Larry E. Anderson

Electric power, pineal function, and the risk of breast cancer

Breast cancer is the leading cause of cancer death in women in the industrialized world, and the rates of breast cancer incidence are rising. Although risk is high in industrialized societies, it is low in nonindustrialized areas. The search for the causes of breast cancer has not yet yielded a convincing explanation for the geographic and temporal patterns in the occurrence of breast cancer. Generation of electric power is a hallmark of industrialization, and two products of electric power, light‐at‐night (LAN) and electromagnetic fields (EMF), may affect breast cancer risk. Exposure to either LAN or EMF can decrease production of melatonin by the pineal gland. Melatonin, in turn, has been shown to suppress mammary tumorigenesis in experimental animals. Moreover, recent epidemiological findings indicate an increased risk of breast cancer in workers occupationally exposed to EMF. On the basis of these considerations, it is proposed that the use of electrical power accounts, in part, for the higher risks of breast cancer in industrialized societies.—Stevens, R. G.; Davis, S.; Thomas, D. B.; Anderson, L. E.; Wilson, B. W. Electric power, pineal function, and the risk of breast cancer. FASEB J. 6: 853‐860; 1992.

Neuroendocrine mediated effects of electromagnetic-field exposure: Possible role of the pineal gland

Reports from recent epidemiological studies have suggested a possible association between extremely low frequency (ELF; including 50- or 60-Hz) electric- and magnetic-field exposure, and increased risk of certain cancers, depression, and miscarriage. ELF field-induced pineal gland dysfunction is a possible etiological factor in these effects. Work in our laboratory and elsewhere has shown that ELF electromagnetic-field exposure can alter the normal circadian rhythm of melatonin synthesis and release in the pineal gland. Consequences of reduced or inappropriately timed melatonin release on the endocrine, neuronal, and immune systems are discussed. Laboratory data linking ELF field exposure to changes in pineal circadian rhythms in both animals and humans are reviewed. The authors suggest that the pineal gland, in addition to being a convenient locus for measuring dyschronogenic effects of ELF field exposure, may play a central role in biological response to these fields via alterations in the melatonin signal.

Reduction of the nocturnal rise in pineal melatonin levels in rats exposed to 60-Hz electric fields in utero and for 23 days after birth

Rats exposed to 60-Hz electric fields of either 10, 65, or 130 kV/m from conception to 23 days of age exhibited reduced peak nighttime pineal melatonin contents compared to unexposed controls. As a group, the exposed rats also exhibited a phase delay, estimated at approximately 1.4 hours, in the occurrence of the nocturnal melatonin peak. No clear dose-response relationship was noticed over the range of electric field strengths used as treatments in these experiments. These are the first studies concerned with the effects of electric field exposure on the pineal melatonin rhythm in immature rats. The findings are generally consistent with those obtained using adult rats, where electric field exposure has been shown to abolish the nighttime rhythm in pineal melatonin concentrations.

BIOLOGICAL EFFECTS OF EXTREMELY LOW-FREQUENCY ELECTROMAGNETIC FIELDS: IN VIVO STUDIES

This paper discusses the biological effects of exposure to extremely low frequency electromagnetic fields observed in animal studies. Three areas of investigation are reported: (1) studies on the nervous system, including behavior and neuroendocrine function; (2) experiments on cancer development in animals; and (3) measurements of currents and electric fields induced in animal models by exposure to external magnetic fields. An attempt is made to evaluate experimental results and interpret them with respect to potential health implications.

Nocturnal 6-hydroxymelatonin sulfate excretion in female workers exposed to magnetic fields

The objective of this study was to determine whether daytime occupational exposure to extremely low frequency magnetic fields (MFs) suppresses nocturnal melatonin production. Sixty female volunteers were recruited. Thirty‐nine worked in a garment factory, and 21 office workers served as a reference group. Exposure assessment was based on the type of sewing machine used and MF measurements around each type of machine. Eye‐level MF flux density was used to classify the operators to higher (>1 μT) and lower (0.3–1 μT) exposure categories. A third group of factory workers had diverse MF exposures from other sources. The reference group had average exposure of about 0.15 μT. Urine samples were collected on Friday and Monday for three consecutive weeks. Melatonin production was assessed as urinary 6‐hydroxymelatonin sulfate (6‐OHMS) excretion. The ratio of Friday morning/Monday morning 6‐OHMS was used to test the hypothesis that melatonin production is suppressed after 4 days of occupational MF exposure with significant recovery during the weekend. Possible chronic suppression of melatonin production was evaluated by studying exposure‐related differences in the Friday values by multivariate regression analysis. The Monday/Friday ratios were close to 1.0, suggesting that there is no increase in melatonin production over the weekend. The average 6‐OHMS excretion on Friday was lower among the factory workers than in the reference group, but no monotonous dose–response was observed. Multivariate regression analysis identified MF exposure, smoking, and age as significant explanatory variables associated with decreased 6‐OHMS excretion.

Learned magnetic compass orientation by the Siberian hamster, Phodopus sungorus

Abstract Magnetic orientation in mammals has been demonstrated convincingly in only two genera of subterranean mole-rats ( Spalax and Cryptomys sp.) by examining the directional placement of nests in radially symmetrical indoor arenas. Mole-rats show a spontaneous directional preference to place their nests to the south or southeast of magnetic north. Using a similar nest-building assay, we show that laboratory-raised Siberian hamsters also use directional information from the magnetic field to position their nests. In contrast to mole-rats, however, the directional preference for nest position shown by Siberian hamsters appears to be learned. Hamsters were housed in rectangular cages aligned along perpendicular axes before testing. When subsequently tested in a radially symmetric arena, the hamsters positioned their nests in a bimodal distribution that coincided with the magnetic direction of the long axis of the holding cages. We also present results from an earlier set of experiments in which hamsters showed consistent orientation only in the ambient magnetic field, and not in experimentally rotated magnetic fields. The conditions under which these earlier experiments were carried out suggest that holding conditions prior to testing and the presence of nonmagnetic cues may influence the expression of magnetic orientation in the Siberian hamster. Failure to consider these and other factors may help to explain why previous attempts to demonstrate magnetic orientation in a number of rodent species have failed or, when positive results have been obtained, have been difficult to replicate. Copyright 2003 Published by Elsevier Science Ltd on behalf of The Association for the Study of Animal Behaviour.

Effect of constant light on DMBA mammary tumorigenesis in rats.

Abstract A study of light, and mammary tumorigenesis was conducted in rats. One-hundred female Sprague–Dawley rats were divided by weight into two groups. One group was exposed to constant light (LL) from 26 days of age, and the second group was exposed to 8 h light and 16 h dark per day (LD). Both groups received an 8 mg dose of a chemical carcinogen, dimethylbenzanthracene (DMBA) at 52 days of age. At 13 weeks post-DMBA, there were significantly fewer mammary tumors in the LL group compared with the LD group. Constant light was clearly demonstrated to have a profound effect on mammary tissue development. Although virgin, the majority of the LL rats (29/50) had gross evidence of lactation at 141 days of age. None of the LD rats (0/50) showed evidence of milk production. These results suggest that constant light not only substantially accelerated mammary gland development, but pushed development of the tissue past the stage normally observed in virgin animals (to the lactation stage).

Effects of 60 Hz magnetic field exposure on the pineal and hypothalamic‐pituitary‐gonadal axis in the Siberian hamster (Phodopus sungorus)

Experiments using the dwarf Siberian hamster Phodopus sungorus were carried out to determine possible neuroendocrine consequences of one-time and repeated exposures to 60 Hz magnetic fields (MF). Animals were maintained in either a short-light (SL, 8 h light:16 h dark) or long-light (LL, 16 h light:8 h dark) photoperiod. Acute (one-time, 15 min) exposure of male SL animals to a linearly polarized, horizontally oriented, 60 Hz MF (0.1 mT) gave rise to a statistically significant (P < .005) reduction in pineal melatonin content as determined 3 and 5 h after onset of darkness. In LL animals, acute exposure to 0.10 mT resulted in a significant decrease in pineal melatonin as measured 4 h after onset of darkness, whereas acute exposure to 50 microT showed no effect compared with sham exposure. In SL animals, an increase in norepinephrine was observed in the medial basal hypothalamus (including the suprachiasmatic nucleus) after acute exposure (P < .01). Daily MF exposure of SL animals to a combination of steady-state and on/off 60 Hz magnetic fields (intermittent exposure) at 0.1 mT for 1 h per day for 16 days was associated with a reduction in melatonin concentrations at 4 h after onset of darkness and an increase in blood prolactin concentrations (P < .05). Exposure of SL animals to a steady state 60 Hz MF for 3 h/day for 42 days resulted in a statistically significant reduction in body weight (ANOVA: P > .05), compared with sham-exposed SL animals. At 42 days, however, no significant changes in overnight melatonin or prolactin levels were detected. In both repeated exposure experiments, gonadal weights were lowest in the MF-exposed groups. This difference was statistically significant (P < .05) after 42 days of exposure. These data indicate that both one-time and repeated exposure to a 0.1 mT, 60 Hz MF can give rise to neuroendocrine responses in Phodopus.

Two-year chronic bioassay study of rats exposed to a 1.6 GHz radiofrequency signal.

Abstract Anderson, L. E., Sheen, D. M., Wilson, B. W., Grumbein, S. L., Creim, J. A. and Sasser, L. B. Two-Year Chronic Bioassay Study of Rats Exposed to a 1.6 GHz Radiofrequency Signal. Radiat. Res. 162, 201–210 (2004). The purpose of this study was to determine whether long-term exposure to a 1.6 GHz radiofrequency (RF) field would affect the incidence of cancer in Fischer 344 rats. Thirty-six timed-pregnant rats were randomly assigned to each of three treatment groups: two groups exposed to a far-field RF Iridium signal and a third group that was sham exposed. Exposures were chosen such that the brain SAR in the fetuses was 0.16 W/kg. Whole-body far-field exposures were initiated at 19 days of gestation and continued at 2 h/day, 7 days/week for dams and pups after parturition until weaning (∼23 days old). The offspring (700) of these dams were selected, 90 males and 90 females for each near-field treatment group, with SAR levels in the brain calculated to be as follows: (1) 1.6 W/kg, (2) 0.16 W/kg and (3) near-field sham controls, with an additional 80 males and 80 females as shelf controls. Confining, head-first, near-field exposures of 2 h/day, 5 days/week were initiated when the offspring were 36 ± 1 days old and continued until the rats were 2 years old. No statistically significant differences were observed among treatment groups for number of live pups/litter, survival index, and weaning weights, nor were there differences in clinical signs or neoplastic lesions among the treatment groups. The percentages of animals surviving at the end of the near-field exposure were not different among the male groups. In females a significant decrease in survival time was observed for the cage control group.

Genotoxic Potential of 1.6 GHz Wireless Communication Signal: In Vivo Two-Year Bioassay

Abstract Vijayalaxmi, Sasser, L. B., Morris, J. E., Wilson, B. W. and Anderson, L. E. Genotoxic Potential of 1.6 GHz Wireless Communication Signal: In Vivo Two-Year Bioassay. Radiat. Res. 159, 558–564 (2003). Timed-pregnant Fischer 344 rats (from nineteenth day of gestation) and their nursing offspring (until weaning) were exposed to a far-field 1.6 GHz Iridium wireless communication signal for 2 h/day, 7 days/week. Far-field whole-body exposures were conducted with a field intensity of 0.43 mW/cm2 and whole-body average specific absorption rate (SAR) of 0.036 to 0.077 W/kg (0.10 to 0.22 W/kg in the brain). This was followed by chronic, head-only exposures of male and female offspring to a near-field 1.6 GHz signal for 2 h/day, 5 days/week, over 2 years. Near-field exposures were conducted at an SAR of 0.16 or 1.6 W/kg in the brain. Concurrent sham-exposed and cage control rats were also included in the study. At the end of 2 years, all rats were necropsied. Bone marrow smears were examined for the extent of genotoxicity, assessed from the presence of micronuclei in polychromatic erythrocytes. The results indicated that the incidence of micronuclei/2000 polychromatic erythrocytes were not significantly different between 1.6 GHz-exposed, sham-exposed and cage control rats. The group mean frequencies were 5.6 ± 1.8 (130 rats exposed to 1.6 GHz at 0.16 W/kg SAR), 5.4 ± 1.5 (135 rats exposed to 1.6 GHz at 1.6 W/kg SAR), 5.6 ± 1.7 (119 sham-exposed rats), and 5.8 ± 1.8 (100 cage control rats). In contrast, positive control rats treated with mitomycin C exhibited significantly elevated incidence of micronuclei/2000 polychromatic erythrocytes in bone marrow cells; the mean frequency was 38.2 ± 7.0 (five rats). Thus there was no evidence for excess genotoxicity in rats that were chronically exposed to 1.6 GHz compared to sham-exposed and cage controls.