Study On The Epidemiological Characteristic Of Pneumoconiosis Course And The Effect Of Particulates On Calcium Channel Of Dorsal Root Ganglion

Dust is a common occupational hazards derived from a lot of workplaces such as mine, metallurgy, construction, manufacture, foundry, chemical plant etc. Exposure to silica-contained dust may induce a variety of occupational pulmonary disorders, of which pneumoconiosis is well known and spreads throughout the world, especially the most serious one of occupational diseases in China. It was reported that there have been about 0.52 million cumulated cases of pneumoconiosis in our country till 1996, and approximate ten thousand of new cases come forth every year. An international program has been set up by ILO/WHO on getting rid of pneumoconiosis in the world. This plan called on all governments or regions to take effective measures to decrease incidences of pneumoconiosis obviously before 2005 and eliminate new cases before 2015. Confronted with much difficulty to perform this program, we should take strong and effective steps to attain the goal. One of important tasks is about identification, measure, evaluation, control and mechanism of occupational hazards and occupational diseases. At present, the main content included as follows: (1) To take much more important attention to the study of dust measure technique and make a standardization of dust measure method. To look for correlation on different monitoring methods so as to communicate with others, share the data in the world, prevent and control pneumoconiosis altogether. (2) To expand epidemiological research widely and to analyze characteristics about its development for perfecting health surveillance criteria. (3) To explore its early biological effect so as to find out occupational injury in time and promote workers' health. It is according to this point that the objective of our study was to compare dust sampling methods, to analyze characteristics of disease course of pneumoconiosis, and to study effects of particulates on calcium current of pulmonary target cells membrane.Part I Comparison of Chinese and US Dust Sampling Methods and ResultsObjective The purpose of this study was to estimate conversion factors between different sampling methods by comparison of Chinese and US dust monitoring methods.Methods The Chinese samplers measured short-term total dust concentration in environment; while the US samplers collected full-shift time-weighted average respirable dust levels and total dust concentration. To collect dust side-by-side from three sampling stations in each of 3 mine and factories in different instruments (including US respirable dust sampler, impinger sampler and Chinese total dust sampler); then to measure the dust concentration in a method of calculating the dust mass and to analyze them by SPSS12.0 software.Results (l)The estimation of conversion coefficient between US Respirable dust levels(Rus) and Chinese short-term total dust concentration(Tchn), Rus and US total dust concentration(Tus) were 53.64% and 39.89%, respectively; and there was obvious difference on the estimation of conversion coefficient in various units and types of work(P <0.05). (2) The total dust concentrations sampled in US sampler were always higher than that of Chinese and the ratio was 1.3:1 (1.1-2.0:1). (3) In tin mine and foundry factory, there were obvious significance about the linear regression and regression coefficient between Rus and Tchn ,Rus and Tus, or Tchn and Tus (P <0.05); the range of identification coefficient(R²) was 0.22 to 0.71 and the range of slope(β) was 0.31 to 1.13. But there were no obvious correlation except between Rus and Tus (P <0.05) in Wuhan steel and iron factory. (4)There were notable differences between tin mine and foundry factory about the conversion factors of Rus and Tchn, Rus and Tus or Tchn and Tus (P <0.05).Conclusion Obviously, it was difficult to determine a common conversion factor between total dust and respirable dust level because there were many uncontrollable factors. It should be, however, practicable and necessary to analyze the correlation and to explore conversion factors in locations.Part II Time interval of pneumoconiosis and its relation to health surveillance for the dust-exposed workersObjectives We aimed to analyze epidemiologic characteristics of silicosis in south central China and provide scientific basis for amending the health surveillance criteria of dust-exposed workers.Method Data of a retrospective cohort study was re-analyzed with emphasis on time interval of pneumoconiosis. 33640 silica dust exposed workers who were employed for at least 1 year from 1972 to 1974 in twenty Chinese mines or pottery factories were involved as subjects, and followed up to December 31, 1994. The cohort included subjects from eight tungsten mines, four tin mines and eight pottery factories.Results As the results showed that the mean latency of pneumoconiosis, for all the cases of the cohorts, was 22.9 ± 9.8 years. Among all cases of pneumoconiosis, 52.2% of pneumoconiosis was diagnosed after dust exposure ceased about 9.1 ± 5. 7 years. The progression rates of silicosis to different stages ( I → II and II →III) were 48.2% and 18.5%, and the duration from stage I to stage II was 4.1 ± 0. 2 years and from stage II to III was 6.8 ±0. 2years. The complication rate of silicosis with pulmonary tuberculosis was 51.3%. The survival times of pneumoconiosis from stage I to II and to III were 21.5, 15.8 and 6.8 years, after diagnosis, respectively. There was 25% of silicosis whose survival time was beyond 33 years. The mean death age of all pneumoconiosis cases was 56.0 years. The death age increased to 65.6 years in the middle of 1990s. Among dust-exposed workers, subject who became suspected case (0⁺) accounted to15.0%. 48.7% of suspected pneumoconiosis cases developed as pneumoconiosis, and average years from suspected to the first stage of pneumoconiosis were 5.1 years. Natural characteristics as mentioned above are different in different mines and factories.Conclusion It was concluded that pneumoconiosis is chronic in nature, but progressive quickly. As a serious occupational disease it reduces the patient's life time significantly. It's meaning to the health surveillance criteria for dust-exposed workers in the paper further discussed.Suggestions (1) An examination should be done every 4 to 5 years for the first 15 years of employment and every 3 years thereafter( without reference to whether the dust-exposed worker is still engaged in dust work or not). (2) An examination when employment ends if more than 6 months have passed since the last examination and every 3 years thereafter. (3) A re-examination at least every 2 years and every 3 to 4 years after 10 years for diagnosed pneumoconiosis. (4) Take much more importance on pulmonary tuberculosis of dust-exposed workers. (5) It is need for suspicion-silicosis to cease dust-exposed work, manage them similar to silicosis, and examine them every year. (6) Health records must be maintained for workers and they must be kept for at least 40 years after termination of employment.Part III Effects of particulates on calcium channel of dorsal root ganglion and alveolar macrophagesObjectives To analyze chemical components of particulates and its characteristic by measure organic or inorganic elements of particulates. To explore the effects of particulates on structure and function of calcium channel by virtue of the change of calcium current derived from macrophage and dorsal root ganglion so as to look for early biological effect.Methods Particulates were collected with Respirble dust sampler. Polycyclic aromatic hydrocarbon (PAH) was measured with High pressure liquid chromatogram in coke oven emission particulates. Quartz was measured with Pyrophosphoric acid quality method in coal dust. Cadmium and arsenic were determined in Graphite oven atomic absorption spectrometry. Lead, nickel, manganese, iron, zinc, calcium, magnesium and copper were determined in Flame atomic absorption spectrometry. Calcium current was recorded with Whole-cell patch clamp recording technique. Graph and data were analyzed with pCLAMP9 and SigmaPlot software.Results Calcium current recording 1 Macrophage There was no HVA calcium current recording in control and quartz groups in this study. 2 Dorsal root ganglion neuron (DRG) (1) Quartz â‘  By comparison with control, maximum calcium current of DRG HVA (I_ca) increased with particulates concentration increase, among which I_ca of 135μg/ml (-95.89±38.82 pA/pF) was obviously higher than control and low concentration group (P<0.05). (2) The mean of I_ca active speed of 135μg/ml group (9.65±5.14 pA/ pF^*ms) and Rise slope from30%-70% (14.08±8.69 pA/ pF^*ms) were higher than control, significantly (F<0.05). (3) The peak time of I_ca in test groups seemed smaller than control, but no significant (P>0.05). â‘£ The mean of I_ca inactive speed (0.43±0.10 pA/ pF^*ms) and maximum inactive slope (0.83±0.49 pA/ pF^*ms) were obviously faster than the control and other test groups (P<0.05). (5) The decrease rate of 135μg/ml group was 63.20±8.23% and its change trend was similar to maximum inactive slope. â‘¥ There were significant differences about conductance between different dose groups (F=9.979, P=0.000), among which the value of 45μg/ml and 135μg/ml groups were significantly bigger than the control and other test groups (P<0.05 or 0.01, 1420.04±655.64 and 2257.44±454.20 pS/μm², respectively) and the value of 135μg/ml was also significantly bigger than 45μg/ml groups (P<0.05). ⑦ There was no obvious variety about the shape of I-V curve and the voltage position of I_ca was in zero, but the calcium current of 45and 135μg/ml group increased in every clamped potential. (8) The change of time-dependent of I_ca was no significance. (9) The value of V_1/2 removed to right of abscissa about 6.0 to 6.5 mV and the differences was significant by comparison with the control, but there had no obvious change about the value of k (P>0.05). (2) Coke oven emission particulates â‘  When DRG was exposed to coke oven emission particulates, the value of I_ca seemed increasing, but there had no significant difference (P>0.05). â‘¡ The mean of I_ca active speed, maximum rise slope, I_max1/2 active speed, and Rise slope from30%-70% of 5μg/ml group were obviously higher than the control (P<0.05), and the values were 5.77±2.56, 16.98±11, 14.20±8.07, 11.90±4.38 pA/ pF^*ms, respectively. â‘¢ The peak time of 5 μg/ml group was significantly shorter than the control (P<0.05), only 11.29±5.71ms. â‘£ The active time constant of 45μg/ml group was smaller than the control, distinctly (P<0.05). (5) The conductance of 135μg/ml group was 1794.39±902.84 pS/μm², obviously bigger than the control (P<0.05). â‘¥ I_ca of test groups was bigger than the control in test pulse of negative 30 mV. (7) About the change of time-dependant, I_ca was large in beginning recording and declined slowly during whole recording duration. ⑧ V_1/2 removed significantly to right of abscissa about 4 mV (P<0.05). (3) Steel plant particulates â‘  The maximum rise slope of 135 μg/ml was 14.29±6.66 pA/ pF^*ms, obviously higher than the control and other test dose groups (P<0.05). (2) The value of conductance of 45μg/ml group was bigger than the control (P<0.01,1542.12±719.79 pS/μm²). (3) The values of I_ca of test groups were all bigger than control in test pulse of negative 30 mV, and showed stability. â‘£ There had no obvious run-down tendency about I_ca whole duration and had no distinct dose-response relation. (5) The value of V_1/2 removed to right evidently about 4.5 mV (P<0.05), except for 135 μg/ml group. (4) East-lake air particulates â‘  Compared with control, the index (mean active speed, maximum rise slope, mean active speed of I_max1/2, and rise slope from 30%-70%) were a certain degree of decrease, but had no notable change (P>0.05). (2) The peak time of 135 μg/ml group was distinctly longer than control and 5μg/ml group (P<0.05, 19.84±5.36 ms). â‘¢ There had no obvious difference about the change of conductance after exposure to East-lake air particulates (P>0.05). â‘£ The value of V_1/2 removed to right evidently about 4.6 to 5.6 mV (P<0.05). (5) Urban air particulates â‘  In spite of no significant difference (P>0.05), the value of I_ca, mean active speed, and rise slope from30%-70% showed run-up tendency. â‘¡ The membrane conductance of 5,wg/ml group was significantly bigger than the control and other test groups (P<0.05). (3) It was noticed that the values of mean decay speed and maximum decay slope were faster than the control (P<0.05). (6) Comparison in different particulates â‘  5 μg/ml group: The values of I_ca, the mean active and inactive speed, exposed to coke oven emission particulates and urban air particulates, were notablely bigger than that of East-lake particulates (P<0.05). The maximum rise slope, exposed to quartz and coke oven emission particulates, was higher than that of others, obviously (P<0.05). The membrane conductance, exposed to urban air particulates, was significantly bigger than that of quartz and East-lake particulates (P<0.05). â‘¡ 15 μg/ml group: There had no distinct change about biological effect after exposure to different particulates; â‘¢ 45μg/m group: The peak time of I_ca became longer than others after exposure to East-lake air particulates (P<0.05), and its decrease rate was slower than that of coke oven emission particulates and urban air particulates (P<0.05). â‘£135 μg/ml group: After exposure to quartz, the changes of I_ca, mean active or inactive speed, maximum decay slope, and conductance were all significantly bigger than that of steel, East-lake and urban air particulates (P<0.05 or 0.01). The maximum rise slope of I_ca, after exposure to quartz and steel plant particulates, ran up faster than that of East-lake particulates (P<0.05). (5) The results of curve fit showed that the value of V_1/2 removed to right significantly about 4.1 to 6.5 mV (p<0.05) after exposure to five types of dust particulates. There was no obvious relation between the change and dose, and was not dependent on particle types, distinctly. Component measure 1 The PAH ingredients mainly included Naphthalin, Phenanthren, Acenaphthylen, and Benzo[a]pyren, etc and the value above oven roof is the highest. The results were 70.0, 5.9,5.2, 1.3 μg/m³,respectively. 2 Results of the heavy metals (lead, manganese, nickel and cadmium) in coal dust were 30.52±15.32, 81.32±63.73, 13.76±7.50, 0.023±0.021μg/g, respectively.Conclusion The feature was different of high-voltage activated calcium channel change of dorsal root ganglion after exposure to different particulates. DRG HVA calcium channel was easy to be activated by quartz in a certain concentration. The active speed of calcium channel became rapid under test voltage, and the calcium current increased distinctly. It was found that the calcium current also ran down fast. So, calcium channels showed an interesting characteristic of increasing current, rapid activation, and quick run-down. Compared with particulates, the dose range of quartz which influenced the calcium channel effectively was relatively wide. The calcium channel was affected by low concentration of coke oven emission particulates, with fast active speed, increasing maximum rise slope, and short peak time. High concentration of steel plant particulates maybe has influence on calcium channel, with an increasing maximum rise slope. Particulates from urban had any influence on inactive phase, with a fast run-down speed and decreasing maximum decay slope. The peak time of calcium current was significantly longer after exposure to East-lake air particulates. There was a tendency that the active speed became slow and the maximum rise slope rose slowly. In a certain degree, the DRG HVA calcium channel was restrained by East-lake air particulates. It was noticed that a change of cells biological effect is an integrated result of all particulates components. It is helpful to study the effect of different particulates on calcium channel of target cells for further exploration of mechanism about occupational hazards (for instance, inflammation, lung fibrosis, even tumor, etc.). There had no significant effect of quartz on HVA calcium channel of alveolar macrophage.