Magnetic Field Levels Research Articles

A Pilot Study Evaluating the Feasibility of Testing for an Acute Impact of Human Exposure to a Power-line Frequency Magnetic Field on Blood Cortisol and Thyroid-Stimulating Hormone.

Numerous studies have been carried out on the potential effects of an extremely low frequency (ELF-0-300 Hz) magnetic field (MF) on human health. However, there is limited data on the effect of a high exposure level to ELF MFs for a prolonged period. Therefore, the objective of this pilot work was to demonstrate the feasibility of a study evaluating the stress hormone concentrations resulting from a 10-min exposure to a 60 Hz MF of several tens of thousands of µT. In this pilot study, human volunteers were thus exposed for the first time to a 60 Hz, 50 mT MF for a duration of 10 min. Stress hormone levels were measured before (once), during (twice) and after (once) this 10-min exposure period. The small sample size (n = 5) did not allow to conduct standard inferential statistical tests and no conclusion regarding the exposure effects can be drawn. However, this study demonstrates the feasibility of using a simple blood testing material in a protocol testing for the effect of a 10-min exposure to a high MF level in healthy human volunteers. © 2022 Bioelectromagnetics Society.

Maternal Exposure to Magnetic Field Non-Ionizing Radiation During Pregnancy and the Increased Risk of Allergic Conditions in Offspring: A Longitudinal Cohort Study with up to 22 Years of Follow-up

BACKGROUND: Emerging epidemiologic studies and experimental animal studies have reported an impact of magnetic field (MF) non-ionizing radiation on the immune system. We examined the relationship between maternal MF exposure level during pregnancy and the risk of severe allergic conditions, having both asthma and atopic dermatitis (AD), in offspring. METHODS: We enrolled 2,060 pregnant members of Kaiser Permanente Northern California. Consented participants were asked to wear an EMDEX meter for 24 hours in early pregnancy to measure MF exposure levels from all MF-emitting sources. To examine the risk of allergic conditions in offspring, 1,568 participants who delivered a livebirth were included. We used the median of the 24-hour MF measurements to determine maternal MF exposure level. Offspring were followed from birth to early adulthood (up to 22 years) to identify those with clinical diagnoses of both asthma and AD. Confounders were ascertained during in-person interviews. Cox Proportional Hazards regression was used for analysis. RESULTS: After controlling for multiple confounders, a linear dose-response relationship between maternal MF exposure level during pregnancy and the risk of having both asthma and AD in offspring was observed. Every one milligauss (mG) increase of maternal MF exposure was associated with 21 percent increased risk of having both asthma and AD diagnoses in offspring: adjusted hazard ratio (aHR)=1.21, 95% confidence interval (CI): 1.03-1.43. Using categorical measures also showed a statistically significant dose-response relationship (p=0.04). CONCLUSIONS: In this large cohort study with rarely-available objectively measured MF exposure, maternal exposure to high MF levels during pregnancy is associated with an increased risk of having both asthma and AD allergic conditions in offspring. This finding suggests that MF exposure could impact the human immune system, especially the fetal immune system which may be especially vulnerable to the impact of MF non-ionizing radiation. KEYWORDS: Magnetic fields, non-ionizing radiation, allergy

Association Between Maternal Exposure to Magnetic Field Nonionizing Radiation During Pregnancy and Risk of Attention-Deficit/Hyperactivity Disorder in Offspring in a Longitudinal Birth Cohort

An association between maternal exposure to magnetic field (MF) nonionizing radiation during pregnancy and the risk of attention-deficit/hyperactivity disorder (ADHD) has been reported in both animal and human studies. To determine whether maternal exposure to high levels of MF nonionizing radiation is associated with an increased risk of ADHD in offspring by using more accurate measurements of MF nonionizing radiation levels and physician-diagnosed ADHD, rather than self-reports, and to determine whether the association differs for the subtypes of ADHD with or without immune-related comorbidities. A longitudinal birth cohort study was conducted at Kaiser Permanente Northern California among 1482 mother-child pairs whose mothers were participants of an existing birth cohort and whose level of exposure to MF nonionizing radiation was captured during pregnancy in 2 studies conducted from October 1, 1996, to October 31, 1998, and from May 1, 2006, to February 29, 2012. The offspring were followed up from May 1, 1997, to December 31, 2017. All participating women wore a monitoring meter for 24 hours during pregnancy to capture the level of exposure to MF nonionizing radiation from any sources. Physician-diagnosed ADHD and immune-related comorbidities of asthma or atopic dermatitis up to 20 years of age in offspring captured in the Kaiser Permanente Northern California electronic medical record from May 1, 1997, to December 31, 2017. Confounders were ascertained during in-person interviews during pregnancy. Among the 1454 mother-child pairs (548 white [37.7%], 110 African American [7.6%], 325 Hispanic [22.4%], 376 Asian or Pacific Islander [25.9%], and 95 other or unknown [6.5%]; mean [SD] maternal age, 31.4 [5.4] years]), 61 children (4.2%) had physician-diagnosed ADHD. Using Cox proportional hazards regression to account for follow-up time and confounders, compared with children whose mothers had a low level of exposure to MF nonionizing radiation during pregnancy, children whose mothers were exposed to higher levels of MF nonionizing radiation had more than twice the risk of ADHD (adjusted hazard ratio [aHR], 2.01; 95% CI, 1.06-3.81). The association was stronger for ADHD that persisted into adolescence (≥12 years of age), with an aHR of 3.38 (95% CI, 1.43-8.02). When the subtypes of ADHD were examined, the association existed primarily for ADHD with immune-related comorbidities (asthma or atopic dermatitis), with an aHR of 4.57 (95% CI, 1.61-12.99) for all ADHD cases and an aHR of 8.27 (95% CI, 1.96-34.79) for persistent cases of ADHD. Consistent with the emerging literature, this study suggests that in utero exposure to high levels of MF nonionizing radiation was associated with an increased risk of ADHD, especially ADHD with immune-related comorbidity. The findings should spur more research to examine the biological association of in utero MF exposure with risk of ADHD in offspring, given that almost everyone is exposed to it.

TOPICALITY OF MONITORING OF INDUSTRIAL FREQUENCY MAGNETIC FIELDS OF 50 HZ IN RESIDENTIAL AND PUBLIC BUILDINGS

The problem of ensuring safety of electric and magnetic fields (EMF) of extremely low frequencies (ELF) is resulted from the development of the first low-frequency generators producing penetrating effect and causing negative biological outcomes. World power resources are doubling every 10 years, and ELF EMF are generated around by such sources. The number of sources on the scale of application, power and design diversity significantly exceeds those generating EMF in other frequency ranges. The population is exposed to 50 Hz ELF at work, in electric transport, in residential and public buildings, in residential areas. ELF EMF was found both to “pollute” the environment, be an environmental health risk factor, and affect negatively the health with potential long-term outcomes. Development of various methods and means of protection against the effect of ELF EMF remains relevant today. Limitation (regulation) of the effect of the factor both in terms of intensity and exposure is the most effective protection. Epidemiological studies to identify the relationship between exposure to ELF magnetic fields (MF) and carcinogenesis are on-going. A task panel group of research experts, established by WHO in 2005, conducted a routine procedure to assess health risks resulting from exposure to ELF MFs and, in particular, cancer and considered them to lack evidence. However, the significance of the data obtained was noted to be reduced due to procedural problems, potential systematic error of assessment. The problem remains unsolved. Research using various types of monitoring: social and hygienic, sanitary and epidemiological, is going on. Spatio-temporal monitoring of 50 Hz ELF MF in enclosed spaces of residential and public buildings, where a variety of equipment, devices, power supply systems, generating different MF levels, is an important area. The population is exposed to these conditions most of the day. Monitoring will allow assessing electromagnetic load at short-term and long-term exposures.

STUDY OF 50 HZ ELECTROMAGNETIC FIELDS IN RESIDENTIAL AREAS AND EXPERT ASSESSMENT OF THE POPULATION HEALTH STATUS

Introduction. The real electromagnetic situation in a residential area in the process of power supply network operation and health status assessment of population living in the vicinity of overhead transmission lines (OTL) of various voltages and transformer substations (TS) are of current interest. The effect of 50 Hz electric fields (EF) and magnetic fields (MF) on human health has not been sufficiently studied. Material and Methods. Measurement and assessment of 50 Hz EF and MF levels generated by 35, 110 and 220 kV OTL and by 6 kinds of closed-type transformer substations were carried out. Chronic overstrain index was used to assess population health status. Questionnaire study data among residents in the vicinity of 110-220 kV OTL were used for calculation of chronic overstrain index. Results. Closed-type transformer plants don’t generate EMF or exceed 50 Hz EF or MF health standards (HS). Electric field intensity levels exceeding HS were registered under 110 and 220 kV OTL. EMF health standards were not exceeded at a distance of 2 m from 110 kV OTL and 10 m from 220 kV OTL. Magnetic field induction levels did not exceed maximum allowable levels. Significant levels of chronic overstrain were revealed in residents living at a distance of under 300 m from 110-220 kV OTL. Conclusions. Closed-type transformer substations do not generate 50-Hz EMF exceeding health standards. Compliance with the electrical safety requirements of overhead transmission lines (overhead line safety zones) provides compliance with the maximum allowable levels of 50 Hz electric and magnetic fields. Population health risk assessment study among the population in the vicinity of OTL is relevant.

Fault Detection and Localization for Overhead 11-kV Distribution Lines With Magnetic Measurements

Electric power distribution network holds a critical role in uninterruptable power supply for modern societies. The distribution network comprising of complex of primary and secondary distribution lines is vulnerable to various short-circuit (SC) faults caused by lightning strikes, storms, growing vegetation, animals, insulation breakdown, and other environmental situations. Most SC faults result in breakdowns that need to be repaired in order to restore electric supply to consumers. Rapid and accurate fault localization method helps in an accelerated system restoration process and thus reduces power outage time. In this paper, a new approach related to the noncontact magnetic field (MF)-based measurement system to localize SC faults on 11-kV overhead distribution lines is presented. The method uses highly sensitive and energy-efficient magnetic sensors to detect variations in MF levels measured along the distribution lines. The fault localization algorithm is developed which identifies SC fault on main feeders and its subbranches and then localize the fault by analyzing MF over window size of 20 cycles. The developed algorithm is implemented on a complex distribution system and tested for different cases. Laboratory experiments were conducted to detect and localize SC faults in a multibranch configuration to validate the proposed method, where measurement uncertainty of less than 5% is observed for the worst case scenario.

In-Utero Exposure to High Magnetic Fields and the Risk of Abnormal Thyroid Hormone Levels in Offspring: A Prospective Cohort Study with up to 20 Years of Follow-Up

Background/Aim: Exposure to magnetic fields (MF) and hypothyroidism in children have been increasing in parallel. Animal studies have shown that MF exposure could impact thyroid hormone levels. Methods: The impact of maternal MF exposure during pregnancy on thyroid hormones in offspring was examined in a prospective cohort study among members of the Kaiser Permanente Northern California (KPNC) healthcare system. Pregnant women were asked to carry an EMDEX meter for 24 hours during early pregnancy to capture MF exposure from all sources. Confounders were ascertained during in-person interviews. Among 1,063 participants, 734 had both a live-born child and valid MF measurements, thus were included in the current study. During 20 years of follow-up, 96 children had laboratory test results for TSH and free T4 thyroid hormones. Those whose TSH and T4 levels were both below the median level were classified as having lower thyroid function. Results: After controlling for multiple confounders using Cox survival analysis using all 734 participating children, those with high in-utero MF exposure [95th percentile MF ≥ 2 milligauss (mG)] had an increased risk of having low thyroid hormone levels [hazard ratio (HR)=2.7, 95% confidence interval (CI): 0.9-7.8] compared to children with lower in-utero MF exposure (< 2 mG). When restricting the analysis to the children who had both TSH and T4 test results, the association was stronger and statistically significant (HR=3.1, 95%CI: 1.1-9.0). There was also a dose-response relationship: HR=2.3 for in-utero MF level 2-4 mG, and HR=5.0 for in-utero MF level > 4 mG). Conclusions: In-Utero exposure to high MF level is associated with increased risk of low thyroid hormone levels, mostly due to low TSH levels. These results indicate a possible adverse impact of MF on the pituitary gland during in-utero fetal brain development. This important novel finding needs be further examined in future studies.

Exposure to Magnetic Field Non-Ionizing Radiation and the Risk of Miscarriage: A Prospective Cohort Study

Magnetic field (MF) non-ionizing radiation is widespread and everyone is exposed to some degree. This prospective cohort study of 913 pregnant women examined the association between high MF exposure and miscarriage risk. Cox (proportional hazards) regression was used to examine the association. After controlling for multiple other factors, women who were exposed to higher MF levels had 2.72 times the risk of miscarriage (hazard ratio = 2.72, 95% CI: 1.42–5.19) than those with lower MF exposure. The increased risk of miscarriage associated with high MF was consistently observed regardless of the sources of high MF. The association was much stronger if MF was measured on a typical day of participants’ pregnancies. The finding also demonstrated that accurate measurement of MF exposure is vital for examining MF health effects. This study provides fresh evidence, directly from a human population, that MF non-ionizing radiation could have adverse biological impacts on human health.

Pengaruh Pemaparan Medan Magnet Pada Media Mandels Yang Dimodifikasi Terhadap Pertumbuhan Dan Aktivitas Enzim Selulase Bacillus Sp.

Enzymes can undergo structural changes due to various environmental factor such as pH,temperature, electricity and magnetic fields. The purpose of this study was to investigate theeffect of magnetic field strength and duration of exposure to the modified of media Mandelsused as a culture medium of Bacillus sp. on the growth and activity of cellulase enzyme fromthe bacterium Bacillus sp. Factorial study group were prepared using the method of fullrandomized design (RKLT). The first factor is the strong magnetic field consists of 4 levels ofmagnetic field strength treatment: 0 mT; 0,1 mT; 0,2 mT; 0.3 mT. The second faktor is theprolonged exposure consisting of 4 levels prolonged exposure treatments 0, 10, 20, 30minutes. each unit treatment was repeated 3 times. The results showed that exposure tomagnetic fields on modified of media Mandels causes a decrease in the relative activity ofthe enzyme cellulase and relative growth of Bacillus sp.Keywords: cellulase enzyme, magnetic field, Mandels modification, Bacillus sp.

Exposure To High Levels Of Magnetic Fields (MF) During Pregnancy And The Risk Of Miscarriage: A Prospective Cohort Study

Introduction: We conducted a prospective cohort study among pregnant members of Kaiser Permanente Northern California (KPNC) region to further examine a previously reported association of an increased risk of miscarriage with higher levels of MF exposure during pregnancy. Methods: Pregnant women were identified through KPNC electronic medical record (EMR) databases. Among 1,627 eligible women, 1,054 participated. Participants were asked to wear an EMDEX Lite meter for 24 hours to measure MF from all sources on a typical day of their pregnancy, and to keep a diary of their activities. We used 99th percentile of the 24-hour MF measurements to determine exposure. Miscarriage was ascertained from EMRs and in-person interviews. Confounders were also ascertained during in-person interviews. After excluding those with incomplete MF measurement data, 913 subjects were included in the final analysis. The Cox proportional hazard model was used for analysis. Results: After controlling for multiple confounders, women who were exposed to higher MF levels [99th percentile ≥ 2.5 milligauss (mG) as measured on the typical day of pregnancy] had 2.78 times the risk of miscarriage [hazard ratio (HR)=2.78, 95% CI: 1.46-5.29] than those whose 99th percentile MF exposure was lower than 2.5 mG. The association was slightly stronger among women without multiple prior miscarriages (≥ 2), HR=3.76 (1.07-13.18), than among those with multiple miscarriages: HR=2.56(1.19-5.50). We did not observe a clear dose-response relationship above 2.5 mG. The associations were not observed if MF was measured on a non-typical day of pregnancy, indicating a diluting effect due to inaccurate measure of MF exposure. Conclusions: Exposure to high MFs during pregnancy is associated with increased risk of miscarriage. This finding further supports previously reported associations. Accurate measurement of MF exposure is likely vital for studies examining EMF health effects.

Characterization of extremely low frequency magnetic fields from diesel, gasoline and hybrid cars under controlled conditions.

This study characterizes extremely low frequency (ELF) magnetic field (MF) levels in 10 car models. Extensive measurements were conducted in three diesel, four gasoline, and three hybrid cars, under similar controlled conditions and negligible background fields. Averaged over all four seats under various driving scenarios the fields were lowest in diesel cars (0.02 μT), higher for gasoline (0.04–0.05 μT) and highest in hybrids (0.06–0.09 μT), but all were in-line with daily exposures from other sources. Hybrid cars had the highest mean and 95th percentile MF levels, and an especially large percentage of measurements above 0.2 μT. These parameters were also higher for moving conditions compared to standing while idling or revving at 2500 RPM and higher still at 80 km/h compared to 40 km/h. Fields in non-hybrid cars were higher at the front seats, while in hybrid cars they were higher at the back seats, particularly the back right seat where 16%–69% of measurements were greater than 0.2 μT. As our results do not include low frequency fields (below 30 Hz) that might be generated by tire rotation, we suggest that net currents flowing through the cars’ metallic chassis may be a possible source of MF. Larger surveys in standardized and well-described settings should be conducted with different types of vehicles and with spectral analysis of fields including lower frequencies due to magnetization of tires.

Synoptic Analysis Clarifies Childhood Leukemia Risk from ELF Magnetic Field Exposure

In spite of 36 years epidemiologic research, there is still an ongoing controversy about a causal link between childhood leukemia (CL) and exposure to extremely low frequency (ELF) magnetic fields (MF). Public concern has been increased by the fact that ELF MF have been classified as possibly carcinogenic to humans (class 2B) while exposure limits still remain three orders of magnitudes above reported CL risk onset levels. In a new synoptic approach rather than few selected ORs, all reported epidemiological risk estimates (ORs) are analyzed, both pooled together as well as separated into sub-pools of different exposure metric as well as of high and low exposure levels. The results explain the worrying offset of ORs towards increased CL risk as well as the reported puzzling dose-response at low MF levels as an artifact caused by the small-number effect. The synoptic analysis clarifies that ORs critically depend on statistical power. With increasing statistical power ORs decrease and finally converge to and stay at zero risk. This is found consistently at the entire data pool as well as at all sub-pools related to investigated exposure parameters (wire code, distance to MF source, and magnetic field value). Former contradictory results can now be explained. The synoptic analysis provides convincing evidence that the risk of childhood leukemia is not increased by exposure to ELF magnetic fields. IARC’s classification of ELF MF needs revision.

Occupational Exposure to Extremely Low-Frequency Magnetic Fields and Neurodegenerative Disease

Previous studies reported associations of occupational electric and magnetic fields (MF) with neurodegenerative diseases (NDDs). Results differ between studies using proxy exposure based on occupational titles and estimated MF levels. We conducted a meta-analysis of occupational MF NDD, primarily Alzheimer disease (AD), and motor neuron diseases (MNDs) studies. We identified 42 peer-reviewed publications and focused our analysis on study characteristics, exposure metrics, and publication bias. We found weak associations for occupational MF exposure proxies with AD and MND. Motor neuron disease risk was associated with occupational titles, whereas AD risk was associated with estimated MF levels. Results varied in study design, with dissimilar variation across diseases. Our results do not support MF as the explanation for observed associations between occupational titles and MND. Disease misclassification, particularly for AD, and imprecise exposure assessment affected most studies.

Assessment of the influence of magnetic fields on aspects of the biology of the adult Mediterranean flour moth Ephestia kuehniella Zeller, 1879 (Lepidoptera: Pyralidae)

All living systems are under the influence of magnetic fields (MFs) from various sources. In this study, experiments were performed to investigate the effect of MFs from a DC power supply on the longevity of adults, fecundity and daily egg laying pattern of female E. kuehniella. Adults of E. kuehniella (24 h old) were exposed to power supply generating MFs of different levels (0, 1.5, 3, 5, 7.5 and 10 mT) at 50 Hz for 24 h exposure time. Mortality increased with increasing MFs level and complete mortality was achieved at the level of 10 mT. Adult viability was highest in control (92%). Pest longevity was significantly reduced with increasing level of MFs (P<0.05). There was no significant difference in the longevity of males and females (P˃0.05). Exposing adults to increasing level of MFs significantly influenced daily egg laying patterns and fecundity of magnetized females. Larval emergence from these eggs was completely prevented at highest level of MFs. The LD50 and LD99 values of MFs against adult stages of E. kuehniella were measured as 5.23 mT and 12.81 mT, respectively. According to these results, 10 mT MFs for 24 h is sufficient to control adult survival and production of progeny in this pest

A Prospective Study of In-utero Exposure to Magnetic Fields and the Risk of Childhood Obesity

We conducted a prospective study to examine whether in-utero exposure to magnetic fields (MFs) increases the risk of childhood obesity. Participating women carried a meter measuring MF levels during pregnancy and 733 of their children were followed up to 13 years to collect clinically recorded information on growth patterns with 33 weight measurements per child on average. Prenatal exposure to high MF level was associated with increased risk of being obese in offspring than those with lower MF level (odds ratio = 1.69, 95% confidence interval: 1.01–2.84). The association demonstrated a dose-response relationship and was stronger (more than 2.3 fold increased risk) among children who were followed up to the end of the study. The association existed only for persistent obesity, but not for transitory (unlikely) obesity. Maternal exposure to high MF during pregnancy may be a new and previously unknown factor contributing to the world-wide epidemic of childhood obesity/overweight.

Maternal Exposure to Magnetic Fields During Pregnancy in Relation to the Risk of Asthma in Offspring

To determine whether maternal exposure to high levels of magnetic fields (MFs) during pregnancy is associated with the risk of asthma in offspring. A prospective cohort study. Kaiser Permanente Northern California. Pregnant Kaiser Permanente Northern California members in the San Francisco area. Asthma was clinically diagnosed among 626 children who were followed up for as long as 13 years. All participants carried a meter to measure their MF levels during pregnancy. After adjustment for potential confounders, a statistically significant linear dose-response relationship was observed between increasing maternal median daily MF exposure level in pregnancy and an increased risk of asthma in offspring: every 1-mG increase of maternal MF level during pregnancy was associated with a 15% increased rate of asthma in offspring (adjusted hazard ratio [aHR], 1.15; 95% confidence interval [CI], 1.04-1.27). Using the categorical MF level, the results showed a similar dose-response relationship: compared with the children whose mothers had a low MF level (median 24-hour MF level, ≤0.3 mG) during pregnancy, children whose mothers had a high MF level (>2.0 mG) had more than a 3.5-fold increased rate of asthma (aHR, 3.52; 95% CI, 1.68-7.35), while children whose mothers had a medium MF level (>0.3-2.0 mG) had a 74% increased rate of asthma (aHR, 1.74; 95% CI, 0.93-3.25). A statistically significant synergistic interaction was observed between the MF effect and a maternal history of asthma and birth order (firstborn). Our findings provide new epidemiological evidence that high maternal MF levels in pregnancy may increase the risk of asthma in offspring.

Assessment of occupational exposure to extremely low frequency magnetic fields in hospital personnel

It has been proposed that chronic exposure to extremely low frequency (ELF) magnetic fields (MF) in occupational environments could represent a risk factor for a number of disorders. Medical and technical workers in hospitals have been reported to be exposed to relatively strong ELF fields. The present work aims to characterize exposure to MF in the 5 Hz to 2 kHz frequency range in a large hospital through both instantaneous environmental measurements and personal monitoring of workers. The study was conducted in different working environments of a hospital with about 4400 employees, many of them working at two or more different work stations and consequently, exposed to MF levels that were expected to be unevenly distributed in space and time. The results indicate that: (1) The dominant frequency at the studied environments was 50 Hz (average 90.8 ± 6% of the total B value); (2) The best descriptive information on a worker's exposure is obtained from personal monitoring of volunteer workers; (3) The arithmetic averages of exposure levels obtained from the monitoring ranged from 0.03 ± 0.01 µT in nurses to 0.39 ± 0.13 µT in physiotherapists; and (4) The description of the MF environment through spot measurements in the workplace, although coherent with the data from personal monitoring, might not adequately estimate MF exposure in some professional categories.

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.

Power-Frequency Magnetic Fields and Childhood Brain Tumors: A Case-Control Study in Japan

BackgroundThe strength of the association between brain tumors in children and residential power-frequency magnetic fields (MF) has varied in previous studies, which may be due in part to possible misclassification of MF exposure. This study aimed to examine this association in Japan by improving measurement techniques, and by extending measurement to a whole week.MethodsThis population-based case-control study encompassed 54% of Japanese children under 15 years of age. After excluding ineligible targeted children, 55 newly diagnosed brain tumor cases and 99 sex-, age-, and residential area-matched controls were included in the analyses. The MF exposures of each set of matching cases and controls were measured in close temporal proximity to control for seasonal variation; the average difference was 12.4 days. The mean interval between diagnosis and MF measurements was 1.1 years. The weekly mean MF level was defined as the exposure. The association was evaluated using conditional logistic regression analysis that controlled for possible confounding factors.ResultsThe odds ratios (95% CI) for exposure categories of 0.1 to 0.2, 0.2 to 0.4, and above 0.4 µT, against a reference category of <0.1 µT, were 0.74 (0.17–3.18), 1.58 (0.25–9.83), and 10.9 (1.05–113), respectively, after adjusting for maternal education. This dose-response pattern was stable when other variables were included in the model as possible confounding factors.ConclusionsA positive association was found between high-level exposure—above 0.4 µT—and the risk of brain tumors. This association could not be explained solely by confounding factors or selection bias.

Exposure to magnetic fields and the risk of poor sperm quality

We conducted a population-based case–control study among healthy sperm donors to study exposure to magnetic fields (MFs) and poor sperm quality. All participants wore a meter to capture daily MF exposure. After controlling for confounders, compared to those with lower MF exposure, those whose 90th percentile MF level ≥1.6 mG had a two-fold increased risk of abnormal sperm motility and morphology (odds ratio (OR): 2.0, 95% confidence interval (CI): 1.0–3.9). Increasing duration of MF exposure above 1.6 mG further increased the risk ( p = 0.03 for trend test). Importantly, the association and dose–response relationship were strengthened when restricted to those whose measurement day reflected their typical day of the previous 3 months (a likely period of spermatogenesis). Age-adjusted Spearman Rank Order Correlations showed an inverse correlation between MF exposure and all semen parameters. Our study provides some evidence for the first time that MF exposure may have an adverse effect on sperm quality.