Very high background radiation areas of Ramsar, Iran: preliminary biological studies

People in some areas of Ramsar, a city in northern Iran, receive an annual radiation absorbed dose from background radiation that is up to 260 mSv y(-1), substantially higher than the 20 mSv y(-1) that is permitted for radiation workers. Inhabitants of Ramsar have lived for many generations in these high background areas. Cytogenetic studies show no significant differences between people in the high background compared to people in normal background areas. An in vitro challenge dose of 1.5 Gy of gamma rays was administered to the lymphocytes, which showed significantly reduced frequency for chromosome aberrations of people living in high background compared to those in normal background areas in and near Ramsar. Specifically, inhabitants of high background radiation areas had about 56% the average number of induced chromosomal abnormalities of normal background radiation area inhabitants following this exposure. This suggests that adaptive response might be induced by chronic exposure to natural background radiation as opposed to acute exposure to higher (tens of mGy) levels of radiation in the laboratory. There were no differences in laboratory tests of the immune systems, and no noted differences in hematological alterations between these two groups of people.

The effects of changing atmospheric oxygen concentrations and background radiation levels on radiogenic DNA damage rates

Both background radiation levels and atmospheric oxygen concentrations have changed dramatically over the history of life on earth. Because oxygen has a strong modifying influence on radiogenic mutation rates, these factors must be considered jointly to determine changes in radiogenic mutation rates over time. Using accepted models that describe how both of these parameters have changed through time, we find that radiogenic mutation rates in organisms have fluctuated between about 1.5 to 2.5 times current levels through most of the history of life. The results of this study have interesting implications that may impact our understanding of how modern organisms respond to radiation damage and of models that use molecular clocks to date species divergence times. It is also possible that changing oxygen levels have served to buffer mutation rate changes that result from changes in background radiation levels over time.

Radiation safety at the University of Rochester's Laser Fusion Research Facility

The fusion research conducted at the Laboratory for Laser Energetics requires large amounts of tritium and generates brief but very high, neutron fluxes. This raises a number of radiological concerns that have been satisfactorily addressed via a combination of engineering controls, training, and administrative controls. These problems encountered and our solutions to them are described in this paper.

Radiation safety considerations for large, multi-user laboratories

Many research institutions are adding new laboratory space in the form of large, multi-user rooms with an open architecture. Unfortunately, many of the features that make such rooms attractive to researchers make them difficult to manage from a radiation safety perspective. In particular, coping with radiological incidents and enforcing radiation safety standards are difficult when several research teams share a common room. This paper discusses the problems noted in such laboratories at the University of Rochester and Yale University and describes the manner in which some of these problems have been addressed.

Conducting subsurface soil and groundwater radiological investigations: a case study from the University of Rochester

The University of Rochester performed subsurface soil and groundwater radiological assessments in the vicinity of a research building to investigate for contamination from possible past releases of licensed radioactive materials. During the course of this investigation, our contractors developed candidate well drilling and sampling plans. The University of Rochester selected one of these plans, which was subsequently modified due to unexpected costs associated with the local geology. This paper describes the factors that were considered during the development and implementation of the drilling and sampling plan, as well as other considerations and concepts that are inherent in many environmental investigations.

University of Rochester laboratory inspection checklist

In early 1999, the University of Rochester significantly revised our laboratory inspection program. As part of this revision, we developed a new checklist to be used during laboratory inspections to help promote consistency between inspections and between inspectors.

Determining and reporting fetal radiation exposure from diagnostic radiation

Pregnant women are sometimes exposed to diagnostic ionizing radiation for any number of legitimate medical reasons. When this occurs, it is important to perform an accurate fetal dose estimate using standard methodologies as quickly as possible and to convey this information to the woman's physician, along with a summary of appropriate published medical guidelines. This will provide the physician and the patient with the information necessary to make an informed decision regarding the potential impact of this radiation exposure on the pregnancy. At the same time, it is important to recognize that not all pregnancies end well, and there is a finite chance that legal action could ensue because of this, even if radiation exposure was negligible. For this reason, it is also important to make sure that standard, accepted protocols are followed in calculating radiation exposure and the health physicist provide advice only in his or her areas of competence.

Apparent high tritium intake by a radiation worker at the University of Rochester

On 20 September 1999, a urine sample submitted by a University of Rochester radiation worker was noted to have a count rate of about 759,500 disintegrations per minute (dpm) per milliliter as analyzed on the Radiation Safety Unit (RSU) Packard liquid sintillation counter. The sample was recounted that day with variable results but each time indicating several hundred thousand dpm of activity present. Calculations indicated this corresponded to a whole-body uptake of about 518 MBq (14 nmCi) and a whole-body dose of about 10 msv (1 rem). An investigation indicated it was unlikely for these analytical results to indicate an actual uptake of tritium and suggested the results were most likely due to chemical luminescence in the sample. Accordingly, no dose was assigned to this worker from the exposure.

Calculations of background beta-gamma radiation dose through geologic time

Life on earth is exposed to a background level of ionizing radiation from a number of sources, including beta and gamma radiation from geologic and biologic materials. Radiation dose from geologic emitters has changed because of the chemical evolution of the continental crust, changes in the relative abundances of 235U and 238U, and the radioactive decay of uranium, thorium, and 40K with time. The radiation dose from internal 40K has decreased by a factor of about eight because of changes in the activity concentration of 40K in potassium over the past 4 billion years. Radiation exposure from geologic materials has decreased from about 1.6 mGy y(-1) to 0.66 mGy y(-1) over the past 4 billion years, and radiation exposure to an organism with a potassium concentration of 250 mmol L(-1) has decreased from about 5.5 to about 0.70 mGy y(-1). Accordingly, background radiation exposure from these two sources has dropped from about 7.0 to 1.35 mGy y(-1) during the time life has existed on Earth. The conservative nature of mutation repair mechanisms in modern organisms suggest that these mechanisms may have evolved in the distant past and that organisms may retain some of the capability of efficiently repairing damage from higher radiation levels than exist at present.