In experimental
studies the person(s) conducting the research directly controls the
conditions of the study. It is difficult to extrapolate results from
cellular and animal studies to the human experience. Radiofrequency
absorption conditions can be different in humans because energy absorption
of RF radiation depends on dielectric properties, orientation, uniformity
of the field, size and geometry of the exposed subject, wavelength
of the radiation, near- or far-field exposure, and partial or whole
body exposure (Stuchly, 1998).
There have been a number of studies of the effects of RF radiation
exposure in human volunteers.
In this section human experimental studies are discussed under the
following headings
Brain
function includes both EEG studies and cognitive
function.
Hermann and Hossmann (Journal of Neurological Sciences 1997; 152:
1- 14) have published a good review of wireless phones and their effect
on brain function. They include details of in vitro
and in vivo research,
as well as some done in humans. They published an update of this review
in 2003
Hamblin and Wood
(2002) have also reviewed studies that examined the effects of mobile
phone emissions on human brain activity and sleep patterns.
Cook and colleagues
(2006) published a review of studies from 2001-2005 that examined
physiological and cognitive effects of ELF magnetic and ELF-modulated
radiofrequency fields. They discuss the different methods of measuring
physiological effects. They include EEG studies that are discussed
in the next section. They point out that functional and metabolic
imaging of the brain can be done using several methods:
- functional magnetic resonance imaging (fMRI, measuring brain blood
flow)
- magnetic resonance spectroscopy (MRS, measuring neurotransmitter
concentrations)
- positron emission tomography (PET, measuring brain blood flow, metabolism
and neuro-receptor occupancy)
- single photon emission tomography (SPECT, measuring blood flow and
metabolism).
They caution that SPECT and PET detectors are sensitive to magnetic
fields at a threshold around 100 µT. Therefore studies using
these methods should use controls to ensure that the SPECT and PET
detectors are themselves not affected by the exposure. This might
be true also for RF exposures, particularly if associated electronics
produce significant ELF components.
Cook et al. also
point out that magnetic resonance systems produce fields that can
have opioid-related behaviours in rodents, and on affective behaviours
in both rodents and humans. Another problem with these methods is
that they detect relatively late events, such as blood flow and metabolism
that occur seconds to minutes after the start of brain activity.
Valentini et al. (2007) carried out a comprehensive review
of the neurophysiological effects of mobile phones emissions. This
review included EEG studies as well as those involving cognitive
function.