Unknown authors · 1998
Researchers studied the effects of 60-Hz magnetic field and ambient light exposures on the pineal hormone melatonin among electric utility workers. Personal exposure was measured at 15-second intervals over 3 consecutive 24-hour periods. Magnetic field intensity, intermittence, or cumulative exposure had little influence on nocturnal 6-OHMS excretion. Residential RCMS magnetic field exposures were associated with lower nocturnal 6-OHMS/cr concentrations. The greatest reductions occurred when RCMS exposures both at work and at home were combined.
Unknown authors · 1998
Researchers measured magnetic field exposure and melatonin levels in electric utility workers over three consecutive days. They found that temporally stable 60 Hz magnetic fields (the kind from power lines) were associated with reduced nighttime melatonin production. This matters because melatonin is crucial for sleep, immune function, and protecting against cancer.
Unknown authors · 1998
Researchers conducted a nationwide mortality study of 21,236 men employed in Danish utility companies between 1900 and 1993. Causes of death from 1974 through 1993 were analyzed by latency and estimated 50-Hz electromagnetic field exposure. Overall mortality was slightly lower than expected with a standardized mortality ratio of 0.96 (95% confidence interval 0.93-0.99). A twofold increase in ALS mortality was observed based on 14 deaths and increased with time since first employment, while a tenfold increase in electrical accident mortality was based on 10 deaths.
Daniells et al. · 1998
Researchers used transgenic Caenorhabditis elegans strain PC72 carrying a heat-shock promoter driving a beta-galactosidase reporter gene. The nematodes were exposed in a transverse electromagnetic cell at 750 MHz and 27 dBm, with the cell held at 25°C in a shielded incubator. Significant stress responses were observed at 2 and 16 hours but not at 4 or 8 hours. Lower power levels of 21 dBm produced greater responses than 27 dBm at both 750 and 300 MHz, a pattern opposite to that expected from simple heating. In a 5 x 5 multiwell plate, wells in rows nearest the exposure showed the strongest response, while the most distant row did not rise above control levels, suggesting a shadow effect.
Unknown authors · 1998
Rats were trained in six sessions to locate a submerged platform in a water maze and exposed to a 1 mT, 60 Hz magnetic field for one hour before each session. There was no significant difference in learning to locate the platform between exposed and control rats. Exposed rats had significantly slower swim speed and spent less time in the target quadrant during a probe trial, with different swim patterns.
Unknown authors · 1998
Researchers exposed rats to 60 Hz magnetic fields (the same frequency as household power lines) for one hour before maze training sessions. While the rats could still learn to find a hidden platform, they swam slower and showed impaired spatial memory when tested later. This suggests power frequency magnetic fields may affect brain function and memory formation.
Unknown authors · 1998
University of Washington researchers exposed rats to 1 mT, 60 Hz magnetic fields (power line frequency) for one hour before each water maze training session. While the rats learned to find the platform normally, they swam slower and showed impaired spatial memory during testing, suggesting the magnetic field changed how their brains processed location information.
de Seze R, Fabbro-Peray P, Miro L · 1998
Researchers measured adrenocorticotropin, thyrotropin, growth hormone, prolactin, luteinizing hormone, and follicle stimulating hormone in nine weekly blood samples taken from three weeks before exposure to two weeks after. Five of the six hormones showed no difference across samples, while thyrotropin decreased 21% on the seventh sample but returned to baseline afterward.
Fetter JG, Ivans V, Benditt DG, Collins J, · 1998
Researchers tested whether NADC/TDMA-50 digital telephones interfere with Medtronic ICDs in 41 patients. No ICDs in the 41 patients were affected by electromagnetic interference from the telephone during the in vivo study. In vitro antenna-generated field testing showed GSM and TDMA-50 modulation frequencies did not cause ICD sensing interference at predicted electric field intensity. Near-field tests with analog and digital phones in service or test mode also showed no interaction with normal ICD operation. However, a static magnetic field from a phone placed within 0.5 cm of the ICD activated the reed switch, temporarily suspending ventricular tachycardia and fibrillation detection.
Szmigielski et al. · 1998
The study enrolled 61 workers exposed to radiofrequency EMF (0.738-1.503 Mhz) and 42 unexposed controls, all following identical 12-24-12-48 hour shift schedules. Exposed workers were divided into low-intensity (20-180 V/m, 38 subjects) and high-intensity (200-550 V/m, 23 subjects) groups. Exposed workers had significantly reduced rhythm amplitudes (P < 0.01) and an earlier acrophase at 1100-1200 h (P < 0.05) for blood pressure and heart rate, with more pronounced effects in the high-intensity group. Diurnal rhythm parameters were derived from 24-hour ambulatory blood pressure recordings using cosinor analysis. The authors conclude that occupational RF EMF exposure can alter diurnal cardiovascular rhythms, but clinical relevance needs further investigation.
Imaida K et al. · 1998
Researchers exposed male F344 rats to a 929.2 MHz electromagnetic near-field for 90 minutes a day, five days a week, over six weeks. The exposed rats showed no significant difference in GST-P positive foci numbers or areas compared to sham-exposed rats. Maximum local specific absorption rates were 7.2 to 6.6 W/kg in the whole body and 2.0 to 1.7 W/kg in the liver.
Adair ER, Kelleher SA, Mack GW, Morocco TS, · 1998
Thermoregulatory responses of heat production and heat loss were measured in seven adult volunteers (four women and three men, aged 21–57 years) during 45-minute dorsal exposures of the whole body to 450 MHz continuous wave RF fields. Two power densities were tested at each of three ambient temperatures (24, 28, and 31 °C), plus control conditions with no RF. No changes in metabolic heat production occurred, and deep body temperature was regulated to within 0.1 °C of the normal level through vigorous increases in sweating rate on the back and chest.
Imaida et al. · 1998
Researchers exposed male F344 rats to a 1.439 GHz TDMA electromagnetic near-field for 90 minutes a day, 5 days a week, over 6 weeks. The rats were initiated with diethylnitrosamine and underwent partial hepatectomy at week 3. Peak liver SARs ranged from 1.91 to 0.937 W/kg and whole-body average SARs from 0.680 to 0.453 W/kg at 0.33 W antenna power. Exposure did not significantly alter the numbers or areas of GST-P-positive foci in the liver compared to sham-exposed rats. Serum levels of corticosterone, ACTH, and melatonin were increased in exposed rats.
Bassen HI, Moore HJ, Ruggera PS · 1998
An in vitro study tested three ICD models for susceptibility to electromagnetic interference from two digital cellular phones and one analog cellular phone operating at maximum output power. All digital cellular phones produced electromagnetic interference to varying degrees. TDMA-modulated digital phones caused the most pronounced effects, including high-voltage firing and inhibition of pacing output. Interference occurred only when phones were within 2.3–5.8 cm of the ICD pulse generator submerged 0.5 cm in 0.18% saline, and performance returned to baseline when phones were removed.
Frei et al. · 1998
Researchers exposed 100 C3H/HeJ mice to continuous-wave 2450 MHz RF radiation at 1.0 W/kg for 78 weeks, 20 hours per day, 7 days per week, while 100 mice were sham-exposed. There was no significant difference in mammary tumor incidence between exposed mice (38%) and sham-exposed mice (30%). Latency to tumor onset was similar: 62.5 weeks for exposed mice and 62.0 weeks for sham-exposed mice. Histopathological evaluation found no significant difference in malignant, metastatic, or benign neoplasms between groups.
Unknown authors · 1998
Researchers exposed primary rat tracheal epithelial cells and two immortalized cell lines to a 50-Hz magnetic field at 100 microT[rms] combined with a 55 microT geomagnetic-like field and to gamma rays from cobalt-60. Both exposures produced similar patterns and amplitudes of c-jun and c-fos protein induction. Combining magnetic field and radiation exposure did not produce a synergistic effect on protein expression.
Unknown authors · 1998
Researchers examined the separate and combined effects of 60 Hz magnetic fields and a phorbol ester on PKC activity in HL60 cells. Exposure to a 1.1 mT magnetic field alone or combined with 2 microM PMA for 1 h did not enhance PKC activity. In a second experiment, cells preexposed to 50 nM PMA for 45 min then exposed to both PMA and magnetic field for 15 min showed a greater decrease in cytosolic PKC activity and a larger increase in membrane activity than PMA treatment alone or PMA with sham exposure. The authors concluded that magnetic fields may act synergistically on an already activated pathway.
Unknown authors · 1998
Researchers exposed human blood cells to 60 Hz magnetic fields (the same frequency as power lines) and found the fields enhanced the activity of protein kinase C, a key enzyme involved in cell signaling. The magnetic fields didn't create new biological effects but amplified existing cellular processes that were already activated.
Unknown authors · 1998
Researchers exposed HL60 cells to 6-microT 60 Hz magnetic fields and measured MYC expression. The assay methods and exposure conditions were as close as practical to those of the investigators that originally reported a positive effect. A chemical agent demonstrated the cells responded to a known stimulus and the system had low basal variability to detect effects of the previously reported magnitude. Using cells from a commercial source and from the original investigators, no evidence was found that EMF exposure induces MYC expression.
Walters TJ et al. · 1998
Researchers measured hypothalamic, cortical, tympanic, and rectal temperatures in rats exposed to 2.06 GHz microwave radiation at two power densities. The high-power density was 1700 mW/cm² with specific absorption rates of 1224 W/kg in hypothalamus and 493 W/kg in cortex, while the low-power density was 170 mW/cm² with SARs of 122.4 W/kg and 49.3 W/kg. During high-power exposure, the hypothalamic temperature rose significantly faster than cortical or rectal temperatures, whereas low-power exposure produced more uniform heating. For comparison, warm-water immersion produced uniform heating, while warm ambient exposure and exercise maintained the pre-existing temperature gradient between hypothalamus and cortex.
Unknown authors · 1998
Researchers used BTK-deficient DT40 B cells reconstituted with the human btk gene to test whether a 1-gauss 60-Hz electromagnetic field alters inositol 1,4,5-trisphosphate production. Blinded exposures with anti-IgM treatment as a positive control showed no significant effect of the field on inositol 1,4,5-trisphosphate production. The researchers also evaluated BTK activation in wild-type DT40 cells and found that while pervanadate activated BTK in a dose- and time-dependent manner, detection of BTK activation depended on the kinase buffer. Using cells from the original investigators, no evidence supported the hypothesis that the magnetic field had a causal effect on protein-tyrosine kinase activities affecting inositol 1,4,5-trisphosphate production.
Unknown authors · 1998
Researchers assessed whether a 60-Hz magnetic field at 0.1 mT could reproduce earlier reported transcription changes in c-fos, c-jun, and c-myc oncogenes in CEM-CM3 cells. Cells were exposed for 15, 30, 60, or 120 minutes to the field or to a sham condition with coils in bucking mode. Transcription rates measured by nuclear run-on assay and transcript levels measured by Northern analysis showed no significant difference between exposed and sham or control cells at any time point.
Unknown authors · 1998
Researchers tested whether 60-Hz magnetic fields at 0.1 mT could trigger cancer-related gene activity in human immune cells, attempting to replicate previous findings. They found no changes in oncogene transcription rates or levels after exposures ranging from 15 minutes to 2 hours. This study failed to reproduce earlier claims that power-line frequency magnetic fields activate cancer genes.
Mickley GA, Cobb BL · 1998
Tolerant rats showed significantly lower hyperthermia on Day 2 and explored the novel object similarly to sham-exposed rats, whereas non-tolerant rats did not show a preference for the new object. Naltrexone (10 mg/kg) administered just before exposure blocked the hyperthermia-induced discrimination deficit in non-tolerant rats, making their exploration pattern resemble that of tolerant and sham-exposed animals.
Novoselova ET, Fesenko EE. · 1998
Researchers studied whether weak electromagnetic waves in the centimeter range could affect tumor necrosis factor production in macrophages from mice. Whole-body microwave irradiation of male NMRI mice, exposure of macrophages in vitro, and irradiation of culture medium with 8.15-18 GHz at a power density of 1 microW/cm2 each caused a significant enhancement of tumor necrosis factor production in peritoneal macrophages.
