Alternate indices of electric and magnetic field exposures among Ontario electrical utility workers

Epidemiologic studies examining the risk of cancer among occupational groups exposed to electric fields (EF) and or magnetic fields (MF) have relied on traditional summaries of exposure such as the time weighted arithmetic or geometric mean exposure. Findings from animal and cellular studies support the consideration of alternative measures of exposure capable of capturing threshold and intermittent measures of field strength. The main objective of this study was to identify a series of suitable exposure metrics for an ongoing cancer incidence study in a cohort of Ontario electric utility workers. Principal components analysis (PCA) and correlational analysis were used to explore the relationships within and between series of EF and MF exposure indices. Exposure data were collected using personal monitors worn by a sample of 820 workers which yielded 4247 worker days of measurement data. For both EF and MF, the first axis of the PCA identified a series of intercorrelated indices that included the geometric mean, median and arithmetic mean. A considerable portion of the variability in EF and MF exposures were accounted for by two other principal component axes. The second axes for EF and MF exposures were representative of the standard deviation (standard deviation) and thresholds of field measures. To a lesser extent, the variability in the exposure variable was explained by time dependent indices which consisted of autocorrelations at 5 min lags and average transitions in field strength. Our results suggest that the variability in exposure data can only be accounted for by using several exposure indices, and consequently, a series of metrics should be used when exploring the risk of cancer owing to MF and EF exposure in this cohort. Furthermore, the poor correlations observed between indices of MF and EF reinforce the need to be take both fields into account when assessing the risk of cancer in this occupational group. Bioelectromagnetics 19:140–151, 1998. © 1998 Wiley-Liss, Inc.     

Correlations among indices of electric and magnetic field exposure in electric utility workers

Power-frequency electric and magnetic fields are known to exhibit marked temporal variation, yet in the absence of clear biological indications, the most appropriate summary indices for use in epidemiologic studies are unknown. In order to assess the statistical patterns among candidate indices, data on 4383 worker-days for magnetic fields and 2082 worker-days for electric fields collected for the Electric and Magnetic Field Project for Electric Utilities using the EMDEX meter [Bracken (1990): Palo Alto, CA: Electric Power Research Institute] were analyzed. We examined correlations at the individual and job title group levels among indices of exposure to both electric and magnetic fields, including the arithmetic mean, geometric mean, median, 20th and 90th percentiles, time above lower cutoffs of 20 V/m and 0.2 μT, and time above higher cutoffs of 100 V/m and 2.0 μT. For both electric and magnetic fields, the arithmetic mean was highly correlated with the 90th percentile; moderately correlated with the geometric mean, median, and lower and higher cutoff scores; and weakly correlated with the 20th percentile. Electric and magnetic field indices were generally weakly correlated with one another. Rank-order correlation coefficients were consistently greater than product-moment correlation coefficients. Job title group summary scores showed higher correlations among electric field indices and magnetic field indices and between electric and magnetic field indices than was found for individual worker-days, with only the 20th percentile clearly independent of the others. These results suggest that individuals' exposures are adequately characterized by a measure of central tendency for electric and magnetic fields, such as the arithmetic or geometric mean, and an indicator of a lower threshold or cutoff for each field type, such as the 20th percentile or proportion of time above 20 V/m or 0.2 μT. A single measure of central tendency for each type of field appears to be adequate when exposures are assessed at the job title level. © 1994 Wiley-Liss, Inc.     

Comparison of indices of ambient exposure to 60-hertz electric and magnetic fields

Occupational, environmental, or domestic exposure of human beings to extremely low-frequency (50- or 60-Hz) electric and magnetic fields varies continuously over time. In epidemiological studies of possible health effects, exposures over long durations must be aggregated in terms of simple summary indices. However, there are many different, biologically plausible, ways of aggregating the data. While awake, each of 20 electric utility personnel and 16 office workers had provided minute-by-minute measures of incident electric (V/m) and magnetic (muT) fields over a 7-day period via personal dosimeters. Once the measures were aggregated as means, medians, peaks, and other indices, intercorrelations between all index pairs were calculated; correlation matrices are presented for the utility and office workers both by group and when pooled. Product-moment coefficients (r) greater that .80 were found between the time-weighted arithmetic mean (TWA) and indices that explicitly emphasize short but highly intense exposures, such as peak values and time above thresholds. Medians and geometric means were less highly correlated with the TWA. Use of only a few indices, perhaps the TWA alone, may sacrifice but little statistical power in most epidemiological studies of utility workers exposed to ELF fields. However, correlations between electric-field strength and magnetic-field density were generally quite weak, as were correlations of either with high-frequency transients; these findings underscore the need to measure each of these variables in epidemiological studies. Indices of exposure incurred outside the workplace were less strongly correlated, which may indicate the need to use several indices in general-population studies.     

Characterization of exposure to extremely low frequency magnetic fields using multidimensional analysis techniques

Our lack of knowledge about the biological mechanisms of 50 Hz magnetic fields makes it hard to improve exposure assessment. To provide better information about these exposure measures, we use multidimensional analysis techniques to examine the relations between different exposure metrics for a group of subjects. We used a combination of a two stage Principal Component Analysis (PCA) followed by an ascending hierarchical classification (AHC) to identify a set of measures that would capture the characteristics of the total exposure. This analysis gives an indication of the aspects of the exposure that are important to capture to get a complete picture of the magnetic field environment. We calculated 44 metrics of exposure measures from 16 exposed EDF employees and 15 control subjects, containing approximately 20,000 recordings of magnetic field measurements, taken every 30 s for 7 days with an EMDEX II dosimeter. These metrics included parameters used routinely or occasionally and some that were new. To eliminate those that expressed the least variability and that were most highly correlated to one another, we began with an initial Principal Component Analysis (PCA). A second PCA of the remaining 12 metrics enabled us to identify from the foreground 82.7% of the variance: the first component (62.0%) was characterized by central tendency metrics, and the second (20.7%) by dispersion characteristics. We were able to use AHC to divide the entire sample (of individuals) into four groups according to the axes that emerged from the PCA. Finally, discriminant analysis tested the discriminant power of the variables in the exposed/control classification as well as those from the AHC classification. The first showed that two subjects had been incorrectly classified, while no classification error was observed in the second. This exploratory study underscores the need to improve exposure measures by using at least two dimensions: intensity and dispersion. It also indicates the usefulness of constructing a typology of magnetic field exposures.     

Evaluation of long-term occupational exposure to styrene vapor on olfactory function

The primary sensory neurons of the olfactory system are chronically exposed to the ambient environment and may therefore be susceptible to damage from occupational exposure to many volatile chemicals. To investigate whether occupational exposure to styrene was associated with olfactory impairment, we examined olfactory function in 2 groups: workers in a German reinforced-plastics boat-manufacturing facility having a minimum of 2 years of styrene exposure (15-25 ppm as calculated from urinary metabolite concentrations, with historical exposures up to 85 ppm) and a group of age-matched workers from the same facility with lower styrene exposures. The results were also compared with normative data previously collected from healthy, unexposed individuals. Multiple measures of olfactory function were evaluated using a standardized battery of clinical assessments from the Monell-Jefferson Chemosensory Clinical Research Center that included tests of threshold sensitivity for phenylethyl alcohol (PEA) and odor identification ability. Thresholds for styrene were also obtained as a measure of occupational olfactory adaptation. Styrene exposure history was calculated through the use of past biological monitoring results for urinary metabolites of styrene (mandelic acid [MA], phenylglyoxylic acid [PGA]); current exposure was determined for each individual using passive air sampling for styrene and biological monitoring for styrene urinary metabolites. Current mean effective styrene exposure during the day of olfactory testing for the group of workers who worked directly with styrene resins was 18 ppm styrene (standard deviation [SD] = 14), 371 g/g creatinine MA + PGA (SD = 289) and that of the group of workers with lower exposures was 4.8 ppm (SD = 5.2), 93 g/g creatinine MA+PGA (SD = 100). Historic annual average exposures for all workers were greater by a factor of up to 6x. No differences unequivocally attributable to exposure status were observed between the Exposed and Comparison groups or between performance of either group and normative population values on thresholds for PEA or odor identification. Although odor identification performance was lower among workers with higher ongoing exposures, performance on this test is not a pure measure of olfactory ability and is influenced by familiarity with the stimuli and their sources. Consistent with exposure-induced sensory adaptation, however, elevated styrene thresholds were significantly associated with higher occupational exposures to styrene. In summary, the present study found no evidence among a cross-section of reinforced-plastics workers that current or historical exposure to styrene was associated with a general impairment of olfactory function. When taken together with prior studies of styrene-exposed workers, these results suggest that styrene is not a significant olfactory toxicant in humans at current exposure levels.     

Analyzing digital vector waveforms of 0–3000 Hz magnetic fields for health studies

To improve the assessment of magnetic field exposures for occupational health studies, the Multiwave® System III (MW3) was developed to capture personal exposures to the three‐dimensional magnetic field vector B (t) in the 0–3000 Hz band. To process hundreds of full‐shift MW3 measurements from epidemiologic studies, new computer programs were developed to calculate the magnetic field's physical properties and its interaction with biological systems through various mechanisms (magnetic induction, radical pair interactions, ion resonance, etc.). For automated calculations in the frequency domain, the software uses new algorithms that remove artifacts in the magnetic field's Fourier transform due to electronic noise and the person's motion through perturbations in the geomagnetic field from steel objects. These algorithms correctly removed the Fourier transform artifacts in 92% of samples and have improved the accuracy of frequency‐dependent metrics by as much as 3300%. The output of the MwBatch software is a matrix of 41 exposure metrics calculated for each 2/15 s sample combined with 8 summary metrics for the person's full‐period exposure, giving 294 summary‐exposure metrics for each person monitored. In addition, the MwVisualizer software graphically explores the magnetic field's vector trace, its component waveforms, and the metrics over time. The output was validated against spreadsheet calculations with pilot data. This software successfully analyzed full‐shift MW3 monitoring with 507 electric utility workers, comprising over 1 million vector waveforms. The software's output can be used to test hypotheses about magnetic field biology and disease with biophysical models and also assess compliance with exposure limits. Bioelectromagnetics 31:391–405, 2010. © 2010 Wiley‐Liss, Inc.     

Magnetic field exposure among utility workers

The Electric and Magnetic Field Measurement Project for Utilities—the Electric Power Research Institute (EPRI) Electric and Magnetic Field Digital Exposure (EMDEX) Project (the EPRI EMDEX Project)—was a multifaceted project that entailed technology transfer, measurement protocol design, data management, and exposure assessment analyses. This paper addresses one specific objective of the project: the collection, analysis, and documentation of power-frequency magnetic field exposures for a diverse population of utility workers. Field exposure data measured by an EMDEX system were collected by volunteer utility employees at 59 sites in four countries between September, 1988, and September, 1989. Specially designed sampling procedures and data collection protocols were used to ensure uniform implementation across sites. Volunteers within 13 job classifications recorded which of eight work or three nonwork environments they occupied while wearing an EMDEX meter. Approximately 50,000 hours of magnetic field exposure records taken at 10 s intervals were obtained, about 70% of which were from work environments. Exposures and time spent in environments were analyzed by primary work environment, by occupied environment, and by job classification. Generally, for utility-specific job classifications related to the generation, transmission, and distribution of electricity, the field and exposure measurements in terms of workday mean field were higher than in more general occupations. The job classifications with the highest (median workday mean) exposure were substation operators (0.7 μT) and electricians (0.5μT). Total variance also tended to be largest for utility-specific job classifications. For these workers, the contributions of between-worker and within-worker variances to total variance were about the same. Measurements in utility-specific environments were higher than in more general environments. Estimates of time-integrated exposure indicated that utility-specific job classifications received about one-half or more of their total exposure on the job. The nonwork field and exposure distributions for workers in all job categories were comparable with median nonworkday means of about 0.09 μT. © 1995 Wiley-Liss, Inc.     

Accuracy of industry and occupation on death certificates of electric utility workers: implications for epidemiologic studies of magnetic fields and cancer

A substantial epidemiologic literature has relied on occupation and industry information from death certificates to make inferences about the association of electric and magnetic field exposure with cancer, but the validity of the occupational data on death certificates is questionable. We compared occupation and industry information from death certificates to company work histories for 793 electric utility workers who died from brain cancer (n=143), leukemia (n=156), lung cancer (n=246, randomly sampled), and non-cancer causes (n=248, randomly sampled). Nearly 75% of death certificates correctly indicated utility industry employment and of those, 48% matched the longest held occupation derived from company work histories. Hence, only 36% matched on both industry and occupation. We computed odds ratios relating occupations involving magnetic field exposure to brain cancer and leukemia both for the occupation listed on the death certificate and for the longest-held occupation based on company records in order to examine the impact of exposure misclassification based on reliance on the death certificate information. For brain cancer, the odds ratio was 1.2 based on death certificates and 1.7 based on company work history, suggesting some attenuation due to misclassification. For leukemia, death certificate information yielded an odds ratio of 0.9, whereas company work histories yielded an odds ratio of 1.3. Although work histories are limited to the period of employment in a specific company, these data suggest that there is substantial misclassification in use of death certificate information on industry and occupation of utility workers, as found in other industries. The limited quality of occupation and industry information on death certificates argues against relying on such information to evaluate modest associations with mortality.     

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

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

Measuring temporal variability in residential magnetic field exposures

Considerable interest has developed during the past ten years regarding the hypothesis that living organisms may respond to temporal variability in ELF magnetic fields to which they are exposed. Consequently, methods to measure various aspects of temporal variability are of interest. In this paper, five measures of temporal variability were examined: Arithmetic means (D(mean)) and rms values (D(rms)) of the first differences (i.e., absolute value of the difference between consecutive measurements) of magnetic field recordings; "standardized" forms of D(rms), denoted RCMS, obtained by dividing D(rms) by the standard deviations of the magnetic field data; and mean (F(mean)) and rms (F(rms)) values of fractional first differences. Theoretical investigations showed that D(mean) and D(rms) are virtually unaffected by long-term systematic trends (changes) in exposure. These measures thus provide rather specific measures of short-term temporal variability. This was also true to a lesser extent for F(mean) and F(rms). In contrast, the RCMS metric was affected by both short-term and long-term exposure variabilities. The metrics were also investigated using a data set consisting of twice-repeated two-calendar-day recordings of bedroom magnetic fields and personal exposures of 203 women residing in the western portion of Washington State. The predominant source of short-term temporal variability in magnetic field exposures arose from the movement of subjects through spatially varying magnetic fields. Spearman correlations between TWA bedroom magnetic fields or TWA personal exposures and five measures of temporal variability were relatively low. Weak to moderate levels of correlation were observed between temporal variability measured during two different sessions separated in time by 3 or 6 months. We conclude that first difference and fractional difference metrics provide specific and fairly independent measures of short-term temporal variability. The RCMS metric does not provide an easily interpreted measure of short-term or long-term temporal variability. This last result raises uncertainties about the interpretation of published studies that use the RCMS metric.     

Occupational 50 Hz magnetic field exposure measurements among female sewing machine operators in Hungary

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 microT (range 0.06-4.27). The average of maximum values was 4.30 microT (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 microT, and for women (n = 41) who operated sewing machines produced after 1990, the average arithmetic mean was 0.43 microT. 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.     

Effects function analysis of ELF magnetic field exposure in the electric utility work environment

The incomplete understanding of the relation between power-frequency fields and biological responses raises problems in defining an appropriate metric for exposure assessment and epidemiological studies. Based on evidence from biological experiments, one can define alternative metrics or effects functions that embody the relationship between field exposure patterns and hypothetical health effects. In this paper, we explore the application of the “effects function” approach to occupational exposure data. Our analysis provides examples of exposure assessments based on a range of plausible effects functions. An EMDEX time series data set of ELF frequency (40–800 Hz) magnetic field exposure measurements for electric utility workers was analyzed with several statistical measures and effects functions: average field strength, combination of threshold and exposure duration, and field strength changes. Results were compared for eight job categories: electrician, substation operator, machinist, welder, plant operator, lineman/splicer, meter reader, and clerical. Average field strength yields a different ranking for these job categories than the ranks obtained using other biologically plausible effects functions. Whereas the group of electricians has the highest exposure by average field strength, the group of substation operators has the highest ranking for most of the other effects functions. Plant operators rank highest in the total number of field strength changes greater than 1 μT per hour. The clerical group remains at the lowest end for all of these effects functions. Our analysis suggests that, although average field strength could be used as a surrogate of field exposure for simply classifying exposure into “low” and “high,” this summary measure may be misleading in the relative ranking of job categories in which workers are in “high” fields. These results indicate the relevance of metrics other than average field strength in occupational exposure assessment and in the design and analysis of epidemiological studies. Bioelectromagnetics 18:365–375, 1997. © 1997 Wiley-Liss, Inc.     

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

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

Environmental hazard in the aetiology of somatic and germ cell aneuploidy

Sources of environmental exposures to potentially aneugenic agents are many and include occupational and therapeutic exposures, and exposures associated with lifestyle habits. In this present study, some of these agents and exposure scenarios are discussed that involve potentially large population targets and/or seem to affect chromosome segregation by previously unsuspected mechanisms: metals, possibly acting by epigenetic mechanisms; nano-sized particles that might directly interact with subcellular components of the mitotic and meiotic machineries; cytostatic drugs in healthcare occupations; anticancer therapies potentially affecting the genetic integrity of gametes; continuously increasing electromagnetic field exposures with some sparse evidence of aneugenic activity; endocrine disruptors and their seemingly elusive effects in mouse oocytes, including the first evidence that prenatal exposure could affect meiotic nondisjunction in adult life. Hazards are considered for both somatic cells at risk of neoplastic transformation or tumour progression by chromosome loss and gain and germ cells at risk of heritable aneuploidies associated with spontaneous abortions or genetic diseases. Finally, possible synergistic interactions between environmental exposure and ageing or genetic predisposition are considered that could influence ultimate risks.     

Health effects of static magnetic fields--a review of the epidemiological evidence

Potential health effects of static magnetic fields have received far less attention than, for example, power frequency or radiofrequency fields. Static fields are found in certain occupational settings, e.g. in the aluminium and chloralkali industries, in arc-welding processes, and certain railways systems. Magnetic resonance imaging (MRI) for medical diagnosis is another source. This paper summarizes the epidemiological evidence of static magnetic field exposure and long-term health effects. There are only a few epidemiological studies available, and the majority of these have focused on cancer risks. There are some reports on reproductive outcomes, and sporadic studies of other outcomes. Overall, few occupational studies have focused specifically on effects of static magnetic field exposure, and exposure assessment have consequently been poor or non-existent. Results from studies that have estimated static magnetic field exposure have not indicated any increased cancer risks, but they are generally based on small numbers of cases and crude exposure assessment. Control of confounding has been limited, and it is likely that the “healthy worker” effect have influenced the results. A few studies have reported results on reproductive outcomes among aluminium workers and MRI operators, but limitations in study designs prevent conclusions. A problem in epidemiological studies of static magnetic fields is that workers in exposed occupations are also exposed to a wide variety of other potentially harmful agents, including some known carcinogens. In conclusion, the available evidence from epidemiological studies is not sufficient to draw any conclusions about potential health effects of static magnetic field exposure.     

A review of the USEPA's single breath canister (SBC) method for exhaled volatile organic biomarkers

Exhaled alveolar breath can provide a great deal of information about an individual's health and previous exposure to potentially harmful xenobiotic materials. Because breath can be obtained non-invasively and its constituents directly reflect concentrations in the blood, its use has many potential applications in the field of biomarker research. This paper reviews the utility and application of the single breath canister (SBC) method of alveolar breath collection and analysis first developed by the US Environmental Protection Agency (USEPA) in the 1990s. This review covers the development of the SBC technique in the laboratory and its application in a range of field studies. Together these studies specifically show how the SBC method (and exhaled breath analysis in general) can be used to clearly demonstrate recent exposure to volatile organic compounds, to link particular activities to specific exposures, to determine compoundspecific uptake and elimination kinetics, and to assess the relative importance of various routes of exposure (i.e. dermal, ingestion, inhalation) in multipathway scenarios. Specific investigations covered in this overview include an assessment of exposures related to the residential use of contaminated groundwater, exposures to gasoline and fuel additives at self-service gas stations, swimmers' exposures to trihalomethanes, and occupational exposures to jet fuel.     

A pilot study about infertile men’s awareness of their reprotoxic exposures and the intervention of occupational medicine to assess them

Background

Male infertility related to professional reprotoxic exposure has been assessed in several studies. Collaboration between occupational physicians and patients can yield information about the preventive measures that can be taken to avoid such exposure. The use of preventive measures is determined by the collaboration between reproductive medicine and occupational medicine and also by the patient’s awareness of reprotoxic occupational exposures. Our andrology laboratory developed a systematic environmental interview that an occupational physician administers before semen analysis to assess patients’ occupational reprotoxic chemical and physical exposures. This observational prospective study evaluated patients’ feelings regarding this interview. The main outcome measure was the participants’ score to determine their general reprotoxicant knowledge. The study also evaluated the patients’ satisfaction about the interview with occupational physician and their attitude about reproductive toxicants.

Results

The mean score for general knowledge of reprotoxicants was 9.6?±?2.7/16. The most frequently underestimated reprotoxic factor was excessive heat (34.7 % correct responses). In cases of semen parameter abnormalities AND recognized occupational reprotoxic exposure, 63.2 % of the patients said they would use individual protective devices, and 55.1 % said they would temporarily adapt their workstation. Regarding the interview with the laboratory’s occupational physician, 80.7 % considered it moderately or very useful. Of the interviewed patients, 46.2 % reported having changed their living habits 2 months after the interview, and 88.5 % were satisfied or very satisfied with the care they received. All of the respondents said it would be useful to extend the interview to include their wives.

Conclusions

The data suggest that patients’ knowledge about reprotoxic exposures can be improved, particularly knowledge related to physical exposure. The vast majority of patients were satisfied with the introduction of this new collaboration between reproductive and occupational medicine.

     

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

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

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

     

EMF exposure assessment in the Finnish garment industry: evaluation of proposed EMF exposure metrics

Recently published studies indicate that having worked in occupations that involve moderate to high electromagnetic field (EMF) exposure is a risk factor for neurodegenerative diseases, including Alzheimer's disease. In these studies, the occupational groups most over-represented for EMF exposure comprised seamstresses, dressmakers, and tailors. Future epidemiologic studies designed to evaluate the possibility of a causal relationship between exposure to EMF and a neuro degenerative disease endpoint such as incidence of Alzheimer's disease, will benefit from the measurement of electromagnetic field metrics with potential biological relevance. Data collection methodology in such studies would be highly dependent upon how the metrics are defined. In this research the authors developed and demonstrated (1) protocols for collecting EMF exposure data suitable for estimating a variety of exposure metrics that may have biological relevance, and (2) analytical methods for calculation of these metrics. The authors show how exposure might be estimated under each of the three prominent EMF health-effects mechanism theories and evaluate the assertion that relative exposure ranking is dependent on which mechanism is assumed. The authors also performed AC RMS magnetic flux density measurements, confirming previously reported findings. The results indicate that seamstresses, as an occupational group, should be considered for study of the possible health effects of long-term EMF exposure.     

A review of the USEPA's single breath canister (SBC) method for exhaled volatile organic biomarkers

Exhaled alveolar breath can provide a great deal of information about an individual's health and previous exposure to potentially harmful xenobiotic materials. Because breath can be obtained non-invasively and its constituents directly reflect concentrations in the blood, its use has many potential applications in the field of biomarker research. This paper reviews the utility and application of the single breath canister (SBC) method of alveolar breath collection and analysis first developed by the US Environmental Protection Agency (USEPA) in the 1990s. This review covers the development of the SBC technique in the laboratory and its application in a range of field studies. Together these studies specifically show how the SBC method (and exhaled breath analysis in general) can be used to clearly demonstrate recent exposure to volatile organic compounds, to link particular activities to specific exposures, to determine compoundspecific uptake and elimination kinetics, and to assess the relative importance of various routes of exposure (i.e. dermal, ingestion, inhalation) in multipathway scenarios. Specific investigations covered in this overview include an assessment of exposures related to the residential use of contaminated groundwater, exposures to gasoline and fuel additives at self-service gas stations, swimmers' exposures to trihalomethanes, and occupational exposures to jet fuel.