Influence of the external and internal radioactive contamination of the body and the clothes on the results of the thyroidal 131I measurements conducted in Belarus after the Chernobyl accident-Part 2: Monte Carlo simulation of response of detectors near the thyroid.

This paper describes the calculation of the response of the most common types of radiation detectors that were used within the first few weeks after the Chernobyl accident to determine the activity of 131I in the thyroids of Belarusian subjects of an epidemiologic study of thyroid cancer. The radiation detectors, which were placed against the necks of the subjects, measured the exposure rates due to the emission of gamma rays resulting from the radioactive decay of 131I in their thyroids. Because of the external and internal radioactive contamination of the monitored subjects, gamma radiation from many radionuclides in various locations contributed to the exposure rates recorded by the detectors. To estimate accurately the contribution from gamma rays emitted from various internal and external parts of the body, the calibration factors of the radiation detectors, expressed in kBq per µR h- 1, were calculated, by means of Monte Carlo simulation, for external irradiation from unit activities of 17 radionuclides located on 19 parts of the body, as well as for internal irradiation from the same 17 radionuclides in the lungs, from caesium radionuclides distributed uniformly in the whole body, and from 131I in the thyroid. The calculations were performed for six body sizes, representative of the age range of the subjects. In a companion paper, the levels of external and internal contamination of the body were estimated for a variety of exposure conditions. The results presented in the two papers were combined to calculate the 131I activities in the thyroids of all 11,732 Belarusian study subjects of an epidemiologic study of thyroid cancer and, in turn, their thyroid doses.

Effects of artificial light at night on human health: A literature review of observational and experimental studies applied to exposure assessment.

It has frequently been reported that exposure to artificial light at night (ALAN) may cause negative health effects, such as breast cancer, circadian phase disruption and sleep disorders. Here, we reviewed the literature assessing the effects of human exposure to ALAN in order to list the health effects of various aspects of ALAN. Several electronic databases were searched for articles, published through August 2014, related to assessing the effects of exposure to ALAN on human health; these also included the details of experiments on such exposure. A total of 85 articles were included in the review. Several observational studies showed that outdoor ALAN levels are a risk factor for breast cancer and reported that indoor light intensity and individual lighting habits were relevant to this risk. Exposure to artificial bright light during the nighttime suppresses melatonin secretion, increases sleep onset latency (SOL) and increases alertness. Circadian misalignment caused by chronic ALAN exposure may have negative effects on the psychological, cardiovascular and/or metabolic functions. ALAN also causes circadian phase disruption, which increases with longer duration of exposure and with exposure later in the evening. It has also been reported that shorter wavelengths of light preferentially disturb melatonin secretion and cause circadian phase shifts, even if the light is not bright. This literature review may be helpful to understand the health effects of ALAN exposure and suggests that it is necessary to consider various characteristics of artificial light, beyond mere intensity.

The distribution of the number of alpha hits per target cell: a new parameter to improve risk assessment for cancer induction using ICRP models.

Doses are calculated from the total energy deposited within the different target regions of the organism. After inhalation exposure, only a few particles can be deposited within the respiratory tract that induces a heterogeneous dose distribution. A decrease in risk for lung tumours induction associated to the presence of hot spots has been reported. This was partly explained by a decrease in the transformation rate per gray when cells received more than one alpha hit. This study provides an estimate of the distribution of alpha hits per target cell of the extra thoracic region (ET2), after inhalation exposure to 238UO2, 239PuO2 or 238PuO2, obtained by a stochastic application of the biokinetic and dosimetric ICRP models. After exposure to one annual limit of intake, homogeneous irradiation of the target cells is observed for 238UO2, whereas, for PuO2, most of the dose is due to cells receiving daily tens or even hundreds of alpha hits. This underlines the uncertainties in risk assessment associated with a dose rate effect.

Therapeutic efficacy as predicted by quantitative assessment of murine RIF-1 tumour pH and phosphorous metabolite response during hyperthermia: an in vivo 31P NMR study.

Described herein are the initial findings from an 'in-magnet' 31P NMR compatible hyperthermia system capable of concurrently heating and monitoring the metabolic response of murine tumours; the murine radiation induced fibrosarcoma (RIF-1) was employed for these studies. At thermal doses sufficient to raise tumour temperature to 41.5 and 43 degrees C for a period of 30 min, a marked and rapid decrease in nucleoside triphosphate concentration and in pH was observed during the heating period, while inorganic phosphate concentration increased significantly but more gradually. These 31P NMR determined metabolic indices remained depressed/elevated throughout a 1.5 h post-hyperthermia monitoring period. Importantly, these metabolic indices correlated significantly with specific growth delay. This suggests a possible role for NMR spectroscopy in early assessment, and perhaps control, of therapeutic response to hyperthermia.