Health and safety implications of exposure to electromagnetic fields in the frequency range 300 Hz to 10 MHz.

An international seminar on health effects of exposure to electromagnetic fields (EMF) in the frequency range from 300 Hz to 10 MHz (referred to as the Intermediate Frequency (IF) range) was held in Maastricht, Netherlands, on 7-8 June 1999. The seminar, organized under the International EMF Project, was sponsored jointly by the World Health Organization (WHO), the International Commission on Non-Ionizing Radiation Protection (ICNIRP), and the Government of the Netherlands. This report does not attempt to summarize all of the material presented at the conference, but focuses on sources of exposure, biophysical and dosimetric considerations pertinent to extrapolating biological data from other frequency ranges to IF and identifies potential health concerns and needs for developing exposure guidelines. This paper is based on presentations at the conference and reports of working groups consisting of the speakers and other experts. It concludes with recommendations for further research aimed at improving health risk assessments in this frequency range.     

Stand fine root biomass and fine root morphology in old-growth beech forests as a function of precipitation and soil fertility

Only very limited information exists on the plasticity in size and structure of fine root systems, and fine root morphology of mature trees as a function of environmental variation. Six northwest German old-growth beech forests (Fagus sylvatica L.) differing in precipitation (520 – 1030 mm year^–1) and soil acidity/fertility (acidic infertile to basic fertile) were studied by soil coring for stand totals of fine root biomass (0–40 cm plus organic horizons), vertical and horizontal root distribution patterns, the fine root necromass/biomass ratio, and fine root morphology (root specific surface area, root tip frequency, and degree of mycorrhizal infection). Stand total of fine root biomass, and vertical and horizontal fine root distribution patterns were similar in beech stands on acidic infertile and basic fertile soils. In five of six stands, stand fine root biomass ranged between 320 and 470 g m^–2; fine root density showed an exponential decrease with soil depth in all profiles irrespective of soil type. An exceptionally small stand fine root biomass (<150 g m^–2) was found in the driest stand with 520 mm year^–1 of rainfall. In all stands, fine root morphological parameters changed markedly from the topsoil to the lower profile; differences in fine root morphology among the six stands, however, were remarkably small. Two parameters, the necromass/biomass ratio and fine root tip density (tips per soil volume), however, were both much higher in acidic than basic soils. We conclude that variation in soil acidity and fertility only weakly influences fine root system size and morphology of F. sylvatica, but affects root system structure and, probably, fine root mortality. It is hypothesized that high root tip densities in acidic infertile soils compensate for low nutrient supply rates, and large necromasses are a consequence of adverse soil chemical conditions. Data from a literature survey support the view that rainfall is another major environmental factor that influences the stand fine root biomass of F. sylvatica.     

Questionnaires and Diaries as Research Instruments in Dream Research: Methodological Issues

Dream questionnaires are widely used in dream research to measure dream recall frequency and various aspects of dream life. The present study has investigated the intercorrelation between questionnaire and diary measures. 285 participants completed a dream questionnaire and kept a dream diary over a two-week period. Results indicate that keeping a dream diary increased dream recall in low and medium dream recallers but decreased dream recall in high dream recallers. The correlation coefficients between questionnaire items measuring aspects of dream content and diary data were large, except for a more complex scale (realism/bizarreness). In the low recall group, however, considerably lower coefficients were found indicating that recall and sampling processes affect the response to global items measuring dream content. Using the example of testing gender differences, the findings of the present study clearly indicate that the measurement technique affects the results. Whereas sufficient internal consistency and retest reliability have been demonstrated for various dream questionnaires, future research should focus on the aspects of validity by comparing questionnaire data to dream content analysis of at least 20 dreams per person.     

Mouse Lymphoma Thymidine Kinase Gene Mutation Assay: International Workshop on Genotoxicity Tests Workgroup Report—Plymouth, UK 2002

The Mouse Lymphoma Assay (MLA) Workgroup of the International Workshop on Genotoxicity Tests (IWGT) met on June 28th and 29th, 2002, in Plymouth, England. This meeting of the MLA group was devoted to discussing the criteria for assay acceptance and appropriate approaches to data evaluation. Prior to the meeting, the group conducted an extensive analysis of data from both the microwell and soft agar versions of the assay. For the establishment of criteria for assay acceptance, 10 laboratories (6 using the microwell method and 4 using soft agar) provided data on their background mutant frequencies, plating efficiencies of the negative/vehicle control, cell suspension growth, and positive control mutant frequencies. Using the distribution curves generated from this data, the Workgroup reached consensus on the range of values that should be used to determine whether an individual experiment is acceptable. In order to establish appropriate approaches for data evaluation, the group used a number of statistical methods to evaluate approximately 400 experimental data sets from 10 laboratories entered into a database created for the earlier MLA Workshop held in New Orleans [Environ. Mol. Mutagen. 40 (2002) 292]. While the Workgroup could not, during this meeting, make a final recommendation for the evaluation of data, a general strategy was developed and the Workgroup members agreed to evaluate this new proposed approach using their own laboratory data. This evaluation should lead to a consensus global approach for data evaluation in the near future.     

Assessing alternative anthropogenic habitats for conserving waterbirds: salinas as buffer areas against the impact of natural habitat loss for shorebirds

Because many natural waterbird habitats are threatened by human disturbance and sea level rise, it is vitally important to identify alternative wetlands that may supplement declining natural habitats. Coastal salinas are anthropogenic habitats used for obtaining salt by evaporation of sea water. These habitats support important numbers of waterbirds around the world, but their importance as feeding habitats is poorly understood. I evaluated salinas as feeding habitats relative to natural intertidal habitats by comparing time spent foraging, prey-size selection, and net energy intake rate of four overwintering small-sized shorebird species on intertidal mudflats and on adjacent salinas. In winter, Dunlin Calidris alpina, Curlew Sandpiper C. ferruginea and Sanderling C. alba predominantly used the mudflats, whereas Little Stint C. minuta fed mainly on the salina. In the pre-migration fattening period, all species preferred to feed on the salina, significantly increasing the time they spent feeding in the supratidal pans. Net energy intake rates (kJ min^–1) were significantly higher on the salina than on the intertidal mudflats in 60% of all comparisons. On average, salina contributed 25.2 ± 24.2% (range: 4–54%) of the daily consumption in winter and 78.7 ± 16.4% (range: 63–100%) of the daily consumption in the pre-migration period. I recommend that modern active salinas maintain flooding conditions in the evaporation pans throughout winter, thus increasing the available surface for foraging waterbirds. I conclude that the conservation of salinas at coastal wetlands is a viable approach for shorebird conservation.     

Monitoring watercourse vegetation, a synecological approach to dynamic gradients

Changes in vegetation under reduced control measures over 3 to 5 years in watercourses in a rural environment in The Netherlands were evaluated. A method to deal with slow changes on a steep gradient is presented. The gradient with various vegetation types between the middle of the watercourse and the bank-top was split up into zones. Species composition of each zone was evaluated using literature on syntaxonomy. Cover of character species, multiplied by the width of the zones, was used to quantify the contribution of various syntaxa in the vegetation. Changes in these contribution data were used to evaluate changes over the years. The method was applied to two experiments in which cleaning frequency was reduced. Submerged vegetation of Callitriche-Ranunculetum penicillati in one and of Potamogetonetalia pectinati in the other case, hardly changed. Emergent vegetation of Nasturtio-Glycerietalia or Sparganio-Glycerietum fluitans tended to expand into the submerged zone. Bank vegetation began to show signs of development into ruderal vegetation, as a shift from Molinio-Arrhenatheretea into Artemisietea was detected. The method allowed the conclusion that conditions were too eutrophic in both experiments for a diverse brook vegetation development without additional habitat improvement.     

Interspawning interval of wild female three-spined stickleback Gasterosteus aculeatus in Alaska

The interspawning interval, or spawning frequency, of wild three-spined stickleback, Gasterosteus aculeatus , was estimated using histological examination of postovulatory follicles (POF). Females in Alaskan lakes appeared to have as much as a 48 h delay between ovulation and ovoposition, yet the POF method could still be used to estimate the interspawning interval. In two Alaskan lakes the interspawning interval was estimated to range from 2·2 to 7·8 days among individual female G. aculeatus . These estimates were consistent with the range (2·5 to 5 days) of previous estimates among individual females from laboratory observations of spawning G. aculeatus , as well as anecdotal accounts of spawning intervals reported from wild populations in Canada (5–10 days). The interspawning interval of females increased during the course of the spawning season in Alaska, showing that the majority of female spawning activity occurred during the earliest portion of the approximate 6-week reproductive season. The increased interspawning interval appears to be related to a previously reported decrease in body condition in reproductive females during the breeding season. Thus, female G. aculeatus may be unable to sustain the initial rate of reproduction as energy stores that support the rapid growth of vitellogenic oocytes are depleted.     

Crop size as an index of chick provisioning in the Greater Flamingo Phoenicopterus roseus

After being fed by their parents, Greater Flamingo chicks store food in their crops, which protrude outwards. We allocated the crop profiles of chicks to four categories to assess the relationship between body mass and crop profile variation, and so determine whether crop size can be used as an accurate index of the amount of food ingested, and to determine the timing and frequency of provisioning. We registered changes in body mass and crop fullness in eight chicks captured with turgid crops and kept in captivity until constant mass was achieved. The meal mass ingested by the chicks during each parental feeding was around 18% of net chick mass and varied greatly with crop profile. Mean transition times between the four crop profile categories ranged from 6 to 14 h. Between 1998 and 2009, 34% of chicks caught for ringing in a breeding colony had empty crops. From crop profiles recorded during the handling of chicks, it was estimated that approximately one‐third of the chicks were fed in the evening and another third during the night. Our results have implications for the estimation of body condition indexes because body mass should be free of the influence of the mass of the food in the crop.     

Features of anti‐inflammatory effects of modulated extremely high‐frequency electromagnetic radiation

Using a model of acute zymosan‐induced paw edema in NMRI mice, we test the hypothesis that anti‐inflammatory effects of extremely high‐frequency electromagnetic radiation (EHF EMR) can be essentially modified by application of pulse modulation with certain frequencies. It has been revealed that a single exposure of animals to continuous EHF EMR for 20 min reduced the exudative edema of inflamed paw on average by 19% at intensities of 0.1–0.7 mW/cm² and frequencies from the range of 42.2–42.6 GHz. At fixed effective carrier frequency of 42.2 GHz, the anti‐inflammatory effect of EHF EMR did not depend on modulation frequencies, that is, application of different modulation frequencies from the range of 0.03–100 Hz did not lead to considerable changes in the effect level. On the contrary, at “ineffective” carrier frequencies of 43.0 and 61.22 GHz, the use of modulation frequencies of 0.07–0.1 and 20–30 Hz has allowed us to restore the effect up to a maximal level. The results obtained show the critical dependence of anti‐inflammatory action of low‐intensity EHF EMR on carrier and modulation frequencies. Within the framework of this study, the possibility of changing the level of expected biological effect of modulated EMR by a special selection of combination of carrier and modulation frequencies is confirmed. Bioelectromagnetics 30:454–461, 2009. © 2009 Wiley‐Liss, Inc.     

Body size variation in insects: a macroecological perspective

Body size is a key feature of organisms and varies continuously because of the effects of natural selection on the size-dependency of resource acquisition and mortality rates. This review provides a critical and synthetic overview of body size variation in insects from a predominantly macroecological (large-scale temporal and spatial) perspective. Because of the importance of understanding the proximate determinants of adult size, it commences with a brief summary of the physiological mechanisms underlying adult body size and its variation, based mostly on findings for the model species Drosophila melanogaster and Manduca sexta . Variation in nutrition and temperature have variable effects on critical weight, the interval to cessation of growth (or terminal growth period) and growth rates, so influencing final adult size. Ontogenetic and phylogenetic variation in size, compensatory growth, scaling at the intra- and interspecific levels, sexual size dimorphism, and body size optimisation are then reviewed in light of their influences on individual and species body size frequency distributions. Explicit attention is given to evolutionary trends, including gigantism, Cope's rule and the rates at which size change has taken place, and to temporal ecological trends such as variation in size with succession and size-selectivity during the invasion process. Large-scale spatial variation in size at the intraspecific, interspecific and assemblage levels is considered, with special attention being given to the mechanisms proposed to underlie clinal variation in adult body size. Finally, areas particularly in need of additional research are identified.