Total electric field intensity in workplace of high-voltage direct current converter stations / 环境与职业医学

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.

Current status of occupational exposure to power frequency electromagnetic field in converter stations / 中国职业医学

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.

An experimental study on the cograft of auto-microskin and allo-dermal matrix / 中华烧伤杂志

<p><b>OBJECTIVE</b>To explore the promoting effects of cograft of auto-microskin and allo-dermal matrix on burn wound healing.</p><p><b>METHODS</b>Forty-six patches of full skin loss wounds were made in the backs of 6 small white swines. Auto-microskin and meshed acellular allo-dermal matrix were simultaneously prepared. The 46 wounds were averagely divided into test (T) and control (C) groups. The wounds in T group were covered with auto-microskin and allo-dermal matrix (1:4) and split-thick allo-porcine skin. While the wounds in C group were grafted with autoskin and allo-dermal matrix.</p><p><b>RESULTS</b>The skin survival rate exhibited no difference between C and T groups (P > 0.05). There was similar histological exhibition in the two groups after skin grafting. The structure of collagen fibres appeared integrated, clear with regular arrangement and steady diameter at 8 - 20 post-operative weeks. Simultaneously, it was revealed by histological examination that normal vascular structure could be identified in the grafted skin and that inflammatory reaction ameliorated gradually and that epithelium combined well with dermis. It was also found that the epidermal papillar across the basement membrane fixed well to allo-dermis. The skin appeared smooth, elastic and functioned well at 5 months after skin grafting.</p><p><b>CONCLUSION</b>The grafted skin survived well after the cograft of auto-microskin and allo-dermal matrix, which might be ideal covering material for the major deep burn wound healing.</p>

INFLUENCE OF VITAMIN E ON THE BLASTOGENIC RESPONSE OF SPLENOCYTES AND LIPID PEROXIDES IN LIVERS OF AGED MICE / 营养学报

Semi-purified diets containing 30 ppm or 500 ppm dl-?-tocopherol (VE) were fed for 8 weeks to young (3 months) and old (18 months) Swiss mice. The blastogenic response of splenocytes as well as serum VE and lipid peroxides (LPO) in livers were measued. The results showed that the old mice fed 500 ppm VE had a significantly higher serum VE level and blastogenic response of splenocytes to Con A and LPS than those fed 30 ppm VE (p