金属硅对焦磷酸法测定呼吸性粉尘中游离二氧化硅含量的干扰研究

目的 探讨焦磷酸法测定金属硅作业场所呼吸性粉尘中游离二氧化硅含量时可能存在的干扰因素对测量结果的影响。方法 主要从焦磷酸对金属硅呼尘的溶解作用、氢氟酸对实验结果的影响、滤膜对游离二氧化硅呼尘检测结果的影响3个环节验证焦磷酸法测定金属硅作业场所呼吸性粉尘中游离二氧化硅含量的可行性。结果 3个环节的实验结果偏离已知指标较大,金属硅的回收率为66.8%;金属硅经氢氟酸处理后的平均回收率为142.5%;游离二氧化硅呼尘的最大回收率仅为43.2%。结论 焦磷酸法测定金属硅作业环境中呼吸性粉尘中游离二氧化硅含量时,检测结果的误差较大。实验结果为进一步研究改进作业场所游离二氧化硅分析检测方法的必要性提供了依据。     

粉尘中游离二氧化硅含量测定的焦磷酸质量法的改进

对粉尘中游离二氧化硅(SiO2)含量测定的焦磷酸质量法进行改进,并建立其操作规程。采用磷酸直接加热溶解<200目的粉尘样品,降低焦磷酸处理样品温度,增加硝酸铵的加入量处理硫化矿物,滤膜采集的粉尘样品的过滤采用抽滤。用改进后的操作规程对比分析,同时测定实际样品及石英混合样品。结果显示,改进前后实际样品检测结果相对偏差为2.95%,测得石英回收率约为95%,实际样品测定的相对标准偏差为0.28%～2.80%,硝酸铵的加入量增加到数百毫克使硫化矿物完全溶解,微孔滤膜抽滤可避免滤膜采集的粉尘样品发生透滤。用改进后的焦磷酸质量法测定工作场所粉尘中游离SiO2含量,简化了操作规程,避免了样品溶解时胶体的产生,排除了硫化矿物的干扰,解决了样品粒度过细时透虑带来的测定误差,此规程适用于工作场所粉尘中游离SiO2的测定。     

焦磷酸法测定粉尘中游离二氧化硅的方法改进

<正>二氧化硅又叫硅石,在自然界中分布广泛,主要用于制造玻璃、陶器、搪瓷、耐火材料、硅铁、型砂、单质硅等[1]。粉尘中的游离二氧化硅是一种不易溶解的物质,不易被吸收、不易排出,在体内沉积可导致肺纤维化,是引起矽肺的主要原因。游离二氧化硅的含量不同对人体的危害程度也不同,因此,在评价粉尘危害程度时要进行粉尘中游离二氧化硅含量的分析测定。粉尘中游离二氧化硅含量的国家标准测定方法有焦磷酸质量法、X线衍射法和红外光谱法[2]。后     

焦磷酸法测定粉尘中游离二氧化硅滤纸及其质控样品的选择

国家标准GBZ/T192.4-2007工作场所空气中粉尘测定第4部分[1]:游离二氧化硅含量,本部分规定了工作场所粉尘中游离二氧化硅含量的测定方法。主要有焦磷酸法、红外分光光度法、X线衍射法。其中焦磷酸法不受仪器条件限制,已被广泛应用,由于该方法操作复杂、耗时长、影响因素多、对检验人员的操作技能要求较高,且目前缺少比较适合的质量控     

实验室粉尘质控样品的制备

目的 建立实验室粉尘质量控制样品(质控样品)的制备方法.方法 使用球磨机、粉尘筛、干燥箱及混合容器等仪器设备制备粉尘质控样品,用焦磷酸法测定粉尘游离二氧化硅含量,并对粉尘质控样品进行均匀性检验.结果 本次使用的铁矿石粉尘游离二氧化硅含量为2.57%,粉煤灰粉尘游离二氧化硅含量为8.21%,石英粉尘的游离二氧化硅含量为97.36%.将石英粉尘分别与粉煤灰粉尘、铁矿石粉尘按一定比例混合,制备的两种粉尘质控样品游离二氧化硅含量分别为10.52%和4.58%,经均匀性检验,每种样品内10个样品之间的游离二氧化硅含量差异无统计学意义(P＞0.05),符合均匀性的要求.结论 该方法适用于实验室粉尘质控样品的制备.     

郧县作业场所粉尘中游离二氧化硅含量测定结果分析

目的 调查了解郧县粉尘作业场所粉尘中游离二氧化硅(SiO2)的含量,为预防矽肺病提供基础资料.方法 采集不同类型作业场所呼吸带粉尘,用焦磷酸质量法测定游离二氧化硅含量.结果 游离SiO2＜ 10％的有煤尘、大理石尘、石灰石尘、水泥尘、重晶石尘,10％≤游离SiO2≤50％的有砂轮尘、50％＜游离SiO2≤80％的有铸造车间混合尘,≥80％的有铸造尘、石英砂;游离SiO2含量以石英砂尘为最高(91.1±3.4％),以重晶石为最低(3.4±0.4％),230份粉尘游离SiO2含量平均值为26.3％.结论 作业场所中不同种类粉尘中游离二氧化硅含量差异较大,在进行粉尘浓度监测时,要根据游离二氧化硅的含量,才能确定是否超过职业接触限值.     

徐州地区2002-2007年作业场所空气粉尘中游离二氧化硅的测定

目的了解徐州地区粉尘作业场所空气粉尘中游离二氧化硅的含量，为预防矽肺病提供基础资料。方法 游离二氧化硅含量的测定采用焦磷酸质量法（GB5748—1985）。结果 该地区粉尘作业场所不同种粉尘中游离二氧化硅含量为：铸造尘92％、煤尘（19．4±11．0）％、煤渣尘（34．02±22．86）％、煤灰尘（11．03±7．74）％、混合性煤尘（19．41±11．07）％。结论 粉尘种类不同，游离二氧化硅的含量不同，对人体危害性质及严重程度有所不同，可依据接触粉尘类型而实施不同的防护措施。     

焦磷酸质量法测定粉尘中游离二氧化硅含量的方法改进与经验探讨

目的改进测定工作场所粉尘中游离二氧化硅含量的测定方法。方法采用焦磷酸质量法。结果可有效提高结果的准确性,缩短检测时间,减少偶然误差与系统误差,避免因粉尘性质判断失误而影响结果的可能性。结论在保证准确性的基础上提高了检测效率。     

焦磷酸法测定粉尘中游离二氧化硅含量的实验条件研究

以《工作场所空气中粉尘测定第4部分:游离二氧化硅含量》(GBZ/T192.4—2007)焦磷酸法为基础对三种不同游离SiO2含量的粉尘(用1、2、3号表示)进行测定,溶解时间为10 min、15 min、20 min,过滤过程采用四种不同来源的慢速定量滤纸进行比对,灰化过程分别采用两种型号马弗炉(用Ⅰ、Ⅱ号表示),灰化时间为30 min、45 min、60min。不同溶解时间测定1号粉尘的游离SiO2含量差异无统计学意义(P0.05),不同溶解时间测定的2、3号粉尘的游离SiO2含量差异有统计学意义(P0.05),其中溶解时间10min测定的游离SiO2结果明显高于溶解时间≥15 min的测定结果 (均P0.05)。采用四种来源的慢速定量滤纸过滤测定1、2、3号粉尘的游离SiO2含量差异均无统计学意义(均P0.05)。Ⅰ号马弗炉30 min的灰化时间测定三种粉尘游离SiO2含量结果均高于标准参考值(P0.05),Ⅱ号马弗炉不同灰化时间(30 min、45 min、60 min)测定三种粉尘的游离SiO2含量结果差异均无统计学意义(P0.05)。焦磷酸法测定粉尘中游离SiO2含量时,溶解时间应不低于标准要求的15min,实验过程中应加强对滤纸过滤效果和马弗炉灰化温度的质控,必要时应适当延长灰化时间。     

电感耦合等离子体质谱法间接测定粉尘中游离二氧化硅含量

采用焦磷酸消解试样,经过滤,将游离二氧化硅分离,利用氢氟酸溶解硅酸盐测得全硅,用电感耦合等离子体质谱(ICP-MS)仪分别测得消解液和滤液中的硅,间接测得游离二氧化硅含量。硅在0~1 000μg/L内呈良好的线性关系(r=0.999 5),方法的检出限小于0.35μg/L,试样加标回收率在91.35%~108.16%,精密度小于3.41%。该方法快速、准确、灵敏、简便,适用于工作场所粉尘中游离二氧化硅含量的测定。     

Quantitative analysis of tridymite and cristobalite crystallized in rice husk ash by heating

The quantities of two forms of crystalline silica, tridymite and cristobalite, in heated rice husk ash (RHA) samples were determined by X-ray diffraction (XRD) and chemical methods. Two RHA samples, containing 93% SiO2 and 2-3% K2O, were prepared from charcoaled rice husk products and heated to above 900 degrees C. The crystalline silica made up over 60-80% of the total silica in the heated RHA samples based on the XRD analysis. The crystalline phases in the two samples were somewhat different: The sample heated in the temperature range of 900 to 1,200 degrees C contained 52-62% cristobalite and 10-17% tridymite, but the other sample heated at a comparable temperature, above 1,100 degrees C, contained 46-66% tridymite and 37-16% cristobalite. Based on a correlation of lower tridymite crystallization temperature with higher potassium content, it was concluded that higher potassium levels were responsible for this difference. The pyrophosphoric acid analysis did not give exact results in the evaluation of total crystalline silica content in these RHA samples. As the combustion of rice husk was considered to cover the demands for energy and silica resource in Asian countries, cristobalite and tridymite crystallized in RHA by burning of rice husk should be assessed precisely by XRD analysis and the airborne dust in relevant workplace be controlled.     

Evaluation of occupational exposure to mixed dusts and polycyclic aromatic hydrocarbons in silicon carbide plants

Workers in the silicon carbide industry have experienced occupational health diseases, particularly lung disorders such as silicosis. The silicon carbide production process mainly employs petroleum coke, sawdust, pure crystalline silica and graphite. Since crystalline silica is present in the occupational environment, the airborne dust content of various polymorphs of silica, especially quartz, cristobalite and tridymite, was determined by X-ray diffraction analysis. The analytical method was modified to eliminate graphite, since it overlaps with the main diffraction plane of quartz. Exploratory field surveys were conducted to identify the minerals present in that occupational environment and to evaluate the validity of the analytical method. The surveys provided information on the mineralogical nature of the dust, its respirable content and the concentration of silica polymorphs. Polycyclic aromatic hydrocarbons also were measured, and the effect of their adsorption on graphite was evaluated.     

Lung dust content and response in guinea pigs inhaling three forms of silica

Guinea pigs were exposed by inhalation to atmospheric suspensions of crystalline free silica (cristobalite), amorphous free silica (diatomaceous earth), and amorphous silicate (volcanic glass). Randomly selected animals were killed at 2-month intervals and their lungs were examined. Tissue samples were collected and analyzed for total silica content and total ash. Total silica content per lung increased linearly throughout at least 21 months in each experiment and total ash weight increased more rapidly than dust was accumulating. Crystalline silica produced a greater increment in ash weight that did the amorphous free silica and the silicate produced the least increase. Furthermore, although atmospheric dust concentrations were roughly comparable for the three preparations, the total amount of silica accumulated varied inversely with the degree of tissue damage occurring. Thus, the maximum total content of the crystalline silica reached only 68 mg per lung, while that of the amorphous silica and silicate was 120 mg and 465 mg, respectively. This suggests that a silicious dust that produces cell damage may be cleared more effectively from the lung than is an innocuous dust.     

Toxicological investigations on silicon carbide. 2. In vitro cell tests and long term injection tests.

Silicon carbide (SiC) dust and other dusts for comparison were injected intratracheally at a high dose (50 mg) into rats and the response of the lungs and the lymph nodes was studied after an appropriate experimental period. The indices studied were: histological changes in the lung and lymph nodes, organ weights, the formation of collagenous fibres, and the appearance of quartz typical areas. According to several epidemiological investigations and previous experimental animal studies, SiC produces silicogenic (fibrogenic) effects. No changes in the tissues studied in terms of damaging fibrogenic effects could be found after eight months (first series) and three and 12 months (second series). In particular, the histological findings and the absence of quartz typical areas as well as the quantitative determination of collagen fibres show that SiC had no harmful effects on tissues. Based on these results, the extent to which other exposures during the production of SiC can be responsible for the established radiological alterations is discussed. Without doubt the following may be confounders: SiC fibres, crystalline SiO2 (quartz, cristobalite, tridymite), and possibly gaslike emissions (SO2). From the hygienic medical point of view the workplaces during SiC manufacture should be examined carefully. The substance SiC dust as such can be considered as inert from the experimental results based on qualitative and extremely sensitive procedures. A revision of the present threshold value for SiC in ther German MAK list is called for.     

The preparation and characterization of fine dusts carried out in the Clinica del Lavoro di Milano in support of experimental studies

This paper aims to illustrate the conditions selected at the Clinica del Lavoro of the University of Milan to prepare and analyze a large number of fine dust samples produced over a period of about 50 years, that were initially used for studies within the Clinic performed in its own facilities, and since 1956 were sent to other Italian and overseas laboratories (Luxembourg, UK, Germany, Norway, Sweden, South Korea, USA). The total quantity of material distributed (with maximum size 7-10 microns) was about 2 kg and consisted of the following mineral and artificial compounds: quartz, HF-treated quartz, tridymite, HF-treated tridymite, cristobalite, chromite, anthracite, quartz sand for foundry moulds, sand from the Lybian desert, vitreous silica, pumice, cement, as well small quantities of metallic oxides, organic resins, chrysotile, crocidolite, fibres (vitreous, cotton and polyamidic). About half of the entire quantity of dusts produced consisted of partially HF-treated tridymite. Initially, research on the etiology of silicosis used quartz dust samples, simply sieved or ventilated (consisting of classes finer than 0.04 mm, containing a 15-20% respirable fraction). From 1956 to 1960 the dusts were produced by manual grinding in an agate mortar, below about 10 microns, starting from quartz from Quincinetto (near Ivrea, Province of Turin), containing about 99.5% quartz: particle size and composition were checked using an optical-petrographic technique, with identification of the free and total silica content. Subsequently, the dusts used for biological research were obtained by grinding coarse material with a cast iron pestle and planetary mills, agate and corundum jars. The grinding products were sized by means of centrifugal classification, using the selector developed by N. Zurlo, ensuring control of dust size both optically and by means of wet levigators and hydraulic classifiers (in cooperation with the Institute of Mines of Turin Polytechnic School). After 1990 pestles and rotating drum mills with autogenic grinding load were used for grinding: the size of the treated samples was reduced to 0.05 mm and an extremely fine fraction was extracted, smaller than 7-10 microns, which was used for pneumoconioses research. The characterization of the dust produced was in any case achieved by means of preliminary examination under the optical microscope (polarized light, sometimes supplemented with phase contrast), followed by quantitative analysis using chemical/petrographic, chemical diffraction or, more commonly, petrographic/diffraction techniques. Microscopic examination, if necessary supplemented with photo-micrography, was also used for particle size control, for numerical counting and subsequent reference to weight proportion. For all operational procedures the essential data on instruments and methods are reported. During studies on production, separation of fine dusts and their characterization, partly performed with support from the European Community (EEC/European Coal and Steel Commission), the following topics in particular were addressed: connections between particle size and free silica content in the measurable dust size fraction of the grinding products and in airborne dusts; characteristics of the dusts and risk indices in Italian iron and pyrite mines; possibility of abatement of the ultrafine classes of airborne dusts in pneumatically filled stopes by the addition of salts; comparison of the latest dust selectors used within the European Community; influence of the grinding methods on the results of fibrous and soft mineral measurement using X-ray diffraction analysis.     

Occupational exposure and analysis of microcrystalline cristobalite in mullite operations

Three analytical methods currently used for crystalline free silica determination in occupational exposure samples were evaluated for their applicability to ceramic materials containing synthetic mullite. X-ray powder diffraction is the only method that can be used with sufficient precision and potentially adequate accuracy for occupational exposure monitoring. Personal respirable dust exposure samples were collected in two foundries. The results of exposure evaluations in Plant A showed overexposure to the dust, particularly in the shakeout area. The cristobalite concentration in the respirable dust exceeded that in the original material for this particular area. This may be related to the preheating of molds to more than 1100 degrees C for the pouring of stainless steel castings, causing conversion of some of the colloidal silica binder to cristobalite, and related to high vibration fracture of the material during removal of castings from molds. In Plant B, quartz was sometimes present along with cristobalite in personal samples. Respirable dust levels exceeded the Occupational Safety and Health Administration's (OSHA) permissible exposure limit (PEL) and the National Institute for Occupational Safety and Health's (NIOSH) recommended time-weighted average (TWA) for crystalline free silica, indicating a need for better engineering controls to reduce dust levels. The inadequacy of reference standards currently available for cristobalite analysis in these types of materials is cited. The need for more toxicological research is emphasized.     

不确定度评定在焦磷酸法测定工作场所粉尘游离二氧化硅中的应用

目的 对焦磷酸法测定工作场所粉尘游离二氧化硅质量分数进行不确定度评定。
方法 依据《测量不确定度评定与表示》(JJF 1059.1-2012)对《工作场所空气中粉尘测定第4部分:游离二氧化硅含量》(GBZ/T 192.4-2007)中焦磷酸法测定带来的不确定度的来源进行识别和评定, 并合成不确定度。
结果 该方法测定过程中产生不确定度分量的主要来源为重复性和温度方面。不经氢氟酸处理的重复性方面相对标准不确定度为8.89×10-2, 经氢氟酸处理后的重复性方面相对标准不确定度为5.90×10-2; 温度计检定的温度方面相对标准不确定度为0.26×10-2, 马弗炉校准的温度方面相对标准不确定度为0.12×10-2。不经氢氟酸处理的工作场所粉尘游离二氧化硅质量分数合成标准不确定度为1.35%, 扩展标准不确定度为2.70%;经氢氟酸处理后的工作场所粉尘游离二氧化硅质量分数合成标准不确定度为0.57%, 扩展标准不确定度为1.14%。工作场所粉尘游离二氧化硅质量分数标准不确定度结果:不经氢氟酸处理为(15.18 ±2.70)%, 经氢氟酸处理后为(9.66 ±1.14)%。
结论 在保持所使用的称量仪器具有良好的精密性、操作性和重复性基础上, 应加强操作培训, 熟悉操作处理全过程, 以减少操作重复性和温度方面产生的不确定度叠加。
     

广州市玻璃制品和宝石加工工作场所粉尘及危害现状调查

目的了解广州市玻璃制品和宝石加工工作场所生产性粉尘及危害状况。方法对玻璃制品和宝石加工行业企业进行职业卫生现状调查。结果28家玻璃制品和宝石加工企业工作场所中粉尘游离SiO2含量中位数为38.80%,81.44%的粉尘为矽尘;粉尘检测超标率为15.98%,玻璃制造行业粉尘超标率明显高于同期其他行业水平;粉尘暴露工作岗位防尘口罩正确佩戴率为53.30%;接尘工人矽肺患者检出率为0.76%(6/786)。结论广州市玻璃制品和宝石加工行业生产性粉尘危害现状不容乐观,加强尘肺防治工作是该行业职业卫生工作的重点。     

Determination of free silica in airborne dust by phosphoric acid method

Free silica content in airborne dust was measured with a modified procedure collecting sample dust on glass fiber filter and heating the dust together with the filter in phosphoric acid. The insoluble phosphoric acid residue of the glass fiber filter used by us was of small amount. Fifteen mg of dust was enough to determine its free silica content correctly. On dust collected at pottery and foundries works, satisfactory coincidence was found between the values of free silica content by our procedure and by X-ray diffraction. It can be concluded that this is a reliable method for determination of free silica content of airborne dust as well as of deposited one.     

Determination of free silica in dust particles: effect of particle size for the X-ray diffraction and phosphoric acid methods

The X-ray diffraction method and the phosphoric acid method are widely used to determine the fraction of free silica (mainly quartz and other silica polymorphs) in respirable dust sampled in working environments in Japan. In this study, we clarified the size effect of quartz dust for the X-ray diffraction method and the phosphoric acid method using size controlled quartz samples. The quartz samples were classified into 6 fractions with different size ranges: 1 microm and smaller, 1 to 3 microm, 3 to 5 microm, 5 to 7 microm, 7 to 10 microm and 10 microm and larger. Both of the determination methods were affected by the particle size, and especially particles smaller than 3 microm fairly dissolved in hot phosphoric acid and reduced X-ray diffraction intensity remarkably. If the content of these fine particles in the standard quartz sample is lower than that of the test samples, the fraction of free silica may be underestimated by these methods. For this reason, the standard quartz sample should have a representative size distribution of the field samples. The dust samples containing quartz were collected at a foundry and dissolved by phosphoric acid to remove non-quartz materials. The size fractions of dissolved samples were 50% for 5-10 microm, 25% for 3-5 microm, 20% for 1-3 microm and 5% for 1 microm and smaller. As the size distribution is similar to the present standard sample widely used in Japan, we concluded that the standard sample is suitable for these determination methods.