Mechanism of refractory ceramic fiber- and rock wool-induced cytotoxicity in alveolar macrophages

Objectives: Man-made vitreous fibers (MMVFs) can induce cytotoxicity in a way similar to that of other particles, including silica and asbestos fibers. However, as yet the mechanism of MMVF-induced cytotoxicity is still not clear. This report aims to clarify the mechanism of MMVF-induced cytotoxicity in the alveolar macrophage (AM). In this mechanism, an attempt to prove the involvement of the adenosine triphosphate (ATP) generation system and the polyinosinic acid-inhibitable scavenger receptors was made. Methods: Several parameters were observed for cytotoxicity, such as cell viability, the release of lactic dehydrogenase (LDH) and ATP levels in rat AM's that were treated with refractory ceramic fibers (RF2) and rock wool (RW1). A specially designed ATP generation system was used to determine the effect of MMVF on ATP generation. A scavenger receptor ligand was applied to evaluate the relationship between scavenger receptors and MMVF-induced ATP depletion. Results: A 3-(4,5-dimethylthiazol)-2,5-diphenyl tetrazolium bromide (MTT) assay indicated that both RF2 and RW1 caused a decrease in cell viability and this decrease was concentration-dependent. RF2 and RW1 increased the release of LDH with increasing fiber concentration. From these parameters, RF2 was shown to exhibit greater cytotoxicity than did RW1. Both fibers decreased the intracellular ATP content and this decrease was concentration-dependent. The decrease was more pronounced in RW1 than in RF2 at all fiber concentrations. These fibers suppressed succinate-triggered oxygen consumption. Polyinosinic acid, a ligand of the scavenger receptor, inhibited the MMVF-induced decrease in ATP concentration. Conclusion: These results suggest that RF2 and RW1 can induce cytotoxicity and ATP depletion in the AM through the polyinosinic acid-inhibitable scavenger receptor. ATP depletion was the important factor in MMVF cytotoxicity, especially by RW1. Received: 4 November 2000 / Accepted: 24 June 2000     

Comparison of cytotoxicity of man-made vitreous fibres

The purpose of the study was to compare the cytotoxicity of man-made vitreous fibres (MMVFs): four refractory ceramic fibres (RCFs 1–4), two glasswool fibres (MMVF 10 and 11), a rockwool fibre (MMVF 21) and a slagwool fibre (MMVF 22). The ability of the fibres to induce haemolysis in sheep erythrocytes, to release lactate dehydrogenase (LDH) from rat alveolar macrophages (AM) and to increase the production of reactive oxygen metabolites (ROMs) in human polymorphonuclear leukocytes (PML) was studied. To assess the relative cytotoxicity of MMVFs, their toxicity was compared with that induced by quartz, chrysotile or titanium dioxide. MMVFs induced a modest, but dose-dependent, increase of haemolysis at doses of 0.5, 2.5 and 5.0 mg ml⁻¹. The amount of haemolysis and LDH release induced by MMVFs was generally similar to that induced by titanium dioxide. Glasswool fibre MMVF 10 induced less LDH release from rat AM than rockwool MMVF 21 or slagwool MMVF 22 fibres, whereas glasswool fibre MMVF 11 induced less LDH release than slagwool fibre MMVF 22 (P<0.05). All fibres also dosedependently increased the production of ROMs at doses between 25 and 500 μg ml⁻¹. The shapes of the time-courses of MMVF-induced production of ROMs suggest that the mechanisms whereby the different fibres induce ROM production may exhibit similar features. There are clear-cut differences in the potency of various MMVFs to induce cytotoxicity and oxidative burst. The present results also emphasize the importance of using several measures of toxicity when assessing the biological activity of various fibres in vitro.     

Differential responses of rat alveolar and peritoneal macrophages to man-made vitreous fibers in vitro

Different approaches, including inhalation and intraperitoneal injection assays, have been used to assess the potential health effects of man-made vitreous fibers (MMVF). The purpose of this study was to compare the phagocytic activity and the formation of reactive oxygen species by rat alveolar macrophages (AM) and peritoneal macrophages (PM) upon exposure to MMVF10 glass wool and MMVF21 rock wool fibers. Macrophage (Mphi) phagocytosis of mineral fibers was assessed by optical videomicroscopy and computer-aided image analysis. Mphi were classified as cells not associated with fibers, cells with attached fibers, cells with incompletely phagocytized fibers (an appearance known as "frustrated phagocytosis"), and cells with completely phagocytized fibers. The production of superoxide anions by AM and PM upon incubation with MMVF10 and MMVF21 fibers was determined by the superoxide dismutase-inhibitable reduction of ferricytochrome C. PM were found to have a lower phagocytic activity than AM. A significantly higher percentage of AM than of PM underwent frustrated phagocytosis of MMVF10 and MMVF21 fibers. In line with these findings, AM generated higher levels of oxygen radicals than PM upon exposure to MMVF21 fibers. In contrast, MMVF10 fibers failed to induce the generation of reactive oxygen species by both AM and PM. Our in vitro results show that the phagocytic activity, in particular the frustrated phagocytosis of mineral fibers, was significantly lower in PM than in AM. The data support the idea that the durability and biopersistence of mineral fibers are higher in the peritoneal cavity than in the lung.     

温石棉与岩棉及硅灰石纤维体外细胞毒性的比较

目的 研究温石棉(CA)与岩棉(RW)和硅灰石(WS)纤维的细胞毒性.方法 将V79细胞分为CA组、RW组及WS组3个实验及1个阴性对照组(200 μl PBS),CA、RW及WS粉尘终质量浓度为100 mg/L,噻唑蓝(MTT)法观察V79细胞存活率,用动力学法测乳酸脱氢酶(LDH)活力,用扫描电子显微镜观察粉尘对V79细胞形态的影响.结果 SiO2均为3种纤维的主要成分,WS中的SiO2含量最高,为50.83%.CA组、RW组、WS的细胞存活率分别为54.5%、64.8%、65.7%,RW组和WS 组的存活率明[显高于CA组,差异有统计学意义(P＜0.01),RW组和WS组的LDH活力[分别为(15.7±0.9)、(12.3±3.7)U/L]明显低于CA组[(20.2±0.9)U/L].差异有统计学意义(P＜0.05).CA组的V79细胞两端堆积大量颗粒状残余体,RW组和WS组V79细胞形态基本正常.结论 RW和WS对V79细胞的毒性低于CA.

Abstract：

Objective To study the cytotoxicity induced by chrysotile asbestos (CA), rock wool (RW)and wollastonite (WS). Methods V79 cells were divided into 4 groups. i.e. CA group, WS group, RW group and control group (200 μ1 PBS). The exposure concentration of dusts was 100 mg/L, The cell viability was detected by MTT and lactate dehydrogenate (LDH) activity assays. The technique of scanning electron microscopy was used to examine the change of V79 cells. Results SiO2 was main constituent for 3 kinds of dusts. In MTT assay, the cell viability of RW and WS groups was 64.8% and 65.7%, respectively, which were significantly higher than that (54.5%) of CA group (P＜0.01). In LDH assay, the LDH activity of RW and WS groups [(15.7±50.9),( 12.3±3.7)U/L, respectively] was significantly lower than that[( 20.2±0.9) U/L]of CA group (P＜0.05). In scanning electron microscopy examination, it was found that the two ends of V79 cells in CA group contained a great deal of fibers remaining bodies, but the V79 cell appearance in RW and WS groups was normal. Conclusion The cytotoxicity induced by RW and WS is significantly lower than that induced by CA for V79 cell.     

Man-made vitreous fibers: Present status of research on health effects

Summary Concerns engendered by inappropriate extrapolation from rat intracavitary cancer experiments stimulated the initiation of new retrospective and prospective epidemiologic studies of man-made vitreous fibers (MMVF). The results of these new studies have confirmed those of previous investigations that MMVF exposure had not caused an increased risk to develop lung cancer or nonmalignant respiratory disease.In contrast to the high pathogenic potential of MMVF (thin long fibers) when injected into the body cavities of rats, the pulmonary reaction of rodents inhaling such fibers has been that of a nuisance-type dust. The results of new experimental inhalation studies have not yet been published.In vitro studies have demonstrated cytotoxicity of thin long MMVF. Although there is a parallelism between the in vitro cytotoxicity results of MMVF and those of the in vivo intracavitary carcinogenesis studies with the same fibers, it is difficult to attach significance to this parallelism insofar as man is concerned because the rat intracavitary carcinogenesis results have no relevance to man.     

Durability of man-made vitreous fibres as assessed by dissolution of silicon,iron and aluminium in rat alveolar macrophages

The dissolution of man-made vitreous fibres (MMVF) by rat alveolar macrophages (AM) was studied in vitro. The fibre samples included refractory ceramic (RCF 1–4), glasswool (MMVF 10, 11), rockwool (MMVF 21) and slagwool fibres (MMVF 22). Experimental fibre REC 1 of calcium silicate type served as an internal control fibre. The fibres were incubated with cultured rat AM or in mere cell-culture medium for 2, 4 or 8 days. The dissolution of the fibres was determined by measuring the amount of silicon (Si), iron (Fe) and aluminium (Al) in the medium with or without rat AM. Si was markedly dissolved only from the glasswool fibres (MMVF 10 and 11) and from the experimental fibre REC 1. Fe was dissolved, in turn, more from rockwool fibres than from the other fibres. Al was effectively dissolved from the ceramic fibres (RCF) 1–3. The dissolution of Fe and Al from the fibres was effective in the presence of AM, whereas the dissolution of Si was greater in the mere culture medium. The results of present study suggest that glasswool fibres (MMVF 10 and 11) are dissolved more readily in mere culture medium where the pH is close to neutral, whereas rockwool fibres are sensitive to the effects of more acidic milieu in AM culture.     

Biological effects of man-made mineral fibers (I)--Reactive oxygen species production and calcium homeostasis in alveolar macrophages

10 types of standard mineral fiber samples (JFM fibers) were tested for their cytotoxicity in alveolar macrophages (AM) in vitro experiments, in which UICC chrysotile B was used as a positive control. The cytotoxicity included the production of superoxide anion radical and hydrogen peroxide, depletion of glutathione (GSH) and increase of intracellular free calcium. The results showed that chrysotile and most of the 10 mineral fibers could increase the production of superoxide anion and hydrogen peroxide, deplete the concentration of GSH and increase the level of free intracellular Ca2+ in AM. But all the effects of JFM fibers were lower than that induced by UICC chrysotile B. Although the cytotoxicity of JFM fibers were lower than that of asbestos, these mineral fibers should be used with highly care for workers in industries.     

In situ microscopic analysis of asbestos and synthetic vitreous fibers retained in hamster lungs following inhalation

Hamsters breathed, nose-only, for 13 weeks, 5 days/week, 6 hr/day, either man-made vitreous fiber (MMVF)10a, MMVF33, or long amosite asbestos at approximately 300 World Health Organization (WHO) fibers/cc or long amosite at 25 WHO fibers/cc. [World Health Organization fibers are longer than 5 microm and thicker than 3 microm, with aspect ratio >3.] After sacrifice, fiber burden was estimated (left lungs) by ashing and scanning electron microscopy (ashing/SEM) or (right middle lobes) by confocal laser scanning microscopy (CLSM) in situ. In situ CLSM also provided three-dimensional views of fibers retained, undisturbed, in lung tissue. Fibers of each type were lodged in alveoli and small airways, especially at airway bifurcations, and were seen fully or partly engulfed by alveolar macrophages. Amosite fibers penetrated into and through alveolar septa. Length densities of fibers in parenchyma (total length of fiber per unit volume of lung) were estimated stereologically from fiber transsections counted on two-dimensional optical sections and were 30.5, 25.3, 20.0, and 81.6 mm/mm3 for MMVF10a, MMVF33, and low- and high-dose amosite, respectively. Lengths of individual fibers were measured in three dimensions by tracking individual fibers through series of optical sections. Length distributions of amosite fibers aerosolized, but before inhalation versus after retention in the lung were similar, whether determined by ashing/SEM or in situ CLSM. In contrast, the fraction of short MMVF10a and MMVF33 fibers increased and the geometric mean fiber lengths of both MMVFs decreased by approximately 60% during retention. Most likely due to fiber deposition pattern and differences in sampling, fiber burdens [MMVF10a, MMVF33, and amosite (high dose; 269 WHO fibers/cc)] determined by ashing/SEM were 1.4, 1. 5, and 3.5 times greater, respectively, than those calculated from in situ CLSM data. In situ CLSM is able to provide detailed information about the anatomic sites of fiber retention and also fiber lengths and burdens in good agreement with ashing/SEM results.     

Evaluation of exposure to man-made vitreous fibers by nasal lavage

The objectives of this study were to develop a biomonitoring method for the assessment of exposure to man-made vitreous fibers (MMVF), to examine the level of exposure to MMVF in the prefabricated house industry, and to study nasal inflammatory reactions and respiratory symptoms associated with MMVF among workers. Nasal lavage was performed on workers from two factories, and concentrations of MMVF were measured by electron microscopy. Cytokines (IL-6, IL-8, TNF-alpha, and IFN-gamma) were also assayed and inflammatory cells (lymphocytes, eosinophils, neutrophils, and macrophages) were counted microscopically. Concentrations of airborne fibers (longer than 5 microm) were measured for comparison. Moreover, the exposure to MMVF and the related symptoms were studied with a structured questionnaire. In nasal lavage samples, the mean concentration of MMVF (length >1.5 microm) was 3260 f/ mL in Factory 1, 1680 f/mL in Factory 2, and below 500 f/mL in the control group. About 52% of the retained fibers were longer than 100 microm. The group-specific mean concentrations of MMVF in nasal lavage samples correlated with production rates and airborne fiber levels in both plants. The airborne concentrations of MMVF both in the breathing zone and fixed-point samples were low (below 0.1 f/cm(3)). No significant differences in the biological response (inflammatory cells, cytokines) were found between the groups exposed and the control group. The workers complained of some irritation of the skin, eyes, and upper respiratory tract, which could be reduced by appropriate protective equipment. It is concluded that nasal lavage can be used as a biomonitoring method in the assessment of MMVF exposure.     

Identification of a P2X7 receptor in GH(4)C(1) rat pituitary cells: a potential target for a bioactive substance produced by Pfiesteria piscicida

We examined the pharmacologic activity of a putative toxin (pPfTx) produced by Pfiesteria piscicida by characterizing the signaling pathways that induce the c-fos luciferase construct in GH(4)C(1) rat pituitary cells. Adenosine-5'-triphosphate (ATP) was determined to increase and, at higher concentrations, decrease luciferase activity in GH(4)C(1) rat pituitary cells that stably express c-fos luciferase. The inhibition of luciferase results from cytotoxicity, characteristic of the putative P. piscicida toxin (pPfTx). The actions of both pPfTx and ATP to induce c-fos luciferase were inhibited by the purinogenic receptor antagonist pyridoxalphosphate-6-azophenyl-2',4'-disulfonic acid (PPADS). Further characterization of a P2X receptor on the GH(4)C(1) cell was determined by the analog selectivity of P2X agonists. The P2X1/P2X3 agonist alpha,beta-methylene ATP (alpha,beta-MeATP) failed to increase or decrease c-fos luciferase. However, the P2X7 agonist 2',3'-(4-benzoyl)benzoyl ATP (BzATP), which had a predominant cytotoxic effect, was more potent than ATP. Immunoblot analysis of GH(4)C(1) cell membranes confirmed the presence of a 70-kDa protein that was immunoreactive to an antibody directed against the carboxy-terminal domain unique to the P2X7 receptor. The P2X7 irreversible antagonist oxidized-ATP (oxATP) inhibited the action of ATP, BzATP, and pPfTx. These findings indicate that GH(4)C(1) cells express purinogenic receptors with selectivity consistent with the P2X7 subtype and that this receptor pathway mediates the induction of the c-fos luciferase reporter gene by ATP and the putative Pfiesteria toxin     

沙尘暴细颗粒物对大鼠肺泡巨噬细胞膜损伤

目的探讨扬沙和沙尘暴细颗粒物(PM2.5)对肺泡巨噬细胞(AM)的毒作用机制.方法于2004年3月采集甘肃省武威市和内蒙古包头市正常天气、扬沙天气和沙尘暴天气中大气PM2.5,并测定其质量浓度.以PM2 5悬液体外处理大鼠肺泡巨噬细胞4 h,通过四甲基偶氮噻唑蓝(MTT)法检测细胞存活率、定磷法检测质膜ATP酶活性、2,4-二硝基苯肼法和4-氨基安替比林法检测细胞培养液中乳酸脱氢酶(LDH)活性和酸性磷酸酶(ACP)活性,并以荧光探针1-苯胺基-8-萘磺酸(ANS)和1,6-二苯基-1,3,5-己三烯(DPH)为标记物检测细胞膜脂的流动性.结果与对照(生理盐水组)相比,扬沙和沙尘暴PM2.5样品可剂量依赖性地降低细胞存活率和质膜Ca2 Mg2 -ATP酶、Na K -ATP酶活性、增大细胞膜表层流动性,并使细胞质内LDH和ACP外渗;与正常天气样品相比,对上述指标的影响差异无统计学意义.结论扬沙和沙尘暴PM2.5可影响AM膜通透性和流动性,导致细胞死亡.由于沙尘天气时大气PM2.5质量浓度大大高于正常天气,其对健康危害作用也相应增大.     

三氯乙烯对人原代角质形成细胞的细胞毒作用

目的研究体外培养条件下有机溶剂三氯乙烯(Trichloroethylene,TCE)对正常人表皮角质形成细胞(normal human epidermal keratinocyte,NHEK)的毒性作用。方法用0.25%的胰蛋白酶经冷温两步消化皮肤,分离得到NHEK,进行体外无血清培养;根据中性红吸附试验测定的NR50结果,确定TCE染毒剂量。测定乳酸脱氢酶(LDH)活力,反映其对细胞膜的损害,测定丙二醛(MDA)含量和超氧化物歧化酶(SOD)活力,反映细胞脂质过氧化作用。结果TCE可引起NHEK细胞活力剂量依赖性降低,TCE对NHEK的NR50值为4.525 mmol/L(3.922~5.128 mmol/L);NHEK细胞用0.125,0.250,0.500,1.000,2.000 mmol/L的TCE处理1,2,3,4 h后,LDH的释放显示明显的时间-剂量-反应关系;同样剂量的TCE处理NHEK,4 h后可引起MDA含量呈浓度依赖性增加(最低浓度为0.500 mmol/L),SOD活力呈浓度依赖性抑制(最低浓度为0.250 mmol/L),与空白对照和溶剂对照组相比较,两者差异均有显著性(P<0.05)。结论在体外培养条件下,有机溶剂三氯乙烯可通过脂质过氧化和氧化应激作用对人角质形成细胞产生明显的细胞毒作用。     

Indoor airborne fiber levels of MMVF in residential and commercial buildings

Man-made vitreous fibers (MMVF) have been used widely in commercial and residential buildings for over 50 years. Concerns have been expressed since the late 1960s that MMVF products may erode and contribute to fiber levels in the indoor environment. This cooperative investigation was undertaken to quantify indoor respirable fiber levels by phase contrast optical microscopy (PCOM) and to differentiate between fiber types using scanning electron microscopy with energy-dispersive X-ray microanalysis (SEM-EDX). A total of 205 stationary samples were collected using standard industrial hygiene methods in 51 residential and commercial buildings. Twenty-one simultaneous outdoor samples were collected at 19 buildings. All samples were analyzed by PCOM following the NIOSH 7400 Fiber method, "B" counting rules, and 50 randomly selected samples were analyzed by SEM-EDX. The PCOM mean value for all respirable fiber levels was 0.008 f/cc with a median value of 0.007 f/cc and a maximum value of 0.029 f/cc. Ninety-seven percent of the respirable fibers identified by SEM-EDX were determined to be organic. MMVF were detected on only two samples. Airborne fiber levels were very low and the respirable fibers present were primarily organic. The inorganic fiber levels determined by SEM-EDX which included MMVF were less than 0.0001 f/cc.     

镍煤尘致细胞毒和锌抗细胞毒作用的研究

本文探讨了锌、镍煤尘的联合作用。实验指标有肺泡巨噬细胞(AM)内ATP、K~+和Zn~(2+)测定以及细胞表面扫描电镜观察。结果提示低锌对镍煤尘的AM毒作用起保护作用,这一作用与其剂量有关。AMK~+含量、ATP水平是反映细胞毒性的敏感指标可用于检测环境毒物。     

Behavior of rock wool in lungs after exposure by nasal inhalation in rats

To evaluate the safety of rock wool (RW fibers), we examined the biopersistence of a RW sample in the lungs of rats, based on the changes of fiber number and fiber size in terms of length and width, by a nose-only inhalation exposure study. Twenty male Fischer 344 rats (6–10 weeks old) were exposed to RW fibers at a concentration of 70 (21) fiber/m³ and 30 (6.6) mg/m³, arithmetic mean (geometric standard deviation), continuously for 3 h daily for five consecutive days. Five rats each were sacrificed shortly and at 1, 2, and 4 weeks after exposure, and their lung tissues were ashed by a low-temperature plasma-asher. Then, the numbers and sizes of fibers in the ashed samples were determined using phase-contrast microscope and computed image analyzer. The fiber numbers in the lungs 4 weeks after exposure significantly decreased from the baseline value, i.e., shortly after exposure (P < 0.05). The half-lives of RW fibers calculated from the one-compartment model were 32 days for total fibers and 10 days for fibers longer than 20 μm. The decrease of fiber number was 53.6% by 4 weeks after exposure (baseline group = 100%). Likewise, fiber sizes significantly decreased by 4 weeks after exposure (P < 0.05), probably because fibers were dissolved in body fluid, ingested by alveolar macrophages or discharged to outside of the body by mucociliary movement. In future studies, it is necessary to examine the long-term persistence of RW fibers in the lungs.     

Behavior of rock wool in rat lungs after exposure by nasal inhalation

To evaluate the safety of rock wool (RW) fibers, we examined the biopersistence of RW fibers in the lungs of rats, based on the changes of fiber number and fiber size in the length and width, in a nose-only inhalation exposure study. Twenty male Fischer 344 rats (6 to 10 wk old) were exposed to RW fibers at a fiber concentration of 70.6 (20.4) fiber/m(3) and a dispersion density of 30.4 (6.6) mg/m(3) [arithmetic mean (SD)] continuously for 3 h daily for 5 consecutive days. Five rats each were sacrificed shortly after exposure ended (baseline group) and at 1, 2, and 4 wk after exposure, and their lung tissues were ashed by a low temperature plasma-asher. The numbers and sizes of fibers in the ash samples were determined using a phase contrast microscope and a computed image analyzer. The fiber numbers in the lungs at 4 wk after exposure had significantly decreased from the baseline value, i. e. shortly after exposure (p<0.05). The half-lives of RW fibers calculated using the one-compartment model were 32 d for total fibers and 10 d for fibers longer than 20 microm in length. Fiber number was 53.6% of the baseline at 4 wk after exposure (baseline group=100%). Likewise, fiber sizes had significantly decreased at 4 wk after exposure (p<0.05), probably because fibers had been dissolved in body fluid, phagocytosed by alveolar macrophages or discharged from the body by mucociliary movement. In future studies, it will be necessary to examine the carcinogenicity of RW fibers through long-term inhalation studies.     

锌抗煤尘肺组织细胞毒性的实验研究

本文采用大鼠短期体内试验方法,研究了锌对煤尘肺组织细胞毒性的拮抗作用。实验结果表明,锌可降低染煤尘大鼠BALF(支气管肺泡灌洗液)中的细胞总数、PMN(多形核中性粒细胞)数,LDH(乳酸脱氢酶)活性及蛋白质浓度,提高细胞存活率及AM(肺泡巨噬细胞)的吞噬功能,提示锌具有抑制肺内由该煤尘所致的炎症反应及细胞损伤,增强细胞活性及功能等作用,证明锌可拮抗该煤尘的细胞毒性,从而对大鼠肺组织细胞起保护作用。上述实验结果,不仅加深了锌与煤尘危害作用关系的认识,同时为进一步研究锌在煤工尘肺防治中的应用提供了一定的实验依据。     

Assessment of past exposure to man-made vitreous fibers in the Swedish prefabricated house industry

Large quantities of man-made vitreous fibers (MMVF) are handled in the Swedish prefabricated wooden house industry. The present study is part of a program to investigate mortality, cancer incidence, and current as well as previous exposure to MMVF among workers in the Swedish prefabricated wooden house industry. Since measurements of historical fiber exposure levels are lacking, these were calculated by the application of a matrix of multipliers to recently measured MMVF levels. The multipliers represented changes over time in production rate, technical properties of the fibers, manual handling vs. automation, and ventilation control. The multipliers were based on a similar matrix, developed for the MMVF-manufacturing industry, which was modified to reflect the conditions in the wooden house industry. The model was developed for the highest-exposed job title in the study, insulators. One hundred and twenty samples of airborne fiber were taken in 11 plants to reflect current exposure levels. The highest mean fiber exposure level for insulators was assessed as 0.18 f/ml (geometric mean), which occurred during the mid-1970s, compared to 0.10 f/ml at the end of the 1980s and the early 1960s. Changes in production rate, improved ventilation control, and the surface area of the total amount of MMVF sheets handled per insulator were the most important variables of the model. No increased risk of lung cancer was found in the present industry. Am. J. Ind. Med. 32:349–354, 1997. © 1997 Wiley-Liss, Inc.     

Defatted milled grape seed protects adriamycin-treated hepatocytes against oxidative damage

Defatted milled grape seed (DMGS) is a wine by-product obtained from the oil extraction of the grape seed that contains different types of phenolic compounds. The present study was designed to evaluate the possible protective effect of DMGS on toxicity induced by adriamycin (ADR) in isolated rat hepatocytes. The study was carried out by examining the results of lactate dehydrogenase (LDH) release to estimate cytotoxicity; the thiobarbituric acid reactant substances (TBARS) and carbonyl group levels were measured as biomarkers of oxidative stress and ATP and GSH levels as estimation of intracellular effect. The results showed that DMGS extract protects the cellular membrane from oxidative damage and consequently prevents protein and lipid oxidation. The levels of ATP and GSH changes for the ADR toxicity were restored to control value in the presence of DMGS extract. The experimental results suggest that this wine by-product may be used to decrease oxidative stress.     

Laryngeal and hypopharyngeal cancer and occupational exposure to asbestos and man-made vitreous fibers: results of a case-control study

BACKGROUND: The data from a case-control study performed in France between 1989 and 1991 were used to test whether exposure to either asbestos or to man-made vitreous fibers (MMVF) is a risk factor for cancer of the larynx or the hypopharynx. METHODS: This study involved 315 incident cases of laryngeal cancer, 206 cases of hypopharyngeal cancer, and 305 hospital-based controls with other types of cancer, all recruited in 15 hospitals in six French cities. The subjects' past occupational exposure to asbestos and to four types of MMVF (mineral wool, refractory ceramic fibers, glass filaments, and microfibers) was evaluated based on their job history, with the aid of a job-exposure matrix. Odds ratios were calculated with unconditional logistic regression, with adjustment for smoking and drinking levels. RESULTS: Exposure to asbestos resulted in a significant increase in the risk of hypopharyngeal cancer (OR = 1.80, 95% CI: 1.08-2.99) and a nonsignificant increase in the risk of laryngeal cancer (OR = 1.24, 95% CI: 0.83-1.90). Risk was highest for the epilarynx (highest cumulative level of exposure: OR = 2.22, 95% CI: 1.05-4.71). Exposure to mineral wools was of borderline significance for the risk of hypopharyngeal cancer (OR = 1.55, 95% CI: 0.99-2.41), and nonsignificantly associated with the risk of laryngeal cancer (OR-1.33, 95% CI: 0.91-1.95). The risk was again highest for the epilarynx (OR = 1.85, 95% CI: 1.08-3.17). No significant results were observed for the other MMVF. CONCLUSIONS: These results suggest that asbestos exposure increases the risk of epilaryngeal and hypopharyngeal cancers. It is difficult to reach a conclusion about the effects of mineral wools, because nearly all the exposed subjects were also exposed to asbestos. The possible effects of other MMVF were difficult to assess in this study, because of the paucity of exposed subjects.