Cataracts among Chernobyl Clean-up Workers: Implications Regarding Permissible Eye Exposures

ICRP publication 118: ICRP statement on tissue reactions and early and late effects of radiation in normal tissues and organs--threshold doses for tissue reactions in a radiation protection context

This report provides a review of early and late effects of radiation in normal tissues and organs with respect to radiation protection. It was instigated following a recommendation in Publication 103 (ICRP, 2007), and it provides updated estimates of 'practical' threshold doses for tissue injury defined at the level of 1% incidence. Estimates are given for morbidity and mortality endpoints in all organ systems following acute, fractionated, or chronic exposure. The organ systems comprise the haematopoietic, immune, reproductive, circulatory, respiratory, musculoskeletal, endocrine, and nervous systems; the digestive and urinary tracts; the skin; and the eye. Particular attention is paid to circulatory disease and cataracts because of recent evidence of higher incidences of injury than expected after lower doses; hence, threshold doses appear to be lower than previously considered. This is largely because of the increasing incidences with increasing times after exposure. In the context of protection, it is the threshold doses for very long follow-up times that are the most relevant for workers and the public; for example, the atomic bomb survivors with 40-50years of follow-up. Radiotherapy data generally apply for shorter follow-up times because of competing causes of death in cancer patients, and hence the risks of radiation-induced circulatory disease at those earlier times are lower. A variety of biological response modifiers have been used to help reduce late reactions in many tissues. These include antioxidants, radical scavengers, inhibitors of apoptosis, anti-inflammatory drugs, angiotensin-converting enzyme inhibitors, growth factors, and cytokines. In many cases, these give dose modification factors of 1.1-1.2, and in a few cases 1.5-2, indicating the potential for increasing threshold doses in known exposure cases. In contrast, there are agents that enhance radiation responses, notably other cytotoxic agents such as antimetabolites, alkylating agents, anti-angiogenic drugs, and antibiotics, as well as genetic and comorbidity factors. Most tissues show a sparing effect of dose fractionation, so that total doses for a given endpoint are higher if the dose is fractionated rather than when given as a single dose. However, for reactions manifesting very late after low total doses, particularly for cataracts and circulatory disease, it appears that the rate of dose delivery does not modify the low incidence. This implies that the injury in these cases and at these low dose levels is caused by single-hit irreparable-type events. For these two tissues, a threshold dose of 0.5Gy is proposed herein for practical purposes, irrespective of the rate of dose delivery, and future studies may elucidate this judgement further.

Radiation safety for anesthesiologists

PURPOSE OF REVIEW

To review the recent literature on the implications of occupational radiation exposure in anesthesia practice.

RECENT FINDINGS

Wide variation and lack of reduction in operator doses of medical radiation strongly suggests that more attention must be paid to the factors influencing radiation dose exposure. The eye is likely the most sensitive organ for radiation injury. Radiation-related cataract formation might be a stochastic effect. Operators are strongly advised to use eye protection at all times. Safe medical radiation ophthalmic dose limits are currently under review and are likely to be lowered. Current data do not suggest a significant risk to the fetus for pregnant women working in the interventional radiology suite as long as proper monitoring and radiation safety measures are implemented.

SUMMARY

Radiation is increasingly utilized in medicine for diagnostic and therapeutic procedures. Anesthesia providers may become exposed to unsafe doses while providing high-quality patient care. Understanding of the physical principles, the sources of radiation exposure, the potential risks, and safe practices helps to minimize the exposure risk and its potential deleterious effects to the anesthesia team.

[The occupational radiation-induced cataract in five industrial radiographers]

The industrial uses of ionizing radiation in Tunisia are expanding, especially in industry and most particularly in the nondestructive testing of welds. Thus workers operating in the non-destructive testing of welds may develop a radiation-induced cataract varying in time to onset depending on the dose.

OBJECTIVES

To describe the characteristics of the radiation-induced cataract in patients exposed to ionizing radiation, determine the risk factors of radiation-induced cataracts.

METHODS

This was an anamnestic, clinical, and environmental study of five cases of radiation-induced cataract in workers employed in non-destructive testing of welds.

RESULTS

This series of five cases had a mean age of 30.2 years and 5.53 years of work experience, ranging from 14 months to 15 years. All the patients were male and industrial radiographers specialized in nondestructive testing of welds. The average duration of exposure to ionizing radiation was 5.53 years. None of the patients had worn protective gear such as eye goggles. The ophthalmic check-up for the five special industrial radiographers showed punctuate opacities in three cases, punctiform opacities in one eye in one case, and phacosclerosis with bilateral lens multiple crystalline stromal opacities in a case of micro-lens opacities in both eyes with opalescence of both eyes in one case. These cataracts had been declared as occupational diseases.

CONCLUSION

The value of a specialized ophthalmologic surveillance among these workers and the early diagnosis of lens opacities must be emphasized.

Determination of minimum effective height of transparent radiation face shielding for fluoroscopy

During interventional procedures, the vast majority of scatter radiation originates from the patient and table and travels in all directions in straight lines. Because the operator's head is much higher than the patient and at an angle upward and to the side of the patient (not directly above), the scatter received by the operator's head is projected in an upward angle. Thus a face shield could potentially be lower than the object it is shielding, e.g., below the eyes. This principle may be used as an advantage to design the lowest shield that effectively protects the head while providing optimum vision, appearance, acoustics, low weight, and sense of openness. A flat acrylic plate shield, 0.5 mm Pb equivalence, was suspended vertically in front of a 451P dosimeter. A phantom patient created scatter in an interventional suite while the dosimeter was placed at the level of the crowns of different operators' heads. Many different configurations were tested to determine which ones would provide effective shielding. The results confirmed that the top of the shield may reside several centimeters below the vertical height of the dosimeter (operator's crown), allowing line of sight to monitor above the shield, and still provide effective shielding equivalent to when the dosimeter is positioned directly behind the center of the shield. The image receptor functioned as an effective shield against scatter. Factors increasing the minimum height of effective shielding included shorter operator, opposite oblique projection of image receptor, and shield closer to the face (in horizontal direction).

Radiation and cataract

When this paper was about to go to press, the International Commission on Radiological Protection released a statement recommending a change in the threshold dose for the eye lens and dose limits for eye for occupationally exposed persons. It is clear that the earlier published threshold for radiation cataract is no longer valid. Epidemiological studies among Chernobyl clean-up workers, A bomb survivors, astronauts, residents of contaminated buildings, radiological technicians and recent surveys of staff in interventional rooms indicate that there is an increased incidence of lens opacities at doses below 1 Gy. Nevertheless, eye lens dosimetry is at a primitive stage and needs to be developed further. Despite uncertainties concerning dose threshold and dosimetry, it is possible to significantly reduce the risk of radiation cataract through the use of appropriate eye protection. By increasing awareness among those at risk and better adoption and increased usage of protective measures, radiation cataract can become preventable despite lowering of dose limits.

Significant reduction in dental cone beam computed tomography (CBCT) eye dose through the use of leaded glasses

OBJECTIVE

In light of the increased recognition of the potential for lens opacification after low-dose radiation exposures, we investigated the effect of leaded eyeglasses worn during dental cone-beam computerized tomography (CBCT) procedures on the radiation absorbed dose to the eye and suggest simple methods to reduce risk of radiation cataract development.

STUDY DESIGN

Dose measurements were conducted with the use of 3 anthropomorphic phantoms: male (Alderson radiation therapy phantom), female (CIRS), and juvenile male (CIRS). All exposures were performed on the same dental CBCT machine (Imtec, Ardmore, OK) using 2 different scanning techniques but with identical machine parameters (120 kVp, 3.8 mA, 7.8 s). Scans were performed with and without leaded glasses and repeated 3 times. All measurements were recorded using calibrated thermoluminescent dosimeters and optical luminescent dosimetry.

RESULTS

Leaded glasses worn by adult and pediatric patients during CBCT scans may reduce radiation dose to the lens of the eye by as much as 67% (from 0.135 ± 0.004 mGy to 0.044 ± 0.002 mGy in pediatric patients).

CONCLUSIONS

Leaded glasses do not appear to have a deleterious effect on the image quality in the area of clinical significance for dental imaging.

The risk of radiation exposure to the eyes of the interventional pain physician

It is widely accepted that the use of medical imaging continues to grow across the globe as does the concern for radiation safety. The danger of lens opacities and cataract formation related to radiation exposure is well documented in the medical literature. However, there continues to be controversy regarding actual dose thresholds of radiation exposure and whether these thresholds are still relevant to cataract formation. Eye safety and the risk involved for the interventional pain physician is not entirely clear. Given the available literature on measured radiation exposure to the interventionist, and the controversy regarding dose thresholds, it is our current recommendation that the interventional pain physician use shielded eyewear. As the breadth of interventional procedures continues to grow, so does the radiation risk to the interventional pain physician. In this paper, we attempt to outline the risk of cataract formation in the scope of practice of an interventional pain physician and describe techniques that may help reduce them.

The Chernobyl accident--an epidemiological perspective

Twenty-five years have passed since radioactive releases from the Chernobyl nuclear accident led to the exposure of millions of people in Europe. Studies of affected populations have provided important new data on the links between radiation and cancer-particularly the risk of thyroid tumours from exposure to iodine isotopes-that are important not only for a fuller scientific understanding of radiation effects, but also for radiation protection. It is now well documented that children and adolescents exposed to radioiodines from Chernobyl fallout have a sizeable dose-related increase in thyroid cancer, with the risk greatest in those youngest at exposure and with a suggestion that deficiency in stable iodine may increase the risk. Data on thyroid cancer risks to other age groups are somewhat less definitive. In addition, there have been reported increases in incidence and mortality from non-thyroid cancers and non-cancer end points. Although some studies are difficult to interpret because of methodological limitations, recent investigations of Chernobyl clean-up workers ('liquidators') have provided evidence of increased risks of leukaemia and other haematological malignancies and of cataracts, and suggestions of an increase in the risk of cardiovascular diseases, following low doses and low dose rates of radiation. Further careful follow-up of these populations, including the establishment and long-term support of life-span study cohorts, could provide additional important information for the quantification of radiation risks and the protection of persons exposed to low doses of radiation.

Eye lens radiation exposure and repeated head CT scans: A problem to keep in mind

OBJECTIVES

The deterministic character of radiation-induced cataract is being called into question, raising the possibility of a risk in patients, especially children, exposed to ionizing radiation in case of repeated head CT-scans. This study aims to estimate the eye lens doses of a pediatric population exposed to repeated head CTs and to assess the feasibility of an epidemiological study.

METHODS

Children treated for a cholesteatoma, who had had at least one CT-scan of the middle ear before their tenth birthday, were included. Radiation exposure has been assessed from medical records and telephone interviews.

RESULTS

Out of the 39 subjects contacted, 32 accepted to participate. A total of 76 CT-scans were retrieved from medical records. At the time of the interview (mean age: 16 years), the mean number of CT per child was 3. Cumulative mean effective and eye lens doses were 1.7mSv and 168mGy, respectively.

CONCLUSION

A relatively high lens radiation dose was observed in children exposed to repeated CT-scans. Due to that exposure and despite the difficulties met when trying to reach patients' families, a large scale epidemiological study should be performed in order to assess the risk of radiation-induced cataracts associated with repeated head CT.

Risk for radiation-induced cataract for staff in interventional cardiology: is there reason for concern?

OBJECTIVES

To examine the prevalence of radiation-associated lens opacities among interventional cardiologists and nurses and correlate with occupational radiation exposure.

BACKGROUND

Interventional cardiology personnel are exposed to relatively high levels of X-rays and based on recent findings of radiation-associated lens opacities in other cohorts, they may be at risk for cataract without use of ocular radiation protection.

METHODS

Eyes of interventional cardiologists, nurses, and age- and sex-matched unexposed controls were screened by dilated slit lamp examination and posterior lens changes graded using a modified Merriam-Focht technique. Individual cumulative lens X-ray exposure was calculated from responses to a questionnaire and personal interview.

RESULTS

The prevalence of radiation-associated posterior lens opacities was 52% (29/56, 95% CI: 35-73) for interventional cardiologists, 45% (5/11, 95% CI: 15-100) for nurses, and 9% (2/22, 95% CI: 1-33) for controls. Relative risks of lens opacity was 5.7 (95% CI: 1.5-22) for interventional cardiologists and 5.0 (95% CI: 1.2-21) for nurses. Estimated cumulative ocular doses ranged from 0.01 to 43 Gy with mean and median values of 3.4 and 1.0 Gy, respectively. A strong dose-response relationship was found between occupational exposure and the prevalence of radiation-associated posterior lens changes.

CONCLUSIONS

These findings demonstrate a dose dependent increased risk of posterior lens opacities for interventional cardiologists and nurses when radiation protection tools are not used. While study of a larger cohort is needed to confirm these findings, the results suggest ocular radio-protection should be utilized.

Doses to operators during interventional radiology procedures: focus on eye lens and extremity dosimetry

The present study is focused on the personnel doses during several types of interventional radiology procedures. Apart from the use of the official whole body dosemeters (thermoluminescence dosemeter type), measurements were performed to the extremities and the eyes using thermoluminescent loose pellets. The mean doses per kerma area product were calculated for the monitored anatomic regions and for the most frequent types of procedures. Higher dose values were measured during therapeutic procedures, especially embolisations. The maximum recorded doses during a single procedure were 1.8 mSv to the finger (nephrostomy), 2.1 mSv to the wrist (liver chemoembolisation), 0.6 mSv to the leg (brain embolisation) and 2.4 mSv to the eye (brain embolisation). The annual doses estimated for the operator with the highest workload according to the measurements and the system's log book were 90.4 mSv to the finger, 107.9 mSv to the wrist, 21.6 mSv to the leg and 49.3 mSv to the eye. Finally, the effect of the beam angulation (i.e. projection) and shielding equipment on the personnel doses was evaluated. The measurements were performed within the framework of the ORAMED (Optimization of RAdiation Protection for MEDical staff) project.

Eye lens dosimetry: task 2 within the ORAMED project

The ORAMED (Optimization of RAdiation protection for MEDical staff) project is funded by EU-EURATOM within the 7° Framework Programme. Task 2 of the project is devoted to study the dose to the eye lens. The study was subdivided into various topics, starting from a critical revision of the operational quantity H(p)(3), with the corresponding proposal of a cylindrical phantom simulating as best as possible the head in which the eyes are located, the production of a complete set of air kerma to dose equivalent conversion coefficients for photons from 10 keV to 10 MeV, and finally, the optimisation of the design of a personal dosemeter well suited to respond in terms of H(p)(3). The paper presents some preliminary results.

Comparing strategies for operator eye protection in the interventional radiology suite

PURPOSE

To evaluate the impact of common radiation-shielding strategies, used alone and in combination, on scattered dose to the fluoroscopy operator's eye.

MATERIALS AND METHODS

With an operator phantom positioned at the groin, upper abdomen, and neck, posteroanterior low-dose fluoroscopy was performed at the phantom patient's upper abdomen. Operator lens radiation dose rate was recorded with a solid-state dosimeter with and without a leaded table skirt, nonleaded and leaded (0.75 mm lead equivalent) eyeglasses, disposable tungsten-antimony drapes (0.25 mm lead equivalent), and suspended and rolling (0.5 mm lead equivalent) transparent leaded shields. Lens dose measurements were also obtained in right and left 15° anterior obliquities with the operator at the upper abdomen and during digital subtraction angiography (two images per second) with the operator at the patient's groin. Each strategy's shielding efficacy was expressed as a reduction factor of the lens dose rate compared with the unshielded condition.

RESULTS

Use of leaded glasses alone reduced the lens dose rate by a factor of five to 10; scatter-shielding drapes alone reduced the dose rate by a factor of five to 25. Use of both implements together was always more protective than either used alone, reducing dose rate by a factor of 25 or more. Lens dose was routinely undetectable when a suspended shield was the only barrier during low-dose fluoroscopy.

CONCLUSIONS

Use of scatter-shielding drapes or leaded glasses decreases operator lens dose by a factor of five to 25, but the use of both barriers together (or use of leaded shields) provides maximal protection to the interventional radiologist's eye.

Clinical radiation management for fluoroscopically guided interventional procedures

The primary goal of radiation management in interventional radiology is to minimize the unnecessary use of radiation. Clinical radiation management minimizes radiation risk to the patient without increasing other risks, such as procedural risks. A number of factors are considered when estimating the likelihood and severity of patient radiation effects. These include demographic factors, medical history factors, and procedure factors. Important aspects of the patient's medical history include coexisting diseases and genetic factors, medication use, radiation history, and pregnancy. As appropriate, these are evaluated as part of the preprocedure patient evaluation; radiation risk to the patient is considered along with other procedural risks. Dose optimization is possible through appropriate use of the basic features of interventional fluoroscopic equipment and intelligent use of dose-reducing technology. For all fluoroscopically guided interventional procedures, it is good practice to monitor radiation dose throughout the procedure and record it in the patient's medical record. Patients who have received a clinically significant radiation dose should be followed up after the procedure for possible deterministic effects. The authors recommend including radiation management as part of the departmental quality assurance program.

Unprotected operator eye lens doses in oncologic interventional radiology are clinically significant: estimation from patient kerma-area-product data

PURPOSE

To correlate operator lens dose to patient-delivered kerma-area-product (P(KA)) to evaluate the usefulness of P(KA) as a surrogate for operator eye dose if collar monitor readings are unavailable or deemed unreliable, and to evaluate if unprotected lens dose is clinically significant.

MATERIALS AND METHODS

A retrospective review of peak skin doses for consecutive interventional radiology procedures performed during 2006 that had P(KA) estimates recorded was performed. Unshielded operator lens dose equivalents (LDE) were obtained from dosimetry monitors worn outside the collar shield of operating interventional radiologists. Operator LDE were correlated with patient P(KA).

RESULTS

Average LDE for 2006 was 35.7 mSv ± 32.7 (range 5.2-89.9 mSv). Patient-delivered P(KA) correlated directly with LDE, where 1 Gy cm(2) to the patient resulted in an average of 4.2 μSv to the unprotected eyes of the primary operator (r(2) = 0.7).

CONCLUSIONS

P(KA) may be useful as a surrogate measure of operator LDE if collar monitor readings are unavailable or deemed unreliable. For this study, the dose-effect threshold for cataract formation could be surpassed for some physicians within 11 years if lens dose-mitigating strategies are not routinely employed.

Occupational cataracts and lens opacities in interventional cardiology (O'CLOC study): are X-Rays involved? Radiation-induced cataracts and lens opacities

Background

The eye is well known to be sensitive to clearly high doses (>2 Gy) of ionizing radiation. In recent years, however, cataracts have been observed in populations exposed to lower doses. Interventional cardiologists are repeatedly and acutely exposed to scattered ionizing radiation (X-rays) during the diagnostic and therapeutic procedures they perform. These "low" exposures may cause damage to the lens of the eye and induce early cataracts, known as radiation-induced cataracts. The O'CLOC study (Occupational Cataracts and Lens Opacities in interventional Cardiology) was designed to test the hypothesis that interventional cardiologists, compared with an unexposed reference group of non-interventional cardiologists, have an increased risk of cataracts.

Method/Design

The O'CLOC study is a cross-sectional study that will include a total of 300 cardiologists aged at least 40 years: one group of exposed interventional cardiologists and another of non-interventional cardiologists. The groups will be matched for age and sex. Individual information, including risk factors for cataracts (age, diabetes, myopia, etc.), will be collected during a telephone interview. A specific section of the questionnaire for the exposed group focuses on occupational history, including a description of the procedures (type, frequency, radiation protection tool) used. These data will be used to classify subjects into "exposure level" groups according to cumulative dose estimates. Eye examinations for all participants will be performed to detect cataracts, even in the early stages (lens opacities, according to LOCS III, the international standard classification). The analysis will provide an estimation of the cataract risk in interventional cardiology compared with the unexposed reference group, while taking other risk factors into account. An analysis comparing the risks according to level of exposure is also planned.

Discussion

This epidemiological study will provide further evidence about the potential risk of radiation-induced cataracts at low doses and contribute to cardiologists' awareness of the importance of radiation protection.

Trial Registration

NCT01061463

Epidemiological studies of cataract risk at low to moderate radiation doses: (not) seeing is believing

The prevailing belief for some decades has been that human radiation-related cataract occurs only after relatively high doses; for instance, the ICRP estimates that brief exposures of at least 0.5-2 Sv are required to cause detectable lens opacities and 5 Sv for vision-impairing cataracts. For protracted exposures, the ICRP estimates the corresponding dose thresholds as 5 Sv and 8 Sv, respectively. However, several studies, especially in the last decade, indicate that radiation-associated opacities occur at much lower doses. Several studies suggest that medical or environmental radiation exposure to the lens confers risk of opacities at doses well under 1 Sv. Among Japanese A-bomb survivors, risks for cataracts necessitating lens surgery were seen at doses under 1 Gy. The confidence interval on the A-bomb dose threshold for cataract surgery prevalence indicated that the data are compatible with a dose threshold ranging from none up to only 0.8 Gy, similar to the dose threshold for minor opacities seen among Chernobyl clean-up workers with primarily protracted exposures. Findings from various studies indicate that radiation risk estimates are probably not due to confounding by other cataract risk factors and that risk is seen after both childhood and adult exposures. The recent data are instigating reassessments of guidelines by various radiation protection bodies regarding permissible levels of radiation to the eye. Among the future epidemiological research directions, the most important research need is for adequate studies of vision-impairing cataract after protracted radiation exposure.

Review and evaluation of updated research on the health effects associated with low-dose ionising radiation

While radiation health risks at low doses have traditionally been estimated from high-dose studies, we have reviewed recent literature and concluded that the mechanisms of action for many biological endpoints may be different at low doses from those observed at high doses; that acute doses <100 mSv may be too small to allow epidemiological detection of excess cancers given the background of naturally occurring cancers; that low-dose radiation research should use holistic approaches such as systems-based methods to develop models that define the shape of the dose-response relationship; and that these results should be combined with the latest epidemiology to produce a comprehensive understanding of radiation effects that addresses both damage, likely with a linear effect, and response, possibly with non-linear consequences. Continued research is needed to understand how radiobiology and epidemiology advances should be used to effectively model radiation worker risks.

Lens exposure during brain scans using multidetector row CT scanners: methods for estimation of lens dose

BACKGROUND AND PURPOSE

Some recent studies on radiation lens injuries have indicated much lower dose thresholds than specified by the current radiation protection guidelines. The purpose of this research was to measure the lens dose during brain CT scans with multidetector row CT and to assess methods for estimating the lens dose.

MATERIALS AND METHODS

With 8 types of multidetector row CT scanners, both axial and helical scans were obtained for the head part of a human-shaped phantom by using normal clinical settings with the orbitomeatal line as the baseline. We measured the doses on both eyelids by using an RPLGD during whole-brain scans including the orbit with the starting point at the level of the inferior orbital rim. To assess the effect of the starting points on the lens doses, we measured the lens doses by using 2 other starting points for scanning (the orbitomeatal line and the superior orbital rim).

RESULTS

The CTDIvols and the lens doses during whole-brain CT including the orbit were 50.9-113.3 mGy and 42.6-103.5 mGy, respectively. The ratios of lens dose to CTDIvol were 80.6%-103.4%. The lens doses decreased as the starting points were set more superiorly. The lens doses during scans from the superior orbital rim were 11.8%-20.9% of the doses during the scans from the inferior orbital rim.

CONCLUSIONS

CTDIvol can be used to estimate the lens dose during whole-brain CT when the orbit is included in the scanning range.

Radiation cataractogenesis: a review of recent studies

The lens of the eye is recognized as one of the most radiosensitive tissues in the human body, and it is known that cataracts can be induced by acute doses of less than 2 Gy of low-LET ionizing radiation and less than 5 Gy of protracted radiation. Although much work has been carried out in this area, the exact mechanisms of radiation cataractogenesis are still not fully understood. In particular, the question of the threshold dose for cataract development is not resolved. Cataracts have been classified as a deterministic effect of radiation exposure with a threshold of approximately 2 Gy. Here we review the combined results of recent mechanistic and human studies regarding induction of cataracts by ionizing radiation. These studies indicate that the threshold for cataract development is certainly less than was previously estimated, of the order of 0.5 Gy, or that radiation cataractogenesis may in fact be more accurately described by a linear, no-threshold model.

Occupational health hazards in the interventional laboratory: time for a safer environment

This document is a consensus statement by the major American societies of physicians who work in the interventional laboratory environment. It reviews available data on the prevalence of occupational health risks and summarizes ongoing epidemiologic studies designed to further elucidate these risks. Its purpose is to affirm that the interventional laboratory poses workplace hazards that must be acknowledged, better understood, and mitigated to the greatest extent possible. Vigorous efforts are advocated to reduce these hazards. Interventional physicians and their professional societies, working together with industry, should strive toward minimizing operator radiation exposure, eliminating the need for personal protective apparel, and ending the orthopedic and ergonomic consequences of the interventional laboratory work environment.

Radiation in the workplace-a review of studies of the risks of occupational exposure to ionising radiation

Many individuals are, or have been, exposed to ionising radiation in the course of their work and the epidemiological study of occupationally irradiated groups offers an important opportunity to complement the estimates of risks to health resulting from exposure to radiation that are obtained from other populations, such as the Japanese survivors of the atomic bombings of Hiroshima and Nagasaki in 1945. Moreover, workplace exposure to radiation usually involves irradiation conditions that are of direct relevance to the principal concern of radiological protection: protracted exposure to low level radiation. Further, some workers have been exposed to radioactive material that has been inadvertently taken into the body, and the study of these groups leads to risk estimates derived directly from the experience of those irradiated by these 'internal emitters', intakes of alpha-particle-emitters being of particular interest. Workforces that have been the subject of epidemiological study include medical staff, aircrews, radium dial luminisers, underground hard-rock miners, Chernobyl clean-up workers, nuclear weapons test participants and nuclear industry workers. The first solid epidemiological evidence of the stochastic effects of irradiation came from a study of occupational exposure to medical x-rays that was reported in 1944, which demonstrated a large excess risk of leukaemia among US radiologists; but the general lack of dose records for early medical staff who tended to experience the highest exposures hampers the derivation of risks per unit dose received by medical workers. The instrument dial luminisers who inadvertently ingested large amounts of radium-based paint and underground hard-rock miners who inhaled large quantities of radon and its decay products suffered markedly raised excess risks of, respectively, bone and lung cancers; the miner studies have provided standard risk estimates for radon-induced lung cancer. The large numbers of nuclear industry workers around the world present a possibility of deriving risk coefficients of direct relevance to radiological protection, and the recently published study of workers from 15 countries illustrates what can be achieved by international collaboration. However, it would appear that there are some problems with this study that require attention before reliance can be placed upon the results. Early workers from the Mayak plutonium production facility in Russia were heavily exposed to external sources of penetrating radiation and to plutonium, and appreciable effort has been expended in obtaining dependable risk estimates from this scientifically valuable group of workers. Those occupationally exposed to low levels of radiation also present an opportunity of studying possible somatic health effects other than cancer, such as heart disease and eye cataracts, that are the subject of much discussion at present. Overall, studies of exposure to ionising radiation in the workplace provide a valuable support to studies of those groups exposed under other circumstances, and in some instances (such as exposure to plutonium) effectively offer the only direct source of epidemiological evidence on risks.

Staff radiation doses in interventional cardiology: correlation with patient exposure

In pediatric interventional cardiology, cardiologists need to stay closer to the patient than during adult catheterization, and the use of biplane systems increases the scatter radiation. Occupational radiation risk is rather high, and estimation of lens doses becomes necessary. Deriving factors for assessing these doses from the patient doses displayed in catheterization laboratories can help in preserving staff radiation safety. A biplane X-ray system and polymethylmethacrylate plates of 4 to 20 cm to simulate pediatric patients have been used. Patient entrance dose rates, dose-area product, and doses to the eyes of the cardiologists for the typical operation modes have been measured. Correlations between patient and staff doses have been obtained. Scatter dose rates increase by a factor of 92 from low fluoroscopy to cine acquisition when phantom thickness increases from 4 to 20 cm. Scatter doses increase linearly with dose-area product for all the thicknesses. Administration of 1 Gy x cm(2) to the patient involves 7 microSv to the eyes of the cardiologist (without extra protection). In conclusion, the experimental correlation factors found between phantom and scatter doses allow a fairly good estimation of staff doses from the dosimetric patient data.

Occupational health hazards in the interventional laboratory: time for a safer environment

This document is a consensus statement by the major American societies of physicians who work in the interventional laboratory environment. It reviews available data on the prevalence of occupational health risks and summarizes ongoing epidemiologic studies designed to further elucidate these risks. Its purpose is to affirm that the interventional laboratory poses workplace hazards that must be acknowledged, better understood, and mitigated to the greatest extent possible. Vigorous efforts are advocated to reduce these hazards. Interventional physicians and their professional societies, working together with industry, should strive toward minimizing operator radiation exposure, eliminating the need for personal protective apparel, and ending the orthopedic and ergonomic consequences of the interventional laboratory work environment.

Risk of cataract after exposure to low doses of ionizing radiation: a 20-year prospective cohort study among US radiologic technologists

The study aim was to determine the risk of cataract among radiologic technologists with respect to occupational and nonoccupational exposures to ionizing radiation and to personal characteristics. A prospective cohort of 35,705 cataract-free US radiologic technologists aged 24-44 years was followed for nearly 20 years (1983-2004) by using two follow-up questionnaires. During the study period, 2,382 cataracts and 647 cataract extractions were reported. Cigarette smoking for >or=5 pack-years; body mass index of >or=25 kg/m(2); and history of diabetes, hypertension, hypercholesterolemia, or arthritis at baseline were significantly (p <or= 0.05) associated with increased risk of cataract. In multivariate models, self-report of >or=3 x-rays to the face/neck was associated with a hazard ratio of cataract of 1.25 (95% confidence interval: 1.06, 1.47). For workers in the highest category (mean, 60 mGy) versus lowest category (mean, 5 mGy) of occupational dose to the lens of the eye, the adjusted hazard ratio of cataract was 1.18 (95% confidence interval: 0.99, 1.40). Findings challenge the National Council on Radiation Protection and International Commission on Radiological Protection assumptions that the lowest cumulative ionizing radiation dose to the lens of the eye that can produce a progressive cataract is approximately 2 Gy, and they support the hypothesis that the lowest cataractogenic dose in humans is substantially less than previously thought.