Risk of cancer in Finnish children living close to power lines.

OBJECTIVE--To investigate the risk of cancer in children living close to overhead power lines with magnetic fields of > or = 0.01 microteslas (microT). DESIGN--Cohort study. SETTING--The whole of Finland. SUBJECTS--68,300 boys and 66,500 girls aged 0-19 years living during 1970-89 within 500 m of overhead power lines of 110-400 kV in magnetic fields calculated to be > or = 0.01 microT. Subjects were identified by record linkages of nationwide registers. MAIN OUTCOME MEASURES--Numbers of observed cases in follow up for cancer and standardised incidence ratios for all cancers and particularly for nervous system tumours, leukaemia, and lymphoma. RESULTS--In the whole cohort 140 cases of cancer were observed (145 expected; standardised incidence ratio 0.97, 95% confidence interval 0.81 to 1.1). No statistically significant increases in all cancers and in leukaemia and lymphoma were found in children at any exposure level. A statistically significant excess of nervous system tumours was found in boys (but not in girls) who were exposed to magnetic fields of > or = 0.20 microT or cumulative exposure of > or = 0.40 microT years. CONCLUSIONS--Residentia magnetic fields of transmission power lines do not constitute a major public health problem regarding childhood cancer. The small numbers do not allow further conclusions about the risk of cancer in stronger magnetic fields.     

Temporal characteristics of transmission-line loadings in the Swedish childhood cancer study

A recent study conducted in Sweden reported that 1) leukemia risk in children who lived near 220 or 400 kV electric-power transmission lines was associated with calculated historical magnetic field levels; 2) children living within a distance of 50 m of transmission lines had an elevated risk of leukemia; and 3) there was no association between leukemia and residential magnetic fields measured many years after diagnosis. Subsequently, these investigators found through logistic regression analysis that disease was more strongly associated with calculated historical fields than with distance. Since the calculated historical fields in that study depended predominantly on distance and transmission-line load current, the logistic regression results suggest that historical load current plays an important role in the epidemiological results. Thus, we studied hourly 1974 load-current data for six transmission lines, and we examined 1958–1985 annual load-current data for 112 transmission lines. Most lines exhibited marked diurnal load-current rhythms during 1974, and all six showed systematic weekday weekend differences. During 1958–1985, average loadings of Swedish 220 and 400 kV lines increased by about 1.3% year. Predictive-value and kappa-statistic analyses indicated that Swedish transmission-line load currents were not stable over long periods, so that contemporaneous load current (or a contemporary magnetic field measurement) was not a good surrogate for historical load current (or historical magnetic fields). The results provide a potential explanation of the failure of the Swedish Study to find an association between leukemia and contemporaneous magnetic field levels measured many years after the etiologic period, and suggest that the inclusion of load-current data could significantly improve the quality of historical field calculations. Bioelectromagnetics 19:354–365, 1998. © 1998 Wiley-Liss, Inc.     

Magnetic fields of high voltage power lines and risk of cancer in Finnish adults: nationwide cohort study.

OBJECTIVE: To investigate the risk of cancer in association with magnetic fields in Finnish adults living close to high voltage power lines. DESIGN: Nationwide cohort study. SUBJECTS: 383,700 people who lived during 1970-89 within 500 metres of overhead power lines of 110-400 kV in a magnetic field calculated to be > or = 0.01 microT. Study subjects were identified by record linkages of nationwide registers. MAIN OUTCOME MEASURES: Numbers of observed and expected cases of cancer, standardised incidence ratios, and incidence rate ratios adjusted for sex, age, calendar year, and social class--for example, by continuous cumulative exposure per 1 microT year with 95% confidence intervals from multiplicative models for all cancers combined and 21 selected types. RESULTS: Altogether 8415 cases of cancer were observed (standardised incidence ratio 0.98; 95% confidence interval 0.96 to 1.00) in adults. All incidence rate ratios for both sexes combined were non-significant and between 0.91 and 1.11. Significant excesses were observed in multiple myeloma in men (incidence rate ratio 1.22) and in colon cancer in women (1.16). CONCLUSIONS: Typical residential magnetic fields generated by high voltage power lines do not seem to be related to the risk of overall cancer in adults. The previously suggested associations between extremely low frequency magnetic fields and tumours of the nervous system, lymphoma, and leukaemia in adults and breast cancer in women were not confirmed.     

Power frequency magnetic fields and risk of childhood leukaemia: Misclassification of exposure from the use of the ‘distance from power line’ exposure surrogate

A recent study examining the relationship between distance to nearby power lines and childhood cancer risk re‐opened the debate about which exposure metrics are appropriate for power frequency magnetic field investigations. Using data from two large population‐based UK and German studies we demonstrate that distance to power lines is a comparatively poor predictor of measured residential magnetic fields. Even at proximities of 50 m or less, the positive predictive value of having a household measurement over 0.2 µT was only 19.4%. Clearly using distance from power lines, without taking account of other variables such as load, results in a poor proxy of residential magnetic field exposure. We conclude that such high levels of exposure misclassification render the findings from studies that rely on distance alone uninterpretable. Bioelectromagnetics 30:183–188, 2009. © 2008 Wiley‐Liss, Inc.     

Extremely low frequency magnetic fields in residences in Germany. Distribution of measurements, comparison of two methods for assessing exposure, and predictors for the occurrence of magnetic fields above background level

We examined the results of 1,835 magnetic field measurements in German residences conducted between November 1997 and September 1999. The measurements were part of an epidemiological study on the relationship between magnetic fields and childhood leukemia. We performed a fixed-location measurement of the magnetic field at 50 Hz and 16 2/3 Hz (frequency of the German railway system) over 24 h in the child’s bedroom in the residence of each study participant. In addition, we conducted a second 24 h-measurement in the living room at 50 Hz, and spot measurements while walking through all rooms of the respective dwelling. Median 50 Hz magnetic fields above 0.2 μT were found to be infrequent in Germany (only 1.4% of all residences). Fields produced by high-voltage power lines (123–420 kV) were lower than expected: the median magnetic field was above 0.2 μT in only 8 (32.0%) of 25 residences located 50 m or closer to a high-voltage power line indicating that power lines in Germany are usually run well below the maximum power load. We found that magnetic fields were correlated with the type of residence and higher magnetic fields were measured in apartment buildings. There was also some evidence for a positive correlation between magnetic fields and traffic density and an inverse association between magnetic fields and family net income. The 24 h-magnetic field measurements correlated well with the spot measurements (r>0.7). However, when dichotomized with a cut-off point of 0.2 μT, there was only a poor agreement between the two measurement methods. A loss of the strength of the association after categorization was also observed when comparing the arithmetic mean and median of the same 24 h-measurement. In summary, these analyses give a valuable overview of magnetic field distributions in German residences. Received: 31 January 2000 / Accepted: 25 July 2000     

Evaluation of current densities and total contact currents in occupational exposure at 400 kV substations and power lines

This investigation studied the current densities in the neck and total contact currents in occupational exposure at 400 kV substations and power lines. Eight voluntary workers simulated their normal work tasks using the helmet–mask measuring system. In all, 151 work tasks with induced current measurements were made. Work situations were: tasks in 400 kV substations, tasks in 400–110 kV towers and the cutting of vegetation under 400 kV power lines. The average current density in the neck was estimated from the current induced in the helmet. The calculated maximum average current densities in the neck varied from 1.5 to 6.4 mA/m² and the maximum total contact currents from 66.8 to 458.4 µA. The study shows that the maximum average current densities and the total contact currents (caused by electric field) in occupational exposure at 400 kV substations and power lines does not exceed the limit and action values (10 mA/m² and 1 mA) of the new EU‐directive 2004/40/EC (live‐line bare‐hand works excluded). Bioelectromagnetics 30:231–240, 2009. © 2009 Wiley‐Liss, Inc.     

Analysis of individual- and school-level clustering of power frequency magnetic fields

This study reports the continuous 8-h monitoring of data on extremely low-frequency magnetic fields (ELF-MF) relating to 14 children and 35 teachers in 11 elementary schools in Northern Taiwan. It was anticipated that the subjects in two of these campuses would have elevated exposure to ELF-MF as a result of their close proximity to high-voltage (161 kilo-Volt, kV) power lines. The results of our analysis reveal that in those schools with high-voltage power lines running through the campuses, the mean ELF-MF exposure level (0.38 +/- 0.51 micro-Tesla (microT), or 0.15, 0.25 and 0.44 microT at the respective 25th, 50th and 75th percentiles) was higher than the mean ELF-MF exposure level for campuses situated far away from such high-voltage power lines (0.14 +/- 0.27 microT, or 0.04, 0.06 and 0.10 microT at the respective 25th, 50th and 75th percentiles). The multi-level analytical technique, which takes individual measurements as the analytical unit, and which also takes into consideration the inter-correlation between measurements from the same individual and/or campus, was also applied to the analysis of the data. We conclude that individual-level and school-level clustering of the measurements, both of which were discernible in this study, should be taken into consideration in any future analysis of data obtained from the continuous monitoring of exposure to ELF-MF.     

The possible role of contact current in cancer risk associated with residential magnetic fields

Residential electrical wiring safety practices in the US result in the possibility of a small voltage (up to a few tenths of a volt) on appliance surfaces with respect to water pipes or other grounded surfaces. This "open circuit voltage" (V(OC)) will cause "contact current" to flow in a person who touches the appliance and completes an electrical circuit to ground. This paper presents data suggesting that contact current due to V(OC) is an exposure that may explain the reported associations of residential magnetic fields with childhood leukemia. Our analysis is based on a computer model of a 40 house (single-unit, detached dwelling) neighborhood with electrical service that is representative of US grounding practices. The analysis was motivated by recent research suggesting that the physical location of power lines in the backyard, in contrast to the street, may be relevant to a relationship of power lines with childhood leukemia. In the model, the highest magnetic field levels and V(OC)s were both associated with backyard lines, and the highest V(OC)s were also associated with long ground paths in the residence. Across the entire neighborhood, magnetic field exposure was highly correlated with V(OC) (r = 0.93). Dosimetric modeling indicates that, compared to a very high residential level of a uniform horizontal magnetic field (10 mu T) or a vertical electric field (100 V/m), a modest level of contact current (approximately 18 mu A) leads to considerably greater induced electric fields (> 1 mV/m) averaged across tissue, such as bone marrow and heart. The correlation of V(OC) with magnetic fields in the model, combined with the dose estimates, lead us to conclude that V(OC) is a potentially important exposure with respect to childhood leukemia risks associated with residential magnetic fields. These findings, nonetheless, may not apply to residential service used in several European countries or to the Scandinavian studies concerned with populations exposed to magnetic fields from overhead transmission lines.     

Experimental validation of a statistical model for evaluating the past or future magnetic field exposures of a population living near power lines

This study was designed to provide an experimental validation for a statistical model predicting past or future exposures to magnetic fields (MF) from power lines. The model estimates exposure, combining the distribution of ambient MF in the absence of power lines with the distribution of past or future MF produced by power lines. In the study, validation is carried out by comparing exposures predicted by the model with the actual measurements obtained from a large-scale epidemiological study. The comparison was made for a group of 220 women living near a 735 kV power line. Knowing that the individual arithmetic means of MF exposures follow a log-normal distribution, the Pearson correlation between the log-transformed measured means and the calculated ones was determined and found to be 0.77. Predicted values of MF exposures were slightly lower than measured values. The calculated geometric mean of the group was 0.33 microT, compared to 0.38 microT for the measured geometric mean. The present study shows good agreement between the measured MF exposure of an individual inside a house near a 735 kV line and the MF exposure calculated using a statistical model.     

Elevated residential exposure to power frequency magnetic field associated with greater average age at diagnosis for patients with brain tumors

To explore whether the age at cancer diagnosis was associated with residential exposure to magnetic field, we compared average ages at diagnosis for cases of leukemia, brain tumor, or female breast cancer with elevated exposure (magnetic flux density >or= 0.2 microT, or residential distance from major power lines 100 m from major power lines). Comparing with brain tumor cases with background magnetic field exposure (n = 506), brain tumor cases with elevated exposure (n = 71) were 6 years older on average at diagnosis (P = 0.01). The difference was greater for males (45.2 vs. 52.1 years, P = 0.01) than for females (44.3 vs. 48.2 years, P = 0.27). No such phenomena at a significant level was observed for leukemia, female breast cancer, or a random sample of general population. We noted an association between magnetic field exposure and a greater mean age at diagnosis for brain tumors. Whether or not these phenomena suggest a delayed occurrence of brain tumors following a higher than background residential magnetic field exposure deserves further investigation.     

Occupational exposure to electric and magnetic fields during work tasks at 110 kV substations in the Tampere region

The occupational exposure to electric and magnetic fields during various work tasks at seven 110 kV substations in Finland's Tampere region was studied. The aim was to investigate if the action values (10 kV/m for the E‐field and 500 µT for the B‐field) of the EU Directive 2004/40/EC were exceeded. Electric and magnetic fields were measured during the following work tasks: (1) walking or operating devices on the ground; (2) working from a service platform; (3) working around the power transformer on the ground or using a ladder; and (4) changing a bulb from a man hoist. In work task 2 “working from a service platform” the measured electric field (maximum value 16.6 kV/m) exceeded 10 kV/m in three cases. In the future it is important to study if the limit value (10 mA/m²) of Directive 2004/40/EC is exceeded at 110 kV substations. The occupational 500 µT action value of the magnetic flux density field (B‐field) was not exceeded in any working situation. Bioelectromagnetics 31:252–254, 2010. © 2009 Wiley‐Liss, Inc.     

Maternal exposure to magnetic fields from high-voltage power lines and the risk of birth defects

The issue of adverse human health effects due to exposure to electromagnetic fields is still unclear, and congenital anomalies are among the outcomes that have been inconsistently associated with such exposure. We conducted a population-based, case-control study to examine the risk of congenital anomalies associated with maternal exposure to magnetic fields (MF) from high-voltage power lines during pregnancy in a community in northern Italy. We identified 228 cases of congenital malformations diagnosed in live births, stillbirths, and induced abortions among women living in the municipality of Reggio Emilia during the period 1998-2006, and a reference group of healthy newborns was matched for year of birth, maternal age, and hospital of birth. We identified maternal residence during early pregnancy and used Geographic Information System to determine whether the residences were within geocoded corridors with MF ≥0.1 μT near high-voltage power lines, then calculated the relative risk (RR) of congenital anomalies associated with maternal exposure. One case and 5 control mothers were classified as exposed, and the RR associated with MF ≥0.1 μT was 0.2 (95% CI: 0.0-2.0) after adjusting for maternal education. While small or moderate effects may have gone undetected due to low statistical power, the results of this study overall do not provide support for major effects of a teratogenic risk due to exposure to MF during early pregnancy.     

Survey of residential 50 Hz EMF exposure from transformer stations

In Hungary it is typical that 10/04 kV transformer stations are being installed in multistory residential and office buildings. Magnetic fields (MFs) up to several tens of microT have been measured in apartments close to transformers. The aim of the present study was to provide systematic assessment of MF exposure of residents living above transformer stations. Out of 41 addresses provided by the electricity supplier, current load of 21 transformers and MF in 21 apartments was measured. Spot MFs at 1 m height and time weighted average 24 h MF exposure at bed height was measured. All-day personal MF exposure was measured at waist and HOME exposure was calculated. BED exposure was measured at bed height. Participants kept a time-activity diary. The time-weighted average 24 h MF exposure (3.03 microT) exceeded the usual residential exposure (<0.2 microT). The mean HOME and BED personal exposure above transformers was 0.825 and 1.033 microT, respectively. Our study provides exposure assessment of a cohort with a wider exposure range, compared to power-line epidemiological studies.     

Chronic exposure of primates to 60-Hz electric and magnetic fields: III. Neurophysiologic effects

The neurophysiologic effects of combined 60-Hz electric (E) and magnetic (B) fields, of magnitudes comparable to those produced by high-voltage powerlines, were investigated in 10 monkeys (Macaca nemestrina). Six animals (experimental group) were each exposed to three different levels of E and B fields: 3 kV/m and 0.1 G, 10 kV/m and 0.3 G, and 30 kV/m and 0.9 G. Field exposures were preceded and followed by sham exposures, during which factors of field generation were present (e.g., heat, vibration, noise, etc.) without E and B fields. Each of the five segments (i.e., the three exposure segments and the initial and final sham exposure segments) lasted 3 weeks. Animals were exposed for 18 h/day (fields on at 1600 h, off at 1000 h). Four other animals (external control group) were given sham exposure for the entire 15-week period. Auditory, visual, and somatosensory evoked potentials were recorded twice a week, during the daily 6-h field-off period. E- and B-field exposure had no effect on the early or mid-latency evoked potential components, suggesting that exposure at these levels has no effect on peripheral or central sensory afferent pathways. However, there was a statistically significant decrease in the amplitudes of late components of the somatosensory evoked potential during the 10kV/m and 0.3 G, and 30 kV/m and 0.9 G exposure levels. This result is possibly related to the opiate antagonist effect of electromagnetic field exposure reported by others.     

On electric fields of power lines and on their perception by freshwater fish

It is ascertained by the results of measurements of intensity of electric fields under above-water passages of power lines in the water environment that the values of intensity of electric fields 50 Hz under power lines of 100 and 220 kV belong to the microvoltage range. By comparative analysis of the intensity levels of fields under power lines with thresholds of electric sensitivity of freshwater fish, it is shown that the electric fields of such levels may influence orientation and behavior of fish characterized by a high electrosensitivity.     

Residential magnetic fields predicted from wiring configurations: II. Relationships To childhood leukemia.

Case-control data on childhood leukemia in Los Angeles County were reanalyzed with residential magnetic fields predicted from the wiring configurations of nearby transmission and distribution lines. As described in a companion paper, the 24-h means of the magnetic field's magnitude in subjects' homes were predicted by a physically based regression model that had been fitted to 24-h measurements and wiring data. In addition, magnetic field exposures were adjusted for the most likely form of exposure assessment errors: classic errors for the 24-h measurements and Berkson errors for the predictions from wire configurations. Although the measured fields had no association with childhood leukemia (P for trend=.88), the risks were significant for predicted magnetic fields above 1.25 mG (odds ratio=2.00, 95% confidence interval=1.03-3.89), and a significant dose-response was seen (P for trend=.02). When exposures were determined by a combination of predictions and measurements that corrects for errors, the odds ratio (odd ratio=2.19, 95% confidence interval=1.12-4.31) and the trend (p =.007) showed somewhat greater significance. These findings support the hypothesis that magnetic fields from electrical lines are causally related to childhood leukemia but that this association has been inconsistent among epidemiologic studies due to different types of exposure assessment error. In these data, the leukemia risks from a child's residential magnetic field exposure appears to be better assessed by wire configurations than by 24-h area measurements. However, the predicted fields only partially account for the effect of the Wertheimer-Leeper wire code in a multivariate analysis and do not completely explain why these wire codes have been so often associated with childhood leukemia. The most plausible explanation for our findings is that the causal factor is another magnetic field exposure metric correlated to both wire code and the field's time-averaged magnitude.     

Elf Dosage in Ellipsoidal Models of Man Due to High Voltage Transmission Lines

The fields, flux, and power density produced inside an ellipsoidal model of man by overhead high-voltage transmission lines have been calculated. The values depend strongly on the conductivity and the shape of the ellipsoid and, in general, vary from point to point within it. The maximum energy flux is the more reliable indicator of exposure to the electromagnetic field.     

Extremely low frequency electric fields and cancer: Assessing the evidence

Much of the research and reviews on extremely low frequency (ELF) electric and magnetic fields (EMFs) have focused on magnetic rather than electric fields. Some have considered such focus to be inappropriate and have argued that electric fields should be part of both epidemiologic and laboratory work. This paper fills the gap by systematically and critically reviewing electric‐fields literature and by comparing overall strength of evidence for electric versus magnetic fields. The review of possible mechanisms does not provide any specific basis for focusing on electric fields. While laboratory studies of electric fields are few, they do not indicate that electric fields should be the exposure of interest. The existing epidemiology on residential electric‐field exposures and appliance use does not support the conclusion of adverse health effects from electric‐field exposure. Workers in close proximity to high‐voltage transmission lines or substation equipment can be exposed to high electric fields. While there are sporadic reports of increase in cancer in some occupational studies, these are inconsistent and fraught with methodologic problems. Overall, there seems little basis to suppose there might be a risk for electric fields, and, in contrast to magnetic fields, and with a possible exception of occupational epidemiology, there seems little basis for continued research into electric fields. Bioelectromagnetics 31:89–101, 2010. © 2009 Wiley‐Liss, Inc.     

Comparison between personal exposure to 60 Hz magnetic fields and stationary home measurements for people living near and away from a 735 kV power line.

This study compares stationary home measurements with a personal exposure monitor of 60 Hz magnetic fields in a group of 18 people living near a 735 kV line and 17 people living far away from the line. Most of them were white collar workers who worked during the day. They wore a personal Positron meter for 24 h, while a similar meter was left in their home, away from any appliances. For people living away from the line, the impact of residential activities appeared rather weak when considering the average intensity of the field during the awake period (at home): 0.22 microT for personal exposure versus 0.18 microT for stationary measurements (P = 0.09). The impact of residential activities during the awake period was more detectable when using the percentage of time with exposure above 0.78 microT: median 0.4 for personal vs. 0.0 for stationary measurements (P =.01). The temporal variability of the exposure during the awake period was also significantly higher for personal exposure than for stationary measurements. For people living near the line, the intensity of the magnetic field from the line dominated the personal exposure when considering the mean of measurements and the percentage of time above a threshold. However, the temporal variability was greater for the personal exposure during the awake period. Although limited due to its small sample size, the present study seems to demonstrate the usefulness of considering different indexes of exposure when assessing residential exposure to 60 Hz magnetic fields.