Asbestos Fiber Concentrations Research Articles

Exposure to airborne asbestos in thermal power plants in Mongolia.

Coal-fired thermal power plants (TPPs) in Mongolia use various types of asbestos-containing materials (ACMs) in thermal insulation of piping systems, furnaces, and other products. To investigate the occupational exposure of insulation workers to airborne asbestos in Mongolian power plants. Forty-seven air samples were collected from four power plants in Mongolia during the progress of insulation work. The samples were analyzed by phase contrast microscopy (PCM) and transmission electron microscopy (TEM). The average phase contrast microscopy equivalent (PCME) asbestos fiber concentration was 0·93 f/cm(3). Sixteen of the 41 personal and one of the area samples exceeded the United States Occupational Safety and Health Administration (US OSHA) short-term exposure limit of 1·0 f/cm(3). If it is assumed that the short-term samples collected are representative of full-shift exposure, then the exposures are approximately 10 times higher than the US OSHA 8-hour permissible exposure limit of 0·1 f/cm(3). Power plant insulation workers are exposed to airborne asbestos at concentrations that exceed the US OSHA Permissible Exposure Limit. Action to mitigate the risks should be taken in Mongolia.

공기 중 석면농도 분석시 관상어용 기포발생기를 개조한 장치와 기존의 상업용 시료 채취기와의 성능 비교

Objectives: The purpose of this study is to estimate the applicability of regional sample collection of environmental samples. The concentration of asbestos fibers were analyzed with two devices. One was an existing commercial air sampling pump that has been proved to be accurate and exact, and the other is a remodeled pump for sample collection which was made from an electric bubble generator originally designed for aquarium fish. Samples were collected with the two devices under the same environmental conditions and collection equipment. A comparative analysis of the concentration of ambient asbestos fiber was then performed. Methods: Based on previous research, six farmhouses with asbestos fiber slate roofs known to have high concentrations of asbestos fiber were selected. Using the existing commercial air sampling pump and the remodeled electric bubble generator, four to seven samples were collected each day one meter downwind from the edge of the slate roof at high volume (about 4 L/min) and low volume (about 1.4 L/min). The analyzer responsible for sample quality control of asbestos fibers counted the number of asbestos fibers with a phase microscope. Results: The rates of flow change of the existed sampler and the remodeled pump at high volume were 0.82% and 0.17%, respectively. The rates of flow change at low volume were 3.83% and 1.09%, but there was not significant difference. The rates of flow change are within the error range (<TEX>${\pm}5%$</TEX>) of OSHA analyzing methods. For the high volume sampler, the average asbestos fiber concentration in the air collected by the existed sampler is 6.270 fibers/L and for the remodeled one 5.527 fibers/L, not a significant difference. For the low volume sampler, the average asbestos fiber concentration in the air collected by the existed sampler is 7.755 fibers/L and for the remodeled one 7.706 fibers/L, not a significant difference. The total area of the slate roof of the targeted farmhouse has an effect on the concentration of asbestos fibers in the air from the existing pump and the remodeled one (p<0.01). Conclusions: The sampling function between the existing commercial pump and the remodeled one shows little difference. Therefore, the remodeled pump is considered a pump with a good availability for collecting ambient air asbestos samples.

Pulmonary fibrosis following household exposure to asbestos dust?

An 81-year-old woman was dying from histologically confirmed pulmonary fibrosis without having had any asbestos exposure in the workplace. The lung dust fibre analysis showed significantly increased “asbestos bodies” (AB) (2,640 AB per gram of wet lung tissue) and asbestos fibre concentrations (8,600,000 amphibole fibres of all lengths and 540,000 amphibole fibres with a length ≥5 μm per gram of dry lung tissue). Asbestos exposure was revealed to have occurred during household contact after 27 years of washing her husband’s industrial clothing that had been contaminated by asbestos at his workplace in an asbestos textile factory. Household asbestos dust exposure as a risk or co-factor in the aetiology of the fatal pulmonary fibrosis is discussed.

Study on the concentration of airbone respirable asbestos fibres in rural areas of the Lublin region in south-east Poland.

The objective of the study was measurement of the concentrations of airborne asbestos fibres in the rural environment of the Lublin Region in south-east Poland. Measurements of concentrations of respirable asbestos fibres were carried out in the rural areas of the Lublin Region (Lublin and Włodawa counties) for a period of 24 months. The studies were conducted on 3 farms with various technical conditions of asbestos-containing materials: Farm A - good technical condition of asbestos products, Farm B - poor technical condition, and Farm C - with no asbestos containing products and no such products in its direct vicinity (up to 500 m). On the selected farms, 3 samples on each were simultaneously collected at 3 measuring sites. During the period 2009-2011, a total number of 216 samples were collected on all farms. Sampling was performed using JSH 16,000 stationary aspirators, with air flow velocity of 16 l/min. and sampling time 60-80 minutes. The number of fibres on filters was determined using an optical phase contrast microscope. The study showed that the mean concentration of respirable asbestos fibres on the farms examined was 296 fibres•m (-3). The highest concentrations were noted on Farm B was 529 fibres•m (-3), on average; on farm A the mean concentration of respirable fibres was 328 fibres•m (-3), whereas the lowest mean concentration of airborne respirable asbestos fibres was noted on farm C, where there were no asbestos products (30 fibres•m(-3)).

Analysis of Asbestos Concentration in 20 Cases of Pseudomesotheliomatous Lung Cancer

Mesothelioma is a rare neoplasm caused by asbestos exposure. The majority of mesotheliomas arise from the pleural lining of the thoracic cavity, but also involve the peritoneal and pericardial cavities. Another type of neoplasm referred to as pseudomesotheliomatous adenocarcinoma is rare. Most “pseudomesotheliomas” arise in the pleural tissue of the chest cavity and resemble pleural mesotheliomas, macroscopically and histologically. While most arise in the pleura, there are some that metastasize to the pleura from another site. We evaluated asbestos fiber concentrations in 20 cases of pseudomesotheliomatous lung cancer and found a significant number to contain an elevated concentration of asbestos in their lung tissue, which is similar with our study of 55 mesothelioma cases published in 1997. This would provide evidence that some pseudomesotheliomatous lung cancers are caused by asbestos.

Artificial and Biological Particles in the Springtime Atmosphere

This study focused on a comprehensive and detailed interpretation for the springtime air quality influenced by both artificial (particulate matter (PM) and asbestos) and biological (pollen) sources in Fukuoka Prefecture, Japan. An intensive measurement of PM was conducted at four characteristic sites (i.e., a heavy traffic area, a residential area, an industrial area, and a desolate area) in the Fukuoka Prefecture during spring of 2007. Analysis of major ionic species in <TEX>$PM_{2.5}$</TEX> was performed by an Ion Chromatography, and asbestos and pollen were identified by Scanning Electron Microscopy with an energy dispersive X-ray spectrometer (EDX). <TEX>$PM_{2.5}$</TEX> concentration (<TEX>$65.3{\mu}gm^{-3}$</TEX>) measured in an industrial area (site C) was extraordinarily high compared to those monitored in other areas; it greatly exceeded the Japan's <TEX>$PM_{2.5}$</TEX> criteria (a daily average of <TEX>$35{\mu}gm^{-3}$</TEX>). NOAA's HYSPLIT dispersion model suggests that this high level of <TEX>$PM_{2.5}$</TEX> monitored at site C is unlikely to affect the Asian continent. The ambient concentrations of <TEX>$PM_{2.5}$</TEX>-related anions (<TEX>$NH_4{^+}$</TEX>, <TEX>$NO_3{^-}$</TEX>, and <TEX>$SO_4{^{2-}}$</TEX>) and their relative contributions to <TEX>$PM_{2.5}$</TEX> were also investigated in four study areas. The concentrations of these major water-soluble ions exhibit not only strong spatial dependence but also different ratios to each other. Asbestos fiber (crocidolite and amosite) concentration values changed in the range of 2.5 to 14.4 f per liter of air. The number of pollen grains showed that Cedar ranked higher in concentration than other types of pollen, with the maximum concentration at site A.

Trends in Asbestos and Non-asbestos Fibre Concentrations in the Lung Tissues of Japanese Patients with Mesothelioma

We aimed to elucidate changes in asbestos and non-asbestos fibre concentrations in the lung tissues of Japanese patients with mesothelioma over time. Lung tissues were obtained from 46 patients with mesothelioma who died or underwent surgery between 1971 and 2005. All of the patients had a history of occupational asbestos exposure. We classified patients into four groups according to the period during which their lung tissue was obtained. Asbestos and non-asbestos fibre concentrations were determined by transmission electron microscopy with energy-dispersive X-ray analysis using a low-temperature ashing procedure. From the 1970s to the 2000s, we observed a decrease in the geometric mean of total asbestos concentration (67.4-1.05 million fibres per gram dry lung), chrysotile concentration (25.0-0.66 million fibres per gram dry lung), amphibole asbestos concentration (21.3-0.76 million fibres per gram dry lung), and non-asbestos fibre concentration (326-19.3 million fibres per gram dry lung). The mean duration of asbestos exposure decreased from 33.7 to 17.6 years, and the mean duration since the last exposure increased from 0.3 to 21.5 years. The percentage of longer fibres to total fibres tended to increase over time, whereas the mean fibre length did not differ significantly. The present study suggested that asbestos and non-asbestos fibre concentrations in the lung tissues of Japanese patients with mesothelioma who have occupational histories of asbestos exposure may have decreased from the 1970s to the 2000s.

Ambient monitoring of airborne asbestos in non-occupational environments in Tehran, Iran

Airborne asbestos fiber concentrations were monitored in the urban areas of Tehran, Iran during the period of 23 August to 21 September 2012. The airborne fiber concentrations of 110 air samples collected from 15 different sites in five regions of Tehran. The monitoring sites were located 2.5 m above ground nearby the main street and heavy traffic jam. The ambient air samples were analyzed using scanning electron microscopy (SEM), with energy-dispersive X-ray analysis and phase-contrast optical microscopy (PCM). The geometric means of the airborne asbestos fiber concentrations in the outdoor living areas was 1.6 × 10−2 SEM f ml−1 (1.18 × 10−3 PCM f ml−1). This criteria is considerably higher than those reported for the levels of asbestos in outdoor living areas in the Europe and the non-occupational environment of the Korea. No clear correlation was found between asbestos fiber concentration and the relative humidity and temperature. The SEM and PLM analysis revealed that all samples examined contained only chrysotile asbestos. It can be concluded that several factor such as heavy traffic, cement sheet and pipe consumption of asbestos, and geographical conditions play an important role for the high airborne asbestos levels in the non-occupational environments.

The analysis of asbestos count data with “nondetects”: The example of asbestos fiber concentrations in the lungs of brake workers

In the analysis of tissue for asbestos fibers, some measurements may be below the analytical detection limit (nondetects). The use of maximum likelihood and survival analysis methods have been recommended to perform comparisons between subjects in the presence of nondetects. When the data consist of "counts" another method is useful. This method is discussed, and illustrated with an analysis of asbestos lung burden data among brake mechanics previously analyzed by other methods. Statistical models for count data, namely Poisson and negative binomial regression, were used to compare the asbestos fiber concentrations in the lungs of brake mechanics with those of control subjects. The fit of the models was assessed with an analysis of residuals. The negative binomial regression models fit the data well. The concentrations of Quebec asbestos fibers in the lungs of the brake mechanics were significantly higher than in the control population. Helsel recommended the use of maximum likelihood and survival analysis methods to perform comparisons in the presence of nondetects. When analyzing asbestos fiber count data, or other count data arising in occupational or environmental health, the use of models such as the Poisson and negative binomial may be added to the analyst's toolbox. Benefits are that neither of these methods requires the substitution of arbitrary values for the nondetects and that programs for the computation of count data models are contained in popular statistical software packages.

Abstract 627: Fiber-induced DNA damage response in human lung epithelial cells.

Abstract Asbestos, a group of naturally occurring mineral fibers, is a significant lung carcinogen. Exposure to asbestos fibers induces the formation of reactive oxygen species in cells and, subsequently, DNA double-strand breaks (DSBs), the most serious form of DNA damage related to transformation of cells. As a part of the DNA damage response, H2AX histone variant molecules are phosphorylated at ser139, producing γH2AX foci at the site of DSBs, and these serve as a docking site for DNA repair molecule complexes. Thereby, γH2AX foci are considered a sensitive marker for DSBs. DNA damage response has not thoroughly been investigated in particle carcinogenesis. Here, we studied fiber-induced DSB formation in two human lung epithelial cell lines, the cancer cell line A549 and the transformed cell line BEAS-2B to provide further knowledge on DNA damage associated with fiber exposure as a risk factor for lung cancer.A sub-lethal asbestos fiber concentration of 2 μg /cm2 was determined, by cell viability tests, as suitable for working with the A549 and BEAS-2B cells. Then, we studied the kinetics of fiber induced DSB formation in terms of H2AX phosphorylation. Foci of γH2AX can be detected using specific antibody in immunocytochemistry assays. A549 and BEAS-2B cells were exposed to asbestos fibers for 4, 24 and 48 h, and γH2AX foci were counted. Concurrent non-exposed control cultures were settled at each time point. At 4 h, the control group displayed remarkable endogenous DSB formation, possibly due to replication stress. In exposed cultures, the formation of γH2AX foci peaked at 24 h. We also explored whether it is possible, by using γH2AX antibody in a chromatin immunoprecipitation followed by next generation sequencing, to find out the distribution of DSBs at 24 h in the fiber-exposed A549 cells. The sequences involved in γH2AX foci were genome-widely distributed. To conclude, the kinetics of fiber-induced γH2AX foci formation in the A549 and BEAS-2B cells was partly interfered by endogenously formed DSBs. This study revealed sequences that may be implicated within γH2AX foci for further elucidation on their contribution to lung tumor progression in particle carcinogenesis. Citation Format: Eeva Kettunen, Päivi Tuominen, Satu Suhonen, Julia Catalán, Sisko L. Anttila, Penny Nymark, Hannu Norppa. Fiber-induced DNA damage response in human lung epithelial cells. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 627. doi:10.1158/1538-7445.AM2013-627

Asbestos Imaging and Detection with Differential Interference Contrast Microscopy

This study presents a new method for imaging and counting the concentration of asbestos fibers. This approach combines the principle of differential interference contrast (DIC) microscopy for imaging fibers with an imaging program to automatically assess their concentration. Asbestos is typically detected by optical microscopy or electron microscopy methods. While optical microscopy techniques (such as phase contrast microscopy and polarized light microscopy) are fast and inexpensive, they cannot ensure a thorough examination due to their low resolutions. In contrast, electron microscopy methods (such as transmission electron microscopy and scanning electron microscopy) provide high resolutions images, but are expensive and the related technology is not widely available.This work thus proposes the DIC method for detecting asbestos fibers, as it can overcome many of the disadvantages of existing methods. It also has good potential for use in portable measuring devices, which can detect asbestos right at the location of possible exposure.

Concentrations of asbestos fibers and metals in drinking water caused by natural crocidolite asbestos in the soil from a rural area

Asbestos fibers and metals in drinking water are of significant importance to the field of asbestos toxicology. However, little is known about asbestos fibers and metals in drinking water caused by naturally occurring asbestos. Therefore, concentrations of asbestos fibers and metals in well and surface waters from asbestos and control areas were measured by scanning electron microscopy (SEM), inductively coupled plasma (ICP) optical emission spectrometer, and ICP-mass spectrometry in this study. The results indicated that the mean concentration of asbestos fibers was 42.34 millions of fibers per liter by SEM, which was much higher than the permission exposure level. The main compositions of both asbestos fibers in crocidolite mineral and in drinking water were Na, Mg, Fe, and Si based on energy dispersive X-ray analysis. This revealed that the drinking water has been contaminated by asbestos fibers from crocidolite mineral in soil and rock. Except for Cr, Pb, Zn, and Mn, the mean concentrations of Ni, Na, Mg, K, Fe, Ca, and SiO2 were much higher in both surface water and well waters from the asbestos area than in well water from the control area. The results of principal component and cluster analyses indicated that the metals in surface and well waters from the asbestos area were significantly influenced by crocidolite mineral in soil and rock. In the asbestos area, the mean concentrations of asbestos fibers and Ni, Na, Mg, K, Fe, Ca, and SiO2 were higher in surface and well waters, indicating that asbestos fibers and the metals were significantly influenced by crocidolite in soil and rock.

Gibt es Unterschiede in den gesundheitsschädlichen Wirkungen von Chrysotil- und Amphibol-Asbest?

Due to the current query whether the predominantly used chrysotile (white) asbestos comprises health risks we performed a literature search including in vitro and animal experiments as well as epidemiological studies.As shown by epidemiological studies chrysotile causes less pleural fibrosis and mesotheliomas when compared with other asbestos types. However, its otherwise inflammatory, toxic, carcinogenic, and fibrosis-inducing effects correspond to those of other occupationally relevant asbestos types. This is based on clinical, animal as well as on in-vitro findings. This means that denying a causal relationship, e. g. in a case with lung fibrosis (= asbestosis) or lung cancer with an asbestos load of 25 fiber-years in the absence of identification of a significant concentration of asbestos fibers or asbestos bodies in the lung (see so-called "hit and run" phenomenon), contradicts the medical-scientific knowledge.

Environmental asbestos pollution — Situation in Poland

Environmental exposure of the general population to asbestos in Poland is mainly due to degradation of very popular asbestos-cement products and the resultant release of the elementary asbestos fibres into the ambient air. Assessments of environmental pollution by asbestos were based on the volume of the raw material used, amount of manufactured asbestos products, and measuring the concentration of fibres in the air. Under the governmental program intended to remove asbestos, measurements of the concentration of asbestos fibres were performed in 2004-2010 in all provinces of Poland. Considering that potential sources of asbestos dust emissions were present in residential areas, 1634 sampling sites were designated. From 2 to 4 air samples were collected at each sampling site. A total of 5962 samples were collected during seven years. A single dose of air collected by 25 mm 0.8 μm pore Sartorius filter was 1,300 litres. The fibres were counted using optical microscopy with phase contrast (PCM) on a polarizing microscope (PLM) at a total magnification of 600×.; method was adapted to determine the concentration of asbestos fibres in non-occupational environment. Mean concentration of asbestos fibres was 492 f/m(3) (95% CI: 467-518). In 82% of the sampling sites, the mean concentrations did not exceed 800 f/m(3). As much as 25.8% of the samples were found to be below the detection limit of the method. Estimated mean concentrations of fibres in different provinces ranged from 146 (95% CI: 106-203) to 709 f/m(3) (95% CI: 591-851). In the areas affected by former asbestos-processing plants, mean concentration was 732 f/m(3) (95% CI: 527-1016) and was significantly higher than levels recorded in other areas of Poland. Asbestos consumption per capita and the recorded moderate levels of asbestos fibres concentration in atmospheric air point to a relatively low level of environmental asbestos pollution in Poland.

Airborne Crocidolite Asbestos Fibers in Indoor and Outdoor Air in a Rural Area, China

Forty-eight air samples were collected in a rural area of China. The concentrations of asbestos fibers in the samples were determined by phase contrast microscopy and scanning electron microscopy in combination with energy-dispersion X-ray analysis. The mean concentrations of asbestos fibers in indoor and outdoor air samples were 0.0038 and 0.0037 f/mL, respectively. The fiber concentration was higher in areas in which outcrop crocidolite asbestos is present in the soil than in areas lacking this feature. Airborne asbestos fibers in the study area might be attributable to the weathering of natural outcrop crocidolite asbestos and the impact of human activities on crocidolite asbestos-containing soils. About 50% of the total asbestos fibers in both indoor and outdoor air samples were ≥ 5 to ≤ 10 µm long. Scanning electron microscopy showed that the crocidolite asbestos fibers were mostly thinner than 0.25 μm. At present, asbestos-containing soils are rarely used to produce asbestos stoves, pave roads, construct houses, or paint walls. However, asbestos fibers are continuously released into the air from these soils, due to natural weathering and human activities, and local residents are thus exposed to asbestos fibers throughout their lifetimes, and thus their health might be adversely affected by long-term inhalation of the fibers.

Identification and Counting of Asbestos and Non-Asbestos Fibers in an Automobile Brake Manufacturing Industry

This study was performed to identify and count both asbestos and non-asbestos fibers during brake manufacture in Iran. A total of 56 respiratory air samples of personnel were measured by phase-contrast microscopy (PCM) and scanning electron microscopy (SEM). The fiber type and its chemical composition were also evaluated by SEM and energy-dispersive X-ray analysis (EDX). Monitoring of total fiber levels demonstrated that its ranges are from 0.23 to 1.50 PCM f/ml. The geometric mean and standard deviation of the airborne asbestos and non-asbestos fiber concentrations were 0.22(1.61) and 0.32(1.61) SEM f/ml respectively. The observed asbestos fiber concentrations in many processes were higher than the threshold limit value (TLV) which is proposed by American Conference of Governmental Industrial Hygienists (ACGIH), as equal as 0.1 f/ml. Based on these findings, the geometric means of the non-asbestos concentrations were considerably lower than TLV of the ACGIH which is 1 f/ml. The SEM data exhibited that fibrous particle consists of chrysotile (40%) and rock wool (60%). It can be concluded that more than 50% of airborne fibers inhaled by the workers were rock wool with fibers greater than 1 μm in diameter. For evaluation of airborne fibers, the PCM method was not able to detect the fibers lower than 0.25 micrometer. This study demonstrated that SEM technique methods are essential elements for accurate characterization of mineral dusts, particularly when dealing with large number of samples.

Asbestos fiber concentrations in the lungs of brake repair workers: commercial amphiboles levels are predictive of chrysotile levels

Objectives: To investigate the impact of extreme data points in Finkelstein’s 2009 findings of no association between lung levels of commercial and non-commercial amphiboles (principally tremolite as a marker for chrysotile asbestos) in brake repair workers with mesothelioma.Methods: We first identified potential outliers, high leverage points, and influential points among lung levels of commercial amphiboles and tremolite among 15 persons whose only known exposure to asbestos was through brake repair work. We used sensitivity analysis and quantile regression to account for extreme data points and model commercial amphibole levels as a predictor of tremolite levels. We also used quantile regression to evaluate whether case-reported duration of employment as a brake repair worker predicted lung levels of commercial amphiboles or tremolite.Results: We found lung levels of commercial amphiboles are a statistically significant predictor of tremolite levels via sensitivity analysis (r = 0.82, slope estimate P-value = 0.001, R2 = 0.68) and quantile regression (slope estimate P-value <0.0001). Our data provide no evidence that duration of employment as a brake repair worker was a predictor of lung levels of tremolite or commercial amphiboles.Conclusions: Our findings suggest that elevated lung levels of tremolite in the lungs of brake repair workers with elevated levels of amphiboles arose from concurrent exposures to commercial amphibole and chrysotile asbestos in occupational settings other than brake repair work. These findings are supported by five new cases. The weight of the scientific evidence does not support a role for occupational exposure to brake dust and other friction products in the development of mesothelioma.

Counting Rules for Estimating Concentrations of Long Asbestos Fibers

Mounting evidence that long asbestos fibers (e.g. >20 or even 40 μm) pose the greatest cancer risk underscores the need for accurate measurement of concentrations of such fibers. These fiber lengths are of the same order of magnitude as the size of openings in the grids (typically ≈90 μm per side) used to analyze asbestos samples by transmission electron microscopy. This means that a substantial proportion of long fibers will cross the edge of a grid opening (GO) and therefore not be completely visible. Counting rules generally deal with such fibers by assigning a length equal to twice the visible length. Using both theoretical and simulation methods, we show that this doubling rule introduces bias into estimates of fiber concentrations and the amount of bias increases with fiber length. We investigate an alternative counting rule that counts only fibers that lie completely within a GO and weights those fibers by the reciprocal of the probability that a fiber of that length lies totally within a GO. This approach does not have the bias inherent in the doubling rule and is essentially unbiased if the stopping rule specifies a fixed number of GOs to be scanned. However, a stopping rule based on successively scanning GOs until a fixed number of fibers have been counted will introduce bias into any counting method, although this bias may typically not be large enough to be of practical concern. We recommend use of the weighted approach as a supplement to use of the doubling rule when estimating concentrations of long fibers, irrespective of the stopping rule employed.

Asbestos Concentrations and Lung Restrictive Patterns

Asbestos applications were limited during past two decades in developed nations due to its debilitating health problems, while in developing countries it’s various usages continues. The main goals of present study were evaluation of asbestos concentrations in ambient outdoor and indoor air and occupational exposure, as well as exposure effects on pulmonary function. Sampling procedure was carried out during May and June 2010 at four outdoor and seven indoor air sampling stations. Ten persons were selected based on their exposure limits including high, moderate and low exposure. Also to assess pulmonary function of workers, 42 spirometry cases were tested. Samples were analyzed by SEM with EDXA. Obtained results revealed that average concentrations of asbestos fibers were 1.885×10-5 f/mL and 0.065 f/mL in outdoor and indoor air, respectively. Occupational exposure contents were between 1.5 ×10-5 – 0.2 f/mL (based on exposure limits). Spirometry tests showed that 28% of workers had impaired lung functions. Lung restrictive pattern in workers were 2% severe, 12% moderate and 14%. Results showed pattern of fibrous particles as actinolite> termolite> chrysotile in indoor air. Generally, it is clear that there is positive meaningful relationship between more than ten occupational ages and malfunction of lungs in studied workers due to asbestos effects.

Assessment of airborne asbestos exposure at an asbestos cement sheet and pipe factory in Iran

Iran imports nearly 55,000 metric tons of asbestos per year, and asbestos cement (AC) plants contribute nearly 94% of the total national usage. In the present study, asbestos fiber concentrations during AC sheet and pipe manufacturing were measured by phase-contrast microscopy (PCM) and polarized light microscopy (PLM) in 98 personal air samples. The fiber type and its chemical composition were also evaluated by scanning electron microscopy (SEM) and energy-dispersive X-ray analysis (EDX). Personal monitoring of fiber levels indicated a range from 0.02 to 0.55 PCM f/ml (0.02–0.69 PLM f/ml). The AC workers’ geometric mean asbestos exposure was 0.09 PCM f/ml (0.11 PLM f/ml), with arithmetic mean of 0.13 PCM f/ml (0.16 PLM f/ml). The observed fiber concentrations in many processes were higher than the threshold limit value (TLV) proposed by the American Conference of Governmental Industrial Hygienists (ACGIH), which is 0.1 f/ml. Based on these findings, the PLM values were approximately 25% higher than PCM values. The SEM data demonstrate that fibrous particles contained chrysotile. The thinnest fiber recognized by SEM had a diameter of 0.2 μm. Mean exposure exceeded the TLV for asbestos in pipe molding and finishing (100%) as well as sheet molding and finishing (45.5–83.3%). In conclusion exposure control may be needed to be in compliance with the ACGIH TLV and other guidance levels. Also, with regard to PCM limitations for airborne fiber analysis, the use of microscopic methods other than PCM can be used to improve the techniques used presently.