Residential magnetic fields predicted from wiring configurations: I. Exposure model.

A physically based model for residential magnetic fields from electric transmission and distribution wiring was developed to reanalyze the Los Angeles study of childhood leukemia by London et al. For this exposure model, magnetic field measurements were fitted to a function of wire configuration attributes that was derived from a multipole expansion of the Law of Biot and Savart. The model parameters were determined by nonlinear regression techniques, using wiring data, distances, and the geometric mean of the ELF magnetic field magnitude from 24-h bedroom measurements taken at 288 homes during the epidemiologic study. The best fit to the measurement data was obtained with separate models for the two major utilities serving Los Angeles County. This model's predictions produced a correlation of 0.40 with the measured fields, an improvement on the 0.27 correlation obtained with the Wertheimer-Leeper (WL) wire code. For the leukemia risk analysis in a companion paper, the regression model predicts exposures to the 24-h geometric mean of the ELF magnetic fields in Los Angeles homes where only wiring data and distances have been obtained. Since these input parameters for the exposure model usually do not change for many years, the predicted magnetic fields will be stable over long time periods, just like the WL code. If the geometric mean is not the exposure metric associated with cancer, this regression technique could be used to estimate long-term exposures to temporal variability metrics and other characteristics of the ELF magnetic field which may be cancer risk factors.     

Development of a protocol for assessing time-weighted-average exposures of young children to power-frequency magnetic fields

A study was carried out in 1990 to guide the development of a protocol for assessing residential exposures of children to time-weighted-average (TWA) power-frequency magnetic fields. The principal goal of this dosimetry study was to determine whether area (i.e., spot and/or 24 h) measurements of power-frequency magnetic fields in the residences and in the schools and daycare centers of 29 children (4 months through 8 years of age) could be used to predict their measured personal 24-h exposures. TWA personal exposures, measured with AMEX-3D meters worn by subjects, were approximately log-normally distributed with both residential and nonresidential geometric means of 0.10 μT (1.0 mG). Between-subjects variability in residential personal exposure levels (geometric standard deviation of 2.4) was substantially greater than that observed for nonresidential personal exposure levels (1.4). The correlation between log-transformed residential and total personal exposure levels was 0.97. Time-weighted averages of the magnetic fields measured in children's bedrooms, family rooms, living rooms, and kitchens were highly correlated with residential personal exposure levels (r = 0.90). In general, magnetic field levels measured in schools and daycare centers attended by subjects were smaller and less variable than measured residential fields and were only weakly correlated with measured nonresidential personal exposures. The final measurement protocol, which will be used in a large US study examining the relationship between childhood leukemia and exposure to magnetic fields, contains the following elements: normal- and low-power spot magnetic field measurements in bedrooms occupied by subjects during the 5 years prior to the date of diagnosis for cases or the corresponding date for controls; spot measurements under normal and low power-usage conditions at the centers of the kitchen and the family room; 24-h magnetic-field recordings near subjects' beds; and wire coding using the Wertheimer-Leeper method. © 1994 Wiley-Liss, Inc.

1 This article is a US Government work and, as such, is in the public domain in the United States of America.

     

Hypothesis: The risk of childhood leukemia is related to combinations of power-frequency and static magnetic fields

We present a hypothesis that the risk of childhood leukemia is related to exposure to specific combinations of static and extremely-low-frequency (ELF) magnetic fields. Laboratory data from calcium efflux and diatom mobility experiments were used with the gyromagnetic equation to predict combinations of 60 Hz and static magnetic fields hypothesized to enhance leukemia risk. The laboratory data predicted 19 bands of the static field magnitude with a bandwidth of 9.1 μT that, together with 60 Hz magnetic fields, are expected to have biological activity. We then assessed the association between this exposure metric and childhood leukemia using data from a case-control study in Los Angeles County. ELF and static magnetic fields were measured in the bedrooms of 124 cases determined from a tumor registry and 99 controls drawn from friends and random digit dialing. Among these subjects, 26 cases and 20 controls were exposed to static magnetic fields lying in the predicted bands of biological activity centered at 38.0 μT and 50.6 μT. Although no association was found for childhood leukemia in relation to measured ELF or static magnetic fields alone, an increasing trend of leukemia risk with measured ELF fields was found for subjects within these static field bands (P for trend = 0.041). The odds ratio (OR) was 3.3 [95% confidence interval (CI) = 0.4–30.5] for subjects exposed to static fields within the derived bands and to ELF magnetic field above 0.30 μT (compared to subjects exposed to static fields outside the bands and ELF magnetic fields below 0.07 μT). When the 60 Hz magnetic fields were assessed according to the Wertheimer-Leeper code for wiring configurations, leukemia risks were again greater with the hypothesized exposure conditions (OR = 9.2 for very high current configurations within the static field bands: 95% CI = 1.3–64.6). Although the risk estimates are based on limited magnetic field measurements for a small number of subjects, these findings suggest that the risk of childhood leukemia may be related to the combined effects of the static and ELF magnetic fields. Further tests of the hypothesis are proposed. © 1995 Wiley-Liss, Inc.     

Magnetic field exposure assessment: a comparison of various methods

The accurate and valid measurement of personal exposure to magnetic fields poses a major challenge for epidemiologic studies. When considering the various methods to assess exposure, it is unclear which measures are most relevant for studies of human disease, if any. Given these uncertainties, the Electromagnetic Fields and Breast Cancer on Long Island Study (EBCLIS) undertook a pilot study to develop the data collection protocol for a case-control study of breast cancer and magnetic fields. The pilot study used and compared various methods to assess residential exposures to magnetic fields, and related these measures to personal exposures. It included 31 women without breast cancer (mean age, 63+/-7 yr) who lived in their present homes for at least 15 yr. The pilot study consisted of an in-home interview, spot and 24-h magnetic field waveforms and broadband recordings, ground currents, wire coding, and personal 24-h broadband measurements. From the regression analyses, the model that best predicted personal magnetic field exposures included 24-h measurements in the bedroom and in the most lived-in room; as well as ground current test loads taken at the center of this most lived in room (r(2)=86%). The addition of other variables in this regression model yielded only small and nonsignificant increases in r(2). As a direct result of this pilot, EBCLIS will include ground current measurements in its protocol, which have not previously been collected as part of an epidemiologic study. Ground currents may be important because they may be richer in 180 Hz components than are the other currents in a power system. EBCLIS will have the opportunity to examine the ground-current hypothesis in the context of female breast cancer.     

The determinants of Canadian children's personal exposures to magnetic fields

Study of the health effects of magnetic fields often depends on identifying determinants and hence indicators of personal exposure. This study identified determinants of children's exposure to magnetic fields and constructed a prediction model for them. For 632 children participating in a case-control study of childhood leukemia, we made direct measures of exposure over 48 h using a portable device, together with observations on candidate determinants. A child's age and sex, the proportion of time spent in the home, and their parents' education or income were very weak predictors of (logged) mean 48 h magnetic field (R(2) < 1%). More important were province (R(2) = 8.0%) and type of residence (R(2) = 11.3%). Low temperatures at the time of measurement were associated with high fields (about 20% increase for each 10 degrees C below 14, R(2) = 4.9%). Several visible attributes of wiring around residences predicted exposure, mostly captured in the Wertheimer-Leeper wire code (R(2) = 13.5%). Stationary 24 h measurement in the bedroom (R(2) = 63.3%) and spot measurements outside the house (R(2) = 40.7%) predicted personal exposures best. Adding other minor predictors increased only slightly variance explained by 24 h stationary (R(2) = 66.2%) and spot (R(2) = 46.8%) measurements. Without spot or stationary measurements, the best model was much less powerful (R(2) = 29.0%). We conclude that spot measurements outside the residence provide a moderately effective basis for estimating exposure for children living there, but do not perform as well as 24 h stationary measurements in the child's bedroom. Although several other easily-observed variables were associated with personal exposure, they were weak determinants, either individually or in combination.     

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.     

Exposure to electrical contact currents and the risk of childhood leukemia

The objectives of this study were to examine the association between contact current exposure and the risk of childhood leukemia and to investigate the relationship between residential contact currents and magnetic fields. Indoor and outdoor contact voltage and magnetic-field measurements were collected for the diagnosis residence of 245 cases and 269 controls recruited in the Northern California Childhood Leukemia Study (2000-2007). Logistic regression techniques produced odds ratios (OR) adjusted for age, sex, Hispanic ethnicity, mother's race and household income. No statistically significant associations were seen between childhood leukemia and indoor contact voltage level [exposure ≥90th percentile (10.5 mV): OR = 0.83, 95% confidence interval (CI): 0.45, 1.54], outdoor contact voltage level [exposure ≥90th percentile (291.2 mV): OR = 0.89, 95% CI: 0.48, 1.63], or indoor magnetic-field levels (>0.20 μT: OR = 0.76, 95% CI: 0.30, 1.93). Contact voltage was weakly correlated with magnetic field; correlation coefficients were r = 0.10 (P = 0.02) for indoor contact voltage and r = 0.15 (P = 0.001) for outdoor contact voltage. In conclusion, in this California population, there was no evidence of an association between childhood leukemia and exposure to contact currents or magnetic fields and a weak correlation between measures of contact current and magnetic fields.     

Determinants of power-frequency magnetic fields in residences located away from overhead power lines.

The Wertheimer-Leeper wire code, originally developed as a surrogate for magnetic-field exposure, has been associated with childhood leukemia in several epidemiologic investigations. However, these and other studies indicate that most between-residence variability in measured magnetic fields remains unexplained by wire codes. To better understand this remaining variability, engineering and demographic data were examined for 333 underground (UG) and very-low current configuration (VLCC) single-family or duplex residences, selected from a database of nearly 1000 residences specifically because their magnetic fields are most likely affected negligibly by overhead power lines. Using linear regression techniques, four factors predictive of the log-transformed residential field were identified: the square-root of the 24-h average net service drop current (this current is equivalent to the current in the grounding system), the log of the number of service drops on the same secondary serving the residence, residence age (four categories), and area type (rural, suburban, or urban). Complete data on ground current and service drops, the two factors with the strongest individual relationships to measured fields, were available for only half of the residences in the sample. However, these data were determined to be "missing at random" according to established statistical criteria. The full-sample or "composite" models thus relied on a method similar to regression imputation, accounting for missing data with binary dummy variables. When applied to the samples from which they were derived, these models accounted for 25% of the variance of the log-spot-measured magnetic field values in the full sample, while models that considered only those residences with complete data (n = 167) explained about 35%. The model validated well against a sample of 201 ordinary low current configuration (OLCC) homes selected from the same database.     

The relationship between residential magnetic fields and contact voltage: a pooled analysis

It has been suggested that residential exposure to contact currents may be more directly associated with the potential for an increased risk of leukemia in childhood than magnetic fields. Contact current exposure occurs when a child contacts a bathtub's water fixtures, which are usually contiguous with a residence's electrical ground, and when the drainpipe is conductive. The Northern California Childhood Leukemia Study (NCCLS) is the only epidemiological study known to address whether contact current may confound the reported association between residential magnetic fields and childhood leukemia. The study contributed contact voltage and magnetic-field data for over 500 residences of leukemia cases and control children. We combined these data with the results of previous measurement studies of contact voltage in other communities to conduct an analysis of the relationship of magnetic fields with contact voltage for a total sample of 702 residences. The Spearman correlation of magnetic field with contact voltage was 0.29 (Spearman, P < 0.0001). Magnetic-field and contact voltage data were both divided into tertiles, with an upper magnetic-field cutpoint of 0.3 μT suggested by values used in epidemiological results and an upper contact voltage cutpoint of 60 mV based on dosimetric considerations. Expressed as an exposure odds ratios (EOR), we report an association of contact voltage with magnetic fields of 15.1 (95% CI 3.6-61) as well as a statistically significant positive trend across magnetic-field strata (EOR of 4.2 per stratum with 95% CI 2.4-7.4). The associations appear to be large enough to support the possibility that contact current could be responsible for the association of childhood leukemia with magnetic fields.     

Pilot study of extremely low frequency magnetic fields emitted by transformers in dwellings. Social aspects

A large number of epidemiologic studies examining the potential effect of residential exposure to extremely-low frequency (ELF) magnetic fields and childhood leukemia have been published. Two pooled analyses [Ahlbom A, Day N, Feychting M, Roman E, Skinner J, Dockerty J, Linet M, et al. (2000). A pooled analysis of magnetic fields and childhood leukaemia. Br J Cancer. 83(5):692–698; Greenland S, Sheppard AR, Kaune WT, Poole C, Kelsh AM (2000). A pooled analysis of magnetic fields, wire codes, and childhood leukemia. Epidemiology. 11(6):624–634], which included the major epidemiologic studies on ELF magnetic fields and childhood leukemia showed twofold increase in childhood leukemia risk in association with residential ELF exposure above 0.3–0.4 μT. Based on “limited” epidemiologic evidence linking ELF exposure to childhood leukemia and “inadequate evidence” for carcinogenicity of ELF in rodent bioassays, the International Agency for Research on Cancer (IARC) classified ELF magnetic fields as a possible human carcinogen (2B classification) [International Agency for Research on Cancer (IARC) (2002). Non-ionizing radiation, Part 1: Static and extremely low-frequency (ELF) electric and magnetic fields. IARC monographs on the evaluation of carcinogenic risks to humans. Vol. 80. IARC Press: Lyon], confirmed by WHO on the basis of studies published after 2000 [World Health Organization. Extremely low frequency fields. In: 238 Environmental health criteria, Geneva: WHO; 2007]. The analysis of more recent studies of ELF magnetic fields and childhood leukemia had small findings and propose methodological improvements concerning the uncertainties in epidemiological approaches and exposure assessment, bias in selection of controls [Kheifets L, Oksuzyan S (2008). Exposure assessment and other challenges in non-ionizing radiation studies of childhood leukaemia. Radiat Prot Dosimetry. 132(2):139–147]. By the end of 2010, 37 countries had been identified for possible participation in the International study TRANSEXPO. The pilot work has been completed in five countries (Finland, Hungary, Israel, Switzerland and Bulgaria). In 2008, Bulgaria through the National Centre of Public Health Protection joined with pilot study in TRANSEXPO Project. At this first stage of the project our investigation was directed to performing measurements in dwellings with built-in transformer stations, collecting data of population and cancer registry and choosing the epidemiology design feasible for continuing the project. Taking into account the available sources of information in Bulgaria (different registers of the population) needed for epidemiological approach, it was found that the most appropriate epidemiology design would be the nested case-control study. Control group could be collected in accordance with the international requirements for such epidemiological studies. This approach could be modified in the course of the further study in order to ensure achievement of the purposes of the main international requirements of the study.     

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.     

Power frequency electric and magnetic fields: A review of genetic toxicology

Epidemiologic studies have reported a modestly increased risk of childhood leukemia associated with certain electric power wire configurations. Since cancer likely involves DNA damage, this review discusses the evidence of direct and indirect genetic toxicity effects for both electric and magnetic fields at 50- and 60-Hz and miscellaneous pulsed exposures. Exposure conditions vary greatly among different end points measured, making comparisons and conclusions among experiments difficult. Although most of the available evidence does not suggest that electric and/or magnetic fields cause DNA damage, the existence of some positive findings and limitations in the set of studies carried out suggest a need for additional work.     

Rate of occurrence of transient magnetic field events in U.S. residences

Recent interest in the transient magnetic field events produced by electrical switching events in residential and occupational environments has been kindled by the possibility that these fields may explain observed associations between childhood cancer and wire codes. This paper reports the results of a study in which the rate of occurrence of magnetic field events with 2-200 kHz frequency content were measured over 24 h or longer periods in 156 U.S. residences. A dual-channel meter was developed for the study that, during 20 s contiguous intervals of time, counted the number of events with peak 2-200 kHz magnetic fields exceeding thresholds of 3. 3 nT and 33 nT. Transient activity exhibited a distinct diurnal rhythm similar to that followed by power frequency magnetic fields in residences. Homes that were electrically grounded to a conductive water system that extended into the street and beyond, had higher levels of 33 nT channel transient activity. Homes located in rural surroundings had less 33 nT transient activity than homes in suburban/urban areas. Finally, while transient activity was perhaps somewhat elevated in homes with OLCC, OHCC, and VHCC wire codes relative to homes with underground (UG) and VLCC codes, the elevation was the smallest in VHCC and the largest in OLCC homes. This result does not provide much support for the hypothesis that transient magnetic fields are the underlying exposure that explains the associations, observed in several epidemiologic studies, between childhood cancer and residence in homes with VHCC, but not OLCC and OHCC, wire codes.     

Children's exposure to magnetic fields produced by U.S. television sets used for viewing programs and playing video games

Two epidemiologic studies have reported increased risk of childhood leukemia associated with the length of time children watched television (TV) programs or played video games connected to TV sets. To evaluate magnetic field exposures resulting from these activities, the static, ELF, and VLF magnetic fields produced by 72 TV sets used by children to watch TV programs and 34 TV sets used to play video games were characterized in a field study conducted in Washington DC and its Maryland suburbs. The resulting TV-specific magnetic field data were combined with information collected through questionnaires to estimate the magnetic field exposure levels associated with TV watching and video game playing. The geometric means of the ELF and VLF exposure levels so calculated were 0.0091 and 0.0016 microT, respectively, for children watching TV programs and 0.023 and 0.0038 microT, respectively, for children playing video games. Geometric means of ambient ELF and VLF levels with TV sets turned off were 0.10 and 0.0027 microT, respectively. Summed over the ELF frequency range (6-3066 Hz), the exposure levels were small compared to ambient levels. However, in restricted ELF frequency ranges (120 Hz and 606-3066 Hz) and in the VLF band, TV exposure levels were comparable to or larger than normal ambient levels. Even so, the strengths of the 120 Hz or 606-3066 Hz components of TV fields were small relative to the overall ambient levels. Consequently, our results provide little support for a linkage between childhood leukemia and exposure to the ELF magnetic fields produced by TV sets. Our results do suggest that any future research on possible health effects of magnetic fields from television sets might focus on the VLF electric and magnetic fields produced by TV sets because of their enhanced ability relative to ELF fields to induce electric currents.     

Residential magnetic and electric fields

A magnetic flux density (MFD) and electric-field (E-field) data-acquisition system was built for characterizing extremely low-frequency fields in residences. Every 2 min during 24-h periods, MFD and E-field measurements were made in 43 homes in King, Pierce, and Snohomish counties of Washington State. The total electrical energy used in each residence during the 24-h measurement period was also recorded, and maps were drawn to scale of the distribution wiring within 43 m (140 ft) of these homes. Finally, on a separate date, field measurements were made in each home during an epidemiological interview. The results of this study can be summarized as follows: 1) 24-h-average MFD measured at two separate points in the family room were correlated, as were a 24-h-average bedroom measurement and the mean of the two family-room measurements. 2) The 24-h-average family-room MFD and E-field measurements were uncorrelated. 3) The 24-h-average total harmonic distortions of family-room MFD and E-fields were less than about 24% and 7%, respectively. 4) Residential MFD exhibited a definite 24-h (diurnal) cycle. 5) The 24-h-average and interviewer-measured MFD were correlated. 6) Residential 24-h-average MFD were correlated with the wiring code developed by Wertheimer and Leeper. 7) An improved prediction of 24-h-average residential MFD was obtained using the total number of service drops, the distance to neighboring transmission lines, and the number of primary phase conductors.     

Magnetic field exposure assessment for adult residents of Maine who live near and far away from overhead transmission lines.

Sixty-Hz magnetic field exposures were measured for 45 adult residents of Maine. Thirty of the subjects resided near rights-of-way (ROWs) with either 345- and 115-kV transmission lines, or ROWs with only 115-kV transmission lines; fifteen resided far from any transmission lines. Personal exposure data for a single 24-hour period was acquired with the EMDEX. The EMDEX's event-marker button was used to partition exposures into Home and Away components. Also, three area measurements were taken for each subject during the personal exposure measurement period: 1) 24-hr fixed-site bedroom measurement with a second EMDEX; 2) Spot measurements in at least three rooms of every residence; and 3) Spot measurements outside each residence. Residence near transmission lines highly loaded during the measurement period was associated with increased Home and Total exposure relative to a far-away population. Average exposure level while away from home was uniform (at about 2 mG) throughout the study population. On a quantitative level, Home exposure was correlated equivalently with Spot-In (r = .70) and the 24-hr fixed site measurement (r = .68). Correlations of area measurements with Total exposure were weaker because of the dilution effect of Away exposure (r = .64 for Spot-In; r = .61 for 24-h Bedroom). Away and Home exposures were not correlated (r = .14), which reinforced our confidence that the participants used the EMDEX correctly. The data suggest the need for caution before inferences are drawn about total personal exposure from area measurements. The study demonstrates the feasibility of obtaining valid measures of magnetic-field exposure with the personal exposure monitors that have been developed.     

Contact voltage measured in residences: implications to the association between magnetic fields and childhood leukemia

We measured magnetic fields and two sources of contact current in 36 homes in Pittsfield, MA. The first source, V(P-W), is the voltage due to current in the grounding wire, which extends from the service panel neutral to the water service line. This voltage can cause contact current to flow upon simultaneous contact with a metallic part of the water system, such as the faucet, and the frame of an appliance, which is connected to the panel neutral through the equipment-grounding conductor. The second is V(W-E), the voltage between the water pipe and earth, attributable to ground currents in the water system and magnetic induction from nearby power lines. In homes with conductive water systems and drains, V(W-E) can produce a voltage between the faucet and drain, which may produce contact current into an individual contacting the faucet while immersed in a bathtub. V(P-W) was not strongly correlated to the magnetic field (both log transformed) (r = 0.28; P < 0.1). On the other hand, V(W-E) was correlated to the residential magnetic field (both log transformed) (r = 0.54; P < 0.001), with the highest voltages occurring in homes near high voltage transmission lines, most likely due to magnetic induction on the grounding system. This correlation, combined with both frequent exposure opportunity for bathing children and substantial dose to bone marrow resulting from contact, lead us to suggest that contact current due to V(W-E) could explain the association between high residential magnetic fields and childhood leukemia.     

Ambient 60-Hz magnetic flux density in an urban neighborhood

A residential neighborhood in Buffalo, NY, was surveyed with a magnetic field meter to evaluate whether or not spot measurements are reliable predictors of the 60-Hz fields at street corners and residences. The results of repeated measurements over 7 days at 33 street corners in this neighborhood indicate that day-to-day variation in power line magnetic fields is negligible (intraclass correlation coefficient = 0.94). Multivariate linear regression analysis of the data indicates that transmission lines and thick, three-phase primary wires near the field measurement site are strong predictors and account for the majority of the ambient magnetic field variance between locations (multiple correlation coefficient squared = 0.60; F ratio = 22.2, P less than .001). Magnetic fields measured at the front sidewalk were highly correlated with fields at the front doorsteps of 45 homes in this neighborhood (gamma = 0.81). These results suggest that ambient power line magnetic field levels at urban residences can be reliably characterized on a one-time site inspection using a hand-held magnetic field meter and a simple wiring classification system.     

Relative contribution of residential and occupational magnetic field exposure over twenty-four hours among people living close to and far from a power line

This study sought to estimate the relative contribution of exposure to 50 Hz magnetic fields experienced at home, at work/school, or elsewhere to the total exposure over 24 hr. Personal exposure meters were carried by 97 adults and children in the Stockholm area. About half of the subjects lived close (<50 m) to a transmission line and half far (>100 m) away. Spot measurements and calculations for the residential exposure were also made. For subjects living<50 m from the line, the exposure at home contributed about 80% of the total magnetic field exposure, measured in mT-hours. Adults living far away experienced only 38% of the total exposure at home, but children still received 55%. Subjects with low time-weighted average (TWA) exposure both at home and at work spent 84% of their time in fields <0.1 microT, and those with high TWA at both locations spent 69% of their time in fields > or = 0.2 microT. This contrast was diluted if only exposure at one location was considered. For spot measurements and calculations of the residential exposure, both sensitivity and specificity was good. However, the intermediate field exposure category (0.1-0.19 microT) showed poor correlation to the 24 hr personal measurements.     

Microwave electromagnetic field regulates gene expression in T-lymphoblastoid leukemia CCRF-CEM cell line exposed to 900 MHz

Electric, magnetic, and electromagnetic fields are ubiquitous in our society, and concerns have been expressed regarding possible adverse effects of these exposures. Research on Extremely Low-Frequency (ELF) magnetic fields has been performed for more than two decades, and the methodology and quality of studies have improved over time. Studies have consistently shown increased risk for childhood leukemia associated with ELF magnetic fields. There are still inadequate data for other outcomes. More recently, focus has shifted toward Radio Frequencies (RF) exposures from mobile telephony. There are no persuasive data suggesting a health risk, but this research field is still immature with regard to the quantity and quality of available data. This technology is constantly changing and there is a need for continued research on this issue. To investigate whether exposure to high-frequency electromagnetic fields (EMF) could induce adverse health effects, we cultured acute T-lymphoblastoid leukemia cells (CCRF-CEM) in the presence of 900?MHz MW-EMF generated by a transverse electromagnetic (TEM) cell at short and long exposure times. We evaluated the effect of high-frequency EMF on gene expression and we identified functional pathways influenced by 900?MHz MW-EMF exposure.