Current densities in a pregnant woman model induced by simultaneous ELF electric and magnetic field exposure.

The pregnant woman model SILVY was studied to ascertain to what extent the electric current densities induced by 50 Hz homogeneous electric and magnetic fields increase in the case of simultaneous exposure. By vectorial addition of the electric current densities, it could be shown that under worst case conditions the basic restrictions recommended by ICNIRP (International Commission on Non-Ionizing Radiation Protection) guidelines are exceeded within the central nervous system (CNS) of the mother, whereas in sole field exposure they are not. However, within the foetus the induced current densities do not comply with basic restrictions, either from single reference-level electric fields or from simultaneous exposure to electric and magnetic fields. Basic limits were considerably exceeded.

RF-EMF exposure of fetus and mother during magnetic resonance imaging.

Magnetic resonance imaging (MRI) avoids risks of genetic damage but may be associated with excess heating of body tissues. To investigate the exposure to MRI radio-frequency (RF) electromagnetic fields (EMF), low-pass and high-pass birdcage coils were simulated and the whole-body pregnant woman model SILVY used to determine local and whole-body specific absorption rates (SAR) in mother and fetus. Resonant RF-EMF of MRI devices were investigated at 0.3, 1, 1.5, 2, 3 and 4 T. Results allow extrapolation also to higher fields. They showed that local SAR in mother's trunk reaches exposure limits first. However, data show that during abdominal MRI meeting exposure limits of the mother is not sufficient to protect the fetus if limits of the general populations are applied to it. In that case fetal whole-body SAR exceeds limits by 7.4-fold. It is up to the physician and/or the ethics commission to decide upon justification for abdominal MRI of pregnant women if limits are exceeded. The results indicate the need for specifically addressing fetal exposure to EMF and elaborating general recommendations by radiation protection bodies.

Magnetic emissions of electric appliances.

More than 1000 electric appliances have been investigated regarding their emission of magnetic fields. It was found that complex frequency spectra are common and single frequency emissions are rare. Since exposure assessment requires frequency-weighted sums, root-mean-square values are not appropriate for comparison with exposure reference levels. It could be shown that they may underestimate emissions up to two orders of magnitude. Analysis of device groups showed a wide span of emission values of up to two orders of magnitude with only weak associations to power consumption. This demonstrates that there is a considerable potential to reduce fields without loss of performance. Exposure to magnetic fields of electric appliances are not negligible in daily life. Many devices considerably exceeded permitted reference levels and would require a closer analysis to demonstrate conformity with basic limits.

Electric emissions from electrical appliances.

Electric emissions from electric appliances are frequently considered negligible, and standards consider electric appliances to comply without testing. By investigating 122 household devices of 63 different categories, it could be shown that emitted electric field levels do not justify general disregard. Electric reference values can be exceeded up to 11-fold. By numerical dosimetry with homogeneous human models, induced intracorporal electric current densities were determined and factors calculated to elevate reference levels to accounting for reduced induction efficiency of inhomogeneous fields. These factors were found not high enough to allow generally concluding on compliance with basic restrictions without testing. Electric appliances usually simultaneously emit both electric and magnetic fields exposing almost the same body region. Since the sum of induced current densities is limited, one field component reduces the available margin for the other. Therefore, superposition of electric current densities induced by either field would merit consideration.

Assessment of inhomogeneous ELF magnetic field exposures.

In daily life as well as at workplaces, exposures to inhomogeneous magnetic fields become very frequent. This makes easily applicable compliance assessment methods increasingly important. Reference levels have been defined linking basic restrictions to levels of homogeneous fields at worst-case exposure conditions. If reference levels are met, compliance with basic restrictions can be assumed. If not, further investigations could still prove compliance. Because of the lower induction efficiency, inhomogeneous magnetic fields such as from electric appliances could be allowed exceeding reference levels. To easily assess inhomogeneous magnetic fields, a quick and flexible multi-step assessment procedure is proposed. On the basis of simulations with numerical, anatomical human models reference factors were calculated elevating reference levels to link hot-spot values measured at source surfaces to basic limits and allowing accounting for different source distance, size, orientation and position. Compliance rules are proposed minimising assessment efforts.

Magnetic emission ranking of electrical appliances. A comprehensive market survey.

Over the last decades emissions of magnetic fields from electric appliances have considerably changed. Based on a comprehensive market survey it could be shown that today magnetic emissions are usually characterised by complex frequency spectra while single-frequency emissions have become rare. Therefore, spectral assessment procedures play a critical role. Compared to frequency-weighted equivalent magnetic induction, rms values may underestimate emissions up to two orders of magnitudes. Therefore, rms measurements are not suitable and emission-ranking lists of devices need revision. Surface hot-spot measurements at nominal load conditions and 230 V/50 Hz supply involved 1146 new electrical devices of 166 different categories. High emissions were not rare. Magnetic emissions of devices of 73 different categories exceeded reference levels up to almost two orders of magnitudes above reference levels. Maximum values were higher than reported so far. Magnetic emissions were high enough to make even conformity with existing basic restrictions not self-evident.

Fetal exposure to low frequency electric and magnetic fields.

To investigate the interaction of low frequency electric and magnetic fields with pregnant women and in particular with the fetus, an anatomical voxel model of an 89 kg woman at week 30 of pregnancy was developed. Intracorporal electric current density distributions due to exposure to homogeneous 50 Hz electric and magnetic fields were calculated and results were compared with basic restrictions recommended by ICNIRP guidelines. It could be shown that the basic restriction is met within the central nervous system (CNS) of the mother at exposure to reference level of either electric or magnetic fields. However, within the fetus the basic restriction is considerably exceeded. Revision of reference levels might be necessary.

Perception of ELF electromagnetic fields: excitation thresholds and inter-individual variability.

So far, in guidelines limiting exposure to electromagnetic fields, basic limits of intracorporal electric current densities have been recommended to prevent from nerve cell stimulation. They were based on experimental data and extrapolated to the general population with limited knowledge on the inter-individual variability. To assess the variability of cellular excitability the perception thresholds for directly applied electric currents were used as surrogate. However, until recently, the data on perception ability of electric currents were gained from small groups only and led to controversial results, differing by more than one order of magnitude. This paper discusses the results of our previous research comprising extensive measurements on 1,071 individuals (349 men and 359 women aging 16 to 60 y, 117 girls and 123 boys aging 9 to 16 years, and 123 individuals older than 60 y). Their electric current perception thresholds fit fairly well with a log-normal distribution. The electric 50 Hz current perception threshold was measured by directly applied pairs of electrodes at the lower forearms. It was found that the inter-individual variability comprises two orders of magnitudes which is one order of magnitude higher than assumed so far. Women were found to be significantly more sensitive than men. Depending on the level of probability p, the perception threshold for women was 0.77-fold (p = 50%) or even 0.45-fold (p = 0.5%) lower than for men. Surprisingly, children turned out to be considerably more sensitive than men but similar to women. The age dependence exhibited a decrease of perception thresholds with age from adult men to boys joining the values of girls at ages around 10 y. The results indicate that existing safety limits for touch currents need critical review. Apart from the inter-individual variability, it was estimated to which place within the distribution of perception levels the basic limits were related. Therefore, numerical simulations were made to calculate intracorporal electric current densities associated with the applied electric currents. The results confirm that the basic limits of intracorporal electric current densities as recommended by ICNIRP are conservative to prevent cellular excitation.

Electromagnetic shielding mats: facts and fiction.

The use of electricity is accompanied by electric and magnetic fields which, intended or not, became a part of our environment. However, fear from environmental electromagnetic fields (EMFs) is widespread and so is business with fear. A number of more or less serious products including miracle products are placed on the market partly at excessive costs. By numerical simulation the efficiency of electromagnetic shielding mats was investigated and claims of manufacturers and their cited expert opinions checked. It could be shown that such products do not fulfil the justified expectations of customers, neither in the extremely low frequency (ELF) nor in the radiofrequency (RF) range. On the contrary, these mats usually make things even worse. The connection to ground, if available, might increase the belief on shielding efficiency, but in fact it even enhances fields instead of improving shielding. The electric conductivity of the mat material plays a minor role in the ELF range and enhances field increase in the RF range. It can not explain the enormous price differences. It could be shown that positive reports can be explained by result picking and exceptional arrangements of selected field sources. Overall, the investigation showed that manufacturer's claims about the shielding effectiveness are misleading and fool the customers about the real situation. Therefore, acquisition and use of electromagnetic shielding mats must be strongly discouraged.

Electromagnetic field spectral evaluation problems in exposure assessment.

Electromagnetic fields have become an omnipresent factor in our daily environment. It has become common that the exposure situations are characterised by a cocktail of spectral contributions from different sources, while exposures to single frequencies are rare. Thirty-two different types of drilling machines were analysed. Even similar devices exhibited large variations of emission levels up to two orders of magnitudes. It was found that emissions are not negligible and could be close or even above reference levels. Already single spectral peaks of magnetic emissions may considerably exceed reference levels, and excess can reach even the 90-fold when evaluating the entire spectrum. It is shown that approaches to assess complex frequency spectra as proposed by the International Commission on Non-Ionising Radiation Protection or defined in compliance standards issued by CENELEC or IEC lead to contradictory conclusions on conformity or non-conformity. There is an urgent need to clarify this discrepancy.

Electric current perception of children: the role of age and gender.

Although it is widely accepted that children merit increased protection, little is known about the quantitative consequences of electric currents when setting safety limits. Measurements were performed on 240 children (117 girls and 123 boys) older than 9 years. It was found that the electrosensitivity of children was higher than that of adults, but did not exceed the overall span of adult electrosensitivity. Girls' results depend only weakly on age. Therefore, no major change should be expected below the age of 9. The electrosensitivity of boys increases with decreasing age; however, it finally approaches and merges with that of girls. The results imply that the factor by which the allowed touch current should be reduced for children depends on the perception probability level considered. The reduction factor of 2, as chosen in the past, would need revision either in regard to its value or to the related perception probability level. If related to the still existing rationale for safety limits the factor would need to be far higher.

Electric current perception of the general population including children and the elderly.

Although the 50 Hz electric current perception threshold is a key parameter for limiting electric touch currents in electrical technology and for limiting indirect effects of external electromagnetic fields, the data available mainly reflect men's perception ability; with only sparse data for women and almost none for children or the elderly. Measurements with 240 children aged 9 - 16 years, and 123 elderly people, allow this gap of knowledge to be filled. Taking into account the demographic age distribution, it was possible to generate a probability distribution representing the perception ability of the overall general population, and thus to provide a more established basis for deriving safety limits. The results show that the existing limit values for electric touch currents are considerably too high if compared with results derived from the new data with the same criteria. On the other hand, it appeared that children do not exhibit such a high sensitivity to electricity as assumed to date. Therefore, former rule-of-thumb estimates to account for higher sensitivities of children lie on the safe side. The presented assessment of the general population's electric current perception ability should stimulate a critical review of the existing regulations.

[Inefficiency of electrosmog-shielding mats. Part 2: radio frequency range]. / Unwirksamkeit von Elektrosmog- Abschirmmatten. Teil 2: Hochfrequenzbereich.

It could already be shown that electromagnetic shielding mats do not reduce but even enhance electric field exposure in daily life situations. By measurements and numerical simulations the claims of manufacturers were checked who pretend that radio frequency electromagnetic fields can be shielded to 99% and more, and transferred to earth by earth cables (if attached). It could be shown that in the radio frequency range such products do not fulfil the justified expectations of customers, but in most cases even cause the opposite. The results depend on the electric properties of the material. Good electric conductivity of shielding mats even considerably increases electromagnetic field exposure. To connect the mats with earth potential by an attached cable might increase the beliefs on a protective effect, however, this is not capable to enhance the shielding effect. The investigation demonstrates that in spite of references made to experts opinions manufacturers claims about the shielding efficiency of radio frequency fields are misleading and fool clients about the real situation. Overall, acquisition and use of electrosmog shielding mats must be discouraged. If at all, shielding can be reached by placing a shielding cover between the source and the person. However, even in this case, efficiency is much lower than promised by manufacturers and decreases even more if it is taken into account that the head naturally remains uncovered and hence unshielded.

[Inefficiency of electrical pollution-shielding mats. 1: low frequency range]. / Unwirksamkeit von Elektrosmog-Abschirmmatten. Teil 1: Niederfrequenzbereich.

Despite of the fact that environmental electric and magnetic fields are magnitudes below the existing limits, fear from electromagnetic pollution increase and so does business with fear by offering more or less plausible products with partly excessively high prices . Based on numerical simulation the claims of manufacturers on the efficiency of electromagnetic shielding mats were tested. It is pretended that electric fields can be shielded to 98% and more, and transferred to earth by earth cables (if attached). It could be shown that in general such products do not fulfil the justified expectations of customers, but in contrary even cause the opposite. To connect the mats with earth potential by an attached cable might increase the beliefs on a protective effect, however, this is not capable to enhance the shielding effect but in most cases this causes even the contrary by partly considerably increasing electric field exposure. The electric conductivity of the used shielding mats plays a neglectable role and cannot explain the considerable price differences. The investigation demonstrates that in spite of references made to expert's opinions manufacturer's claims about the shielding efficiency are misleading and fooling clients about the real situation.

Joint report of the Third International Workshop of Canine Immunogenetics. II. Analysis of the serological typing of cells.

Using a standardized microlymphocytotoxicity assay, seven international laboratories evaluated 144 anti-dog lymphocyte antigen (DLA) sera in 319 mixed breed and 152 Beagle dogs. The workshop confirmed the serological definitions for DLA-A2, A3, A9; DLA-B4, B5, B6, B13; DLA-C11(Cwl); and C12(Cw2). Two new specificities were assigned to the DLA-A locus (Aw14 and Aw15) in only the mixed breed dogs. A third specificity (Cw3), was assigned to the DLA-C locus. The antigen and gene frequencies of these alleles differed between the two groups of dogs, but the frequencies of the "blank" were similar in both groups. Future international collaborations will be necessary to definite more completely the polymorphisms of the major histocompatibility complex (MHC) of the dog. Those efforts will benefit from the standard serological test established in this workshop.

Inhibited hypothalamic-pituitary-thyroid axis in type I pseudohypoparathyroidism.

OBJECTIVE: To assess the hypothalamic-pituitary-thyroid axis in two patients with the diagnosis of type I pseudohypoparathyroidism established previously by characteristic clinical features and laboratory findings, including low serum Ca++, high parathyroid hormone concentration, and subnormal urinary cyclic adenosine monophosphate (cAMP) responses to exogenous administration of parathyroid hormone. METHODS: We determined serum thyroxine, triiodothyronine (T(3)), T(3) resin uptake, and 24-hour thyroidal uptake of 123 I before and after subcutaneous administration of thyroid-stimulating hormone (TSH), 10 U daily for 3 days. Serum TSH levels were determined before and again at 15, 30, 45, and 60 minutes after intravenous administration of thyrotropin-releasing hormone (TRH) (400 microg) after an overnight fast. Values noted in the two patients with type I pseudohypoparathyroidism were compared with those obtained in 10 normal volunteer control subjects. RESULTS: Serum thyroxine (T(4)), triiodothyronine (T(3)), T(3) resin uptake, and 24-hour 123 I uptake values for both patients with type I pseudohypoparathyroidism were within the normal ranges (5.5 to 11.5 microg/dL for T(4), 90 to 190 ng/dL for T(3), 35 to 45% for T(3) resin uptake, and 10 to 35% for 24-hour 123I uptake). Their responses to administration of TSH, however, were all significantly lower in comparison with the mean values for the 10 healthy control subjects. Basal TSH was higher in both patients with type I pseudohypoparathyroidism than in normal subjects, but TSH responses after administration of TRH, although not significantly different from normal, were blunted in relationship to the basal concentrations, as expressed as a percentage increase in TSH as well as a cumulative TSH response. CONCLUSION: The responses of pituitary thyrotrophs to TRH and the thyroid gland to TSH were both considerably inhibited in the patients with type I pseudohypoparathyroidism in comparison with normal control subjects. This finding may be yet another evidence of the lack of adequate generation of cAMP, an important second messenger needed for normal functioning of most polypeptide hormones, including TRH and TSH, in this syndrome.

[Investigation of sleep disorders in the vicinity of high frequency transmitters]. / Untersuchung von Schlafstörungen um Hochfrequenz-Sendeanlagen.

To investigate the potential impact of RF electromagnetic fields of transmitters on the sleep quality of nearby residents, a new study design is presented. In a double-blind crossover field study the effect of on-site shielding, rather than of additional exposure, is investigated. For improved sleep quality differentiation the polysomnographic parameters are expanded by additional parameters. The feasibility study showed that checking the raw data and correcting the software-generated results by visual reading of the polysomnographic recordings is essential. Long-term RF measurement showed that exposure may vary considerably throughout the night, as well as from one night to the next. This variation may be greater than the GSM contribution itself. Mostly, the contributions of USW radio frequency fields dominated over GSM. Thus, continuous broadband RF recording is required for reliable interpretation of the results, in particular with regard to the potential role of mobile telephony emissions. Results show that simple sleep monitoring systems based on single-channel EEG analysis without acces to original biosignals are not adequate for sleep studies.

[Comparison of optical and ultrasound biometry and assessment of using both methods in practice]. / Srovnání optické a ultrazvukové biometrie a zhodnocení uzívání obou metod v praxi.

PURPOSE: The present study compares accuracy of optical biometry (OB) and ultrasound biometry (UB) based on postoperative best corrected visual acuity (BCVA) results, and assesses the extent of the usage of the measurement methods in current practice. METHODS: 335 eyes in total were operated for cataract at Beskydské ocní centrum (Beskydy Eye Centre; BOC), Frýdek-Místek hospital, in the period between 7 February 2007 and 7 April 2010. All patients were examined using both IOL-Master and Ocu-Scan prior to the surgery. All surgeries were performed using microcoaxial phacoemulsification, 2,2 mm incision, implanting IOL AcrySof SP, SPN or SPN IQ. BCVA was examined three months after the surgery. We first calculated medians of anterior-posterior axial length (AL) values measured using both methods; with both the whole set and individual subsets created according to the eye length. Difference between the two methods was calculated in mm. We calculated accurate dioptric power of the IOL, which should have been implanted in the lens bag to ensure postoperative emmetropia, using BCVA results. With each eye, we determined the size of diopter variation of the IOLs dioptric power value for emmetropia determined by an optical biometer from the accurate value of the IOLs dioptric power. Ultrasound biometry results were processed in the same way. The SRK-T formula was used for calculation with each biometry. We also calculated the number of variations above 1 D and 2 D with both biometric methods. RESULTS: The median of axial eye length measured using an optical biometer was 23,08 mm, and the median of axial eye length measured using ultrasound biometry was 22,93 mm. The difference between these values was 0,15 mm (150 microns), which equals the difference between average values of coincident measurement results. Average variation of dioptric power of an implanted IOL from retrospectively established optimum value of the IOLs optical power was 0,40 D lower with optical biometry and 0,16 D lower with ultrasound biometry. In the context of assessing the course of the curves of both methods created using a polynomial graph, this result confirms that the two methods correspond significantly, and therefore selecting any of the methods could not negatively impact determination of the implanted IOLs dioptric power. Comparing the frequency of variations above 1D and 2,0 D with OB and UB from the accurate value of the IOLs dioptric power, we discovered a substantially higher percentage of variations with UB - up to 25 % of the total set above 1,0 D. CONCLUSION: RESULTS of comparing accuracy and comfort of AL measurement with both methods justify unambiguous preference of optical biometry over ultrasound biometry in current practice. If measurement using ultrasound probe is done correctly, results of both methods correspond significantly, and so the methods are mutually replaceable. Using ultrasound biometry is therefore adequate in case optical biometry cannot be used.

[Assessment of postoperative anterior-posterior shift of AcrySof SP lens in time and its impact on resulting refraction]. / Vyhodnocení pooperacního predozadního posunu cocek AcrySof Single-piece v case a posouzení jeho vlivu na výslednou refrakci.

PURPOSE: The present study assesses the anterior-posterior shift of the AcrySof SP intraocular lens in the eye between the third and fifteenth month after surgery. METHODS: The observed set contained a total of 241 eyes operated for cataract at Beskydské ocní centrum (Beskydy Eye Centre; BOC), Frýdek-Místek hospital from 7 February 2007 to 7 April 2010. All surgeries were performed through microcoaxial phacoemulsification and a 2,2 mm incision, with intraocular lens (IOL) AcrySof type SP implanted. For each eye, we examined BCVA, as well as anterior chamber depth by optical biometry (IOL-Master, Carl Zeiss GmbH, Jena), 3 and 15 months after the surgery. Average depths were calculated and compared; and their variations converted from mm to diopters. Based on the BCVA results, we were able to determine optimum dioptric power of the IOL, which should have been implanted in the eye to ensure postoperative emmetropia. Averages of all values were calculated and results thereof compared. RESULTS: We noted a slight average deepening of the anterior chamber depth (0,03 mm) causing a hypermetropic shift of 0,05 D, insignificant in terms of refraction. Though comparison of average optimum IOL values calculated based on examinations carried out 3 and 15 months after surgery, we ascertained an actual zero difference between the two values. CONCLUSION: Through our own calculations, we verified very good stability of the implanted hydrophobic acrylic SP AcrySof lenses in our set, with zero haptic angulation. There is de facto no anterior-posterior shift of the IOL between 3 and 15 months after surgery, and therefore no change in refraction noticeable by the patient.