Abstract: Several epidemiological studies have indicated that residential or occupational exposure to 50 or 60 Hz magnetic fields (MF) may increase the risk of breast cancer, possibly by suppression of pineal production of the oncostatic hormone melatonin. In view of the methodological problems of epidemiological studies on MF exposure and cancer risk, laboratory studies are needed to determine whether 50/60 Hz exposure can initiate, promote or copromote mammary cancer. In the present study, 216 female Sprague-Dawley rats were divided into four groups. Two of the groups (with 99 animals each) received oral applications of 7,12-dimethylbenz[a]anthracene (DMBA) and were either sham-exposed or exposed in a 50 Hz, 100 muT MF for 24 h/day 7 days/week for a period of 91 days. The other two groups (nine animals each) were either sham-exposed or MF-exposed without DMBA treatment. The exposure chambers and all other environmental factors were identical for MF-exposed and sham-exposed animals. At the end of the 3 month period of MF exposure, all rats were used for histopathological diagnosis of lesions. At the time of necropsy, significantly more MF-exposed DMBA-treated rats exhibited macroscopically visible mammary tumours than DMBA-treated controls. Furthermore, the size of mammary tumours was significantly larger in MF-exposed rats. Histopathological examination of the mammary gland showed that the number of neoplastic and non-neoplastic lesions did not significantly differ between groups, indicating that MF exposure had not altered the incidence of mammary lesions but had only accelerated tumour growth, consistent with a co-promoting effect. In the MF-exposed group, significantly more rats exhibited malignant mammary tumours than in controls, indicating that MF exposure had affected the progression of DMBA-induced lesions. The number of metastases of mammary tumours or of primary lesions in other organs in response to DMBA was not affected by MF exposure. In rats without DMBA application, no non-neoplastic or neoplastic lesions were determined. The data demonstrate that long-term exposure of DMBA-treated female rats promotes the growth and progression of mammary tumours, while tumour incidence is not affected, at least under the experimental conditions of the present study. The data thus add to the accumulating evidence that MF exposure exerts tumour co-promoting effects.

Abstract: In Europe household appliances are a major source of indoor 50 Hz magnetic field exposure. A number of epidemiological studies have reported associations between leukemia risk and personal use of household appliances. In the “Norddeutsche Leukamie und Lymphomstudie” (NLL), which was conducted in Northern Germany (Schleswig-Holstein and Lower Saxony) between 1997 and 2001, lifetime use of a preselected array of electric appliances (microwave ovens, hair-dryers, motorized electrical alarm clocks (i.e. that use a motor to move their hands or digits), electric blankets and pillows, heated waterbeds, computers with conventional screens, TVs, and electric sewing machines) was recorded in a standardized, personal, computerized interview. Exposure was assessed on three different levels of precision: ever use, cumulative appliance-years, and average time of daily use. Additional questions referred to exposure modifying factors, including distance from screen while watching TV, position of an alarm clock at the bed etc.). Exposure to ELF-EMF from household appliances was quantified as ever vs. never use, gross and net appliance-years of lifetime use and cumulative microT-hours. Flux densities were based on measurements of appliances from the published literature. These were used as weighting factors to account for the different device-specific contributions to overall ELF-EMF exposure. Resulting distributions (as quartiles) for exposure scores revealed systematic differences for different levels of precision. Our analysis indicates that valid assessment of ELF-EMF exposure from household appliances should be based on the highest possible degree of precision and hence provides a considerable challenge in analytic epidemiology.

Abstract: Although overall incidence is rare, leukemia is the most common type of childhood cancer. It accounts for 30% of all cancers diagnosed in children younger than 15 years. Within this population, acute lymphocytic leukemia (ALL) occurs approximately five times more frequently than acute myelogenous leukemia (AML) and accounts for approximately 78% of all childhood leukemia diagnoses. Epidemiologic studies of acute leukemias in children have examined possible risk factors, including genetic, infectious, and environmental, in an attempt to determine etiology. Only one environmental risk factor (ionizing radiation) has been significantly linked to ALL or AML. Most environmental risk factors have been found to be weakly and inconsistently associated with either form of acute childhood leukemia. Our review focuses on the demographics of childhood leukemia and the risk factors that have been associated with the development of childhood ALL or AML. The environmental risk factors discussed include ionizing radiation, non-ionizing radiation, hydrocarbons, pesticides, alcohol use, cigarette smoking, and illicit drug use. Knowledge of these particular risk factors can be used to support measures to reduce potentially harmful exposures and decrease the risk of disease. We also review genetic and infectious risk factors and other variables, including maternal reproductive history and birth characteristics.