ABSTRACT
<p><b>OBJECTIVE</b>Dust sample mass gain is too smaller to satisfy the limit of detection (LOD) even in most cases during dust sampling at workplaces nowdays, especially for respirable fraction. Therefore, it is aimed to solve the problem by increasing sample load with high flow rate samplers.</p><p><b>METHODS</b>In A and B two shipyards respirable welding fume was sampled by high flow rate cyclone samplers of FSP-10 (10 L/min) for 2-2.5 hours and normal flow rate FSP-2 (2 L/min) for 3-4 hours with a stratigy of parallele sampling at the same workpalce, in order to compare their mass gain, coincidence rate with LOD, and airborn dust concentration.</p><p><b>RESULTS</b>Sample mass gain of 0.97±0.40 mg and 1.61±0.86 mg respectively in the two factories by FSP-10 was significantly higher than that of 0.29±0.12 mg and 0.51±0.27 mg by FSP-2 (t-test, P<0.05 in both cases) , increasing herewith the coincidence rate with LOD from 26.8% (when sampling with FSP-2, calculated together with samples of the two factories) to 89.7%. However there was no significant difference in dust concentrations by the two different samplers, 0.53±1.88 vs 0.73±1.61 mg/m(3) by FSP-2 and FSP-10 in the shipyard A and 1.14±1.78 vs 1.01±1.63 mg/m(3) in the factory B (t-test, P>0.05 in every case) . In addtion, sample loading by FSP-2 was found to be correlated to sampling time (R(2)=0.7906, y=0.002 6x) , therefore, it has to sample for ≥192.3 min to meet the LOD (0.5 mg) in case of normal flow rate.</p><p><b>CONCLUSION</b>By using of high flow rate cyclone FSP-10 the problem of LOD could be solved, along with increased sample mass and similar respirable dust concentration by the two samplers. Some techincal improvements of FSP-10 and increasing of LOD coincidence rate by other methods was also disscussed.</p>
Subject(s)
Air Pollutants, Occupational , Construction Industry , Dust , Environmental Monitoring , Occupational Exposure , Ships , WorkplaceABSTRACT
<p><b>OBJECTIVE</b>To investigate the role of calcium activated-potassium channels (KCa) in the injury to rat alveolar macrophages induced by quartz.</p><p><b>METHODS</b>The experiments were conducted on a rat alveolar macrophage cell line (NR8383) in vitro, where crystal silica (100 üg/ml) and amorphous silica (100 üg/ml) were used as the test substances and the cells without any treatment as negative controls. At first the effects of two kinds of quartz were compared. Then KCa special inhibitors (Paxilline for BK, Tram-34 for IK, Apamin for SK) were added in different doses to the in vitro test system with 100 üg/ml crystal quartz as matrix, to observe the function of such channels. Cell viability, lactate dehydrogenase (LDH), interleukin-1β (IL-1β) and tumor necrosis factor-a (TNF-α) were tested.</p><p><b>RESULTS</b>Comparing to the negative control group, cell viability reduced, LDH leakage, IL-1β and TNF-α release increased significantly in the amorphous quartz group, furthermore, the effects by crystal quartz were much more serious than those by amorphous quartz, with a statistical significance (P < 0.01). Comparing to the crystal quartz group, IK blockers (Tram-34) led to increase in cell viability significantly, with a statistical significance (P < 0.01); all the KCa specific blockers (Paxilline, Tram-34, Apamin) could reduce LDH leakage and IL-1β release, with a statistical significance (P < 0.05); meanwhile, BK and IK blockers (Paxilline,Tram-34) were able to reduce TNF-α release,with a statistical significance (P < 0.05).Reduction of IL-1β and TNF-α by Tram-34 was dose-dependent, but not so in the other two blockers.</p><p><b>CONCLUSION</b>Blocking calcium-activated potassium channels (KCa) could reduce cell membrane damage as well as IL-1β and TNF-α release induced by crystal quartz in the rat alveolar macrophages cell line in vitro, which might serve as a signal in the early regulation of inflammatory responses by quartz.</p>
Subject(s)
Animals , Rats , Calcium , Metabolism , Cell Line , Interleukin-1beta , Metabolism , Macrophages, Alveolar , Cell Biology , Metabolism , Potassium Channels, Calcium-Activated , Metabolism , Quartz , Toxicity , Tumor Necrosis Factor-alpha , MetabolismABSTRACT
There are actually no sufficient data for lifting technique assessment. A laboratory study was undertaken to determine the effect of 3 regular lifting techniques on erector muscle activation, cardiovascular strain and subjective response. Thirty student volunteers participated in the study, and were required to lift a weight with different techniques. Stoop-, squat-, semi-squat-lifting resulted in 3, 2 and 1 time of the highest percentage of the maximum voluntary electrical activation (MVE%) respectively. In the same order, the lowest median frequency (MF) existed 1, 1 and 2 times. Muscle fatigue was 4 times in squat, 36 in semi-squat and 43 in stoop lifting. Heart rate was the highest in squat and lowest in stoop respectively, with a middle level in semi-squat lifting. It may be recommended to adopt mainly the semi-squat technique for daily lifting works. For heavy lifting, it should use the squat technique. Stoop lifting may also be used alternatively but for light things.
ABSTRACT
There are actually no sufficient data for lifting technique assessment. A laboratory study was undertaken to determine the effect of 3 regular lifting techniques on erector muscle activation, cardiovascular strain and subjective response. Thirty student volunteers participated in the study, and were required to lift a weight with different techniques. Stoop-, squat-, semi-squat-lifting resulted in 3, 2 and 1 time of the highest percentage of the maximum voluntary electrical activation (MVE%) respectively. In the same order, the lowest median frequency (MF) existed 1, 1 and 2 times. Muscle fatigue was 4 times in squat, 36 in semi-squat and 43 in stoop lifting. Heart rate was the highest in squat and lowest in stoop respectively, with a middle level in semi-squat lifting. It may be recommended to adopt mainly the semi-squat technique for daily lifting works. For heavy lifting, it should use the squat technique. Stoop lifting may also be used alternatively but for light things.
Subject(s)
Adult , Female , Humans , Male , Young Adult , Biomechanical Phenomena , Physiology , Lifting , Muscle Fatigue , Physiology , Muscle, Skeletal , PhysiologyABSTRACT
The roles of voltage-dependent K(+) channels during activation and damage in alveolar macrophages (AMs) exposed to different silica particles were examined. Rat AMs were collected by means of bronchoalveolar lavage, and were adjusted to 5x10(5)/mL. After AMs were exposed to different concentrations (0, 25, 50, 100, 200 mug/mL) of quartz particles and 100 mug/mL amorphous silica particles for 24 h, the voltage-depended K(+) current in AMs was measured by using patch clamp technique. Meanwhile the leakage of lactate dehydrogenase (LDH) and the viability of AMs were detected respectively. Patch clamp studies demonstrated that AMs possessed outward delayed and inward rectifying K(+) current. Exposure to quartz particles increased the outward delayed K(+) current but it had no effect on inward rectifier K(+) current in AMs. Neither of the two K(+) channels in AMs was affected by amorphous silica particles. Cytotoxicity test showed that both silica particles could damage AM membrane and result in significant leakage of LDH (P<0.05). MTT studies, however, showed that only quartz particles reduced viability of AMs (P<0.05). It is concluded that quartz particles can activate the outward delayed K(+) channel in AMs, which may act as an activating signal in AMs to initiate an inflammatory response during damage and necrosis in AMs induced by exposure to quartz particle. K(+) channels do not contribute to the membrane damage of AMs.
ABSTRACT
The purpose of this study was to examine whether repetitive muscle tasks in low weight load might influence the fatigue of forearm muscles, and to identify ergonomic risk factors of forearm muscle fatigue in these tasks. Sixteen healthy male volunteers performed eight wrist extensions in different frequency, weight and angle loads while being instructed to keep a dominant upper limb posture as constant as possible. Surface electromyograph (sEMG) was recorded from right extensors digitorium (ED), flexor carpi radialis (FCR), flexor carpi ulnaris (FCU) and extensor carpi ulnaris (ECU) during the task performance. Our results showed that mean power frequency (MPF) and median frequency (MF) values of ED, FCR and FCU were significantly lower (P<0.05) at high frequency load level than at low load level. However, MPF and MF values of ED were significantly lower (P<0.01) in higher load groups of frequency, angle and weight than in lower load groups. These results indicated that the fatigue of muscles varied in the same task, and the number-one risk factor of ECU, ED and FCR was angle load.
Subject(s)
Young Adult , Cumulative Trauma Disorders/complications , Cumulative Trauma Disorders/physiopathology , Electromyography , Forearm/physiology , Muscle Fatigue/physiology , Muscle, Skeletal/physiopathologyABSTRACT
The purpose of this study was to examine whether repetitive muscle tasks in low weight load might influence the fatigue of forearm muscles, and to identify ergonomic risk factors of forearm muscle fatigue in these tasks. Sixteen healthy male volunteers performed eight wrist extensions in different frequency, weight and angle loads while being instructed to keep a dominant upper limb posture as constant as possible. Surface electromyograph (sEMG) was recorded from right extensors digitorium (ED), flexor carpi radialis (FCR), flexor carpi ulnaris (FCU) and extensor carpi ulnaris (ECU) during the task performance. Our results showed that mean power frequency (MPF) and median frequency (MF) values of ED, FCR and FCU were significantly lower (P＜0.05) at high frequency load level than at low load level. However, MPF and MF values of ED were significantly lower (P＜0.01) in higher load groups of frequency, angle and weight than in lower load groups. These results indicated that the fatigue of muscles varied in the same task, and the number-one risk factor of ECU, ED and FCR was angle load.
ABSTRACT
The purpose of this study was to evaluate the ergonomic risk factors associated with manual lifting tasks using surface electromyography (EMG). 13 volunteers lifted loads of 6 and 13 kg at two speeds and at two horizontal distances in 3 different postures and three boxes of different sizes, from floor to knuckle height, performing 72 lifting tasks. For each lift, the surface electromyography signals from the erector spinae muscles, bilaterally at T10 and L3, was recorded. The ergonomic risk factors associated with manual lifting tasks were evaluated by comparing the average amplitude of EMG signals from the erector spinae muscles. The EMG average amplitude for lifting the load of 13 kg was 14.3% greater than that for lifting the load of 6 kg (t=-10.93, P<0.01). The EMG average amplitude at the site of L3 was 10.3% greater than that at the site of T10 (t=-7.98, P<0.01). The EMG average amplitude when performing "fast" lift was 5.9% greater than the "slow" lift (t=-4.63, P<0.01). The posture of lifting affected the EMG average amplitude. It was lowest with semi-squat posture and greatest with squat posture (F=27.76, P<0.01). The result of multiple stepwise regression analysis showed that the loads of lifting, the size of box, horizontal distance, posture of lifting, the site of the spine subjected to force, lifting speed were the factors affecting the EMG average amplitude. The most significant factor was the loads of lifting, followed by the site of the spine subjected to force and the lifting speed in terms of risk. The ergonomic risk factors associated with manual lifting tasks includes the loads, posture, lifting speed, horizontal distance, the site of the spine subjected to force etc. The results of signal amplitude of EMG from the erector spinae muscles showed that semi-squat posture is the best posture for lifting tasks.
Subject(s)
Back , Electromyography , Physical Exertion/physiology , Low Back Pain/prevention & control , Muscle, Skeletal/injuries , Muscle, Skeletal/physiology , Posture , Regression Analysis , Risk Factors , Weight-BearingABSTRACT
The purpose of this study was to evaluate the ergonomic risk factors associated with manual lifting tasks using surface electromyography (EMG). 13 volunteers lifted loads of 6 and 13 kg at two speeds and at two horizontal distances in 3 different postures and three boxes of different sizes, from floor to knuckle height, performing 72 lifting tasks. For each lift, the surface electromyography signals from the erector spinae muscles, bilaterally at T10 and L3, was recorded. The ergonomic risk factors associated with manual lifting tasks were evaluated by comparing the average amplitude of EMG signals from the erector spinae muscles. The EMG average amplitude for lifting the load of 13 kg was 14.3% greater than that for lifting the load of 6 kg (t=-10.93, P<0.01). The EMG average amplitude at the site of L3 was 10.3% greater than that at the site of T10 (t=-7.98, P<0.01). The EMG average amplitude when performing "fast" lift was 5.9% greater than the "slow" lift (t=-4.63, P<0.01). The posture of lifting affected the EMG average amplitude. It was lowest with semi-squat posture and greatest with squat posture (F=27.76, P<0.01). The result of multiple stepwise regression analysis showed that the loads of lifting, the size of box, horizontal distance, posture of lifting, the site of the spine subjected to force, lifting speed were the factors affecting the EMG average amplitude. The most significant factor was the loads of lifting, followed by the site of the spine subjected to force and the lifting speed in terms of risk. The ergonomic risk factors associated with manual lifting tasks includes the loads, posture, lifting speed, horizontal distance, the site of the spine subjected to force etc. The results of signal amplitude of EMG from the erector spinae muscles showed that semi-squat posture is the best posture for lifting tasks.
Subject(s)
Adult , Humans , Male , Back , Electromyography , Low Back Pain , Muscle, Skeletal , Wounds and Injuries , Physiology , Physical Exertion , Physiology , Posture , Regression Analysis , Risk Factors , Weight-BearingABSTRACT
In this strdy, the nutrients of Oyster O. denselamellosa Lischke from Bohai Bay has been analysis. The result showed that the characteristic of oyster's nutrient in higher content of taurine (50 umol/g wet wt. , zinc, selenium; but lower in fat and cholesterol, it also cotains some EPA and DHA (20. 4% in all FA);and is rich in minerals and vitamins. This study results provide the scientific basis for exploiting and developing oyster health food.