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Background The converter stations of high-voltage direct current (HVDC) transmission lines generate special total electric fields. At present, few investigations have been conducted on total electric fields in the workplace of converter stations from an perspective of occupational health. Objective To understand the current situation of total electric field strength in the workplace of converter stations. Methods Using purposive sampling, a calibrated HDEM-1 direct current (DC) total electric field strength measurement system was used to measure the total electric fields of 12 converter stations serving 6 DC lines in Southeast and Southwest China according to the Measurement method for total electric field strength and ion current density of the converter stations and DC transmission lines (DL/T 1089—2008). The results were evaluated according to occupational exposure limits recommended by The limits of electromagnetic environment at ±800 kV UHV DC converter station (DL/T 275—2012), the American Conference of Governmental Industrial Hygienists (ACGIH), and the International Commission on Non-Ionizing Radiation Protection (ICNIRP). Results A total of 615 check points were planned, the total electric field strength was 0.05-37.05 kV·m−1, and the median was 10.45 kV·m−1. The total electric field strength of 39 check points (6.3%) exceeded 25 kV·m−1 (the limits of ACGIH and ICNIRP), and the total electric field strength of 12 check points (2.0%) exceeded 30 kV·m−1 (the limit of DL/T 275—2012). There were statistically significant differences in the total electric field strength values and the proportions of exceeding 25 kV·m−1 between the neutral regions and the positive regions and between the neutral regions and the negative regions (P < 0.01). The proportion of total electric field strength exceeding 30 kV·m−1 in the negative regions was higher than that in the positive regions (P < 0.01). There were no significant differences in the total electric field strength of converter stations at different voltage levels and different altitudes (P > 0.05). There were no significant differences in the proportions of total electric field exceeding 25 kV·m−1 and exceeding 30 kV·m−1 in converter stations at different voltage levels and different altitudes (P > 0.05). Conclusion The total electric field in some workplace of converter stations exceeds selected limits. Converter station operators may be exposed to high-strength total electric field for a short time.
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Objective: To analyze the status of noise hazard in workplace of key industries in Guangdong Province. Methods: A total of 1 061 enterprises from 14 key industries in 21 prefecture-level cities in Guangdong Province were selected as the research subjects using stratified sampling method. The occupational health survey was carried out, and the noise intensity in the workplace was detected. Results: There were 12 606 workplaces and 5 570 work sites involved among 1 061 enterprises. The median and the 0-100th percentile value ［M (P0-P100)］ of noise intensity in workplace were 82.6 (46.5-112.6) dB(A), and 35.03% of the workplace exceeded the national noise intensity standard. The regions and industry with the highest rate of noise exceeded the national noise intensity standard in workplace were in the northern part of Guangdong and the stone processing industry respectively. The M (P0-P100) of noise intensity in the work sites was 83.7 (47.5-106.2) dB(A), and 36.00% of the work sites exceeded the national noise intensity standard. The regions and industry with the highest rate of noise exceeded the national noise intensity standard in work sites were in the Pearl River Delta region and the ferrous metal mining and dressing industry respectively. The rate of noise protection facilities setting was 66.45%, and the validity of personal protection was 61.73%. The occupational medical examination was performed in 73.24% of the research subjects, and 3.25% of the result was abnormal. The industry with the highest occupational medical examination rate was nonferrous metal smelting and rolling processing, and the industry with the highest abnormal rate of occupational medical examination was stone processing industry. Conclusion: Noise hazards in workplaces of key industries in Guangdong Province are relatively severe, necessitating strengthened supervision and management, noise control measures, and efforts to reduce noise exposure levels in workplaces and work sites.
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Background Wearing anti-vibration gloves is a simple and effective way to prevent hand-arm vibration disease. The requirements for vibration damping gloves are varied by types of operations exposed to vibration. Objective To study the vibration attenuation and dexterity of different types of protective gloves, and to provide reference for scientific wearing of vibration damping gloves for people working with vibration exposure. Methods Nine kinds of common protective gloves (A and B were dipping gloves; C, D, and E were rubber gloves; F and G were textile and fabric gloves; H was cotton gloves; I was leather gloves) used by workers exposed to vibration in 28 factories in Guangdong Province were selected as research objects by typical case sampling method, and the basic parameters of included protective gloves were investigated and measured. According to ISO 10819:2013, a glove vibration transmissibility (GVT) test system was used to detect the vibration transmissibility values and analyze vibration attenuation characteristics of the subjects wearing different protective gloves. The dexterity was tested by Minnesota Manual Dexterity Test. Pearson test was used to analyze the correlations among glove thickness, vibration transmissibility, dexterity score, and grip strength score. Results For rubber gloves (C, D, and E), the associated average adjusted vibration transmissibility at middle and low frequencies \begin{document}$ {\overline T _{\text{M}}} $\end{document} and average adjusted vibration transmissibility at high frequency \begin{document}$ {\overline T _{\text{H}}} $\end{document} were lower than those of other gloves (0.89-0.91 and 0.59-0.80 respectively), the vibration transmissibility values of 50-200 Hz frequency band was 0.81-0.97, and the vibration transmissibility values of 315-1250 Hz frequency band decreased with the increase of frequency (the minimum value was 0.13). For other types of gloves (A, B, F, G, H, and I), the \begin{document}$ {\overline T _{\text{M}}} $\end{document} and \begin{document}$ {\overline T _{\text{H}}} $\end{document} were 0.95-0.98 and 1.03-1.11 respectively, the vibration transmissibility values of 50-200 Hz frequency band was 0.96-1.02, and the vibration transmissibility values of 400-1250 Hz frequency band increased (the maximum value was 1.29). The \begin{document}$ {\overline T _{\text{M}}} $\end{document}, \begin{document}$ {\overline T _{\text{H}}} $\end{document}, and vibration transmissibility values of 40-1250 Hz frequency band of rubber gloves with double-layer protective materials (C, D, and E) were significantly lower than those of gloves with single-layer protective materials. But the \begin{document}$ {\overline T _{\text{M}}} $\end{document} and \begin{document}$ {\overline T _{\text{H}}} $\end{document} of gloves of other types with double-layer materials (F, H, and I) were still greater than 0.9 and 1.0 respectively. Compared with single-layer protective materials, the gloves of other types with double-layer materials showed no significant changes in the vibration transmissibility values of 25-200 frequency band (0.91-1.06), and an increase in the vibration transmissibility values of 250-630 Hz frequency band (the maximum value was 1.22). The dexterity scores and grip strength scores of dipping gloves (A and B) were the lowest. Rubber gloves C had the highest dexterity score and grip strength score. The thickness of protective gloves was negatively correlated with the vibration transmissibility values, and positively correlated with the dexterity score and the grip strength score (P < 0.05). The vibration transmissibility value was negatively correlated with the dexterity score and the grip strength score (P < 0.05). Conclusion Among the 9 kinds of gloves, cotton gloves and leather gloves have no damping effect. Rubber gloves have certain vibration reduction effect, and the vibration reduction effect on high frequency band is better than that on low frequency band. The thicker the damping material is, the better the damping effect is, but the less the dexterity is. Appropriate damping gloves should be selected according to actual vibration operations.
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OBJECTIVE: To analyze the current status of occupational exposure to power frequency electromagnetic field in converter stations. METHODS: Eight converter stations with voltage levels of ±500 kV and ±800 kV within normal operation were selected as the research subjects using the typical sampling method. Power frequency electric field and power frequency magnetic field strengths were measured and calculated according to the GBZ/T 189.3-2018 Measurement of Physical Agents in Workplace--Part 3: Electric Field and Magnetic Field between 1 Hz and 100 kHz. The GBZ 2.2-2007 Occupational Exposure Limits for Hazardous Factors in the Workplace--Part 2: Physical Factors were used to evaluate whether the power frequency electric field strength exceeds the regulatory limit(the occupational exposure limit of power frequency electric field in 8 hours workplace is 5.000 kV/m). Meanwhile, the test results were evaluated according to the short-term occupational exposure limit of 50 Hz electric field and magnetic field recommended by the International Committee on Nonionizing Radiation Protection in 2010 that are 10.000 kV/m and 1 000.00 μT. RESULTS: The power frequency electric field and magnetic field strengths of 582 working environment detection points were measured. The median and 0-100 th percentile of power frequency electric field and power frequency magnetic field strength were 4.342(0.001-12.003) kV/m and 5.51(0.10-186.90) μT, respectively.The exceeding standard rate of power frequency electric field strength in converter station workplaces was 37.8%(220/582), which concentrated in 500 kV alternating current filter area and 500 kV alternating current field area. Among them, 5 detection points had power frequency electric field strength exceeding 10.000 kV/m. The magnetic flux density of all the detection points did not exceed 1 000.00 μT. The power frequency electric field strength in ultra-high voltage region was higher than that in high voltage region(P<0.01). There was no significant difference in power frequency magnetic field strength(P>0.05). There was no significant difference in power frequency electric field and magnetic field between rectifier stations and inverter stations(P>0.05). The 8 hours time weighted average(TWA) value of power frequency electric field strength of 8 converter station operators was 1.044-2.335 kV/m, which did not exceed the occupational exposure limit. CONCLUSION: The converter station operators might be exposed to excessive power frequency electric fields for a short time, but the 8 hours TWA value of the power frequency electric field meets the requirements of standards, and the power frequency magnetic field exposure strength also meets the requirements of the relevant standards.
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OBJECTIVE: To analyze the characteristics of noise hazard in a nuclear power station. METHODS: The workplaces and working posts which exposed to occupational noise from two 1 000 MW power units in one nuclear power station in Guangdong Province was selected as study subjects using the convenience sampling method. Occupational health survey, noise measurement in the workplace and personal noise dosage measurement were used to monitor noise exposure, and to analyze the characteristics of occupational noise in the nuclear power station. RESULTS: The noise sources of the nuclear power plant were mainly distributed in the nuclear island, conventional island, and peripheral workshops. A total of 237 points of noise intensity were measured in the workplace. The intensity of noise ranged from 66.0 to 99.6 dB(A). The noise intensity in 62.4%(148/237) of points was equal or greater than 80.0 dB(A) and 34.2%(81/237) equal or greater than 85.0 dB(A). The percentage of detection points with noise intensity was equal or greater than 85.0 dB(A) from low to high were nuclear island, conventional island, and peripheral workshops with 22.0%, 37.5% and 53.8% respectively(P<0.01). The personal noise intensity of three positions including inspectors of operation department, preparation and main engine positions of mechanical department exceeded the occupational exposure limit(OEL), and the percentage of positions whose noise intensity exceeded the OEL was 9.7%(3/31). CONCLUSION: High-intensity noise sources of the nuclear power plant are widely distributed in the workshop areas of nuclear island, conventional island, and peripheral workshops. The noise level of some positions exceeded the standards of noise intensity. The prevention and control measures of noise hazards in posts with excessive noise should be strengthened.
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OBJECTIVE: To analyze the influence of noise measuring skills by continuous inter-laboratory comparison among occupational hygiene technical service organizations. METHODS: The results of 68, 55 and 50 occupational hygiene technical service organizations(reference organizations) participating in the inter-laboratory comparison of workplace noise measurement in 2014, 2017 and 2018 respectively were collected. The measurement operation and the calculation of equivalent sound level were evaluated according to the GBZ/T 189.8-2007 Measurement of Physical Agents in Workplace--Part 8: Noise.The measured results were analyzed by z score evaluation method. RESULTS: The results of noise measurement field operation of the reference organizations in the year 2014, 2017 and 2018 show that the accuracy rates of instrument setting was 89.7%, 98.2% and 100.0%, the accuracy rates of measuring position were 52.9%, 81.8% and 94.0%, the accuracy rates of sound level meter holding were 54.4%, 80.0% and 92.0%, the accuracy rates of microphone pointing were 98.5%, 98.2% and 94.0%, and the accuracy rates of noise type recognition were 83.8%, 92.7% and 84.0%, respectively. Among them, the accuracy of instrument setting, measurement position and sound level meter holding showed an increasing trend year by year(P<0.01). The pass rates of measurement results were 91.2%, 94.5% and 88.0% in 2014, 2017 and 2018 respectively. The pass rates of equivalent sound level calculation were 73.5%, 92.7% and 88.0%. The pass rates of comprehensive evaluation were 70.6%, 89.1% and 80.0% respectively. Among them, the pass rates of equivalent sound level calculation and comprehensive evaluation in 2017 were higher than that in 2014(P<0.017). There was no significant difference in the three-year comprehensive assessment total pass rate between private organizations and non-private organizations(84.0 % vs 75.5%, P>0.05). There was no significant difference in the total pass rate of three-year comprehensive evaluation between non-Pearl-River-Delta organizations and Pearl-River-Delta organizations(70.3% vs 81.6%, P>0.05). CONCLUSION: Continuous inter-laboratory comparison in occupational hygiene technical service organizations is beneficial to improve on-site noise measure capability.
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OBJECTIVE: To evaluate the interlaboratory comparison results of noise measuring instruments in the occupational hygiene technical service institutions. METHODS: The basic performance data, multi-frequency acoustic calibration measurement results and simulated workplace noise at fixed points of 60 noise measuring instruments were collected. The instruments were from 60 occupational health technical service institutions who participate in the inter-laboratory comparison study in noise measuring instruments. The results of the measurements were analyzed using quartile robust statistical technology and z score evaluation method.RESULTS: All 60 participating comparison noise measuring instruments were examined or calibrated, and 58 instruments(96.7%) were used within the term of validity of examination or calibration. The 58 instruments were tested by multi-frequency noise calibration measurement. The comparative passing rate of the instrument accuracy was 94.8%(55/58); and the linearity test passing rate was 87.9%(51/58). There were 59 instruments participated in the simulated workplace noise at fixed points. The z-score pass rate of the two comparison measurement points was 89.8%(53/58). A total of 57 enterprises participated all the instrument performance comparison tests, with a pass rate of 94.7%(54/57). CONCLUSION: Performance of noise measuring instruments from the occupational hygiene technical service institutions is generally good. However, there are a small number of instruments have poor accuracy and linearity, and there are measurement bias that require improvement.
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OBJECTIVE: To explore the effect of ultra-high frequency radiation on psychomotor neurological behavior in workers with exposure. METHODS: A total of 85 workers who exposed to 40.68 MHz radiofrequency were recruited as the exposure group by judgment sampling method. A group of 121 workers without occupational EMR exposure were recruited as the control group. Workers in both groups were from the same shoe factory. The electric field intensity(EFI) of ultra-high frequency radiation of workplace in the exposure group was measured. The computerized neurobehavioral evaluation system in Chinese version 3 was used to evaluate the psychomotor neurobehavioral function which included the neurobehavioral ability index(NAI) of simple visual reaction time(SVRT), digital screening and fit curve and the general NAI(GNAI) of the above 3 indexes. RESULTS: The median of the workplace EFI of ultra-high frequency radiation in the exposure group was 119.0 V/m, and all of them exceeded the national occupational exposure limit. NAI of digital screening in exposure group was lower than that in the control group(P<0.05). There is no statistically significant difference in the NAI of SVRT, fit curve and GNAI(P>0.05). Meanwhile, there is no statistically significant difference in abnormal rate of NAI of SVRT, digital screening, fit curve and GNAI(P>0.05). The results of multiple linear regression analysis showed that the ultra-high frequency radiation EFI exposure was negatively correlated with NAI of digital screening(P<0.05) after eliminating the influence of confounding factors such as age, working age, gender, education level, smoking, drinking and staying up late. CONCLUSION: The digital screening of psychomotor neurobehavioral function in the exposure workers was adversely affected by the ultra-high frequency radiation. The neural behavioral ability of eye-hand coordination and precise movement may be the specific performance.
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OBJECTIVE: To evaluate the exposure status of hand-transmitted vibration(HTV)in golf ball head grinding workers.METHODS: The golf ball head grinding positions in a sports equipment factory were selected as the research subjects by the judgement sampling method.The HTV exposure level of the workers in 66 grinding positions was measured,the key control points for HTV hazards were identified,and the damage of HTV was classified.RESULTS: The median(M)of 4 hours energy equivalent frequency-weighted acceleration to vibration[a_(hw(4))]of grinding positions in this sports equipment factory was 4.21 m/s~2,and the a_(hw(4)) over standard rate was 50.0%(33/66).The a_(hw(4)) of rough grinding positions was higher than that of fine grinding positions(M:5.50 v.s 3.94 m/s~2,P<0.05).In both rough grinding positions and fine grinding positions,the a_(hw(4)) of different ball head grinding types from high to low were hollow titanium alloy ball heads, hollow stainless steel ball heads,and solid stainless steel ball heads(rough grinding positions M:7.41 vs4.43 vs 3.11 m/s~2,P<0.01; fine grinding p ositions M:5.24 vs 4.21 vs 2.93 m/s~2,P<0.01).For the hollow titanium alloy ball head grinding positions,the a_(hw(4)) of rough grinding was higher than that of fine grinding(M:7.47 vs 5.24 m/s~2,P<0.01).Rough grinding positions,especially hollow stainless steel ball heads and hollow titanium alloy ball head grinding positions were key control points for HTV hazards.In the 66 grinding positions,the HTV hazards were classified as grade 0,Ⅰ,Ⅱ,and Ⅲ in the grinding positions accounted for 3.0%,47.0%,40.9%,and 9.1%,respectively,and those with grade Ⅱ and above were 50.0%(33/66). CONCLUSION: The exposure level of HTV in golf ball head grinding workers is high,with a trend of exceeding the standard.The golf ball head grinding workers have a high occupational health risk.
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Objective To investigate and analyze the clinical effect of laryngeal mask airway inhalation anesthe-sia with sevoflurane on pediatric colic surgery.Methods From July 2014 to November 2016,92 cases with pediatric hernia in Jiaxing Hospital of Zhejiang Corps of Armed Police Force were randomly divided into study group and control group according to the digital table ,with 46 patients in each group.All patients were selected according to the specific circumstances given hernia surgery ,sevoflurane inhalation anesthesia with laryngeal mask airway in the study group in the operation,the control group was given tracheal intubation anesthesia.The changes of vital signs ,the anesthesia effect and treatment satisfaction etc.were observed and analyzed.Results All the patients were treated by surgery , the heart rate (HR) and mean arterial pressure(MAP) changes in the study group were significantly better than those in the control group(all P＜0.05).The eye opening time and awake time in the study group were (7.28 ±1.07)min, (12.96 ±1.38 ) min, respectively, which were significantly better than those in the control group [ ( 13.02 ± 1.75)min,(21.13 ±2.82)min] (t＝18.979,P＝0.001;t＝17.649,P＝0.001).The total satisfaction rate of the study group was 97.83%,which was significantly higher than 82.61%of the control group (χ2＝13.126＝0.002). Conclusion The application of laryngeal surgery in children with hernia in mask ventilation of sevoflurane anesthe -sia,has good anesthetic effect ,it has less influence on hemodynamics in children ,and rapid postoperative recovery.
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OBJECTIVE: To evaluate the feasibility of the inter-laboratory comparison of microwave radiation measuring instruments which uses cellphone signal shielding device as standard source,and to establish inter-laboratory comparison method of microwave radiation.METHODS: The typical sampling method has been used by selecting twenty-one measuring instruments of microwave radiation from 21 occupational hygiene technical service organizations as study subjects.A cellphone signal shielding device was applied as standard source.Measurement points were measured by surveyors at a distance of 1.0 and 1.5 meter to the standard source,and the measurement results were analyzed by four robust technology and z-score evaluation method.RESULTS: Stability test showed that there was no statistical difference among the power density of standard source which were measurement at three diffluent time [(26.10 ± 0.94) vs(25.78 ± 0.27) vs(25.83 ±0.47) μW/cm~2,P>0.05].The standard source stability can also satisfy the requirement of inter-laboratory comparison.Among the 21 selected equipments,one of the 21 measuring instruments was not calibrated,one calibration certificate of the instruments was expired,and one calibration result of the instruments was unqualified.The z score of inter-laboratory(z_B) of 21 measuring instruments ranged from-1.27 to 4.85,while z score of within-laboratory(z_w) ranged from-1.42 to 2.18.One | z_B| of the instruments was above 3.00,while | z_W| was above 2.00.Comprehensive evaluation of the above results showed that only one instrument was unqualified.CONCLUSION: It is feasible that a cellphone signal shielding device could be applied as standard source.The method developed in this study can be used to understand the performance of microwave radiation instruments.
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Objective To analyze and discuss the effect of heat preservation on the recovery time of BIS and the concentration of propofol in the recovery period of the elderly patients with general anesthesia in order to provide guidance for clinical treatment.Methods78 elderly patients with general anesthesia were selected as the subjects, and the patients were divided into the control group and the study group with 39 cases in each group.The patients were divided into the control group and the study group.Control group, only to be liquid input and covered by drapes, research group take liquid input and peritoneal flushing fluid heating and heating blanket coverage of insulation measures, were recorded and compared between the two groups from anesthesia began to operation to complete the different time points of esophageal temperature and MAP, and to observe the recovery time of patients and effect compartment concentration differences.ResultsTwo groups at T0, T1 esophageal temperature no significant difference, study group t2-t6 esophageal temperatures were significantly higher than those of the control group (P<0.05), maps of the other two groups at different time points had no significant difference;when two groups of patients with propofol withdrawal BIS values had no significant difference (P<0.05), and in the time of discontinuation BIS is more than or equal to 80 recovery time and effect compartment concentration have significant difference (P<0.05).ConclusionThe surgical treatment of elderly patients with general anesthesia can help maintain the body temperature, shorten the recovery time of BIS and reduce the concentration of propofol in the recovery period.
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Acute pulmonary embolism after surgery of multiple maxillofacial fractures is rare. This paper reported a case of multiple maxillofacial fractures who experienced acute pulmonary embolism after operation and died.