Effects of vibration on arm and shoulder muscles in three body postures

The electromyographic responses of arm and shoulder muscles to vibrations were studied in three postures similar to the postures of drilling in a ceiling, drilling in a wall and drilling in a floor. This experiment was performed within the defined parameters of: vibrational frequency at 30 Hz, acceleration level 40 m.s-2 (rms), pushing force expressed as percentage maximal voluntary contraction, and gripping force which was set at 100 N. The exposure time for each test was 5 min. The general findings from these three body postures show that all the examined muscles were affected by exposure to vibration. The EMG index increased as follows: trapezius muscle 39% (p less than 0.05), lower-arm flexor muscles 23% (p less than 0.05), infraspinatus muscle 14% (p less than 0.05), lower-arm extensor muscles 14% (p less than 0.1) and biceps muscle 6% (p less than 0.1). The muscle most affected by vibration was found to be the trapezius muscle. It should be taken into consideration that vibration can be a contributing factor in neck/shoulder disorders among power handtool operators. The general conclusion from this study is that changes in working posture give different transmissions of vibration in the upper extremities. It seems as if the prime movers and muscles with an increased muscle length or increased degree of contraction are most affected by vibration.     

Biodynamic response of human fingers in a power grip subjected to a random vibration

BACKGROUND: Knowledge of the biodynamic response (BR) of the human hand-arm system is an important part of the foundation for the measurement and assessment of hand-transmitted vibration exposure. This study investigated the BR of human fingers in a power grip subjected to a random vibration. METHOD: Ten male subjects were used in the experiment. Each subject applied three coupling actions to a simulated tool handle at three different finger grip force levels. RESULTS AND CONCLUSIONS: The BR is practically independent of the hand coupling actions for frequencies at or above 100 Hz. Above 50 Hz, the BR is correlated to finger and hand sizes. Increasing the finger coupling force significantly increases the BR. Therefore, hand forces should be measured and used when assessing hand-transmitted vibration exposure. The results also show that under a constant-velocity vibration, the finger vibration power absorption at frequencies above 200 Hz is approximately twice that at frequencies below 100 Hz. This suggests that the frequency weighting specified in the current ISO 5349-1 (2001) may underestimate the high frequency effect on vibration-induced finger disorders.     

Acute effects of 50 Hz magnetic field exposure on human visual task and cardiovascular performance

One hundred subjects, males and females with ages ranging between 18 and 48 years, were studied under both field-exposed and sham-exposed conditions. A 50 Hz, 100 μT magnetic field (MF) was used. To examine the effect of field exposure on performance, a two-alternative, forced-choice, duration-discrimination task with three levels of difficulty was used. The subject's task was to decide which of two sequentially presented light flashes had the longer duration. The standard duration was 50 ms, and the alternative durations were 65, 100, or 125 ms. Both reaction time and percentage of correct responses were recorded for each subject. MF and sham exposure were for 9 min each. Blood pressure and heart rate were also measured before and following MF exposure and sham-exposure trials. The study was performed double blind, with the exposure order counterbalanced. Compared to sham exposure, MF exposure significantly decreased reaction time on the hardest level of the performance task. MF exposure did not reliably affect percentage correct or cardiovascular performance. It was demonstrated that a relatively high level of statistical power was the basis for the observed MF effect, and the need to pay closer attention to power levels in future research is discussed. © 1996 Wiley-Liss, Inc.     

Leaf appearance, tillering and their coordination in response to NxP fertilization in barley

The aim of this work was to study the effects of nitrogen (N) and phosphorus (P) deficiencies and their interaction on the appearance of leaves and tillers of barley (Hordeum vulgare spp. distichum L.) by analyzing the rate and duration of the appearance period. Three microcrops experiments were carried out in 200 L containers using malting barley cv. Quilmes Palomar. Treatments were a factorial combination of two levels on N and two or three levels of P fertilization. Both N and P deficiencies delayed leaf and tiller appearance rates but leaf appearance was less susceptible to nutrient deficiencies than tiller appearance. P deficiency effects on leaf emergence differed from N effects. While N deficiency diminished the rate of leaf appearance (RLA), it has no significant effect on the duration of leaf appearance or on the duration of the period from emergence to flowering. On the other hand, P deficiency diminished RLA, and increased both the duration of leaf appearance and the duration of the period from emergence to flowering.     

Quantal melatonin suppression by exposure to low intensity light in man

Plasma melatonin concentrations were examined following three relatively low intensities of artificial light. Six normal, healthy control subjects were all exposed to (a) 200 lux, (b) 400 lux and (c) 600 lux for a three hour duration from midnight to 0300 h. Blood was also collected on a control night where light intensity was less than 10 lux throughout. Significant suppression of melatonin was observed following light of 400 lux and 600 lux intensity when compared to the control night (p less than 0.05; Mann-Whitney U-test). 200 lux light did not produce a statistically significant melatonin suppression when compared with control samples. Each light intensity produced its own individual maximal melatonin suppression by one hour of exposure. Increased duration of exposure to the light had no further influence on melatonin plasma concentrations. These data confirm a dose response relationship between light and melatonin suppression, and indicate that there is no reciprocal relationship between the effects of light intensity and the duration of exposure on maximal melatonin suppression in man.     

Body mass index as a risk prediction and prevention factor for professional mixed low-intensity EMF burden

Abstract

The exposure conditions in the physiotherapy are characterized with various sources emitting electromagnetic fields (EMF) in different frequency ranges. Very little is known about the exposure modalities' influence on the operators. In this article, we present the effects of EMF on personnel morbidity profile dependent on the body mass index (BMI) increase. By cross-tabulation, the role of higher BMI on enhancing the EMF vulnerability potential is confirmed. The correlation of the higher BMI with some serious diseases and conditions’ development has been evidenced statistically significant. Вy the whole-studied group, a general tendency for allergy, cardiovascular diseases, sleep disruption and age-shortened menopause, as well as allergy and leiomyoma in the expositional criteria subgroups (ESG), formed for the purposes of this study, is evidenced. The three ESGs are formed on work residence duration in the electrolight therapy section. The first – up to four working hour daily, the second – the entire working day (7?h) and the third group is not residenced in the electrolight therapy section. We hypothesize two signaling ways of interaction of the chronically low-intensity EMF and the higher BMI as the most likely: hormonal – by melatonin levels decrease due to estrogen levels increasing and endocrine – mast-cells auto replication and degranulation stimulation. Based on the results of the study, the BMI increase as an observed control factor in the prediction of the professional risk can be recommended.     

毛健夜蛾幼虫假死行为诱导因子研究

【目的】探明毛健夜蛾Brithys crini Fabricius幼虫另类假死行为的规律和特点。【方法】在实验室条件下观察毛健夜蛾幼虫体重、连续刺激、作用力的大小、背景声音和背景LED光色对假死发生率和假死持续时间的影响。【结果】(1)假死持续时间有随幼虫体重增加而延长的趋势,但相关性不显著。(2)假死持续时间有随刺激次数增加而缩短的趋势,与刺激次数呈显著性负相关;前10次刺激的平均假死持续时间(85.6 s)显著长于后10次(67.3 s)。(3)2、5和10 N力处理组间假死持续时间(分别为82.3、97.4和78.3 s)无显著差异,但三者均显著短于6 N力处理组的假死持续时间(157.0 s)。(4)风声处理组假死持续时间(65.6 s)显著短于鸟鸣声和蛙叫声处理组(分别为144.8 s和134.1 s)。(5)不同颜色背景LED光源处理下,假死持续时间有显著差异性,红色闪光、红色、黄色、绿色、白色和蓝色处理组假死持续时间分别为54.7、64.3、82.7、90.6、96.9、112.3 s。各处理假死发生率没有显著性差异。【结论】毛健夜蛾幼虫假死行为可因内外环境因素不同而异。     

Study of Biomechanical Response of Human Hand-Arm to Random Vibrations of Steering Wheel of Tractor

This paper reports a study on the biomechanical response of a human hand-arm model to random vibrations of the steering wheel of a tractor. An anatomically accurate bone-only hand-arm model from TurboSquidTM was used to obtain a finite element (FE) model to understand the Hand-arm vibration syndrome (HAVS), which is a neurological and vascular disorder caused by exposure of the human hand-arm to prolonged vibrations. Modal analysis has been done to find out the first few natural frequencies and mode shapes of the system. Coupling of degrees of freedom (DOF) had to be done in the FE idealization to do modal analysis, as the bones were not attached to each other in the TurboSquidTM model. The shoulder bone, scapula, has been constrained at one end for eigenvalue analysis. It was observed that the first five natural frequencies were in the range of 0-250 Hz, which is the range in which the effect of HAVS is the highest. Harmonic analysis was done by giving a swept sine excitation in the frequency range 0 to 200 Hz. For this, a force input of 25 N was imparted at nodes perpendicular to the hand, the force value chosen being the nominal force in most applications involving powered hand-held tools and steering wheels of tractors. The nodes chosen for force application were determined experimentally from observations made by gripping the steering wheel. The frequency response function (FRF) plots were obtained in the x, y and z directions. Random vibration analysis was done next by giving force power spectral densities (PSD) in the form of nodal excitation as input to the FE model of hand-arm, and computing the output acceleration PSDs. The input force PSDs were measured using FlexiForce® sensors along the three axes. The acceleration responses at the steering wheel were also measured using tri-axial accelerometers for validating the computed results. The output acceleration PSDs were then weighted using the frequency weighting curves for hand-arm vibration and the total daily exposure A(8), computed using ISO 5349-1 standards, was compared with the vibration action and limit values. The A(8) values obtained are found to be higher than the vibration limit values.     

A replication study of human exposure to 60-Hz fields: effects on neurobehavioral measures.

The purpose of this study was to reproduce and extend an earlier investigation of the effects of human exposure to combined, 60-Hz electric and magnetic fields. This paper presents the neurobehavioral results. Thirty men participated in one training session and four testing sessions. Subjects were randomly assigned to two groups. The 18 subjects in Group I were exposed (9 kV/m, 20 microT) and sham exposed in two counterbalanced orders. In Group II, half of 12 subjects were exposed (9 kV/m, 20 microT) every session, and the remaining half were sham exposed every session. The study was doubly blinded. Measures of cardiac interbeat interval, event-related brain potentials, and performance were obtained before, during, and after exposures. As in the earlier study, exposure to the combined field resulted in a statistically significant slowing of heart rate, in changes in late components of event-related brain potentials, and in decreased errors on a choice reaction-time task. In addition, field effects on several other measures approached statistical significance. The physiological measures obtained during exposure indicated that effects were greatest soon after the field was switched on, and again when it was switched off. The data indicate that changes in exposure level may be more important than duration of exposure for producing effects in human beings.     

Formation of DNA adducts and induction of mutagenic effects in rats following 4 weeks inhalation exposure to ethylene oxide as a basis for cancer risk assessment

Ethylene oxide (EO) is mutagenic in various in vitro and in vivo test systems and carcinogenic in rodents. EO forms different adducts upon reaction with DNA, N7-(2-hydroxyethyl)guanine (N7-HEG) being the main adduct. The major objectives of this study were: (a) to determine the formation and persistence of N7-HEG adducts in liver DNA of adult male rats exposed to 0, 50, 100 and 200 ppm by inhalation (4 weeks, 5 days/week, 6 h/day) and (b) to assess dose-response relationships for Hprt gene mutations and various types of chromosomal changes in splenic lymphocytes.N7-HEG adducts were measured 5, 21, 35 and 49 days after cessation of exposure. By extrapolation, the mean concentrations of N7-HEG immediately after cessation of exposure ('day 0') to 50, 100 and 200 ppm were calculated as 310, 558 and 1202 adducts/10(8) nucleotides, respectively, while the mean concentration in control rats was 2.6 adducts/10(8) nucleotides. At 49 days, N7-HEG values had returned close to background levels. The mean levels of N-(2-hydroxyethylvaline) adducts in haemoglobin were also determined and amounted 61.7, 114 and 247 nmol/g globin, respectively. Statistically significant linear relationships were found between mean N7-HEG levels ('day 0') and Hprt mutant frequencies at expression times 21/22 and 49/50 days and between mean N7-HEG ('day 0') and sister-chromatid exchanges (SCEs) or high frequency cells (HFC) measured 5 days post-exposure. At day 21 post-exposure, SCEs and HFCs in-part persisted and were significantly correlated with persistent N7-HEG adducts. No statistically significant dose effect relationships were observed for induction of micronuclei, nor for chromosome breaks or translocations.In conclusion, this study indicates that following sub-chronic exposure, EO is only weakly mutagenic in adult rats. Using the data of this study to predict cancer risk in man resulting from low level EO exposures in conjunction with other published data, i.e., those on (a) genotoxic effects of EO in humans and rats, (b) DNA binding of other carcinogens, (c) natural background DNA binding and (d) genotoxic potency of low energy transfer (LET) radiation, it is not expected that long term occupational exposure to airborne concentrations of EO at or below 1 ppm EO produces an unacceptable increased risk in man.     

The effects of precision demands during a low intensity pinching task on muscle activation and load sharing of the fingers.

High precision demands in manual tasks can be expected to cause more selective use of a part of the muscular synergy involved. To test this expectation, load sharing of the index finger and middle finger was investigated during a pinching task. Myoelectric activation of lower arm and neck-shoulder muscles was measured to see if overall level of effort was affected by precision demands. Ten healthy female subjects performed pinching tasks with three levels of force and three levels of precision demands. The force level did not significantly affect the relative contribution of the index and middle finger to the force. Higher precision demands, however, led to higher contribution of the index finger to the pinch force. Consequently, a more selective load of the forearm and hand occurs during tasks with high precision demands. The variability of the force contribution of the fingers increased during the task. No effects of precision demand on the activation of forearm and neck-shoulder muscles were found. Force level did affect the EMG parameters of several muscles. The effects were most apparent in the muscles responsible for the pinch force, the forearm muscles. Activation of these muscles was higher at higher force levels. In the trapezius muscle at the dominant side EMG amplitudes were lower at the high pinch force compared to the low force and median force conditions.     

Effects of whole body vibration on outer hair cells’ hearing response to distortion product otoacoustic emissions

Whole body vibration (WBV) is one of the most vexing problems in industries. There is a debate about the effect of WBV exposure on hearing system as vibration-induced hearing loss. The purpose of this study was to investigate outer hair cells' (OHCs') hearing response hearing response to distortion product otoacoustic emissions (DPOAEs) in rabbits exposed to WBV. It was hypothesized that the DPOAE response amplitudes (A(dp)) in rabbits exposed to WBV would be lower than those in control rabbits not exposed to WBV. New Zealand white (NZW) rabbits as vibration group (n = 6, exposed to WBV in the z-axis at 4-8 Hz and 1.0 ms(-2) root mean square for 8 h per day during five consecutive days) and NZW rabbits as control group (n = 6, not exposed to any WBV) were participated. A(dp) and noise floor levels (L(nf)) were examined on three occasions: day 0 (i.e., baseline), day 8 (i.e., immediately 1 h after exposure), and day 11 (i.e., 72 h following exposure) with f(2) frequencies ranging from 500 to 10,000 Hz and primaries L(1) and L(2) levels of 65 and 55 dB sound pressure level, respectively. Main effects were statistically found to be significant for group, time, and frequency (p < 0.05). DPOAE amplitudes were significantly larger for rabbits exposed to WBV, larger on day 8 and larger for mid to high f(2) frequencies (at and above 5,888.50 Hz). Main effects were not statistically found to be significant for ear (p > 0.05). Also, four statistically significant interactions including time by ear, time by frequency, group by frequency, and group by time were detected (p < 0.05). Contrary to the main hypothesis, DPOAE amplitudes were significantly larger for rabbits exposed to WBV. WBV exposure significantly led to enhanced mean A(dp) at mid to high frequencies rather than at low ones.     

Experience acquisition by Trichogramma australicum Girault (Hymenoptera: Trichogrammatidae)

We investigated experience acquisition (alpha-conditioning) by females of the parasitoid Trichogramma australicum using host eggs of the noctuid moth Helicoverpa armigera (Hübner). We compared the acceptance of a host egg by females with different levels of ovipositional experience. The level of experience was designated using the standard oviposition sequence: (1) host contact (C); (2) host examination (E); (3) drilling (D); (4) full insertion (FI); and (5) oviposition (O). Each treatment consisted of a single experience level, but together these consituted a qualitative behavioural continuum of oviposition experience from naive (N) to experienced wasps. We found that host experience by adult T. australicum females can modify their behaviour. Mean duration of host finding was: N = C > E = D > FI = O. Mean duration of host examination and full insertion were: N = C > E = D = FI = O. Drilling was constant for all experience levels. Experience in drilling of the chorion during the previous host-exposure process represents a critical experience for a female and results in efficient handling and more ready acceptance of a subsequently encountered host egg.     

Intensity-time dependence dosing criterion in the EMF exposure guidelines in Russia

Major approaches of the Russian Federation in setting of exposure guidelines to electromagnetic fields (EMF) in occupational and public environments are discussed in this paper.

EMF exposure guidelines in Russia are based on the results of hygienic, clinical, physiological, epidemiological and experimental studies and are frequency-dependent. The concept of a threshold principle of occupational and environmental factors due to hazardous exposure effects has been used to set permissible exposure levels of different EMF frequency ranges. The data of experimental studies showed hazardous threshold levels of EMF effects. The main criteria of EMF hazardous exposure evaluated in the experimental study concerned both estimation of threshold levels of chronic (long-term) and acute exposure. Also, this paper contains some recent experimental study data on correlation of long-term radiofrequency and power-frequency EMF exposure effects with regard to time duration, the so-called time-dependence approach. It enables identification of the value of permissible EMF exposure levels depending on exposure duration. This approach is used in occupational exposure guideline setting and requires the introduction of “power exposition” (PE) and “maximal permissible level” (MPL). In general, EMF exposure guidelines are established with regard to possible duration of exposure per day.     

Monospermy and polyspermy after partial zona dissection of reinseminated human oocytes

Partial zona dissection (PZD), a zona drilling method that uses mechanical force to open the zona pcllucida while the oocyte is shrunken in a sucrose solution, was applied to 121 unfertilized 1-day-old mature human oocytes prior to reinsemination. The 115 surviving oocytes were divided into three groups in which the duration between sucrose addition and reinsemination was varied: I) Less than 20 minutes, II) 21 to 45 minutes, and III) longer than 45 minutes. There was a trend toward a reduced fertilization and polyspermy rate as the time between sucrose exposure and insemination in sucrose-free medium increased. Moreover, there was a statistically significant reduction in the number of oocytes penetrated by more than four sperm in group III (0/41) versus group I (7/34), and in group III, parthcnogcnctic development was observed. The incidence of polyspermy was also increased in oocytes manipulated more than 25 hours after retrieval compared with those manipulated 21-24 hours after recovery, supporting the idea that aged oocytes have a reduced ability to block polyspermy. Oocyte contraction in sucrose occurred in three different patterns: spherical, pear-shaped, and crenated. Both the fertilization and polyspermy rates were significantly higher in the crenated group. These results indicate that changes resembling activation occur following sucrose exposure and that sucrose activation can be used to reduce the risk of polyspermic fertilization in zona drilling procedures. In addition, the pattern of shrinkage in sucrose can be used as an indicator of oocyte receptivity to sperm penetration.     

Effect of feed zone in fed-batch fermentations of Saccharomyces cerevisiae

In production-scale, fed-batch fermentations, feed is often added to a single point at the top of the fermentor, which, combined with poor mixing, results in formation of a "feed zone" rich in nutrients. Frequent exposure of the culture to high concentrations of nutrients in the feed zone for sufficient duration can produce unexpected effects on its performance. The effect of the feed zone was evaluated by conducting aerobic fed-batch fermentations of Saccharomyces cerevisiae with both complex and defined media. The broth was recirculated between a recycle loop and a bench-scale fermentor, and feed was intermittently added into the recycle loop to simulate the circulation of cells through the feed zone. Experiments were carried out for a range of residence times in the recycle loop from 0.5 to 12 min. Biomass yields from the complex-media fermentations were not affected by exposure to high nutrient levels in the recycle loop for residence times up to 12 min. Ethanol consumption was reduced by as much as 50% for residence time in the loop up to 3 min. Very long exposure of yeast cells to excess nutrient levels (12 min) gave acetic acid formation. In a defined medium, the simulated feed zone effect increased biomass yield by up to 10%, but had no effect on ethanol levels. This study indicates that the feed zone effect on biomass yield in yeast fermentation, using complex substrates, will be negligible under fully aerobic conditions.     

Fluctuations in plantar flexion force are reduced after prolonged tendon vibration.

The purpose of the study was to examine the effect of prolonged vibration on the force fluctuations during a force-matching task performed at low-force levels. Fourteen young healthy men performed a submaximal force-matching task of isometric plantar flexion before and after Achilles tendon vibration (n = 8, vibration subjects) or lying without vibration (n = 6, control subjects) for 30 min. The target forces were 2.5-10% of the previbration maximal voluntary contraction force. The standard deviation of force decreased by a mean of 29 +/- 20% across target forces after vibration, whereas it did not decrease significantly in control subjects (-5 +/- 12%). This change was significantly greater compared with control subjects (P < 0.01 for both). Power spectral density of the force was predominantly composed of signals of low-frequency bandwidth (相似文献   

A selective inhibitor of N8-acetylspermidine deacetylation in mice and HeLa cells without effects on histone deacetylation

The inhibitory effects of 7-[N-(3-aminopropyl)amino]heptan-2-one (APAH) on N8-acetylspermidine deacetylation were studied. In in vitro studies, APAH produced inhibition (apparent Ki of 0.18 microM) of N8-acetylspermidine deacetylation by the 100,000g supernatant fraction of rat liver. This apparent Ki was 60-fold less than the apparent Km (11 microM) for deacetylation of the substrate, N8-acetylspermidine, suggesting that APAH could be a potent, effective inhibitor in vivo. APAH was administered to mice by intraperitoneal injection at a dose of 200 mg/kg, and polyamine and acetylpolyamine levels in liver and spleen were measured. In tissues of control mice, N8-acetylspermidine was not detectable but increased to detectable levels 30-360 min after APAH treatment. These data are consistent with inhibition of the deacetylase by APAH. Increases in putrescine and N1-acetylspermidine levels occurred in liver after APAH treatment with increases in N1-acetylspermidine levels observed in spleen. In HeLa cells, a significant increase in N8-acetylspermidine was observed following 24 h exposure to 10 microM APAH while no change occurred in the acetylation level of HeLa cell histones. In contrast, 24 h exposure to 10 mM sodium butyrate produced no change in N8-acetylspermidine levels and an increase in the acetylation level of histones H4 and H2B. These results suggest that APAH has a relatively selective inhibitory effect on N8-acetylspermidine but not histone deacetylation. This is the first report of significant levels of N8-acetylspermidine in animal tissues and of the effects of in vivo inhibition of N8-acetylspermidine deacetylase.     

Evaluation of Fluoride-Induced Oxidative Stress in Rat Brain: A Multigeneration Study

Multigenerational evaluation was made in rats on exposure to high fluoride (100 and 200 ppm) to assess neurotoxic potential of fluoride in discrete areas of the brain in terms of lipid peroxidation and the activity of antioxidant enzyme system. The rats were given fluoride through drinking water (100 and 200 ppm) and maintained subsequently for three generations. Fluoride treatment significantly increased the lipid peroxidation and decreased the activity of antioxidant enzymes viz, catalase, superoxide dismutase, glutathione peroxidase, glutathione S-transferase, and glutathione level in first-generation rats and these alterations were more pronounced in the subsequent second and third-generation rats in both the doses tested. Decreased feed and water consumption, litter size and organ (brain) somatic index, marginal drop in body growth rate and mortality were observed in all three generations. Decreased antioxidant enzyme activity and increased malondialdehyde levels found in the present study might be related to oxidative damage that occurs variably in discrete regions of the brain. Results of this study can be taken as an index of neurotoxicity in rats exposed to water fluoridation over several generations.     

Chronic exposure of primates to 60-Hz electric and magnetic fields: III. Neurophysiologic effects

The neurophysiologic effects of combined 60-Hz electric (E) and magnetic (B) fields, of magnitudes comparable to those produced by high-voltage powerlines, were investigated in 10 monkeys (Macaca nemestrina). Six animals (experimental group) were each exposed to three different levels of E and B fields: 3 kV/m and 0.1 G, 10 kV/m and 0.3 G, and 30 kV/m and 0.9 G. Field exposures were preceded and followed by sham exposures, during which factors of field generation were present (e.g., heat, vibration, noise, etc.) without E and B fields. Each of the five segments (i.e., the three exposure segments and the initial and final sham exposure segments) lasted 3 weeks. Animals were exposed for 18 h/day (fields on at 1600 h, off at 1000 h). Four other animals (external control group) were given sham exposure for the entire 15-week period. Auditory, visual, and somatosensory evoked potentials were recorded twice a week, during the daily 6-h field-off period. E- and B-field exposure had no effect on the early or mid-latency evoked potential components, suggesting that exposure at these levels has no effect on peripheral or central sensory afferent pathways. However, there was a statistically significant decrease in the amplitudes of late components of the somatosensory evoked potential during the 10kV/m and 0.3 G, and 30 kV/m and 0.9 G exposure levels. This result is possibly related to the opiate antagonist effect of electromagnetic field exposure reported by others.