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As the first case–control study of malignant mesothelioma of the pericardium and the tunica vaginalis testis (mTVT), the paper by Marinaccio et al (1) is potentially an important epidemiologic contribution. A careful review of the paper, however, raises a number of methodological issues. Any case–control study can be viewed as being nested within a conceptual cohort, with controls being sampled from the at-risk cohort as cases arise over time. This view of case–control studies leads to the concept of incidence-density sampling of controls (eg, 2, 3). For Marinaccio et al (1) this would mean that, as cases were registered over the study period, each would be matched to an individual control or set of controls of the same gender, age, and region of the country (since asbestos exposure varies by time and region [4]). For example, if a case were 50 years old in 1995, then any matched control should be close to age 50 in 1995 and of the same gender and from the same region as the case. Matching for age in this fashion automatically results in matching for year of birth, which is essential in this context because birth-cohort effects are determinants of asbestos exposure and mesothelioma incidence (eg, 5–8). If Marinaccio et al (1) used this scheme for age-matching, one would expect to see similar distributions of cases (table 1) and controls (table S3 in the supplemental material) by period of birth. Among males, however, the distributions of mesothelioma cases (whether pericardial or mTVT) and controls by period of birth are clearly different (P

There is increasing concern that use of mobile phones, a source of low-level radio-frequency electromagnetic fields, may be associated with poor semen quality, but the epidemiologic evidence is limited and conflicting. The relationship between mobile phone use patterns and markers of semen quality was explored in a longitudinal cohort study of 153 men that attended an academic fertility clinic in Boston, Massachusetts. Information on mobile phone use duration, headset or earpiece use, and the body location in which the mobile phone was carried was ascertained via nurse-administered questionnaire. Semen samples (n=350) were collected and analyzed onsite. To account for multiple semen samples per man, linear mixed models with random intercepts were used to investigate the association between mobile phone use and semen parameters. Overall, there was no evidence for a relationship between mobile phone use and semen quality.

BACKGROUND: The electric power industry represents a unique subset of the U.S. workforce. We aimed to evaluate the relationships between occupational category, nature of injury, and injury severity among electric power industry workers. METHODS: The Occupational Health and Safety Database (1995-2013) was used to calculate injury rates, assess patterns of injury severity, and identify at-risk occupations in this population. RESULTS: Over the surveillance period, a total of 63,193 injuries were reported. Overall, and severe injury rates were 3.20 and 0.52 per 100 employee-years, respectively. The fatal injury rate was 3.29 per 100,000 employee-years. Line workers experienced the highest risk for fatal injuries and second highest for non-fatal severe injuries, following meter readers. The most severe non-fatal injuries were hernia and rupture; multiple injuries; and CTD/RSI. Fatal injuries were most commonly associated with vehicle collisions and contact with electric current. CONCLUSIONS: Industry specific surveillance and interventions tailored to high-risk occupations are needed to further reduce severe injuries in this population. Am. J. Ind. Med. © 2016 Wiley Periodicals, Inc.© 2016 Wiley Periodicals, Inc. Language: en

The southwest region of the United States is expected to experience an expansion of commercial solar photovoltaic generation facilities over the next 25 years. A solar facility converts direct current generated by the solar panels to three-phase 60-Hz power that is fed to the grid. This conversion involves sequential processing of the direct current through an inverter that produces low-voltage three-phase power, which is stepped up to distribution voltage (∼12 kV) through a transformer. This study characterized magnetic and electric fields between the frequencies of 0 Hz and 3 GHz at two facilities operated by the Southern California Edison Company in Porterville, CA and San Bernardino, CA. Static magnetic fields were very small compared to exposure limits established by IEEE and ICNIRP. The highest 60-Hz magnetic fields were measured adjacent to transformers and inverters, and radiofrequency fields from 5-100 kHz were associated with the inverters. The fields measured complied in every case with IEEE controlled and ICNIRP occupational exposure limits. In all cases, electric fields were negligible compared to IEEE and ICNIRP limits across the spectrum measured and when compared to the FCC limits (≥0.3 MHz).

We conducted a large registry-based study in California to investigate the association between race/ethnicity and childhood leukaemia focusing on two subtypes: acute lymphoblastic leukaemia (ALL) and acute myeloid leukaemia (AML).We obtained information on 5788 cases and 5788 controls by linking California cancer and birth registries. We evaluated relative risk of childhood leukaemia by race and ethnicity of the child and their parents using conditional logistic regression, with adjustment for potential confounders.Compared with Whites, Black children had lower risk of ALL (OR=0.54, 95% CI 0.45 to 0.66) as well as children of Black/Asian parents (OR=0.31, 95% CI 0.10 to 0.94). Asian race was associated with increased risk of AML with OR=1.643, 95% CI 1.10 to 2.46 for Asian vs Whites; and OR=1.67, 95% CI 1.04 to 2.70 for Asian/Asian vs White/White. Hispanic ethnicity was associated with increased risk of ALL (OR=1.37, 95% CI 1.22 to 1.52). A gradient in risk of ALL was observed while comparing Hispanic children with both parents Hispanic, one parent Hispanic and non-Hispanic children (p Value for trend0.0001). The highest risk of ALL was observed for children with a combination of Hispanic ethnicity and White race compared with non-Hispanic whites (OR=1.27, 95% CI 1.12 to 1.44). The lowest risk was observed for non-Hispanic blacks (OR=0.46, 95% CI 0.36 to 0.60). Associations for total childhood leukaemia were similar to ALL.Our results confirm that there are ethnic and racial differences in the incidence of childhood leukaemia. These differences indicate that some genetic and/or environmental/cultural factors are involved in aetiology of childhood leukaemia.

While malignant mesothelioma has generally been associated with exposure to asbestos, several lines of evidence suggest strongly that, like all other cancers, it can and does occur spontaneously and that age is a strong risk factor for its development. This includes not only pleural mesothelioma, the most common site for this disease, but also extra-pleural sites (peritoneum, pericardium, tunica vaginalis testis). Recent epidemiologic studies show that ionizing radiation is another risk factor. The discovery of a germline mutation in the BRCA1 associated protein 1 (BAP1) gene, the inheritance of which increases greatly the risk of developing mesothelioma, may provide the first step in the understanding of the underlying genetic events in the pathogenesis of mesothelioma. Whether and how inheritance of this mutation interacts with other risk factors remains an open question. The diminution of the impact of asbestos on mesothelioma incidence in western countries due to its phase-out may enable the discovery of more modest risk factors. Exposure-response relationships are probably determined by the entire temporal history of exposure, not just the cumulative exposure to fibers. The concept of latency is more nuanced than appears at first sight.

The aim of this study was to investigate the possible association between residential distance to high-voltage power lines and neurodegenerative diseases, especially Alzheimer's disease. A Swiss study previously found increased risk of Alzheimer's disease for people living within 50 m of a power line. A register-based case-control study including all patients diagnosed with neurodegenerative diseases during the years 1994-2010 was conducted among the entire adult population of Denmark. Using conditional logistic regression models, hazard ratios for ever living close to a power line in the time period 5-20 years before diagnosis were computed. The risks for developing dementia, Parkinson's disease, multiple sclerosis, and motor neuron disease were not increased in persons living within close vicinity of a power line. The risk of Alzheimer's disease was not increased for ever living within 50 m of a power line (hazard ratio = 1.04, 95% confidence interval: 0.69, 1.56). No dose-response according to number of years of living within 50 m of a power line was observed, but there were weak indications of an increased risk for persons diagnosed by the age of 75 years. Overall, there was little support for an association between neurodegenerative disease and living close to power lines.

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.

Introduction Workers in the electric power industry face many risks of injury due to the high diversity of work tasks performed in potentially hazardous and unpredictable work environments. Method We calculated injury rates by age, sex, occupational group, and injury type among workers in the Electric Power Research Institute’s (EPRI) Occupational Health and Safety Database (OHSD), which contains recordable injury, medical claims, and personnel data from 18 participating electric power companies from 1995 to 2013. Results The OHSD includes a total of 63,193 injuries over 1,977,436 employee-years of follow-up, for an overall injury rate of 3.20 injuries per 100 employee-years. Annual injury rates steadily decreased from 1995 to 2000, increased sharply in 2001, and subsequently decreased to their lowest rate of 1.31 injuries per 100 employee-years in 2013. Occupations with the highest injury rates were welders (13.56 per 100 employee-years, 95% CI 12.74–14.37), meter readers (12.04 per 100 employee-years, 95% CI 11.77–12.31), and line workers (10.37 per 100 employee-years, 95% CI 10.19–10.56). Males had an overall higher injury rate compared to females (2.74 vs. 1.61 per 100 employee-years) although some occupations, such as meter reader, had higher injury rates for females. For all workers, injury rates were highest for those in the 21 to 30 age group (3.70 per 100 employee-years) and decreased with age. Welders and machinists did not follow this trend and had higher injury rates in the 65 + age group. There were 63 fatalities over the 1995 to 2013 period, with 21 fatalities (33.3%) occurring among line workers. Conclusions Although injury rates have decreased over time, certain high-risk groups remain (i.e., line workers, mechanics, young males, older welders and machinists, and female meter readers). Practical applications Protective measures and targeted safety programs may be warranted to ensure the safety of electric power workers.

We conducted a large registry-based study in California to investigate the association of perinatal factors and childhood leukemia with analysis of two major subtypes, acute lymphocytic leukemia (ALL) and acute myeloid leukemia (AML).We linked California cancer and birth registries to obtain information on 5788 cases and 5788 controls matched on age and sex (1:1). We examined the association of birth weight, gestational age, birth and pregnancy order, parental ages, and specific conditions during pregnancy and risk of total leukemia, ALL and AML using conditional logistic regression, with adjustment for potential confounders.The odds ratio (OR) per 1000 g increase in birth weight was 1.11 for both total leukemia and ALL. The OR were highest for babies weighing ≥ 4500 g with reference2500 g: 1.59 (95% CI: 1.05-2.40) and 1.70 (95% CI: 1.08-2.68) for total leukemia and ALL, respectively. For AML, increase in risk was also observed but the estimate was imprecise due to small numbers. Compared to average-for-gestational age (AGA), large-for-gestational age (LGA) babies were at slightly increased risk of total childhood leukemia (OR = 1.10) and both ALL and AML (OR = 1.07 and OR = 1.13, respectively) but estimates were imprecise. Being small-for-gestational age (SGA) was associated with reduced risk of childhood leukemia (OR = 0.81, 95% CI: 0.67-0.97) and ALL (OR = 0.77, 95% CI: 0.63-0.94), but not AML. Being first-born was associated with decreased risk of AML only (OR = 0.70; 95% CI: 0.53-0.93). Compared to children with paternal age25 years, children with paternal age between 35 and 45 years were at increased risk of total childhood leukemia (OR = 1.12; 95% CI: 1.04-1.40) and ALL (OR = 1.23; 95% CI: 1.04-1.47). None of conditions during pregnancy examined or maternal age were associated with increased risk of childhood leukemia or its subtypes.Our results suggest that high birth weight and LGA were associated with increased risk and SGA with decreased risk of total childhood leukemia and ALL, being first-born was associated with decreased risk of AML, and advanced paternal age was associated with increased risk of ALL. These findings suggest that associations of childhood leukemia and perinatal factors depend highly on subtype of leukemia.

This study presents measurement data that describe radiofrequency emission levels and patterns from smart meters (rated nominally at 1 W) currently deployed in Pacific Gas and Electric Company's service territory in northern California. The smart meters in our investigation could not be set to operate continuously and required a Field Service Unit to induce short periods of emitted fields. To obtain peak field data under both laboratory and ambient conditions, a spectrum analyzer scanned across the 83 transmitting channels between 902 and 928 MHz used by the smart meter on a random frequency-hopping basis. To obtain data describing temporal emission patterns, the analyzer operated in scope mode. Duty cycle was estimated using transmit data acquired by the system operator from over 88,000 m. Instantaneous peak fields at 0.3 m in front of the meters were no more than 15% of the US Federal Communications Commission (FCC) exposure limit for the general public, and 99.9% of the meters operated with a duty cycle of 1.12% or less during the sampling period. In a sample of measurements in six single-detached residences equipped with individual smart meters, no interior measurement of peak field exceeded 1% of the FCC's general public exposure limit.

Introduction: Although selection bias in case-control studies has been studied extensively, little is known about selection of cases and controls among various ethnic groups. This study compares racial differences in childhood cancer rates as estimated by case-control studies with various design features. It also compares estimates of racial distribution among cases as reported by case-control studies to those observed for an ideal case series with complete ascertainment of cases for these studies or in population-based cancer registries in corresponding geographic regions and calendar periods. Methods: Peer-reviewed publications on childhood leukemia and brain tumors from North America, published between 1980 and 2007, were reviewed. Incidence data by race/ethnicity were compiled from research publications, federal cancer statistics, and cancer registries. Meta-analysis was conducted to assess racial/ethnic differences by study characteristics. Racial distributions of cases from published case-control studies were compared to those of a presumably noncensored case distribution (i.e. include both participating and non-participating cases in a case-control study) or cases recorded by cancer registries. Results: In interview-based case-control studies of childhood cancer, the proportion of Whites compared to non-Whites tended to be higher among controls than among cases; however, the opposite was true for record-based case-control studies. Additionally, the proportion of Whites tended to be higher among the participating cases in the published case-control studies compared to the proportion of Whites among the non-participating cases or in cancer registries. Conclusions: Investigators need to consider differential participation by racial group as a potential source of bias in the interpretation of case-control study results.

This study examined radiofrequency (RF) emissions from smart electric power meters deployed in two service territories in California for the purpose of evaluating potential human exposure. These meters included transmitters operating in a local area mesh network (RF LAN, ∼250 mW); a cell relay, which uses a wireless wide area network (WWAN, ∼1 W); and a transmitter serving a home area network (HAN, ∼70 mW). In all instances, RF fields were found to comply by a wide margin with the RF exposure limits established by the US Federal Communications Commission. The study included specialised measurement techniques and reported the spatial distribution of the fields near the meters and their duty cycles (typically

With the increased interest in the possible adverse health effects attributed to inhalation of fine particle matter, this study was conducted to gather preliminary information about workplace exposures at coal- and gas-fired power plants to fine particles (PM(1); i.e.

As part of a collaborative approach involving electric utility companies, university researchers, individual contractors and a not-for-profit research institute, two ergonomics teams consisting of skilled utility workers and trained ergonomists, were assembled. These teams were to identify tasks with risk factors for musculoskeletal disorders (MSDs) among workers in fossil-fueled generating stations and and to propose ergonomic interventions for these tasks. One team focused on tasks of electricians and the other focused on tasks of plant operators and mechanics. Several of the tasks were tested in an ergonomics laboratory and at one of the utility's generating stations. We present a sample of the recommended interventions in this paper. An anthropometric analysis of electrical box height recommended the appropriate height for electrical boxes. The results of a field experiment showed that low rolling resistance wheels decreased the forces to initiate and sustain pushing a cart. The same experiment also demonstrated that the forces required to turn a cart with six wheels were lower than the forces equired to turn a cart with four wheels. A collaborative approach to ergonomics proved to be an effective method to identify and assess tasks that are problematic for workers and to develop best practices for these tasks in the electric power industry. This method could be used by other industries in their attempt to decrease the incidence, cost and severity of workplace MSDs.

Pooled analyses may provide etiologic insight about associations between exposure and disease. In contrast to childhood leukemia, no pooled analyses of childhood brain tumors and exposure to extremely low-frequency magnetic fields (ELF-MFs) have been conducted. The authors carried out a pooled analysis based on primary data (1960–2001) from 10 studies of ELF-MF exposure and childhood brain tumors to assess whether the combined results, adjusted for potential confounding, indicated an association. The odds ratios for childhood brain tumors in ELF-MF exposure categories of 0.1–

To advance our understanding of an association between exposure to power frequency magnetic fields (MFs) and the risk of childhood leukemia, we should conduct a study that is convincingly free of selection and response bias, with highly accurate exposure assessment and a large number of highly exposed individuals. Previous measurements revealed that MF in apartments located above internal transformer stations (ITSs) are higher than in other apartments in the same building. An international epidemiologic study of childhood leukemia, TransExpo, was designed to take advantage of this scenario. This article presents the results of an exposure assessment study performed in apartment buildings with ITS in Israel. Measurements were performed in 41 apartments within 10 buildings. Average MF at the height of 0.5 m was 0.40 μT in apartments above the ITS and 0.06-0.12 μT in all other apartments. These results confirm that classification of MF exposure based on apartment location is feasible with remarkable specificity (0.98 and 0.96 for cutoff points of 0.2 and 0.4 μT, respectively) and sensitivity (1.00 for both cutoff points). Because the location of an apartment relative to the ITS can be easily determined, an exposure assessment can reliably be performed without obtaining access to residences.

To describe the incidence and impact of neck injuries among electric utility workers.Rates of neck injuries per 10,000 employee-years were calculated for various demographic and occupational factors using data from an injury surveillance database established among 17 electric utility companies over the period 1995-2007.The overall rate of neck injuries was 13.3. Male workers had a slightly higher rate than females, and younger workers (30) had the highest neck injury rates. Trade/craft workers experienced the highest rates of neck injuries, whereas office-based experienced the lowest. The majority of neck injuries (69%) were sprain/strains and resulted in less than 1 lost day of work (76.7%).The occurrence of neck injuries in the electric utility workforce varies widely with respect to age, sex, and occupational groups with different characteristics, activities, and work environments. Industry-wide surveillance allows easier identification of injury patterns and risk factors of various injury types and facilitates the development of targeted prevention and intervention strategies to reduce the occurrence of these injuries.

The occupational epidemiological literature on extremely low frequency electric and magnetic fields (EMF) and health encompasses a large number of studies of varying design and quality that have addressed many health outcomes, including various cancers, cardiovascular disease, depression and suicide, and neurodegenerative diseases, such as Alzheimer disease and amyotrophic lateral sclerosis (ALS). At a 2006 workshop we reviewed studies of occupational EMF exposure with an emphasis on methodological weaknesses, and proposed analytical ways to address some of these. We also developed research priorities that we hope will address remaining uncertainties. Broadly speaking, extensive epidemiological research conducted during the past 20 years on occupational EMF exposure does not indicate strong or consistent associations with cancer or any other health outcomes. Inconsistent results for many of the outcomes may be attributable to numerous shortcomings in the studies, most notably in exposure assessment. There is, however, no obvious correlation between exposure assessment quality and observed associations. Nevertheless, for future research, the highest priorities emerge in both the areas of exposure assessment and investigation of ALS. To better assess exposure, we call for the development of a more complete job-exposure matrix that combines job title, work environment and task, and an index of exposure to electric fields, magnetic fields, spark discharge, contact current, and other chemical and physical agents. For ALS, we propose an international collaborative study capable of illuminating a reported association with electrical occupations by disentangling the potential roles of electric shocks, magnetic fields and bias. Such a study will potentially lead to evidence-based measures to protect public health.

Exposure to 50 Hz magnetic field (MF) was evaluated in 31 multi-level apartment buildings with built-in step-down transformer stations. In each building, three apartments were selected: one apartment located immediately above the transformer room (index apartment), one located on the same floor and one on a higher floor. The mean value of measured MFs was 0.98 microT in apartments above transformers, 0.13 microT on the same floor, and 0.1 microT in on higher floors. The mean measured MF value was higher than 0.2 microT in 30 (97%) index apartments, 4 (14%) on the same floor as the index apartments and 4 (13%) on higher floors. The corresponding numbers were 25 (81%), 0 and 0, respectively, when 0.4 microT was used as cut-point. It is concluded that apartments in building with built-in transformers can be reliably classified into high and low-exposure categories based on their location in relation to transformers.

To update past meta-analyses on occupational electromagnetic fields (EMF) and adult brain cancer and leukemia.We collected and evaluated all relevant 1993 to 2007 publications. Summary estimates were obtained using various weighting schemes. To explore sources of heterogeneity, study characteristics were examined using regression analysis.Overall, for new studies, both brain cancer and leukemia showed small increases in risk estimates, 10% and 13%, respectively. Notably, pooled risk estimates were lower than in past meta-analyses, and leukemia subtypes showed no consistent pattern when past and present meta-analyses were compared.The lack of a clear pattern of EMF exposure and outcome risk does not support a hypothesis that these exposures are responsible for the observed excess risk. Findings were not sensitive to assumptions, influential studies, weighting schemes, publication bias, study characteristics, or funding source.

We conducted a meta-analysis of studies on magnetic field exposure and childhood brain tumors to evaluate homogeneity in the results, to examine reasons for heterogeneity, and to derive a summary effect estimate. Comparison of results from studies of childhood brain cancer and childhood leukemia may also help to assess the potential for selection bias in childhood leukemia studies.We included results from 13 studies. Using an inverse variance-weighted method, summary effect estimates were calculated separately for distance, wire codes, and measured and calculated magnetic fields. Sensitivity analyses were conducted to assess the influence of individual studies, the potential for selection bias, and the possibility of publication bias.With the exception of wire-code studies, results were compatible with homogeneity across studies. The summary odds ratios (95% confidence intervals) were 0.88 (0.57-1.37) for distance50 m and 1.14 (0.78-1.67) for calculated or measured magnetic fields above 0.2 microT. For measured or calculated exposures above 0.3 or 0.4 microT, the summary odds ratio was 1.68 (0.83-3.43), with no differences by method of exposure assessment. No single study had a substantial effect on the summary estimates. There was no indication of publication bias.With the exception of high cut-point analyses (0.3/0.4 microT), where the possibility of a moderate risk increase cannot be excluded, no increase in childhood brain cancer risk was evident for any of the exposure metrics.

Many epidemiological studies have investigated residential exposure to extremely-low-frequency magnetic field (ELF-MF) for children, but exposure at schools where children may stay up to 8 h every weekday was rarely considered. Between March and June 2004, we carried out a field study in Taipei City and County of northern Taiwan to explore ELF-MF exposure pattern among children at schools with high voltage transmission lines (HVTL) running through the campuses. One hundred and one children attending 14 schools with nearby HVTL (exposed group) and 123 children of 18 schools at least 100 m away from HVTL (unexposed group) were monitored for 24-hour personal ELF-MF exposure. Selected classrooms and playgrounds within the buffer regions (i.e., within 30 m of HVTL) and those away from the buffer regions were also assessed, using spot measurements, to determine the extent to which HVTL may contribute to the environmental exposure on campuses. Results show that the two groups didn't differ significantly for both mean exposure and proportion of exposure greater than 0.4 micro-Tesla (microT) estimated for 24 h. However, we noted that 17.8% of the exposed children had a personal mean exposure greater than 0.4 microT during school hours, significantly (p=0.011) higher than that (6.5%) estimated for the unexposed children. An even higher percentage (27.3%) was observed for 11 students with their classrooms intersecting the buffer regions. Playgrounds near buffer regions showed a significantly higher ELF-MF than the other areas of the exposed schools (0.70 vs 0.18 microT, p=0.043). The study demonstrates a wide range of exposures to ELF-MF among school children at campuses adjacent to HVTL. Children attending the exposed schools may have a higher chance of experiencing a mean exposure greater than 0.4 microT during school hours.

Objective: To investigate the association between individual- and community-level socio-economic status (SES) and childhood leukemia, particularly its subtypes: acute lymphoblastic leukemia (ALL) and acute myeloid leukemia (AML). Study design: We conducted a large case-control registry-based study in California. Methods: Information on 5788 cases and 5788 controls was obtained by linking California cancer and birth registries. We evaluated relative risk of childhood leukemia by community- (census-based) and individual-level SES measures (parental education and source of payment for delivery) using conditional logistic regression. Results: Children in higher census-based SES categories had a tendency toward slightly decreased risk of total childhood leukemia and ALL compared to children of the lowest SES. Compared to < 12 years of school, 13 and more years of parental education were associated with slightly decreased risk of total childhood leukemia, ALL and AML; however, confidence intervals were imprecise. Source of payment for delivery was not associated with either childhood leukemia nor with its subtypes. Conclusion: We found little evidence to support the suggestion that SES is associated with risk of childhood leukemia or either major subtype. It is likely that results of many previous studies that found an association between childhood leukemia and SES were influenced by selection or ecological bias.

Occupational magnetic field (MF) exposure is less thoroughly characterized in occupations typically held by women. Our objective was to characterize occupational 50 Hz MF personal exposure (PE) among female sewing machine operators. We measured the full shift PE of 51 seamstresses, who worked in two shifts (6–14 and 14–22 h) according to their normal work routine. Measurements were conducted using EMDEX PAL meters at chest level. The average duration of the measurement periods was 449 min (range 420–470). The average arithmetic mean exposure for all women was 0.76 µT (range 0.06–4.27). The average of maximum values was 4.30 µT (range 0.55–14.80). Women working with older sewing machines experienced higher exposure than women working on newer sewing machines. For women (n = 10) who operated sewing machines produced in 1990 or earlier, the average arithmetic mean exposure was 2.09 µT, and for women (n = 41) who operated sewing machines produced after 1990, the average arithmetic mean was 0.43 µT. We conclude that women working as sewing machine operators experience higher than average occupational MF exposure compared to other working women. Most important determinant of the women's personal MF exposure was the age of the sewing machine the women operated. Bioelectromagnetics 27:451–457, 2006.© 2006 Wiley-Liss, Inc.

The authors examined the relation between neighborhood income, as a measure of socioeconomic status, and childhood cancer. Incident cases of childhood solid tumor and lymphoma in 1985-2001 were identified from provincial cancer registries in Canada. Residential postal codes at the time of diagnosis were used to assign cases to census neighborhoods. Person-years at risk were determined from quintiles of population by neighborhood income, sex, and 5-year age group, constructed using census population data. Poisson regression was used to calculate incidence rate ratios across neighborhood income quintiles. Compared with the incidence rate in the richest income quintile, moderately lower rate ratios of 0.73 (95% confidence interval: 0.63, 0.86) and 0.84 (95% confidence interval: 0.69, 1.04) were observed, respectively, for carcinomas and renal tumors in the poorest income quintile. No association was found for other types of cancer. Although a potential relation between socioeconomic status and childhood cancer cannot be excluded, the overall pattern seems compatible with random variation.

Two previous epidemiologic studies reported an association between the maximum magnetic field exposure logged during a 24-h measurement period and risk of miscarriage. A hypothesis was put forth which argued that the observed association may be the result of behavioral differences between women with healthy pregnancies (less physically active) and women with miscarriage. We analyzed four existing data sets with power-frequency magnetic-field personal exposure (PE) measurements to investigate the characteristics of peak-exposure measures. We found that the value of the measured maximum magnetic-field exposure varied inversely with the sampling interval between magnetic-field measurements and that maximum values demonstrated less stability over time in repeated measurements, compared to time-weighted average and 95th and 99th -percentile values. We also found that the number of activity categories entered by study subjects could be used to estimate the proportion of subjects with exposure above various threshold values. Exposure metrics based on maximum values exceeding thresholds tend to classify active people into higher exposure categories. These findings are consistent with the hypothesis suggesting that the association between maximum magnetic fields and miscarriage are possibly the result of behavioral differences between women with healthy pregnancies and women who experience miscarriages. Thus, generalization from a given study to more global exposure characterization should be made with particular caution and with due consideration to sampling interval and other characteristics of the measurement protocol potentially influencing the measured maximum. Future epidemiologic studies of peak magnetic field exposure and spontaneous abortion should carefully evaluate the potential confounding effect of the women's activity level during pregnancy.

Background: The objectives of this study were to compare the incidence, onset, duration and pain scores of transient neurologic symptoms (TNS) with 1% versus 5% hyperbaric lidocaine in spinal anesthesia for short urological procedures in a large prospective study. This study would also evaluate patient satisfaction, and impact of TNS on functional recovery to assess the clinical significance of TNS. Methods: This was a multicenter, double-blind, randomized controlled trial. Four hundred fifty-three patients undergoing short transurethral procedures were randomized to receive 1% or 5% hyperbaric lidocaine. Eighty milligrams of 1% or 5% hyperbaric lidocaine was administered. During the first 3 days after surgery, the presence of TNS, its intensity and duration, and patient functional level were recorded. An intention-totreat analysis was used. Results: There was no difference in the incidence of TNS (21% vs. 18%) between 1% versus 5% lidocaine. Patients with TNS had significantly higher pain scores (5.3 3 vs. 2.3 3) than patients without TNS during the first 24 h. This difference in pain scores persisted until 72 h postoperatively. There was a significant difference in the daily activities functional scores (2.2 1 vs. 1.4 0.8) of TNS versus non-TNS patients during the first 24 h postoperatively. Conclusions: There was no difference in the incidence of TNS between the 1% versus 5% spinal lidocaine groups. Pain scores were higher in patients with TNS than those who did not have TNS. During the first 48 h postop, a small proportion of patients who had TNS experienced functional impairment of walking, sitting, and sleeping. SINCE 1993, case series 1–5 have documented the occurrence of transient radicular irritation syndrome or transient neurologic symptoms (TNS) following spinal anesthesia with hyperbaric 5% lidocaine. These symptoms have been described as pain and dysesthesia in the buttock, thighs or calves, occurring after the recovery from spinal anesthesia, usually within 24 h and resolving within 72 h. The most common factors among these case series were small gauge needles, hyperbaricity, lithotomy position, and the 5% concentration of lidocaine. 1–5 A large multicenter observational study found that outpatient status also increased the risk of TNS for patients receiving lidocaine. 6 Prospective, randomized trials reveal an incidence of TNS with lidocaine spinal anesthesia between 4 and 37%. 7–12 The etiology of TNS is unclear, and controversy exists regarding the use of lidocaine, particularly, hyperbaric lidocaine. 13–14 The incidence of TNS was found to be equivalent in two studies comparing 5% and 2% lidocaine 7,8 in 50 patients undergoing gynecological surgery, and 159 patients undergoing knee arthroscopy or inguinal hernia surgery, respectively. Dilution of lidocaine concentration to 2%, 1%, or 0.5% was found to have no effect on the incidence of TNS in one study of 109 patients having knee arthroscopy. 12 Despite the controversy surrounding this issue, the functional impact of TNS on patients has never been evaluated. This study would evaluate the impact of TNS on different aspects of daily activities in order to shed light on the clinical significance of TNS. We decided to investigate the 1% concentration as this is the highest safe concentration established in animal data, which is most likely to

The Childhood Leukemia Survival Study is examining the possible association between magnetic field exposure and survival of children with newly diagnosed acute lymphocytic leukemia (ALL). We report the results of serial 24-h personal magnetic field monitoring for 412 US and Canadian children and present the correlations between annual values. The mean time-weighted average (TWA) and geometric mean (GM) were similar for first, second, and third year measurements [TWA: 0.11 microT (n = 412), 0.13 microT (n = 304), and 0.12 microT (n = 134), respectively]. There were no consistent differences in mean TWA or GM based on age or gender. Significantly lower mean TWA and GM were found for children living in rural areas. Higher exposures were noted among children living in urban areas, among apartments dwellers, and those living in rental homes. Measurements taken during summer months and among children residing in the northeast and Canada also tended to be higher. Correlations for most metrics were increased among children who had annual measurements performed during the same season. The metric with the highest year-to-year correlation was the GM. The lowest correlations were found for metrics estimating field intermittency and temporal stability. First to second year GMs were well correlated when taken in the same home (Spearman rank correlation = 0.70), but a lower correlation (0.44) was noted among residentially mobile children. Our findings suggest that summarizing exposure using a single measurement of GM can estimate exposures for residentially stable children, but is not a good predictor of personal exposures among children who change residence during the study interval.

Purpose Malignant mesothelioma most commonly arises in the pleura and peritoneum but also occurs rarely at other anatomical sites with mesothelial tissue, namely, the pericardium and tunica vaginalis testis (TVT). This review provides a better understanding of the epidemiology of mesothelioma of these extrapleural sites. Methods We conducted a systematic review of the epidemiologic and clinical literature on pericardial mesothelioma and mesothelioma of the TVT. We also analyzed U.S. Surveillance, Epidemiology, and End Results cancer registry data to describe incidence patterns of these malignancies. Results An etiologic role of asbestos exposure has been hypothesized for pericardial and TVT mesotheliomas, but no analytical case-control epidemiologic studies exist to test this relationship. A substantial proportion of cases with these malignancies report no known asbestos exposure. In large occupational cohorts with heavy asbestos exposures, no cases of pericardial or TVT mesothelioma have been reported. Trends in the incidence of these malignancies do not match those of pleural mesothelioma, which correspond to historical trends of commercial asbestos use. A male preponderance of pericardial mesothelioma is not evident. Conclusions In the absence of analytic epidemiologic studies, the etiologic role of environmental risk factors for mesothelioma of the pericardium and TVT remains elusive.

Background It has been suggested that the study of the relationship between extremely low-frequency magnetic fields (ELF-MF) and childhood acute leukemia (AL) must continue, particularly, in countr...

Down syndrome (DS) is a common congenital anomaly, and children with DS have a substantially higher risk of leukemia. Although understanding of genetic and epigenetic changes of childhood leukemia has improved, the causes of childhood leukemia and the potential role of environmental exposures in leukemogenesis remain largely unknown. Although many epidemiologic studies have examined a variety of environmental exposures, ionizing radiation remains the only generally accepted environmental risk factor for childhood leukemia. Among suspected risk factors, infections, exposure to pesticides, and extremely low frequency magnetic fields are notable. While there are well-defined differences between leukemia in children with and without DS, studies of risk factors for leukemia among DS children are generally consistent with trends seen among non-DS (NDS) children. We provide background on DS epidemiology and review the similarities and differences in biological and epidemiologic features of leukemia in children with and without DS. We propose that both acute lymphoblastic and acute myeloblastic leukemia among DS children can serve as an informative model for development of childhood leukemia. Further, the high rates of leukemia among DS children make it possible to study this disease using a cohort approach, a powerful method that is unfeasible in the general population due to the rarity of childhood leukemia.

We characterized the distribution of exposure to magnetic fields (MFs) during daily activities and during household appliance use, and estimated the relative contribution of various activities and appliances to total daily exposure. One hundred sixty-two subjects provided information on their patterns of appliance use and wore personal monitors for 24 h to collect MF exposure data. Of total exposure, 27% accumulated while subjects were in bed; 41% while at home but not in bed; 9% at work; and 24% elsewhere. Less than 2% of the total MF exposure accumulated during the use of each of the eight individual appliances considered, except computers, during the use of which 9% of the total exposure accumulated. Of the time subjects spent at exposure levels higher than 2 microT, 8% accumulated while they were using microwave ovens, and 4% and 3% while using computers and electric stoves, respectively. Mean MF measurements tended to be lowest when subjects were in bed and highest at work and during the use of microwave ovens, coffee grinders, hair dryers, and electric shavers. Results from questionnaires on household appliance use in the past year were not useful in predicting the total mean exposure level and over-threshold exposures measured by 24-h personal monitors. Significant MF exposure accumulates at home, at work, and elsewhere; therefore, accurate exposure assessment needs to consider residential, occupational, and other sources together. Questionnaire-based information on appliance use has limited value in the assessment of average and over-threshold exposure to MFs.

Background Iletrospective studies fail to identify predictors of postoperative nausea and vomiting (PONV). The authors prospectively studied 17,638 consecutive outpatients who had surgery to identify predictors. Methods Data on medical conditions, anesthesia, surgery, and PONV were collected in the post-anesthesia care unit, in the ambulatory surgical unit, and in telephone interviews conducted 24 h after surgery. Multiple logistic regression with backward stepwise elimination was used to develop a predictive model An independent set of patients was used to validate the model Results Age (younger or older), sex (female or male), smoking status (nonsmokers or smokers), previous PONV, type of anesthesia (general or other), duration of anesthesia (longer or shorter), and type of surgery (plastic, orthopedic shoulder, or other) were independent predictors of PONV. A 10-yr increase in age decreased the likelihood of PONV by 13%. The risk for men was one third that for women. A 30-min increase in the duration of anesthesia increased the likelihood of PONV by 59%. General anesthesia increased the likelihood of PONV 11 times compared with other types of anesthesia. Patients with plastic and orthopedic shoulder surgery had a sixfold increase in the risk for PONV. The model predicted PONV accurately and yielded an area under the receiver operating characteristic curve of 0.785+/-0.011 using an independent validation set. Conclusions A validated mathematical model is provided to calculate the risk of PONV in outpatients having surgery. Knowing the factors that predict PONV will help anesthesiologists determine which patients will need antiemetic therapy.

In 2002, two studies were published, both of which reported that indices of peak magnetic field exposure were associated with an increased risk of miscarriage, whereas measures of central tendency of magnetic field exposure were not (Lee et al., 2002; Li et al., 2002). These were the first epidemiological studies of reproductive health outcomes to consider measures of peak exposure. In the spirit of opening further dialogue and to advance the understanding of the relationship between peak magnetic field exposure and miscarriage, Savitz (2002) introduced a testable hypothesis in an accompanying commentary. According to this hypothesis, the status and ultimate outcome of a woman's pregnancy may (through discomfort or cumbersomeness) affect her mobility and physical activity, which in turn could affect the measurement of her magnetic field exposure (Figure 1). In the wake of these papers and commentary, two studies were conducted to empirically address specific elements of Savitz' hypothesis of a non-causal basis for the association between peak magnetic field exposure and miscarriage. These efforts were intended to provide empirical data to help discriminate between causal and non-causal explanations for the observed EMF–miscarriage association. These are the papers that form the subject of the Neutra–Li letter.

We examined the association between magnetic field (MF) exposure and the presence of prognostic risk factors among 482 children diagnosed with acute lymphoblastic leukemia (ALL) between 1996 and 2001. Personal 24-h MF measurements were obtained for 412 children; 386 children were included in analyses. There were no trends seen between increasing exposure to MF and the presence of adverse clinical and tumor-specific prognostic factors. Our results suggest that exposure to MF is not associated with the presence of unfavorable cytogenetic abnormalities in leukemic blast cells or with clinical factors at the time of diagnosis that predict poor survival. Bioelectromagnetics. © 2006 Wiley-Liss, Inc.

We investigated the relationship between occupational exposure to electric shocks (ES) and magnetic fields (MF) and amyotrophic lateral sclerosis (ALS) using 1991-1999 US mortality data. For each of the 5886 included ALS deaths, 10 controls-matched on sex-, age-, year- and region-were selected from among other deaths. Usual occupation as reported on death certificates was linked to job-exposure matrices for ES and MF. Education and electric occupations were associated with moderately increased ALS risks (odds ratio (OR)=1.85, 95% confidence interval (CI)=1.67, 2.04; OR=1.23, 95% CI=1.04, 1.47, respectively). For ES, ALS mortality OR were 0.73 (95% CI=0.67, 0.79) for high and 0.90 (95% CI=0.84, 0.97) for medium exposure compared with low exposure. For MF, ALS ORs were 1.09 (95% CI=1.00, 1.19) for high and 1.09 (95% CI=0.96, 1.23) for medium exposure as compared with low exposure. For electric occupations, ALS ORs were insensitive to adjustments for ES, MF or both. Consistent with previous publications, an association between electric occupations and ALS was observed. Findings do not support occupational exposure to ES or MF as an explanation.

Purpose Data from the Northern California Childhood Leukemia Study (NCCLS) were used to assess whether selection bias may explain the association between residential magnetic fields (assessed by wire codes) and childhood leukemia as previously observed in case–control studies. Methods Wiring codes were calculated for participating cases, n =310; and non-participating cases, n =66; as well as for three control groups: first-choice participating, n =174; first-choice non-participating, n =252; and replacement (non-first choice participating controls), n =220. Results Participating controls tended to be of higher socioeconomic status than non-participating controls, and lower socioeconomic status was related to higher wire-codes. The odds ratio (OR) for developing childhood leukemia associated with high wire-codes was 1.18 (95% CI: 0.85, 1.64) when all cases were compared to all first-choice controls (participating and non-participating). The OR for developing childhood leukemia in the high current category was 1.43 (95% CI: 0.91, 2.26) when participating cases were compared to first-choice participating controls, but no associations were observed when participating cases were compared to non-participating controls (OR=1.06, 95% CI: 0.71, 1.57) or to replacement controls (OR=1.06, 95% CI: 0.71, 1.60). Conclusions The observed risk estimates vary by type of control group, and no statistically significant association between wire codes and childhood leukemia is observed in the California population participating in the NCCLS.

Previous studies have shown that populations of multiapartment buildings with indoor transformer stations may serve as a basis for improved epidemiological studies on the relationship between childhood leukaemia and extremely-low-frequency (ELF) magnetic fields (MFs). This study investigated whether classification based on structural characteristics of the transformer stations would improve ELF MF exposure assessment. The data included MF measurements in apartments directly above transformer stations ("exposed" apartments) in 30 buildings in Finland, and reference apartments in the same buildings. Transformer structural characteristics (type and location of low-voltage conductors) were used to classify exposed apartments into high-exposure (HE) and intermediate-exposure (IE) categories. An exposure gradient was observed: both the time-average MF and time above a threshold (0.4 μT) were highest in the HE apartments and lowest in the reference apartments, showing a statistically significant trend. The differences between HE and IE apartments, however, were not statistically significant. A simulation exercise showed that the three-category classification did not perform better than a two-category classification (exposed and reference apartments) in detecting the existence of an increased risk. However, data on the structural characteristics of transformers is potentially useful for evaluating exposure-response relationship.

We conducted a large epidemiologic case-control study in California to examine the association between childhood cancer risk and distance from the home address at birth to the nearest high-voltage overhead transmission line as a replication of the study of Draper et al. in the United Kingdom. We present a detailed description of the study design, methods of case ascertainment, control selection, exposure assessment and data analysis plan. A total of 5788 childhood leukemia cases and 3308 childhood central nervous system cancer cases (included for comparison) and matched controls were available for analysis. Birth and diagnosis addresses of cases and birth addresses of controls were geocoded. Distance from the home to nearby overhead transmission lines was ascertained on the basis of the electric power companies' geographic information system (GIS) databases, additional Google Earth aerial evaluation and site visits to selected residences. We evaluated distances to power lines up to 2000 m and included consideration of lower voltages (60-69 kV). Distance measures based on GIS and Google Earth evaluation showed close agreement (Pearson correlation >0.99). Our three-tiered approach to exposure assessment allowed us to achieve high specificity, which is crucial for studies of rare diseases with low exposure prevalence.

We conducted a large registry-based study in California to investigate the association of perinatal factors and childhood CNS tumors, with analysis by tumor subtype.We linked California cancer and birth registries to obtain information on 3308 cases and 3308 controls matched on age and sex. We examined the association of birth weight, gestational age, birth order, parental ages, maternal conditions during pregnancy, newborn abnormalities and the risk of childhood CNS tumors using conditional logistic regression, with adjustment for potential confounders.The odds ratio (OR) per 1000 g increase in birth weight was 1.11 (95% CI: 0.99-1.24) for total childhood CNS tumors, 1.17 (95% CI: 0.97-1.42) for astrocytoma and 1.28 (95% CI: 0.90-1.83) for medulloblastoma. Compared to average-for-gestational age, large-for-gestational age infants were at increased risk of glioma (OR=1.86, 95% CI: 0.99-3.48), while small-for-gestational age infants were at increased risk of ependimoma (OR=2.64, 95% CI: 1.10-6.30). Increased risk of childhood CNS tumors was observed for 5-year increase in maternal and paternal ages (OR=1.06, 95% CI: 1.00-1.12 and 1.05, 95% CI: 1.00-1.10 respectively). Increased risk of astrocytoma was detected for 5-year increase in paternal age (OR=1.08; 95% CI: 1.00-1.16) and increased risk of glioma for maternal age ≥ 35 years old (OR=1.87; 95% CI: 1.00-3.52). Maternal genital herpes during pregnancy was associated with a pronounced increase in risk of total CNS tumors (OR=2.74; 95% CI: 1.16-6.51). Other (non-sexually transmitted) infections during pregnancy were associated with decreased risk of total CNS tumors (OR=0.28, 95% CI: 0.09-0.85). Maternal blood/immune disorders during pregnancy were linked to increased risk of CNS tumors (OR=2.28, 95% CI: 1.08-4.83) and medulloblastoma (OR=7.13, 95% CI: 0.82-61.03). Newborn CNS abnormalities were also associated with high risk of childhood CNS tumors (OR=4.08, 95% CI: 1.13-14.76).Our results suggest that maternal genital herpes, blood and immunological disorders during pregnancy and newborn CNS abnormalities were associated with increased risk of CNS tumors. Maternal infections during pregnancy were associated with decreased risk of CNS tumors. Advanced maternal and paternal ages may be associated with a slightly increased risk of CNS tumors. Factors associated with CNS tumor subtypes varied by subtype, an indicator of different etiology for different subtypes.

Background Sore throat is a common complication of anaesthesia that affects patient satisfaction after surgery. Methods We studied 5264 ambulatory surgical patients prospectively to determine the patient, anaesthetic, and surgical factors associated with sore throat. Results In 5264 patients, 12.1% reported a sore throat. Patients with tracheal tube had the greatest incidence, 45.4%, followed by patients with laryngeal mask airway, 17.5%, while patients with a facemask had a lower incidence of sore throat, 3.3%. Female patients had more sore throats than male patients (13.4 vs 9.1%). Airway management had the strongest influence on the incidence of sore throat. Sore throat in ambulatory surgical patients was associated with female sex, younger patients, use of succinylcholine, and gynaecological surgery. Conclusion Airway management, female sex, younger patients, surgery for gynaecological procedure, and succinylcholine predicts postoperative sore throat. Increased awareness of the predictive factors can help to avoid this combination and improve patient satisfaction.

The aim of this study was to evaluate an exposure assessment method that classifies apartments in three exposure categories of extremely low frequency magnetic fields (ELF-MF) based on the location of the apartment relative to the transformer room. We completed measurements in 39 apartments in 18 buildings. In each room of the apartments ELF-MF was concurrently measured with 5 to 6 EMDEX II meters for 10 min. Measured arithmetic mean ELF-MF was 0.59 μT in 8 apartments that were fully adjacent to a transformer room, either directly above the transformer or touching the transformer room wall-to-wall. In apartments that only partly touched the transformer room at corners or edges, average ELF-MF level was 0.14 μT. Average exposure in the remaining apartments was 0.10 μT. Kappa coefficient for exposure classification was 0.64 (95%-CI: 0.45–0.82) if only fully adjacent apartments were considered as highly exposed (> 0.4 μT). We found a distinct ELF-MF exposure gradient in buildings with transformer. Exposure classification based on the location of the apartment relative to the transformer room appears feasible. Such an approach considerably reduces effort for exposure assessment and may be used to eliminate selection bias in future epidemiologic studies.

BackgroundPrevious pooled analyses have reported an association between magnetic fields and childhood leukaemia. We present a pooled analysis based on primary data from studies on residential magnetic fields and childhood leukaemia published after 2000.MethodsSeven studies with a total of 10,865 cases and 12,853 controls were included. The main analysis focused on 24-h magnetic field measurements or calculated fields in residences.ResultsIn the combined results, risk increased with increase in exposure, but the estimates were imprecise. The odds ratios for exposure categories of 0.1-0.2 μT, 0.2-0.3 μT and ≥0.3 μT, compared with

The authors evaluated the role of selection bias in the 1999 Canadian case-control study of residential magnetic field exposure and childhood leukemia. They included cases, participating controls, and first-choice nonparticipating controls in their analyses. Exposure was assessed by wire coding, a classification system based on the distribution line characteristics near homes. Although an imperfect measure of magnetic field exposure, wire coding is the only method applicable to nonparticipating subjects. First-choice nonparticipant controls tended to be of lower socioeconomic status than their replacements (non-first-choice participant controls), and lower socioeconomic status was related to higher wire code categories. The odds ratios for developing childhood leukemia in the highest exposure category were 1.6 (95% confidence interval: 1.0, 2.6) when the actual participating controls were used and 1.3 (95% confidence interval: 0.8, 2.1) when the first-choice ideal controls were used, regardless of their participation. Overall, the authors conclude that, although there is some evidence for control selection or participation bias in the Canadian study, it is unlikely to explain entirely the observed association between magnetic field exposure and childhood leukemia. Inherent problems in exposure assessment for nonparticipating subjects, however, limit the interpretations of these results, and the role of selection bias cannot entirely be dismissed on the basis of these results alone.

It has been hypothesized that nighttime bedroom measurements of extremely low frequency electromagnetic fields (ELF EMF) may represent a more accurate reflection of exposure and have greater biologic relevance than previously used 24-/48-hour measurements. Accordingly, the authors extended a pooled analysis of case-control studies on ELF EMF exposure and risk of childhood leukemia to examine nighttime residential exposures. Data from four countries (Canada, Germany, the United Kingdom, and the United States) were included in the analysis, comprising 1,842 children diagnosed with leukemia and 3,099 controls (diagnosis dates ranged from 1988 to 1996). The odds ratios for nighttime ELF EMF exposure for categories of 0.1–

Background: Peak magnetic field exposure was associated with increased risk of miscarriage in 2 recent studies. Reduced physical activity levels in healthy pregnancies may affect measured exposure and thus bias results. Methods: We recruited 100 pregnant women to wear an Actigraph accelerometer and EMDEX magnetic field monitor for a 7-day period. We evaluated the association between physical activity and magnetic field exposure (peaks and time-weighted average) using generalized estimating equations and linear mixed models. Results: We found a positive association between level of activity and likelihood of incurring elevated exposure in the person-day analysis, most strongly for cutpoints of 16 or 20 mG, for both working and nonworking women among whom odds ratios in the uppermost quartile ranged from 2.1 to 2.6. A positive association was found using person-minutes only among nonworking women. Conclusion: Physical activity may affect peak magnetic field exposure. If the early nausea and later cumbersomeness of healthy pregnancies leads to reduced physical activity, this could distort measured magnetic field‐health outcome associations.