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[Biological effects of nonionizing radiation: low frequency electromagnetic fields].

This article reviews various studies on effects of electric and magnetic fields of extremely low frequencies on human health and gives an overview of residential and occupational exposure to different sources, currently established exposure limitations, and protection measures. Throughout the evolution biological systems adapted to natural electric and magnetic fields. Only hundred years ago human exposure to radiation was limited to electric and magnetic fields arising either from extraterrestrial or terrestrial sources, yet both natural. For the past fifty years there has been large growth of artificial sources of electric and magnetic fields, especially with frequencies of 50 and 60 Hz (power generating and distribution systems). The concern about long-term exposure to artificial fields and possible adverse effects on human health has been entirely justified and led to numerous intensive epidemiological and laboratory studies. Results of several epidemiological studies confirm the connection between exposure to electric and magnetic fields of extremely low frequencies (up to 300 Hz) and increased risk of leukemia and brain tumor in children and adults. In addition, the risk of breast cancer in occupationally exposed population has increased. Laboratory studies on animal models, in vitro systems, and human volunteers did not confirm this connection. There is a growing interest in investigation of other possible adverse health effects such as neurodegenerative diseases (Alzheimer's disease and other forms of dementia, amyotrophic lateral sclerosis), cardiovascular disorders (arrhythmias and acute myocardial infarction), psychiatric disorders, and electrosensitivity.

Animals↗

[Role of nonspecific cellular resistance factors in hygienic evaluation of electromagnetic nonionizing radiation].

The most sensitive indices of the blood system at EMF exposure (disorders of megakaryocytes differentiation, unspecific reactions, repopulation of the blasts cells a. al.) have been determined by the cytologic investigations. At has been revealed that allowable UVF levels effect are situated below the threshold of activisation of adaptive reactions (less than 0.01 mV/cm2), for occupational conditions--at the level of compensatory processes (0.05-0.1 mV/cm2). The intensities higher than 0.5 mV/cm2 were estimated as critical. Involution of megakaryocytes, polimorphism and disturbances the structure of leucocytes a. al. were revealed as EMF markers which allow to carry out an express-diagnostic.

Adaptation, Physiological↗

[Nonionizing radiation and electromagnetic fields].

Nonionising radiation comprises all kinds of radiation and fields of the electromagnetic spectrum where biological matter is not ionised, as well as mechanical waves such as infrasound and ultrasound. The electromagnetic spectrum is subdivided into individual sections and includes: Static and low-frequency electric and magnetic fields including technical applications of energy with mains frequency, radio frequency fields, microwaves and optic radiation (infrared, visible light, ultraviolet radiation including laser). The following categories of persons can be affected by emissions by non-ionising radiation: Persons in the environment and in the household, workers, patients undergoing medical diagnosis or treatment. If the radiation is sufficiently intense, or if the fields are of appropriate strength, a multitude of effects can occur (depending on the type of radiation), such as heat and stimulating or irritating action, inflammations of the skin or eyes, changes in the blood picture, burns or in some cases cancer as a late sequel. The ability of radiation to penetrate into the human body, as well as the types of interaction with biological tissue, with organs and organisms, differs significantly for the various kinds of nonionising radiation. The following aspects of nonionising radiation are discussed: protection of humans against excessive sunlight rays when sunbathing and when exposed to UV radiation (e.g. in solaria); health risks of radio and microwaves (safety of microwave cookers and mobile radio units); effects on human health by electric and magnetic fields in everyday life.

Air Pollution, Indoor↗

Alterations in alpha-adrenergic and muscarinic cholinergic receptor binding in rat brain following nonionizing radiation.

Microwave radiation produces hyperthermia. The mammalian thermoregulatory system defends against changes in temperature by mobilizing diverse control mechanisms. Neurotransmitters play a major role in eliciting thermoregulatory responses. The involvement of adrenergic and muscarinic cholinergic receptors was investigated in radiation-induced hyperthermia. Rats were subjected to radiation at 700 MHz frequency and 15 mW/cm2 power density and the body temperature was raised by 2.5 degrees C. Of six brain regions investigated only the hypothalamus showed significant changes in receptor states, confirming its pivotal role in thermoregulation. Adrenergic receptors, studied by [3H]clonidine binding, showed a 36% decrease in binding following radiation after a 2.5 degrees C increase in body temperature, suggesting a mechanism to facilitate norepinephrine release. Norepinephrine may be speculated to maintain thermal homeostasis by activating heat dissipation. Muscarinic cholinergic receptors, studied by [3H]quinuclidinyl benzilate binding, showed a 65% increase in binding at the onset of radiation. This may be attributed to the release of acetylcholine in the hypothalamus in response to heat cumulation. The continued elevated binding during the period of cooling after radiation was shut off may suggest the existence of an extra-hypothalamic heat-loss pathway.

Animals↗

[Mechanism of the effect of nonionizing radiation on animals at the level of sensory systems].

In three series of experiments on mice (CBA X C57BL)F1 and Wistar rats a study was made of the effect of microwaves (0.9 GGz, 0.4 mW/cm2, 10 min) on the EEG reaction of adopting the photostimulation rhythm by rats; the effect of microwaves (0.6 GGZ, 0.04 mW/cm2, 5 min) and gamma-quanta (60Co, 0.5 Gy) on the reaction of avoiding by mice of cooled surfaces, and the effect of microwaves (9.8 GGz, 0.04 mW/cm2, 5 min) on the reaction of avoiding the water pool. The results obtained are discussed with regard to the hypothesis that the biological effects of weak microwave radiation may be realized at the nervous system level via cutaneous ceptors.

Animals↗