This thesis aims to increase the knowledge on people with symptoms attributed to electromagnetic fields (EMF) by investigating the effects of EMF exposure and by additional description of the heterogeneous group of people reporting EMF-related symptoms. The effect of mobile phone (MP)-like radio frequency (RF) fields on symptoms, autonomic nervous system (ANS) parameters, short-term memory, and reaction time in persons with MP-related symptoms (MP participants) was investigated in a provocation study. A second provocation study investigated the effect of similar exposure on serum concentration of biomarkers in persons with atopic dermatitis. No effect of exposure was detected in either study. MP participants displayed changes in heart rate variability (HRV) during cognitive tests, but not during rest. This contrasts with earlier findings, participants with symptoms attributed to EMF sources in general (EHS participants) displayed an elevated sympathetic nervous system activity both during cognitive tests and during rest. Proposed differences between subgroups of persons with EMF-related symptoms with respect to symptoms, personality traits and stress were investigated in a questionnaire study. MP participants reported primarily symptoms from the head; EHS participants reported symptoms from many organ systems. Furthermore, EHS participants reported higher levels of anxiety, depression, stress, and exhaustion when compared with a reference group. MP participants reported higher levels of anxiety and exhaustion only. In a pilot study, 24-hour and short-term HRV were investigated in EHS participants, to examine whether the previously observed sympathovagal imbalance would still be present. There was a tendency toward increased parasympathetic activity compared with earlier recordings, and a reduction of symptoms. Twenty-four hour and short-term recordings were fairly similar for each participant; however, there were large between-subject differences. The results do not support the hypothesis of effects of MP-like RF exposure on symptoms, ANS activity, CFFT, cognitive function, or biomarkers. However, they do support the hypothesis that persons with different symptom attribution (MP and EHS) may differ also in ANS activity and psychological aspects.

The overall aim of this thesis is to increase our knowledge of the physical environment of office workers with special focus on electromagnetic fields and to address the question of whether electromagnetic fields can directly or indirectly contribute to symptoms or discomfort among video display terminal ( VDT) workers. Furthermore, we have measured light modulation from various commonly used light sources in laboratory conditions and, as a second step, used modulated light as stimulus for provocation of neurophysiological responses in persons with perceived “electrical hypersensitivity” (EHS).During the last 20 years work-related illness among office workers has received increased attention. Changes in the physical environment, the introduction of VDTs and other electrical equipment and changes in light conditions have been discussed in this context. The basis for this thesis is the interdisciplinary Office Illness Project in Northern Sweden. Using a questionnaire completed by 4,943 office workers, 150 VDT workers with or without facial skin symptoms were selected for a case referent study of the electromagnetic fields in offices.When the measurements in the offices were performed in 1989, the general level of the 50 Hz magnetic fields in the offices was rather low, but in 5% of the offices the flux density exceeded 0.5 pT. At this level VDT monitors were shown to display detectable instability (jitter). Furthermore, the ability of test subjects (healthy volunteers) to detect jitter was shown to depend on both the amplitude and frequency characteristics of this instability. The study indicates that the instability of computer monitors and thereby the instability of the visual image of the VDT screen might be an increasing problem since it is known that the harmonic content of the general magnetic field in offices is on the rise.VDT monitors contributed to the magnetic field level at VDT workplaces in both extremely low and very low frequency ranges. However, the dominant source of electric fields in rooms was ungrounded electrical equipment, not VDT screens.High electric fields in the extremely low frequency range in the offices were associated with skin symptoms among VDT workers. The causal nature of this association cannot be determined since it may depend on undetected factors related to exposure. No associations were found, however, for any of the VDT-related electromagnetic fields and skin symptoms.Commonly used fluorescent tubes in our office environment have a degree of modulation of the light (flicker) that varies widely from less than 1% (fluorescent tubes with high frequency gear) up to nearly 100%. When persons with perceived EHS were exposed to flickering light, a higher amplitude of brain cortex responses were found at all tested frequencies compared with control subjects. These findings are of considerable interest, but further studies are required in order to establish a possible relationship between flickering light and discomfort/symptoms in persons with perceived EHS. / digitalisering@umu