Benzene Inhalation by Parts Washers: New Estimates Based on Measures of Occupational Exposure to Solvent Coaromatics

Questions persist regarding assessment of workers’ exposures to products containing low levels of benzene, such as mineral spirit solvent (MSS). This study summarizes previously unpublished data for parts‐washing activities, and evaluates potential daily and lifetime cumulative benzene exposures incurred by workers who used historical and current formulations of a recycled mineral spirits solvent in manual parts washers. Measured benzene concentrations in historical samples from parts‐washing operations were frequently below analytical detection limits. To better assess benzene exposure among these workers, air‐to‐solvent concentration ratios measured for toluene, ethylbenzene, and xylenes (TEX) were used to predict those for benzene based on a statistical model, conditional on physical‐chemical theory supported by new thermodynamic calculations of TEX and benzene activity coefficients in a modeled MSS‐type solvent. Using probabilistic methods, the distributions of benzene concentrations were then combined with distributions of other exposure parameters to estimate eight‐hour time‐weighted average (TWA) exposure concentration distributions and corresponding daily respiratory dose distributions for workers using these solvents in parts washers. The estimated 50th (95th) percentile of the daily respiratory dose and corresponding eight‐hour TWA air concentration for workers performing parts washing are 0.079 (0.77) mg and 0.0030 (0.028) parts per million by volume (ppm) for historical solvent, and 0.020 (0.20) mg and 0.00078 (0.0075) ppm for current solvent, respectively. Both 95th percentile eight‐hour TWA respiratory exposure estimates for solvent formulations are less than 10% of the current Occupational Safety and Health Administration permissible exposure limit of 1.0 ppm for benzene.     

Insulin-like growth factor-1 is a mediator of age-related decline of bone health status in men

Abstract

Objective: The role of insulin-like growth factor-1 (IGF-1) in bone health in men is debatable. This study aimed to determine whether IGF-1 is a mediator in age-related decline of bone health status measured by calcaneal speed of sound (SOS) in Malaysian men.

Methods: The study recruited 279 Chinese and Malay men. Their demographic data, weight, height, calcaneal SOS were taken and fasting blood was collected for total testosterone, sex-hormone binding globulin and IGF-1 assays. The associations between the studied variables were assessed using multiple linear regression (MLR) analysis. Mediator analysis was performed using Sobel test.

Results: There was a significant and parallel decrease of IGF-1 and SOS with age (p?<?0.05). Serum IGF-1 was significantly and positively associated with SOS (p < 0.05) but after further adjustment for age, the significance was lost (p?>?0.05). The strength of the association between age and SOS decreased after adjusting for IGF-1 level but it remained significant (p?<?0.05). Sobel test revealed that IGF-1 was a significant partial mediator in the relationship between age and SOS (z?=??4.3).

Conclusion: Serum IGF-1 is a partial mediator in the age-related decline of bone health in men as determined by calcaneal ultrasound. A prospective study should be performed to validate this relationship.     

血清NTx和BSP对老年骨转移癌的临床意义

目的观察骨代谢生物标志物Ⅰ型胶原交联氨基末端肽（NTx）和骨唾液酸蛋白（BSP）在老年恶性肿瘤骨转移中的临床意义。方法老年恶性肿瘤患者96例,密切随访6个月以上,在入选时用ELISA法测定所有患者血清NTx和BSP基线水平,入选和随访6个月时应用影像学检查评估患者是否合并骨转移癌。结果骨转移癌组患者血清NTx和BSP基线水平均明显高于无骨转移组,NTx（25．70±12．67）nmol／L vs（11．20±4．74）nmol/L,P〈0．01;BSP（46．68±14．24）ng／mLvs（26．58±13．61）ng／mL,P〈0．01。骨痛程度与血清NTx和BSP基线水平正相关。随访中出现新发骨转移癌患者血清NTx和BSP基线水平显著高于无骨转移癌者,P〈0．01。结论血清NTx和BSP在老年恶性肿瘤骨转移的早期识别和预测中有重要的临床价值。     

采矿用地使用权的取得——以地役权解“采矿用地”之结

采矿权是矿业的核心权利,但我国采矿权的客体仅为特定的矿产,于是,矿地使用权的享有成为采矿权行使的前提。然而,当采矿权和矿地使用权分别属于不同主体时,如何取得矿地使用权？立法上没有予以明确规定,实务中现行的取得方式弊端诸多。为了合理、合法地最大限度地实现矿产资源所有者的经济利益,又基于采矿权民事权利性质的确定,应以地役权解“采矿用地”之结。     

从“落叶归根”到“落地生根”——小说《骨》中华裔美国人身份的蝉变

《骨》是华裔美国女作家伍慧明的开山之作《骨》。伍慧明通过美国旧金山唐人街梁家的故事,编织了一个关于个人、家庭及民族的历史与政治问题的民族寓言。从后殖民主义批评的视角小说《骨》借助“落叶归根”和“落地生根”两类形象展现了华工移民及其子女在融入美国社会并成为关国人时所经历的身份变化,揭示了华裔美国人身份的建构之意。     

矿物加工工程专业学分制培养方案特色探讨——以安徽理工大学为例

在对国内主要矿物加工专业的本科培养方案进行分析基础上,对安徽理工大学矿物加工专业学分制培养方案中的专业培养特色进行了探讨,提出注重学科交叉性与应用性课程开设、改革教学方法与手段及加强实践教学环节是人才培养的关键.     

殷商甲骨文初造字造字机制研究

文字系统内字符的形成是有先后层次的。按文字系统中字符形成是否参考了系统内已有的字符将其分成两个层次———初造字与新造字。根据此造字机制理论对殷商甲骨文初造字的造字机制作分析。甲骨文属自源文字,其初造字存在仿拟机制和吸纳机制两种造字机制,两种造字机制分别有各自的特点,并且不同的造字机制对符号体态的影响也是存在区别的。     

体育运动对老年人骨矿物质含量影响的研究

通过对老年人体育活动者与非体育活动者进行活体骨矿物质含量的测试。结果发现，老年人活体骨矿物质含量存在明显的性别差异；骨矿含量随着年龄增加而逐年降低。在体育运动对骨矿含量影响的调查中发现，有体育运动组骨矿含量和骨密度显著高于普通老年组；纵向追综结果表明，尽管受试者骨矿含量均有不同程度的下降，但是体育运动组下降幅度低于普通组。这充分说明坚持长期的体育运动（如长跑）对保持老年人活体骨矿物质含量和延缓骨质丢失现象的出现都有着积极的作用。     

矿物加工工程“一体化、双层次＂实验体系构建

为了满足高校矿物加工工程专业人才培养的需求,在实验室建设、实验课程设置、实验室开放等方面进行了矿物加工工程专业“一体化、双层次”实验体系的构建。经实践检验,该实验体系可明显提高教师和学生的实践动手能力和科研能力,实验和教学都获得了良好的效果。     

Biochemical markers of bone metabolism in healthy elderly men. The relationship to physical activity

The purpose of the present study was to examine the serum levels of bone turnover markers and interleukin 1β in healthy elderly men with different levels of habitual physical activity. The study was conducted on 40 healthy men aged between 65 and 85 years (mean 74.0?±?7.55 years). The study population was divided into two groups with respect to the level of physical activity: 22 less active subjects (energy expenditure related to physical activity below 1600?kcal per week) and 18 more active subjects (above 1600?kcal per week). To estimate the physical activity of the study population, weekly energy expenditure was measured in each subject with use of Caltrac accelerometer. In the blood serum levels of bone formation marker – osteocalcin and resorption marker – the C-terminal telopeptide of collagen I (ICTP), and interleukin-1β were determined. Concentrations of osteocalcin and ICTP in less active subjects were significantly higher (by 3.62?ng/ml and by 1.21?μg/l respectively, p?<?0.05), reflecting the higher bone turnover in comparison to values determined in more active subjects. Positive correlations between ICTP and osteocalcin levels (r?=?0.5814 and r?=?0.6526; p?<?0.05), and between ICTP and IL-1β (r?=?0.5823 and r =?0.6040; p?<?0.05) in less and more active men were found. On the ground of the presented study it can be concluded that the decreased bone turnover occurred in men with higher level of habitual physical activity. This study showed the relationship between serum level of IL-1β and bone resorption but the habitual physical activity has no effect on this cytokine activity.