Residential exposures to pesticides and childhood leukaemia

Like many chemicals, carcinogenicity of pesticides is poorly characterised in humans, especially in children, so that the present knowledge about childhood leukaemia risk derives primarily from epidemiological studies. Overall, case-control studies published in the last decade have reported positive associations with home use of insecticides, mostly before the child's birth, while findings for herbicides are mixed. Previous studies relied solely on self-reports, therefore lacking information on active ingredients and effects of potential recall bias. Few series to date have examined the influence of children's genetic susceptibility related to transport and metabolism of pesticides. To overcome these limitations, investigators of the Northern California Childhood Leukaemia Study (NCCLS) have undertaken, in collaboration with a multidisciplinary team, a comprehensive assessment of residential pesticide exposure, including: (1) quality control of self-reports; (2) home pesticide inventory and linkage to the Environmental Protection Agency to obtain data on active ingredients; (3) collection and laboratory analyses of approximately 600 home dust samples for over 60 pesticides and (4) geographic information studies using California environmental databases to assess exposure to agricultural pesticides. The NCCLS is also conducting large-scale genotyping to evaluate the role of genes in xenobiotic pathways relevant to the transport and metabolism of pesticides. A better quantification of children's exposures to pesticides at home is critical to the evaluation of childhood leukaemia risk, especially for future gene-environment interaction studies.     

Evaluation of patient doses due to fluoroscopic exposures

The present study measures entrance surface doses of radiation administered to patients during various fluoroscopic procedures using a dose-area product meter as well as the duration of each procedure. A conversion factor for entrance skin dose to patients was calculated. The average dose to patient during the insertion of intravenous hyperalimentation was 10.2 (maximum, 74.0) mGy, during a barium meal, 58.4 (maximum, 184.0) mGy, for endoscopic retrograde cholangio-pancreatography (ERCP), 97.3 (maximum, 376.0) mGy and for a barium enema, 86.1 (maximum, 271.0) mGy. Doses tended to increase in the abdominal domain and when patients undergo not only diagnostic evaluation but also treatment requiring procedures such as drainage. The management of radiation doses determined using a dose-area product meter is very important and that of individual patients is enabled using the Radiation Information System (RIS).     

Biologically driven fractionation of airborne mutagens

Abstract

A three‐level separation scheme applied in the bioassay‐directed search for major airborne mutagenic compounds on inhalable particulate matter has been employed. The biologically “hot” fractions are separated and analyzed chemically or subfractionated to isolate “hot” subfractions which are then chemically analyzed by GC/MS, GC/NCIMS, FTIR, HPLC, Fluorescence and Photodiode Array UV. The mutagenicity assay has involved TA98, TA100, TA98NR and TA98DNP strains. In essence, we are using mutagenicity as our chromatographic detector to pinpoint the most bioactive fractions and compounds in the air which are assumed to be responsible for human health impact, and then identify them as well as assess their reactivity. The comparison of winter and summer samples indicates that the profiles are similar in the two periods. However, levels of polycyclic aromatic hydrocarbons (PAH) are significantly greater in winter as compared to summer. The major mutagenic substances derived from PAH in airborne particulate matter are polar PAH derivatives and the higher contribution of these polar compounds in summer relative to winter suggests that chemical and photochemical reactions during the warm season are important.     

Workplace monitoring for exposures to radon and to other natural sources in Europe: integration of monitoring for internal and external exposures

Part of the action of the EURADOS working group (European Radiation Dosimetry Group) on "Harmonisation of Individual Monitoring in Europe" was to investigate how the results from personal dosemeters for external radiation, from monitoring for internal exposure and from workplace monitoring, can be combined into a complete and consistent system of individual monitoring. To facilitate this work, the "EURADOS questionnaire Q3" relating to radon and other natural sources of radiation in the workplace was distributed to relevant institutes across Europe. A total of 24 countries replied to the questionnaire. This study offers an important overview on actual regulations, national standards and reference levels for protection of employees from radon and other natural sources in different workplace scenarios. Information was also collected on individual monitoring and area monitoring to determine individual doses in workplaces with elevated levels of natural radiation. The article discusses in detail the results obtained showing by country the reference level in workplaces for radon gas and other natural sources. In both instances, exposures in mines, other underground workplaces, industry workplaces/waterworks, offices, schools and day-care homes were considered. The resultant data clearly indicate that there is a need for harmonisation among countries, not least in the areas of regulation and use of reference levels in the workplace.     

Monitoring for exposures to TENORM sources in Vojvodina region

TENORM are found in a wide variety of waste materials, some raw mineral ores and in some consumer products (in trace amounts) where molecules of radionuclides may be bound to specific minerals used in the manufacturing process and can result in increases in radiation exposures to workers and the public. The aim of this paper is to understand this problem and to develop effective ways to protect humans and the environment from harmful exposure to the radiation in TENORM materials in the Vojvodina region. The results of measurement of indoor radon concentration in schools and kindergartens and dose-rate and gamma-spectrometry measurements of the workplace with TENORM materials are presented.     

A study of early Los Alamos internal exposures to plutonium

Internal dose caused by exposure to (239)Pu/(240)Pu is calculated for a group of 210 former Los Alamos workers who participated in the urine bioassay programme during the years 1944-45. An iterative Bayesian procedure is employed, where the distribution of intake amounts resulting from an initial calculation is used to define a prior probability distribution of inhalation intakes for an iterated second calculation. The urine bioassay data from this time period were not of high quality, and the more accurate intake prior tempers the effect of spurious high samples, which were probably caused by sample contamination.     

Evaluation of occupational exposures to natural radiation in the Czech Republic

The Czech approach to limit the occupational exposures to natural radiation is based on the rules given by the Atomic Act and by the Decree of the State Office for Nuclear Safety (SONS) on radiation protection. Workplaces with potential risk of increased exposure to natural sources are specified explicitly. A new method to perform the above-mentioned measurements and to determine the effective doses of workers was proposed in 2005 and accepted by the SONS in 2007. The first experience illustrates its applicability.     

Assessment of personal exposures to optical radiation in large entertainment venues

Workplace exposure to optical radiation from artificial sources is regulated in Europe under the Artificial Optical Radiation Directive 2006/25/EC implemented in the UK as The Control of Artificial Optical Radiation at Work Regulations 2010. The entertainment environment often presents an extremely complex situation for the assessment of occupational exposures. Multiple illumination sources, continuously changing illumination conditions and people moving during performances add further complexity to the assessment. This document proposes a methodology for assessing the risks arising from exposure to optical radiation and presents detailed case studies of practical assessment for two large entertainment venues.     

In vivo EPR dosimetry to quantify exposures to clinically significant doses of ionising radiation

As a result of terrorism, accident or war, populations potentially can be exposed to doses of ionising radiation that could cause direct clinical effects within days or weeks. There is a critical need to determine the magnitude of the exposure to individuals so that those with significant risk can have appropriate procedures initiated immediately, while those without a significant probability of acute effects can be reassured and removed from the need for further consideration in the medical/emergency system. It is extremely unlikely that adequate dosemeters will be worn by the potential victims, and it also will be unlikely that prompt and accurate dose reconstruction at the level of individuals will be possible. Therefore, there is a critical need for a method to measure the dose from radiation-induced effects that occur within the individual. In vivo EPR measurements of radiation-induced changes in the enamel of teeth is a method, perhaps the only such method, which can differentiate among doses sufficiently to classify individuals into categories for treatment with sufficient accuracy to facilitate decisions on medical treatment. In its current state, the in vivo EPR dosemeter can provide estimates of absorbed dose of +/- 0.5 Gy in the range from 1 to >10 Gy. The lower limit and the precision are expected to improve, with improvements in the resonator and the algorithm for acquiring and calculating the dose. In its current state of development, the method is already sufficient for decision-making action for individuals with regard to acute effects from exposure to ionising radiation for most applications related to terrorism, accidents or nuclear warfare.     

Ethical issues in medico-legal exposures

The Medical Exposure Directive (MED) 97/43/Euratom defines medico-legal procedures as 'procedures performed for insurance or legal purposes without a medical indication'. The term 'medico-legal exposures' covers a wide range of possible types of exposures, very different in nature, for which the only feature in common is the fact that the main reason for performing them does not relate directly to the health of the individual being exposed to ionising radiation. The key issue in medico-legal exposures is justification. Balancing the advantages and disadvantages of such exposures is complex because not only can these be difficult to quantify and hence compare, but often the advantage may be to society whereas the disadvantage is usually to an individual. This adds an additional layer of ethical complexity to the problem and one, which requires input from a number of sources beyond the established radiation protection community. Because medico-legal exposures are considered to be medical exposures, they are not subject to dose limits. In medico-legal exposures where the benefit is not necessarily to the individual undergoing the exposure, the question must be asked as to whether or not this is an appropriate framework within which to conduct such exposures. This paper looks at the current situation in Europe, highlighting some of the particular problems that have arisen, and tries to identify the areas, which require further clarification and guidance.     

The use of caffeine to assess high dose exposures to ionising radiation by dicentric analysis

Dicentric analysis is considered as a 'gold standard' method for biological dosimetry. However, due to the radiation-induced mitotic delay or inability to reach mitosis of heavily damaged cells, the analysis of dicentrics is restricted to doses up to 4-5 Gy. For higher doses, the analysis by premature chromosome condensation technique has been proposed. Here, it is presented a preliminary study is presented in which an alternative method to analyse dicentrics after high dose exposures to ionising radiation (IR) is evaluated. The method is based on the effect of caffeine in preventing the G2/M checkpoint allowing damaged cells to reach mitosis. The results obtained indicate that the co-treatment with Colcemid and caffeine increases significantly increases the mitotic index, and hence allows a more feasible analysis of dicentrics. Moreover in the dose range analysed, from 0 to 15 Gy, the dicentric cell distribution followed the Poisson distribution, and a simulated partial-body exposure has been clearly detected. Overall, the results presented here suggest that caffeine has a great potential to be used for dose-assessment after high dose exposure to IR.     

Raman spectroscopy-based metabolomics for differentiating exposures to triazole fungicides using rat urine

Normal Raman spectroscopy was evaluated as a metabolomic tool for assessing the impacts of exposure to environmental contaminants, using rat urine collected during the course of a toxicological study. Specifically, one of three triazole fungicides, myclobutanil, propiconazole, or triadimefon, was administered daily via oral gavage to male Sprague-Dawley rats at doses of 300, 300, or 175 mg/kg, respectively. Urine was collected from all three treatment groups and also from vehicle control rats on day six, following five consecutive days of exposure. Spectra were acquired with a CCD-based dispersive Raman spectrometer, using 785-nm diode laser excitation. To optimize the signal-to-noise ratio, urine samples were filtered through a stirred ultrafiltration cell with a 500 nominal molecular weight limit filter to remove large, unwanted urine components that can degrade the spectrum via fluorescence. However, a subsequent investigation suggested that suitable spectra can be obtained in a high-throughput fashion, with little or no Raman-specific sample preparation. For the sake of comparison, a parallel 1H NMR-based metabolomic analysis was also conducted on the unfiltered samples. Results from multivariate data analysis demonstrated that the Raman method compares favorably with NMR in regard to the ability to differentiate responses from these three contaminants.     

Radiation dosimetry for diagnostic medical exposures

The number and complexity of medical procedures using X rays or radioactive materials are both steadily increasing. As a result, the dose from medical exposures now makes up the largest component of the radiation dose to the population in some developed countries. Key developments include the change from film to digital radiography, the increasing sophistication of interventional radiology allowing more complex procedures and the speed and facilities available with multi-slice computed tomography scanners that have extended the range of applications. It is crucial to have accurate dosimetry to monitor the impact of these developments, to ensure that techniques are optimised, and to provide information on health risk that clinicians can consider when justifying exposures. There are two aspects to dosimetry in radiology, assessment of doses to patients and measurement of equipment performance. The techniques that are used will be described, factors that influence doses and that must be considered when making measurements will be discussed, and future developments will be considered.     

Chromosome aberration analysis in radiotherapy patients and simulated partial body exposures: biological dosimetry for non-uniform exposures

Chromosome aberration analysis was carried out in peripheral blood lymphocytes of cancer patients following radiotherapy of lungs, cervix and spine. Radiotherapy in the pelvic region involving large doses (6 Gy) showed an overdispersed distribution of dicentrics. However, when the doses were fractionated (three fractions of 2 Gy) distribution was found to be near Poisson. Spine irradiation covering almost all the lymphocytes pools, indicated a Poisson distribution. The data show that depending on the sites of exposure, the distribution of dicentrics in cells varies and hence there is a non-uniform distribution of lymphocytes in the body. The average dose to the lymphocytes was found to be one sixth of the partial body dose. Based on the non-Poisson distribution of aberrations, the fraction of lymphocytes irradiated, mean dose to the fraction and part of the body exposed was calculated in a case of acute 6 Gy pelvic irradiation. The fraction of cells irradiated was calculated to be 4.11% and the portion of the body exposed was approximately 16.8%. The dose to the irradiated fraction was found to be 5.4 Gy, which is in agreement with the given dose of 6 Gy. In simulated exposures the u values increased systematically with the decrease in fraction of irradiated cells and the calculated dose to the fraction was also in good agreement with the true dose.     

Assessment of inhomogeneous ELF magnetic field exposures

In daily life as well as at workplaces, exposures to inhomogeneous magnetic fields become very frequent. This makes easily applicable compliance assessment methods increasingly important. Reference levels have been defined linking basic restrictions to levels of homogeneous fields at worst-case exposure conditions. If reference levels are met, compliance with basic restrictions can be assumed. If not, further investigations could still prove compliance. Because of the lower induction efficiency, inhomogeneous magnetic fields such as from electric appliances could be allowed exceeding reference levels. To easily assess inhomogeneous magnetic fields, a quick and flexible multi-step assessment procedure is proposed. On the basis of simulations with numerical, anatomical human models reference factors were calculated elevating reference levels to link hot-spot values measured at source surfaces to basic limits and allowing accounting for different source distance, size, orientation and position. Compliance rules are proposed minimising assessment efforts.     

Microbial sensor for preliminary screening of mutagens utilizing a phage induction test

For the preliminary screening of mutagens, a novel microbial sensor system was developed utilizing a phage induction test. Escherichia coli lysogenic strain GY5027 and nonlysogenic strain GY5026 were used in this study. The number of living cells was determined by measuring the respiration of cells immobilized onto an oxygen electrode. The injection of a mutagen, such as AF-2 and MNNG, caused the phage induction in the lysogenic strain, resulting in the decreased respiration of only the lysogenic strain immobilized onto the oxygen electrode but not of nonlysogenic strain. The rate of current increase correlated well with the concentration of mutagens. The sensor responses to the antibiotics and bactericides were definitely different from those of mutagens. Therefore, utilization of this microbial sensor system makes possible the estimation of a substrate's mutagenicity.     

Medical exposures directive: implications for interventional radiology

The new European Directive on Medical Exposures (97/43/EURATOM) specifically mentions 'high dose procedures' among the areas requiring special attention. This is universally interpreted as including the interventional procedures in radiology, cardiology and many of the special procedures involving fluoroscopy in these and related areas. This communication will focus on a definition of interventional procedures. It will examine the equipment, processes and patient and staff risks involved. From this examination it will be evident that new development is rapid in these areas and proceeding at a rate that is well ahead of both supporting research and regulatory framework. It will further note that the level of patient risk which is acceptable may be higher than in many other procedures. Finally it will note where the general provisions of the new Directive must be brought to bear on this new and developing field.