Exposure to silica and silicosis among tin miners in China: exposure-response analyses and risk assessment

OBJECTIVES—To investigate the risk of silicosis among tin miners and to investigate the relation between silicosis and cumulative exposure to dust (Chinese total dust and respirable crystalline silica dust).
METHODS—A cohort study of 3010 miners exposed to silica dust and employed for at least 1 year during 1960-5 in any of four Chinese tin mines was conducted. Historical total dust data from China were used to create a job exposure matrix for facility, job title, and calendar year. The total dust exposure data from China were converted to estimates of exposure to respirable crystalline silica for comparison with findings from other epidemiological studies of silicosis. Each worker''s work history was abstracted from the complete employment records in mine files. Diagnoses of silicosis were based on 1986 Chinese pneumoconiosis Roentgen diagnostic criteria, which classified silicosis as stages I-III—similar to an International Labour Organisation (ILO) classification of 1/1 or greater.
RESULTS—There were 1015 (33.7%) miners identified with silicosis, who had a mean age of 48.3 years, with a mean of 21.3 years after first exposure (equivalent to 11.0 net years in a dusty job). Among those who had silicosis, 684 miners (67.4%) developed silicosis after exposure ended (a mean of 3.7 years after). The risk of silicosis was strongly related to cumulative exposure to silica dust and was well fitted by the Weibull distribution, with the risk of silicosis less than 0.1% when the Chinese measure of cumulative exposure to total dust (CTD) was under 10 mg/m³-years (or 0.36 mg/m³-years of respirable crystalline silica), increasing to 68.7% when CTD exposure was 150 mg/m³-years (or 5.4 mg/m³-years of respirable crystalline silica). Latency period was not correlated to the risk of silicosis or cumulative dose of exposure. This study predicts about a 36% cumulative risk of silicosis for a 45 year lifetime exposure to these tin mine dusts at the CTD exposure standard of 2 mg/m³, and a 55% risk at 45 years exposure to the current United States Occupational Safety and Health Administration and Mine Safety and Health Administration standards of 0.1 mg/m³ 100% respirable crystalline silica dust.
CONCLUSIONS—A clear exposure-response relation was detected for silicosis in Chinese tin miners. The study results were similar to most, but not all, findings from other large scale exposure-response studies.


     

Mortality among unionized construction plasterers and cement masons

BACKGROUND: Plasterers perform a variety of duties including interior and exterior plastering of drywall, cement, stucco, and stone imitation; the preparation, installation, and repair of all interior and exterior insulation systems; and the fireproofing of steel beams and columns. Some of the current potential toxic exposures among plasterers include plaster of Paris, silica, fiberglass, talc, and 1,1,1-trichloroethylene; asbestos had been used by the plasterers in the past. Cement masons, on the other hand, are involved in concrete construction of buildings, bridges, curbs and gutters, sidewalks, highways, streets and roads, floors and pavements and the finishing of same, when necessary, by sandblasting or any other method. Exposures include cement dust, silica, asphalt, and various solvents. METHODS: Proportionate mortality ratios (PMRs) and proportionate cancer mortality ratios (PCMRs) were calculated for 99 causes of death among 12,873 members of the Operative Plasterers' and Cement Masons' International Association who died between 1972 and 1996 using United States age-, race-, and calender-specific death rates. Statistical significance (P value) of results was based upon the Poisson distribution. RESULTS: Among plasterers, statistically significant elevated mortality was observed for asbestosis, where the PMR reached 1,657 (P < 0.01) with eleven observed deaths and less than one death expected, for lung cancer (PCMR = 124, P < 0.01), and for benign neoplasms (PMR = 210, P < 0.05). Among cement masons, statistically significant elevated mortality was observed for cancer of the stomach (PCMR = 133, P < 0.01), benign neoplasms (PMR = 132, P < 0.01), and poisonings (PMR = 159, P < 0.05). Except for poisonings, which were not thought to be occupationally related, all of the statistically significant results occurred among those members who entered the union prior to 1950. However, the risk for lung cancer among plasterers was still elevated among those entering the union after 1970 as was the risk for stomach cancer among cement masons who entered the union after 1950. CONCLUSIONS: The present study suggests that plasterers and cement masons still have elevated risks for certain diseases, especially lung and stomach cancer. Therefore, union members currently living should be screened for asbestos-related diseases and educated about the future risks for these diseases.     

手掌参醇提取物处理染矽尘大鼠肺纤维化及肿瘤坏死因子-α表达的变化

目的研究手掌参醇提起物对染矽尘大鼠肺纤维化及组织肿瘤坏死因子-α(TNF-α)表达的影响。方法将120只Wistar大鼠随机分为对照组、染矽尘组和手掌参醇提取物与SiO2联合处理组(联合处理组)。采用气管暴露法给予染矽尘组和联合处理组大鼠气管内灌注矽尘,对照组大鼠气管内则给予灌注等量生理盐水。联合处理组自染尘后第1天起每日灌胃手掌参醇提取物2ml(10g/kg),对照组和染矽尘组则给予等量生理盐水每日灌胃直至大鼠处死。天狼猩红染色法结合偏振光显微镜观察肺组织Ⅰ、Ⅲ型胶原合成。制作大鼠肺组织芯片,用免疫组织化学PV法检测组织芯片TNF-α的表达。结果与染矽尘组比较,联合处理组的大鼠各时间点的肺系数明显降低(P<0.01)。与染矽尘组比较,联合处理组各时间点Ⅰ胶原低于染矽尘组(P<0.01);与染矽尘组比较,联合处理组各时间点Ⅲ胶原均低于染矽尘组,14天和21天差异有显著性(P<0.05,P<0.01)。与染矽尘组比较,联合处理组各时间点肺组织TNF-α的积分光密度低于染矽尘组(P<0.01)。结论手掌参醇提取物可抑制矽尘诱导的大鼠肺纤维化和大鼠肺组织TNF-α蛋白的表达。     

静脉与硅胶管小间隙桥接神经的实验研究

目的 探讨一种新的神经缝合方法,并比较静脉与硅胶管两种桥接物的优劣。方法 应用静脉,硅胶管作为再生室,对大白鼠股神经断裂进行小间隙桥接的实验对比,５周后做显微解剖和组织病理学观测。结果 小间隙桥接有利于神经的选择性再生,而静脉更明显优于硅胶管组。     

Synthesis of sol-gel mesoporous silica materials providing a slow release of doxorubicin

Samples of mesoporous base-catalysed silica xerogel materials made by the sol-gel process were impregnated with an anticancer drug—doxorubicin, followed by different times of ageing at room temperature. The effect of ageing time on the physical and structural properties as well as sorption–desorption of the drug was investigated. The obtained results suggest an inverse relationship with a solid density and surface area increasing as the pore size and volume decrease during ageing time. These results also revealed the effect of ageing time on the efficiency of sorption–desorption of the drug. An increase in ageing time results in an increase of the efficiency of drug sorption and a decrease in the rate of drug release.     

几种预制硅胶薄层层析板的性能考察

本文考察了几种预制硅胶薄层层析板的性能,结果表明实验所用四川省中药研究所研制的薄层铺板器与瑞士Camag公司铺板器所预制硅胶薄层板的性能相近似,质量较好,优于国内某厂所产硅胶预制板。     

50例煤矿工人肺组织化学成份分析

本文报告了50例尸解煤矿工人肺组织生化成份及SiO_2含量(mg/g干肺)的分析结果。测定结果表明,矽肺和煤矽肺组总类脂与胆固醇含量均明显高于对照组(P<0.05),矽肺组磷脂亦有显著增高(p<0.01)。Ⅰ期煤工尘肺的总类脂、磷脂显著高于对照组(P<0.05),而Ⅱ期煤工尘肺的SiO_2含量显著增高(P<0.01),胶原亦有增高的趋势。当煤工并发肺癌或结核时,胆固醇明显增高(P<0.05)。 由此可见,肺组织化学成份的含量随煤工尘肺的不同类型和不同期别,以及有无合并症而有不同。     

红外分光光度法与焦磷酸重量法测定粉尘中游离二氧化硅的比较

本文对矿山粉尘和铸造粉尘的游离二氧化硅含量进行了红外分光光度法和焦磷酸重量法的对比测定。结果表明,红外法与重量法的结果之间有很好的相关性,其测定值在统计学上无显著性差异。两法测定值的相关回归方程:(?)=1.0001×-2.0610,r=0.947997。红外法的测定不受灰化的影响,对滤膜采集的粉尘中游离二氧化硅的含量测定是一简便、快速的方法,可较好地排除粉尘中难溶或不溶物质和无定形二氧化硅等因素的干扰,克服了重量法的不足。     

Estimation of Surface Polarity of Silicas by Absorption Spectroscopy of Glycerin Suspensions of Adsorbed 6-Nitrobenzoindolinopyran

The title compound (6-NO₂-BIPS) is adsorptiochromic, becoming colored upon adsorption to a polar surface. Powders of 6-NO₂-BIPS adsorbed to silica gel or silicic acid are suspended in glycerin, and the absorption spectrum of the adsorbate is recorded by conventional absorption spectroscopy. The wave number of maximum absorption is related to the effective surface polarity by v*/cm^–1 = 90.85 Z + 11,571, where Z is the Kosower polarity measure. Silica surface polarity corresponds to Z = 86–89.     

Well-ordered mesoporous bioactive glasses (MBG): A promising bioactive drug delivery system

The local drug release system is considered to be an alternative to treat the bone infection. In this paper, well-ordered mesoporous bioactive glasses (MBG) with high specific surface area have been synthesized in aqueous solution by a two-step acid-catalyzed self-assembly process combined with hydrothermal treatment. Gentamicin was encapsulated into the MBG by adsorption method and in vitro release of gentamicin from MBG was performed in distilled water and modified simulated body fluid (SBF), respectively. The results showed that the amount of drug loading of MBG was three times more than that of conventional sol-gel 58S. The outcomes of drug release in distilled water and in SBF showed that M58S effectively decreased the initial burst. During the release period, gentamicin was released from the M58S at a much lower release rate as compared to that from 58S after soaking in distilled water and SBF. Furthermore, the drug release was sensitive to the pH and ionic concentration of the release medium suggesting possible controls of the release rate. In addition, in contrast to conventional sol-gel 58S, M58S had higher ability to induce hydroxyapatite (HAp) formation. Therefore, well-ordered mesoporous bioactive glasses might be used as a bioactive drug release system for preparation of bone implant materials.