk may have a substantial effect on risk estimates, especially when conducting studies of low cumulative dose and, accordingly, low statistical power. Pooled analysis or meta-analysis of nuclear workers for solid cancers needs to take this point into account.

Oral cavity cancer risk in relation to tobacco chewing and bidi smoking among men in Karunagappally, Kerala, India: Karunagappally cohort study.

The Karunagapally cohort in Kerala, India was established in the 1990s. The present study examined oral cancer risk among 66,277 men aged 30-84 years in the cohort, using Poisson regression analysis of grouped data, stratified on attained age, calendar time, education, and family income. By the end of 2005, 160 oral cancer cases were identified by the Karunagapally Cancer Registry. Tobacco chewing increased oral cancer risk (P < 0.001). Particularly increased was the risk of cancers of the gum and mouth (relative risk [RR] = 4.7; 95% confidence interval [CI] = 2.8-7.9), which increased with higher daily frequencies (P < 0.001) and longer duration (P < 0.001) of tobacco chewing. Alcohol drinking was not significantly related to oral cancer risk regardless of tobacco chewing. Bidi smoking significantly increased oral cancer risk (RR = 2.6; 95%CI = 1.4-4.9) only among men without tobacco chewing habits. The risk increased with higher daily consumption (P < 0.001), longer duration (P = 0.001), and younger age at start of bidi smoking (P = 0.007). In location-specific analysis, bidi smoking was significantly associated with cancer of the gum and mouth (RR = 3.6; 95%CI = 1.1-12.1), and its risk significantly increased with larger daily consumption of bidis (P = 0.013) and younger age at the start of smoking (P = 0.044). Tongue cancer risk was significantly increased among men who smoked bidis for 30 years or longer, and men started bidi smoking at 18 years old or younger. The present study is the first cohort study showing that tobacco chewing increases cancers of the gum and mouth among men keeping chewing tobacco in the cheek, and that bidi smoking strongly increased oral cancer risk among men without a tobacco chewing habit.

Human papillomavirus infection in lung and esophageal cancers: analysis of 485 Asian cases.

The role of human papillomavirus (HPV) in the development of lung and esophageal cancer remains inconclusive, which is in contrast to the established role HPV plays in the development of uterine cervical cancer. One of the reasons for this is the difference among reported HPV infection rates in these cancers. An analysis of 485 lung and esophageal cancers (176 lung squamous cell carcinoma, 128 lung adenocarcinoma, 181 esophageal carcinoma) in eight institutions in Asia (Tokyo, Kochi, Kagoshima, and Okinawa, Japan; Seoul and Daegu, Korea; Changhua, Republic of China (Taiwan); Singapore, Singapore) was carried out in order to clarify infection rates with HPV. Samples were examined in one laboratory of the Department of Pathology, the University of Tokyo, Japan in order to avoid inter-laboratory variation using a combination of polymerase chain reaction and in situ hybridization (ISH). HPV was found in 6.3%, 7%, and 9.4% of patients with lung squamous cell carcinoma, lung adenocarcinoma, and esophageal cancer, respectively. Among the geographic areas surveyed, Kagoshima exhibited a significantly higher prevalence of HPV infection in cases of esophageal carcinoma (24.1%). There was no geographical difference in the infection rates of HPV in lung carcinomas. Subtype-specific ISH was also performed, which identified the high-risk HPV types 16/18 in the majority (75.7%) of the patients with lung and esophageal cancer positive for HPV.

A case-case study of mobile phone use and acoustic neuroma risk in Japan.

Results of case-control studies of mobile phone use and acoustic neuroma have been inconsistent. We conducted a case-case study of mobile phone use and acoustic neuroma using a self-administered postal questionnaire. A total of 1589 cases identified in 22 hospitals throughout Japan were invited to participate, and 787 cases (51%) actually participated. Associations between laterality of mobile phone use prior to the reference dates (1 and 5 years before diagnosis) and tumor location were analyzed. The overall risk ratio was 1.08 (95% confidence interval (CI), 0.93-1.28) for regular mobile phone use until 1 year before diagnosis and 1.14 (95% CI, 0.96-1.40) for regular mobile phone use until 5 years before diagnosis. A significantly increased risk was identified for mobile phone use for >20 min/day on average, with risk ratios of 2.74 at 1 year before diagnosis, and 3.08 at 5 years before diagnosis. Cases with ipsilateral combination of tumor location and more frequently used ear were found to have tumors with smaller diameters, suggesting an effect of detection bias. Furthermore, analysis of the distribution of left and right tumors suggested an effect of tumor-side-related recall bias for recall of mobile phone use at 5 years before diagnosis. The increased risk identified for mobile phone users with average call duration >20 min/day should be interpreted with caution, taking into account the possibilities of detection and recall biases. However, we could not conclude that the increased risk was entirely explicable by these biases, leaving open the possibility that mobile phone use increased the risk of acoustic neuroma.

Esophageal cancer in relation to alcohol drinking and tobacco use among men in Kerala, India - Karunagappally cohort.

BACKGROUND: In the Karunagappally cohort, esophageal cancer is the third most common cancer with an age-adjusted incidence rate of 6.2 per 100,000 person-years among men. The present study analyzed the risk of esophageal cancer in relation to alcohol drinking and tobacco use. METHODS: The study included 65,528 men aged 30-84 years in the Karunagappally cohort, India. RESULTS: Poisson regression analysis showed that alcohol drinking significantly increased (P = 0.027) the risk of esophageal cancer and the relative risk (RR) for current drinkers was 1.6, (95 % confidence interval (CI) = 1.1-2.3). The risk increased significantly in heavy alcohol drinkers (250 g of ethanol or above per day) (RR = 2.1, 95 % CI = 1.2-3.5) (P for trend = 0.014) and among current arrack consumers (RR = 1.8, 95 % CI = 0.99-3.29) (P for trend = 0.025). Current bidi and cigarette smokers showed an increase in the trend of cancer risk. A significantly higher risk was seen in those who had started smoking bidi before the age of 18 years, RR = 1.9 (95 % CI = 1.1-3.3) (P for trend = 0.044). Furthermore, increased RR for heavy bidi and cigarette smokers were 1.6 (95 % CI = 1.1-2.5) and 2.4 (95 % CI = 1.3-4.5), respectively. CONCLUSION: To the best of our knowledge, this is the first cohort study in India to report an increased esophageal cancer risk with respect to alcohol drinking.

Lens opacity prevalence among the residents in high natural background radiation area in Yangjiang, China.

The aim of the study was to evaluate the risk and threshold doses of lens opacity among residents exposed to low-dose radiation. Residents aged ≥45 years were recruited from a high natural background radiation (HNBR) area in Yangjiang City and a control area selected from nearby Enping City. Lens opacities (LOPs) were classified according to the Lens Opacities Classification System (LOCS) III system. Face-to-face interviews were conducted to collect information on lifestyles, migration and medical history. Life-time cumulative doses were estimated using gender, age, occupancy factors and environmental radiation doses received indoors and outdoors. Logistic regression analyses were conducted to estimate the dose response and determine thresholds. In the HNBR area, among 479 study participants, 101 (21.1%), 245(51.1%) and 23 cases (4.8%), respectively, of cortical, nuclear and posterior subcapsular (PSC) LOPs were found. In the control area, those types of LOPs were identified among 58 cases (12.6%), 206 cases (51.2%) and 6 cases (1.3%) of 462 examinees, respectively. Cumulative eye lens dose was estimated to be 189.5 ± 36.5 mGy in the HNBR area. Logistic analyses gave odds ratios at 100 mGy of 1.26 [95% confidence interval (CI) 1.00-1.60], 0.81 (95% CI 0.64-1.01) and 1.73 (95% CI 1.05-2.85) for cortical, nuclear and PSC LOPs, respectively. For cortical LOPs, a logistic analysis with a threshold dose gave a threshold estimate of 140 mGy (90% CI 110-160 mGy). The results indicated that population exposed to life-time, low-dose-rate environmental radiation was at an elevated risk of cortical and PSC LOPs. A statistically significant threshold dose was obtained for cortical LOPs and no threshold dose for PSC LOPs.

The First Attempt to Reevaluate Radon and Thoron Exposure in Gansu Province Study Using Radon-Thoron Discriminating Measurement Technique.

Although the epidemiological studies provide evidence for an increased risk of lung cancer risk associated with residential radon, an issue of radon-thoron discrimination remains to be solved. In this study, an updated evaluation of lung cancer risk among the residents in Gansu, China was performed where one of the major epidemiological studies on indoor radon demonstrated an increased risk of lung cancer. We analyzed data from a hospital-based case-control study that included 30 lung cancer cases and 39 controls with special attention to internal exposure assessment based on the discriminative measurement technique of radon isotopes. Results from the analyses showed non-significant increased lung cancer risks; odds ratios (ORs) adjusted for age, smoking, and total income were 0.35 (95% CI: 0.07-1.74) and 0.27 (95% CI: 0.04-1.74) for groups living in residences with indoor radon concentrations of 50-100 Bq m-3 and over 100 Bq m-3, respectively, compared with those with < 50 Bq m-3 indoor radon concentrations. Although the small sample size hampers the usefulness of present analyses, our study suggests that reevaluation of lung cancer risk associated with residential radon in the epidemiological studies will be required on the basis of precise exposure assessment.

Power-frequency magnetic fields and childhood brain tumors: a case-control study in Japan.

BACKGROUND: The strength of the association between brain tumors in children and residential power-frequency magnetic fields (MF) has varied in previous studies, which may be due in part to possible misclassification of MF exposure. This study aimed to examine this association in Japan by improving measurement techniques, and by extending measurement to a whole week. METHODS: This population-based case-control study encompassed 54% of Japanese children under 15 years of age. After excluding ineligible targeted children, 55 newly diagnosed brain tumor cases and 99 sex-, age-, and residential area-matched controls were included in the analyses. The MF exposures of each set of matching cases and controls were measured in close temporal proximity to control for seasonal variation; the average difference was 12.4 days. The mean interval between diagnosis and MF measurements was 1.1 years. The weekly mean MF level was defined as the exposure. The association was evaluated using conditional logistic regression analysis that controlled for possible confounding factors. RESULTS: The odds ratios (95% CI) for exposure categories of 0.1 to 0.2, 0.2 to 0.4, and above 0.4 microT, against a reference category of <0.1 microT, were 0.74 (0.17-3.18), 1.58 (0.25-9.83), and 10.9 (1.05-113), respectively, after adjusting for maternal education. This dose-response pattern was stable when other variables were included in the model as possible confounding factors. CONCLUSIONS: A positive association was found between high-level exposure-above 0.4 microT-and the risk of brain tumors. This association could not be explained solely by confounding factors or selection bias.

Mercury distribution in seawater of Kagoshima Bay near the active Volcano, Mt. Sakurajima in Japan.

Kagoshima bay has a highly active volcano in its center. In the filtered seawater and suspended matter collected from 200-m deep fumaroles at the bottom of the inner bay, the geometric mean concentrations of total mercury were 7.6 and 65.0 ng/L, respectively. The surface seawater collected at the inner bay had a higher concentration of mercury when compared to that in the bay entrance (average: 1.0 vs. 0.5 ng/L). In July, however, no such difference was observed. The fumaroles seem to contribute to relatively high concentrations of mercury in the inner bay except in summer, when thermal cline is formed.