Association between exposure to pulsed electromagnetic fields and cancer in electric utility workers in Quebec, Canada, and France.

The authors report the association between exposure to pulsed electromagnetic fields (PEMFs) and cancer in a nested case-control study of electric utility workers in Quebec, Canada (follow-up, 1970-1988), and France (follow-up, 1978-1989), among whom 2,679 cases of cancer were identified. Exposures were assessed through a job-exposure matrix based on about 1,000 person-weeks of measurements from exposure meters worn by workers. Exposures were considerably higher in Quebec than in France. No association was found between PEMFs and cancers previously suspected of association with magnetic fields (leukemia, other hematopoietic cancers, brain cancer, or melanoma). However, there was a clear association between cumulative exposure to PEMFs and lung cancer, with odds ratios rising to 3.11 (95% confidence interval (CI) 1.60-6.04) in the highest exposure group (84 cases). This association with largely confined to Quebec, where there was a monotonic exposure-response relation with an odds ratio of 6.67 (95% CI 2.68-16.57) in the highest exposure group (32 cases). The association is substantial and was not explained by smoking or other occupational exposures. However, several factors limit the strength of the evidence for a causal relation: lack of precision in what the meters measured; little previous evidence for this association; and no elevated risk for lung cancer in the utility workers overall in comparison with the general population.

Monitoring living tissues by electrical impedance spectroscopy.

Solving the experimental difficulties associated with measurement of the electrical impedance of living tissues gives access to valuable tissue compartment parameters which are sensed within seconds using minimally invasive, simple metallic electrodes. Extracellular conductivity and cell membrane capacitance can be followed over time under conditions of metabolic toxicity, perfusion loss and thermal stress in liver, brain cortex, and muscle, respectively. Application of this technique in burns therapy allows an accurate estimation of the severity of thermal injury to skeletal muscle, supporting predictions on tissue survival.

A dosimeter for assessment of exposures to ELF fields.

There are currently no biological indicators of electromagnetic field exposure to aid investigation of the biological effects of ELF fields, but this hiatus is partly compensated for by the ease with which the external fields can be measured. The subject of this report is a small electronic instrument that can log electric-, magnetic-, and transient-field intensities of individual subjects for a duration of two weeks, thus allowing exposure to be assessed in considerable detail. A preliminary survey conducted with the instrument has shown clear differences in domestic and occupational exposures of specific groups. Simple analytical models can be fitted to the field-exposure data by adjusting a few parameters such as current, intensity, and distance. Such modeling may be increasingly useful as the data base on exposures expands.

High-voltage electrical injury: chronic wound evolution.

A chronic electrical burn model employing documentary and diagnostic techniques was designed in the primate for investigating wound evolution up to 10 days after injury. A standardized 40-kJ, 3500-V, 4.2-A, 2.5-s bilateral, symmetrical upper extremity electrical injury was performed. Gross observation studies documented tissue injury extending more proximally on the deep surfaces of individual muscles and between muscle layers. Specific regions, or "choke" points, in the forearm exist in which decreased cross-sectional areas and highly resistant tissue composition resulted in increased heat production and more severe tissue damage. Muscle injury was analyzed using light microscopy, revealing patchy cellular necrosis intermixed with viable cells. Digital subtraction angiography demonstrated segmental narrowing and "pruning" of large vascular trunks with a significant decrease in nutrient vessels in affected areas. Ulnar nerve conduction studies showed loss of conduction proximal to the cubital fossa with no recovery. Although characteristic patterns of injury were documented in skin, muscle, vessels, and nerves, no experimental evidence was found for progressive necrosis.

Occupational and residential 60-Hz electromagnetic fields and high-frequency electric transients: exposure assessment using a new dosimeter.

One problem that has limited past epidemiologic studies of cancer and exposure to extremely low-frequency (0-100 Hz) electric and magnetic fields has been the lack of adequate methods for assessing personal exposure to these fields. A new 60-Hz electromagnetic field dosimeter was tested to assess occupational and residential exposures of a group of electrical utility workers and a comparison background group over a 7-day period. Comparing work periods only, utility workers' exposures were significantly higher than background levels by a factor of about 10 for electric (E) and magnetic (B) fields and by a factor of 171 for high-frequency transient electric (HFTE) fields. When overall weekly time-weighted averages combining work and nonwork exposures were compared, ratios of the exposed to background groups were lower. B and HFTE exposure ratios remained statistically significant, with values of 3.5 and 58, respectively, whereas the electric field exposure ratio was no longer significant, with a value of 1.7. E-field exposures of the background group were the highest during the nonwork period, probably reflecting the use of electrical appliances at home. Residential E- and B-field exposures were in the same range as published results from other surveys, whereas occupational E-field exposures tended to be lower than exposures reported in other studies. The high variability associated with occupational exposures probably accounts for the latter discrepancy. Worker acceptance of wearing the dosimeter was good: 95% of participants found it to be of little or no inconvenience while at work. At home, 37% found the device to be inconvenient in its present form but would not object to wearing a slightly smaller and lighter dosimeter.

High-voltage electrical injury: acute pathophysiology.

A reproducible high-voltage electrical injury model was established in the primate using a new approach to energy administration, measurement instrumentation, and data acquisition. Patterns of current repartition and temperature generation were examined in 24 primates. The predominant current load was carried in muscle, which is the tissue group occupying the largest cross-sectional area. Highest temperature values observed were in muscles of small cross-sectional diameter and in tissues of high inherent resistance. Surgeons should be aware of the principles and the pattern of current distribution when performing early debridement and/or definitive coverage procedures.

60-Hz electric and magnetic fields generated by a distribution network.

From a mobile unit, 60-Hz electric and magnetic fields generated by Hydro-Québec's distribution network were measured. Nine runs, representative of various human environments, were investigated. Typical values were 32 V/m and 0.16 microT. The electrical distribution networks investigated were major contributors to the electric and magnetic environments.