Proceedings from the International workshop: Clinical and physiological investigations of people highly exposed to electromagnetic fields. St. Petersburg, Russia, 16-17 October, 2000

Biological effects of exposure to low-level, non-thermal radiofrequency (RF) fields were reported in different experimental systems in vitro and in vivo, however health risks and clinical relevance of these effects remain unknown. RF radiation at non-thermal intensities is considered as a relatively weak environmental/occupational factor and its bioeffects can be in most cases effectively balanced by trigerring of adaptative, compensative and/or regenerative mechanisms of the responding physiologic systems. There are no convincing data which confirm the possibility of development of specific diseases which could be causally linked to long-term exposures in RF fields, however there exist reports on increased risk of various functional abnormalities in subjects who work in RF environment.These functional abnormalities may be, at least partially, related to bioeffects of RF exposures which develop in the central nervous system. One of the possible outcomes of such effects may be dysregulation of autonomic control of various physiologic systems, including the cardiovascular system. Some time ago we reported increased number of slight, subclinical ECG abnormalities, accompanied by symptoms of sympathicotony in heart rate variability (HRV), lowered day/nigh ratio of blood pressure and heart rate (Bortkiewicz A et al, 1995), as well as shifts in diurnal rhythms of blood pressure and heart rate (Szmigielski S et al, 1998) in a group of 77 workers of AM radio broadcasting stations who were exposed to 0.7-1.5 MHz RFs. In the present study a group of 38 workers of radio transmitting centres (RTC), exposed to 1030 MHz RFs, were examined with identical cardiological tests (ECG at rest, HRV, 24-hr Holter ECG, 24-hr ambulatory blood pressure – ABP), as the above mentioned wotkers of AM radio broadcating stations. RF exposure was monitored during whole 12-hr shifts and expressed in maximal levels (Emax), average levels (Eav) and time of exposure (Texp) during the shift. From these data daily exposure dose rates for the shift (Dsf) and life exposure dose rates (Dlf) were calculated. It was found that during the 12-hr shift individual workers were exposed in RF fields in series of 3-5-min. periods, counting for a total exposure time of 0.5 – 2 hr per shift. Individual exposure levels differed considerably (Emax from 9 to 174 V/m; Eav from 0.5 to 11.4 V/m) with the daily exposure dose rates for the shift ranging from 22 to 3120 (V/m) x h. With such large individual differences in RF exposure levels the most conclusive relations between the exposure and results of cardiac tests could be obtained by multistep correlation of single parameters. Statistically significant correlation with RF exposure parameters (Dsf and Eav) was found for HRV (fast/slow component ratio), HR and BP day/night ratio and parameters of BP and HR diurnal rhythms (acrophase and amplitude, but not mean value). In general, the results indicate dysregulation of autonomic control of cardiac function with shift toward sympathicotony, a phenomenon similar to that observed in workers of AM radio broadcasting stations, who are exposed to lower frequencies of RFs (0.7-1.5 MHz).