The effect of chicken blood and its components on wastewater characteristics and sewage surcharges.

Local wastewater treatment authorities levy surcharges from their non-residential customers that are based, in part, on the concentration of various pollutants in the customer's wastewater. Blood has long been recognized as the most potent contributor to pollutant loads in chicken processing plant wastewater. Quantification of the impact of blood on wastewater characteristics and sewage surcharges is hindered by lack of information on specific characteristics of chicken blood, and by the highly variable methods used by local authorities for calculating surcharges. In this study, the most commonly used wastewater characteristics are determined for whole chicken blood as well as its individual components. The characteristics measured include biochemical oxygen demand, chemical oxygen demand, total suspended solids, fats oil and grease, total Kjeldahl nitrogen, ammonia, and total phosphorus. Sewage surcharge calculation methods were collected from 71 local wastewater authorities. The results show all components of the blood to be extremely high-strength pollutants. The impact of blood on sewage surcharges is shown to be highly variable depending on the rates applied by the local authority.

Dose Estimation for a Study of Nuclear Workers in France, the United Kingdom and the United States of America: Methods for the International Nuclear Workers Study (INWORKS).

In the framework of the International Nuclear Workers Study conducted in France, the UK and the U.S. (INWORKS), updated and expanded methods were developed to convert recorded doses of ionizing radiation to estimates of organ doses or individual personal dose equivalent [H(p)(10)] for a total number of 308,297 workers, including 40,035 women. This approach accounts for differences in dosimeter response to predominant workplace energy and geometry of exposure and for the recently published ICRP report on dose coefficients for men and women separately. The overall mean annual individual personal dose equivalent, including zero doses, is 1.73 mSv [median = 0.42; interquartile range (IQR): 0.07, 1.59]. Associated individual organ doses were estimated. INWORKS includes workers who had potential for exposure to neutrons. Therefore, we analyzed neutron dosimetry data to identify workers potentially exposed to neutrons. We created a time-varying indicator for each worker, classifying them according to whether they had a positive recorded neutron dose and if so, whether their neutron dose ever exceeded 10% of their total external penetrating radiation dose. The number of workers flagged as being exposed to neutrons was 13% for the full cohort, with 15% of the cohort in France, 12% of the cohort in the UK and 14% in the U.S. We also used available information on in vivo and bioassay monitoring to identify workers with known depositions or suspected internal contaminations. As a result of this work, information is now available that will allow various types of sensitivity analyses.

Cerebrovascular diseases incidence and mortality in an extended Mayak Worker Cohort 1948-1982.

Incidence and mortality from cerebrovascular disease (CVD) [International Classification of Diseases 9th revision (ICD-9) codes: 430-438] was studied in a cohort of 22,377 workers first employed at the Mayak Production Association (Mayak PA) in 1948-1982 and followed up to the end of 2008. The cohort size was increased by 19% and follow-up extended by 3 years over the previous analysis. Radiation doses were estimated using an updated dosimetry system: Mayak Worker Dosimetry System 2008 (MWDS-2008). For the first time, in an analysis of this cohort, quantitative smoking data were used. Workers of the study cohort were exposed occupationally to prolonged external gamma rays and internal alpha particles. The mean (±standard deviation) total dose from external gamma rays was 0.54 ± 0.76 Gy (95% percentile 2.21 Gy) for males and 0.44 ± 0.65 Gy (95% percentile 1.87 Gy) for females. The mean plutonium body burden in the 31% of workers monitored for internal exposure was 1.32 ± 4.87 kBq (95% percentile 4.71 kBq) for males and 2.21 ± 13.24 kBq (95% percentile 4.56 kBq) for females. The mean total absorbed alpha-particles dose to the liver from incorporated plutonium was 0.23 ± 0.77 Gy (95% percentile 0.89 Gy) in males and 0.44 ± 2.11 Gy (95% percentile 1.25 Gy) in females. After adjusting for nonradiation factors (gender, age, calendar period, employment period, facility, smoking, alcohol consumption), there were significantly increasing trends in CVD incidence associated with total absorbed dose from external gamma rays and total absorbed dose to the liver from internal alpha-particle radiation exposure. Excess relative risks per Gy (ERR/Gy) were 0.46 (95% CI 0.37, 0.57) and 0.28 (95% CI 0.16, 0.42), respectively, based on a linear dose-response model. Adjustments for additional factors (hypertension, body mass index, duration of employment, smoking index and total absorbed dose to the liver from internal exposure during the analysis of external exposure and vice versa) had little effect on the results. The categorical analyses showed that CVD incidence was significantly higher among workers with total absorbed external gamma-ray doses greater than 0.1 Gy compared to those exposed to lower doses and that CVD incidence was also significantly higher among workers with total absorbed internal alpha-particle doses to the liver from incorporated plutonium greater than 0.01 Gy compared to those exposed to lower doses. The results of the categorical analyses of CVD incidence were in good agreement with a linear dose response for external gamma-ray doses but for internal alpha-particle doses the picture was less clear. For the first time an excess risk of CVD mortality was seen in workers whose livers were exposed to internal alpha-particle doses greater than 0.1 Gy compared to those workers who were exposed to doses of less than 0.01 Gy. A significant increasing trend for CVD mortality with internal alpha-particle dose was revealed in the subcohort of workers exposed at doses <1.0 Gy after having adjusted for nonradiation factors, ERR/Gy = 0.84 (95% CI, 0.09, 1.92). These updated results provide good evidence for a linear trend in risk of CVD incidence with external gamma-ray dose. The trend for CVD incidence with internal alpha-particle dose is less clear due to the impact of issues concerning the use of dose estimates based on below the limit of detection bioassay measurements.

Chronic bronchitis in the cohort of Mayak workers first employed 1948-1958.

Incidence of chronic bronchitis has been studied in a cohort of 12,210 workers first employed at one of the main plants of the Mayak nuclear facility during 1948-1958 and followed up to 31 December 2005. Information on external gamma doses is available for virtually all of these workers; in contrast, plutonium body burden was measured only for 30% of workers. During the follow-up period in the study cohort 1,175 incident cases of chronic bronchitis were verified. The analyses of nonradiation factors revealed that the underlying risk of chronic bronchitis incidence increased with increasing attained age and was higher among smokers compared with never-smokers as would be expected. The most interesting finding in relationship to nonradiation factors was a sharp increase in the baseline chronic bronchitis risk before 1960. The cause of this is not clear but a number of factors may play a role. Based on the follow-up data after 1960, the analysis showed a statistically significant linear dose response relationship with cumulative external gamma-ray dose (ERR/Gy = 0.14, 95% CI 0.01, 0.32). Based on the same subset but with an additional restriction to members with cumulative internal lung dose below 1 Gy, a statistically significant linear dose response relationship with internal alpha-radiation lung dose from incorporated plutonium was found (ERR/Gy = 2.70, 95% CI 1.20, 4.87). In both cases, adjustment was made for nonradiation factors, including smoking and either internal or external dose as appropriate. At present there are no similar incidence studies with which to compare results. However, the most recent data from the atomic bomb survivor cohort (the Life Span Study) showed statistically significant excess mortality risk for respiratory diseases of 22% per Gy and this value is within the confidence bounds of the point estimate of the risk from this study in relation to external dose.

[Risk of cerebrovascular disease incidence in the cohort of Mayak production association workers first employed during 1948-1958].

Incidence of cerebrovascular diseases (CVD) has been studied in a cohort of 12210 workers first employed at one of the main plants (reactors, radiochemical or plutonium) of the Mayak nuclear facility during 1948-1958 and followed up to the end of 2000. Information on external gamma doses is available for virtually all (99.9%) of these workers; the mean (+/- one standard deviation) total gamma dose was 0.91 +/- 0.95 Gy (99% percentile 3.9 Gy) for men and 0.65 +/- 0.75 Gy (99% percentile 2.99 Gy) for women. Plutonium body burden was measured only for 30.0% of workers. Amongst those monitored, the mean (+/- standard deviation) cumulative liver dose from plutonium alpha exposure was 0.40 +/- 1.15 Gy (99% percentile 5.88 Gy) for men and 0.81 +/- 4.60 Gy (99% percentile 15.95 Gy) for women 4418 cases (first diagnosis) of CVD were identified in the studied cohort. A statistically significant increasing trend in CVD incidence with total external gamma dose was revealed after adjustment for non-radiation factors and internal exposure from incorporated plutonium-239. Excess relative risk per Gy was 0.464 (95% confidence interval 0.360-0.567). Incidence of CVD was statistically significantly higher for the workers chronically exposed to external gamma rays at a dose above 1.0 Gy A statistically significant increasing trend in CVD incidence with internal liver dose from plutonium alpha exposure was observed after adjustment for non-radiation factors and external exposure. ERR per Gy was 0.155 (95% confidence interval 0.075-0.235). CVD incidence was statistically significantly higher among workers with a plutonium liver dose above 0.1 Gy, although the trend estimates differed between workers at different plants. The incidence risk estimates for external radiation are generally compatible with estimates from the study of Chernobyl clean-up workers, although the incidence data point to higher risk estimates compared to those from the Japanese A-bomb survivors.

[Mortality risk of cardiovascular diseases for occupationally exposed workers].

Results of the risk analysis of mortality from ischemic heart disease (IHD) in the cohort of Mayak nuclear workers (18763 individuals) first employed in 1948-1972, with follow-up to 31.12.2005, were summarized. The mortality risk of IHD in the cohort of Mayak workers depended on the non-radiation factors such as gender, age, calendar period, smoking, alcohol consumption, arterial hypertension, body mass index. There was no statistically significant relationship between mortality from 1HD and total external dose. The risk of mortality from IHD was significantly higher for workers exposed to the total absorbed dose to liver > 0.025 Gy from internal alpha-radiation. There was a significantly increasing trend (ERR/Gy) of the IHD mortality with the total absorbed dose to liver from internal alpha-radiation due to incorporated plutonium. However, there was a decreasing trend of ERR/Gy with restriction of the follow-up to Ozyorsk and adjustment for the external dose.

Cerebrovascular diseases in the cohort of workers first employed at Mayak PA in 1948-1958.

The incidence of and mortality from cerebrovascular diseases (CVD) have been studied in a cohort of 12,210 workers first employed at one of the main plants of the Mayak nuclear facility during 1948-1958 and followed up to 31 December 2000. Information on external γ-ray doses is available for virtually all of these workers (99.9%); the mean total γ-ray dose (± SD) was 0.91 ± 0.95 Gy (99th percentile 3.9 Gy) for men and 0.65 ± 0.75 Gy (99th percentile 2.99 Gy) for women. In contrast, plutonium body burden was measured only for 30.0% of workers; among those monitored, the mean cumulative liver dose from plutonium α-particle exposure (± SD) was 0.40 ± 1.15 Gy (99th percentile 5.88 Gy) for men and 0.81 ± 4.60 Gy (99th percentile 15.95 Gy) for women. A total of 4418 cases of CVD, including 665 cases of stroke, and 753 deaths from CVD, including 404 deaths from stroke, were identified in the study cohort. Having adjusted for non-radiation factors, there were statistically significant increasing trends in CVD incidence but not mortality with both total external γ-ray dose and internal liver dose. Much of the evidence for increased incidence in relation to external dose arose for workers with cumulative doses above 1 Gy. Although the dose response is consistent with linearity, the statistical power to detect non-linearity at external doses below 1 Gy was low. CVD incidence was statistically significantly higher among workers with a plutonium liver dose above 0.1 Gy. There was a statistically significant increasing trend in incidence with increasing internal dose, even after adjusting for external dose, although the trend estimates differed between workers at different plants. The risk estimates for external radiation are generally compatible with those from other large occupational studies, although the incidence data point to higher risk estimates compared to those from the Japanese A-bomb survivors.

Cardiovascular diseases in the cohort of workers first employed at Mayak PA in 1948-1958.

Incidence of and mortality from cardiovascular diseases have been studied in a cohort of 12,210 workers first employed at one of the main plants of the Mayak nuclear facility during 1948-1958 and followed up to 31 December 2000. Information on external gamma-ray doses is available for virtually all of these workers (99.9%); the mean total gamma-ray dose (+/-SD) was 0.91 +/- 0.95 Gy (99% percentile 3.9 Gy) for men and 0.65 +/- 0.75 Gy (99% percentile 2.99 Gy) for women. In contrast, plutonium body burden was measured for only 30.0% of workers; among those monitored, the mean cumulative liver dose from plutonium alpha exposure (+/- SD) was 0.40 +/- 1.15 Gy (99% percentile 5.88 Gy) for men and 0.81 +/- 4.60 Gy (99% percentile 15.95 Gy) for women. A total of 3751 cases of ischemic heart disease (IHD), including 683 cases of acute myocardial infarction (AMI), and 1495 IHD deaths, including 338 AMI deaths, were identified in the study cohort during the follow-up period. Having adjusted for non-radiation factors, there were statistically significant increasing trends with both total external gamma-ray dose and internal liver dose in IHD incidence. The trend with internal dose was weaker and was not statistically significant after adjusting for external dose, whereas the external dose trend was little changed after adjusting for internal dose. The trend with external dose in IHD mortality was not statistically significantly greater than zero but was consistent with the corresponding trend in IHD incidence. The estimated trend in IHD mortality with internal dose was lower and was not statistically significant once adjustment was made for external dose. There was a statistically significantly increasing trend in AMI incidence but not AMI incidence with external dose. The risk estimates for IHD in relation to external radiation are generally compatible with those from other large occupational studies and the Japanese A-bomb survivors.

Mortality and cancer incidence following occupational radiation exposure: third analysis of the National Registry for Radiation Workers.

Mortality and cancer incidence were studied in the National Registry for Radiation Workers in, relative to earlier analyses, an enlarged cohort of 174 541 persons, with longer follow-up (to 2001) and, for the first time, cancer registration data. SMRs for all causes and all malignant neoplasms were 81 and 84 respectively, demonstrating a 'healthy worker effect'. Within the cohort, mortality and incidence from both leukaemia excluding CLL and the grouping of all malignant neoplasms excluding leukaemia increased to a statistically significant extent with increasing radiation dose. Estimates of the trend in risk with dose were similar to those for the Japanese A-bomb survivors, with 90% confidence intervals that excluded both risks more than 2-3 times greater than the A-bomb values and no raised risk. Some evidence of an increasing trend with dose in mortality from all circulatory diseases may, at least partly, be due to confounding by smoking. This analysis provides the most precise estimates to date of mortality and cancer risks following occupational radiation exposure and strengthens the evidence for raised risks from these exposures. The cancer risk estimates are consistent with values used to set radiation protection standards.

Carcinogenicity of radon/radon decay product inhalation in rats--effect of dose, dose rate and unattached fraction.

PURPOSE: The effects of inhalation of radon/radon decay products at different total doses, dose rates and 'unattached' fractions were investigated in a life span study in rats. MATERIALS AND METHODS: 1574 rats inhaled radon/radon decay products in a purpose-built recirculating exposure system that provided stable/reproducible exposure conditions. 501 were maintained as controls. RESULTS: Lung tumour incidences were significantly elevated in most exposed groups. The study power was insufficient to resolve the shape of the dose and dose rate response curves, but combination of this data with that from other studies demonstrated that for high cumulative exposures, the lifetime excess absolute risk increases with increasing exposure durations and for low cumulative exposures the opposite trend occurs. Exposure did not increase leukaemia incidences. A small number of non-lung tumour types including mammary fibroadenoma showed elevated incidences in some exposed groups, however not consistently across all exposure groups and showed no dose or dose rate relationship. CONCLUSIONS: Radon/radon decay product exposure caused excess lung tumours in rats along with limited non-lung effects. The results are consistent with the findings that at low cumulative exposures decreasing exposure concentrations or protracting the time over which the dose is delivered, reduces lung tumour risk. At higher levels, decreasing exposure concentrations or protracting exposure time increases lung tumour risk.

Epidemiological studies of UK test veterans: II. Mortality and cancer incidence.

An epidemiological study was set up in the 1980s of UK participants in the UK atmospheric nuclear weapons testing programme. A large cohort of test participants was established along with a closely matched comparison or control group. Three analyses of mortality and cancer incidence have been carried out. This review describes the development of the evidence on possible effects on test participants with especial emphasis on the most recent analysis. Other sources of evidence, particularly from studies of other groups of test participants, are also considered. It was concluded that overall levels of mortality and cancer incidence in UK nuclear weapons test participants were similar to those in a matched control group, and overall mortality was lower than expected from national rates. There was no evidence of an increased raised risk of multiple myeloma among test participants in recent years, and the suggestion in the first analysis of this cohort of a raised myeloma risk relative to controls is likely to have been a chance finding. There was some evidence of a raised risk of leukaemia other than chronic lymphatic leukaemia among test participants relative to controls, particularly in the early years after the tests. Whilst this could be a chance finding, the possibility that test participation caused a small absolute risk of leukaemia other than chronic lymphatic leukaemia cannot be ruled out.

Cancer in the offspring of radiation workers: an investigation of employment timing and a reanalysis using updated dose information.

An earlier case-control study found no evidence of paternal preconceptional irradiation (PPI) as a cause of childhood leukaemia and non-Hodgkin's lymphoma (LNHL). Although fathers of children with LNHL were more likely to have been radiation workers, the risk was most marked in those with doses below the level of detection. The timing of paternal employment as a radiation worker has now been examined. The previously reported elevated risk of LNHL in the children of male radiation workers was limited to those whose fathers were still radiation workers at conception or whose employment also continued until diagnosis. Children whose fathers stopped radiation work prior to their conception were found to have no excess risk of LNHL. It was not possible to distinguish between the risks associated with paternal radiation work at conception and at the time of diagnosis. A reanalysis of the original study hypothesis incorporating updated dosimetric information gave similar results to those obtained previously. In particular, the risks of LNHL did not show an association with radiation doses received by the father before conception. It seems likely that the increased risk of LNHL among the children of male radiation workers is associated with an increased exposure to some infective agent consequent on high levels of population mixing.

Follow up of mortality and incidence of cancer 1952-98 in men from the UK who participated in the UK's atmospheric nuclear weapon tests and experimental programmes.

AIMS: To extend and analyse follow up of mortality and cancer incidence among men who took part in the UK's atmospheric nuclear weapon tests and experimental programmes 40-50 years ago, with particular reference to multiple myeloma and leukaemia. METHODS: A total of 21,357 servicemen and male civilians from the UK who participated in the tests and a control group of 22,333 male controls were followed over the period 1952-98. Analyses were conducted of mortality from various causes, and of mortality and incidence for 27 types of cancer. RESULTS: Rates of mortality from all causes continued to be similar among test participants and controls with the longer follow up, with standardised mortality ratios (SMRs) of 89 and 88 respectively over the full follow up period. For all cancers, the corresponding SMRs were 93 for participants and 92 for controls. Mortality from multiple myeloma was consistent with national rates both for participants and controls, and the relative risk (RR) of myeloma incidence among participants relative to controls was 1.14 (90% CI 0.74 to 1.74) over the full follow up period and 0.79 (90% CI 0.45 to 1.38) during the extended period of follow up (1991-98). Over the full follow up period, leukaemia mortality among participants was consistent with national rates, while rates among controls were significantly lower, and there was a suggestion of a raised risk among test participants relative to controls (RR 1.45, 90% CI 0.96 to 2.17); the corresponding RR for leukaemia incidence was 1.33 (90% CI 0.97 to 1.84). After excluding chronic lymphatic leukaemia (CLL), which is not thought to be radiation inducible, the RR of leukaemia mortality increased to 1.83 (90% CI 1.15 to 2.93), while that for incidence was little changed. Analysis of subgroups of participants with greater potential for exposure provided little evidence of increased risks, although the numbers of men involved were smaller and the statistical power was therefore less. Among other types of cancer, only for liver cancer incidence was there evidence of differences in rates between participants and controls in both the earlier and in the additional period of follow up. Mortality rates among test participants from causes other than cancer were generally similar to those among the controls. CONCLUSIONS: Overall levels of mortality and cancer incidence in UK nuclear weapons test participants have continued to be similar to those in a matched control group, and overall mortality has remained lower than expected from national rates. There was no evidence of an increased raised risk of multiple myeloma among test participants in recent years, and the suggestion in the first analysis of this study of a raised myeloma risk is likely to have been a chance finding. There was some evidence of a raised risk of leukaemia other than CLL among test participants relative to controls, particularly in the early years after the tests, although a small risk may have persisted more recently. This could be a chance finding, in view of low rates among the controls and the generally small radiation doses recorded for test participants. However, the possibility that test participation caused a small absolute risk of leukaemia other than CLL cannot be ruled out.

Modelling lung tumour risk in radon-exposed uranium miners using generalizations of the two-mutation model of Moolgavkar, Venzon and Knudson.

PURPOSES: To model radon-induced lung cancer in uranium miners using a quasi-biological model of carcinogenesis. MATERIALS AND METHODS: Fitting of generalizations of the stochastic two-mutation carcinogenesis model of Moolgavkar, Venzon and Knudson to a case-control dataset nested within the cohort and to the full cohort of lung cancer mortality in the Colorado Plateau uranium miners, taking account of exposure to cigarette smoke and to radon daughters. RESULTS: Models with three mutations gave adequate descriptions of the time and age patterns of radon-daughter-induced excess lung tumour mortality. The overall fit of the two-mutation model to the case-control data was somewhat worse than that of the three-mutation model. For both the optimal two- and three-mutation models radon daughters and cigarette smoke were assumed to act on the first mutation rate. In the optimal two-mutation model, radon daughters also modified the intermediate cell death or differentiation rate. In the optimal three-mutation model, radon daughters modified the second mutation rate. In all models, the action of radon daughters and cigarette smoke was markedly non-linear, particularly in their action on the mutation rates. The optimal two- and three-mutation models fitted to the cohort data were of slightly different form to those fitted to the case-control data. The model fits to the cohort data are preferred to those to the case-control data on grounds of plausibility. CONCLUSIONS: Quasi-biological carcinogenesis models with three mutations give adequate descriptions of the time and age patterns of radon-daughter-induced excess lung tumour mortality. The overall fit of the two-mutation model is somewhat worse than that of the three-mutation model.

Single, brief exposure to a 50 Hz magnetic field does not affect the performance of an object recognition task in adult mice.

A number of studies have shown that power frequency magnetic fields may affect spatial memory functions in rodents. An experiment was performed using a spontaneous object recognition task to investigate if nonspatial working memory was similarly affected. Memory changes in adult, male C57BL/6J mice were assessed by measuring the relative time within which the animals explored familiar or novel stimulus objects. Between initial testing and retesting, the animals were exposed for 45 min to a 50 Hz magnetic field at either 7.5 microT, 75 microT or 0.75 mT. Other animals were sham-exposed with ambient fields of less than 50 nT. No significant field-dependent effects on the performance of the task were observed at any flux density (for all measures, P > 0.05). These data provide no evidence to suggest that nonspatial working memory was affected in mice by acute exposure to an intense 50 Hz magnetic field.

Quantification of Clostridium botulinum toxin gene expression by competitive reverse transcription-PCR.

Clostridium botulinum produces a characteristic botulinum neurotoxin which can cause an often fatal neuroparalytic condition known as botulism. Although food-borne botulism is rare, critical screening by food companies is necessary to ensure that food products are safe. At present, the food industry assesses the risks of botulinum neurotoxin production by challenge testing to check any new food products and to check the efficacy of new storage regimes. Challenge testing involves artificial introduction of defined strains of microorganisms into food, and microbial growth and possible toxin production are then monitored. Botulinum toxin is normally analyzed by using the mouse bioassay. However, the mouse bioassay is expensive, slow, and politically sensitive because of animal rights issues. In this paper we describe adaptation of a new assay, competitive reverse transcription-PCR (RT-PCR), to monitor botulinum neurotoxin production. This method accurately measures the level of toxin-encoding mRNA in C. botulinum cells. Measurement of mRNA should provide a good indication of gene expression as mRNA is turned over rapidly in bacterial cells. In addition, the method is rapid, specific, and sensitive. The competitive RT-PCR method was developed to examine C. botulinum E VH toxin gene expression and was used to investigate the level of toxin production by C. botulinum E VH when the organism was grown in two different types of broth. The results which we obtained with the competitive RT-PCR method demonstrated that this method is more rapid and more sensitive than the mouse bioassay.

Low-level exposure to pulsed 900 MHz microwave radiation does not cause deficits in the performance of a spatial learning task in mice.

There is some concern that short-term memory loss or other cognitive effects may be associated with the use of mobile cellular telephones. In this experiment, the effect of repeated, acute exposure to a low intensity 900 MHz radiofrequency (RF) field pulsed at 217 Hz was explored using an appetitively-motivated spatial learning and working memory task. Adult male C57BL/6J mice were exposed under far field conditions in a GTEM cell for 45 min each day for 10 days at an average whole-body specific energy absorption rate (SAR) of 0.05 W/kg. Their performance in an 8-arm radial maze was compared to that of sham-exposed control animals. All behavioral assessments were performed without handlers having knowledge of the exposure status of the animals. Animals were tested in the maze immediately following exposure or after a delay of 15 or 30 min. No significant field-dependent effects on performance were observed in choice accuracy or in total times to complete the task across the experiment. These results suggest that exposure to RF radiation simulating a digital wireless telephone (GSM) signal under the conditions of this experiment does not affect the acquisition of the learned response. Further studies are planned to explore the effects of other SARs on learned behavior. Bioelectromagnetics 21:151-158, 2000. Published 2000 Wiley-Liss, Inc.

50 Hz magnetic field exposure alters onset of S-phase in normal human fibroblasts.

This study was undertaken to investigate whether power frequency magnetic fields can affect the kinetics of cell cycle progression in exposed human cells. To achieve this, cultures of normal human fibroblasts were synchronised in the G(0) phase of the cell cycle and exposed to 50 Hz magnetic fields at a range of flux densities. Progression through the cycle was monitored by examining the timing of entry into S phase, as characterised by the onset of DNA synthesis. Simultaneous positive controls were exposed to human recombinant fibroblast growth factor to demonstrate that the system was responsive to external stimuli. Exposure to magnetic fields at 20 and 200 microT induced a small but significant increase in the length of the G(1) phase of the cell cycle. However, exposure at higher flux densities of 2 and 20 mT had no significant effect. These results are discussed in relation to weak magnetic field effects on free radical concentration.

Occupational radiation exposure and mortality: second analysis of the National Registry for Radiation Workers.

The National Registry for Radiation Workers (NRRW) is the largest epidemiological study of UK radiation workers. Following the first analysis published in 1992, a second analysis has been conducted using an enlarged cohort of 124,743 workers, updated dosimetry and personal data for some workers, and a longer follow-up. Overall levels of mortality were found to be less than those expected from national rates; the standardised mortality ratio for all causes was 82, increasing to 89 after adjusting for social class. This 'healthy worker effect' was particularly strong for lung cancer and for some smoking-related non-malignant diseases. Analysis of potential radiation effects involved testing for any trend in mortality risk with external dose, after adjusting for likely confounding factors. For leukaemia, excluding chronic lymphatic leukaemia (CLL), the central estimate of excess relative risk (ERR) per Sv was similar to that estimated for the Japanese atomic bomb survivors at low doses (without the incorporation of a dose-rate correction factor); the corresponding 90% confidence limits for this trend were tighter than in the first analysis, ranging from just under four times the risk estimated at low doses from the Japanese atomic bomb survivors to about zero. For the grouping of all malignancies other than leukaemia, the central estimate of the trend in risk with dose was closer to zero than in the first analysis; also, the 90% confidence limits were tighter than before and included zero. Since results for lung cancer and non-malignant smoking-related diseases suggested the possibility of confounding by smoking, an examination was made, as in the first analysis, of all malignancies other than leukaemia and lung cancer. In this instance the central estimate of the ERR per Sv was similar to that from the A-bomb data (without the incorporation of a dose-rate correction factor), with a 90% confidence interval ranging from about four times the A-bomb value to less than zero. For multiple myeloma there was an indication of an increasing trend in risk with external dose (p = 0.06), although the evidence for this trend disappeared after omitting workers monitored for exposure to internal emitters. The second NRRW analysis provides stronger inferences than the first on occupational radiation exposure and cancer mortality; the 90% confidence intervals for the risk per unit dose are tighter than before, and now exclude values which are greater than four times those seen among the Japanese A-bomb survivors, although they are also generally consistent with an observation of no raised risk. Furthermore, there is evidence, of borderline statistical significance, of an increasing risk for leukaemia excluding CLL, and, as with solid cancers, the data are consistent with the A-bomb findings.