Asbestos in water sources of the Bazhenovskoye chrysotile asbestos deposit

The paper provides measurements of asbestos fiber levels in water sources from the area of the Bazhenovskoye chrysotile asbestos deposit. All study water samples contained asbestos fibers at concentrations one to three orders below the values standardized in the USA (7 x 10(6) fibers/liter). All the identified fibers belonged to chrysotile asbestos and no amphibole asbestos, such as tremolite asbestos, has been identified. The anthropogenic load of asbestos fibers in Asbest City's environment is increasing in the volume of 5.770 x 10(14) fibers/liter or 10.2 kg of chrysotile asbestos. The authors consider it advisable to continue studies to measure asbestos levels in the water sources in the areas located in the vicinity of other Russian asbestos deposits.     

Amphibole fibres in Chinese chrysotile asbestos

Ten chrysotile bulk samples originating from six Chinese chrysotile mines were studied for amphibole fibres. Five of the mines operate on ultramafic rocks whereas one exploits a dolomite-hosted deposit. The asbestos fibre content in lung tissue was examined from seven deceased workers of the Shenyang asbestos plant using these raw materials. The bulk samples were pretreated with acid/alkali-digestion, and thereafter, scanning and transmission electron microscopy, X-ray microanalysis, selected area electron diffraction and X-ray powder diffractometry were used to identify the minerals. Sample preparation of lung tissue involved drying and low-temperature ashing.All of the bulk samples contained amphibole fibres as an impurity. The amphibole asbestos contents were between 0.002 and 0.310 w-%. Tremolite fibres were detected in every sample but anthophyllite fibres were present only in the sample originating from the dolomite-hosted deposit. In comparison, anthophyllite (71%), tremolite (9%) and chrysotile (10%) were the main fibre types in the lung tissue samples indicating faster pulmonary clearance of chrysotile fibres. The total levels ranged from 2.4 to 148.3 million fibres (over 1 microm in length) per gram of dry tissue, and they were consistent with heavy occupational exposure to asbestos.     

Mineral fibres, fibrosis, and asbestos bodies in lung tissue from deceased asbestos cement workers

Lung tissue from 76 deceased asbestos cement workers (seven with mesothelioma) exposed to chrysotile asbestos and small amounts of amphiboles, has been studied by transmission electron microscopy, together with lung tissue from 96 controls. The exposed workers with mesothelioma had a significantly higher total content of asbestos fibre in the lungs than those without mesothelioma, who in turn, had higher concentrations than the controls (medians 189, 50, and 29 x 10(6) fibres/g (f/g]. Chrysotile was the major type of fibre. The differences were most pronounced for the amphibole fibres (62, 4.7, and 0.15 f/g), especially crocidolite (54, 1.8 and less than 0.001 f/g), but were evident also for tremolite (2.9, less than 0.001, and less than 0.001 f/g) and anthophyllite (1.7, less than 0.001, and less than 0.001 f/g). For amosite, there was no statistically significant difference between lungs from workers with and without mesothelioma; the lungs of workers had, however, higher concentrations than the controls. Strong correlations were found between duration of exposure and content of amphibole fibres in the lungs. Asbestos bodies, counted by light microscopy, were significantly correlated with the amphibole but not with the chrysotile contents. Fibrosis was correlated with the tremolite but not the chrysotile content in lungs from both exposed workers and controls. Overall, similar results were obtained using fibre counts and estimates of mass.     

Mineral fibres, fibrosis, and asbestos bodies in lung tissue from deceased asbestos cement workers.

Lung tissue from 76 deceased asbestos cement workers (seven with mesothelioma) exposed to chrysotile asbestos and small amounts of amphiboles, has been studied by transmission electron microscopy, together with lung tissue from 96 controls. The exposed workers with mesothelioma had a significantly higher total content of asbestos fibre in the lungs than those without mesothelioma, who in turn, had higher concentrations than the controls (medians 189, 50, and 29 x 10(6) fibres/g (f/g]. Chrysotile was the major type of fibre. The differences were most pronounced for the amphibole fibres (62, 4.7, and 0.15 f/g), especially crocidolite (54, 1.8 and less than 0.001 f/g), but were evident also for tremolite (2.9, less than 0.001, and less than 0.001 f/g) and anthophyllite (1.7, less than 0.001, and less than 0.001 f/g). For amosite, there was no statistically significant difference between lungs from workers with and without mesothelioma; the lungs of workers had, however, higher concentrations than the controls. Strong correlations were found between duration of exposure and content of amphibole fibres in the lungs. Asbestos bodies, counted by light microscopy, were significantly correlated with the amphibole but not with the chrysotile contents. Fibrosis was correlated with the tremolite but not the chrysotile content in lungs from both exposed workers and controls. Overall, similar results were obtained using fibre counts and estimates of mass.     

Asbestos bodies and the diagnosis of asbestosis in chrysotile workers

It has been suggested that because chrysotile asbestos forms asbestos bodies poorly, use of the traditional histologic requirements (diffuse interstitial fibrosis plus asbestos bodies) for the diagnosis of asbestosis, may lead to an underdiagnosis of this condition in workers exposed only to chrysotile. We examined lungs from 25 chrysotile miners with diffuse interstitial fibrosis. Asbestos bodies were found easily in histologic section using hematoxylin and eosin stains in all cases. Mineralogic analysis of four cases showed that 46 of 72 (64%) bodies isolated and examined contained chrysotile cores, and 21 of 72 (29%) bodies contained cores of the amphiboles tremolite and actinolite. By contrast, tremolite and actinolite constituted the majority of uncoated fibers in these cases. The mean length for bodies formed on chrysotile was 35 micron, and for bodies formed on tremolite or actinolite, 36 micron. We conclude that (1) the usual histologic criteria for the diagnosis of asbestos are applicable to chrysotile-exposed workers; (2) in workers with occupational chrysotile exposure, bodies form readily on this mineral; and (3) asbestos bodies in these lungs reflect the presence of long asbestos fibers.     

Evaluation of asbestos exposure during brake repair and replacement

Occupational exposure to asbestos fiber of brake repair job (auto mechanics) has seldom been evaluated in Iran. Accordingly, we evaluated asbestos fiber concentrations in the breathing zone of auto mechanics between July 2008 and December 2008. The asbestos fiber concentrations of 60 personal air samples collected from 30 cars and trucks brake replacement and they were analyzed by phase-contrast optical microscopy (PCM) and scanning electron microscopy (SEM) by energy-dispersive X-ray analysis. The geometric means of the personal monitoring fiber concentrations were 0.92 PCM f/ml and 0.46 PCM f/ml respectively in car and passenger heavy truck auto shops. There was a significant differences in the asbestos fiber concentrations between the car and truck auto shops (p=0.006). Based on these findings, auto mechanics who worked with asbestos containing brake may have been exposed to asbestos concentrations approximately 7 times higher than the current occupational safety and health agency (OSHA) permissible exposure limit (PEL) of 0.1 f/ml. Fiber morphology and energy dispersive X-ray analysis by SEM revealed that amphibole fibers such as tremolite and actinolite existed in the brakes dust and that the vast majority (>30%) of the airborne chrysotile fibers were greater than 1 μm in diameter. It can be concluded that the imported chrysotile asbestos contains trace amounts of tremolite and actinolite fibers and they are responsible for the high airborne asbestos levels and occupational exposure to amphibole asbestos in auto mechanics job in Iran. Thus, it is to be expected that the auto mechanics will suffer negative health effects due to exposure to the serpentine and amphibole asbestos fibers.     

Fibers in lung tissues of mesothelioma cases among miners and millers of the township of asbestos,quebec

Twenty cases of mesothelioma among miners of the township of Asbestos, Quebec, Canada, have been reported. To further explore the mineral characteristics of various fibrous material, we studied the fibrous inorganic content of postmortem lung tissues of 12 of 20 available cases. In each case, we measured concentrations of chrysotile, amosite, crocidolite, tremolite, talc-anthophyllite, and other fibrous minerals. The average diameter, length, and length-to-diameter ratio of each type of fiber were also calculated. For total fibers > 5 μm, we found > 1,000 asbestos fibers per mg tissue (f/mg) in all cases; tremolite was above 1,000 f/mg in 8 cases, chrysotile in 6 cases, crocidolite in 4 cases, and talc anthophyllite in 5 cases. Among cases with asbestos fibers, the tremolite count was highest in 7 cases, chrysotile in 3 cases, and crocidolite in 2 cases. The geometric mean concentrations of fibers ? 5 μm were in the following decreasing order: tremolite > crocidolite > chrysotile > other fibers > talc-anthophyllite > amosite. For total fibers < 5 μm, we found > 1,000 fibers per mg tissue (f/mg) in all cases; tremolite was above 1,000 f/mg in 12 cases, chrysotile in 8 cases, crocidolite in 7 cases, and talc-anthophyllite in 6 cases. Tremolite was highest in 8 cases, chrysotile in 2 cases, and crocidolite and amosite in 2 cases. The geometric mean concentrations of fibers < 5 μm were in the following decreasing order: tremolite > other fibers > chrysotile > crocidolite > talc-anthophyllite > amosite. We conclude, on the basis of the lung burden analyses of 12 mesothelioma cases from the Asbestos township of Quebec, that the imported amphibole (crocidolite and amosite) were the dominant fibers retained in the lung tissue in 2/12 cases. In 10/12 cases, fibers from the mine site (chrysotile and tremolite) were found at highest counts; tremolite was clearly the highest in 6, chrysotile in 2, and 2 cases had about the same counts for tremolite and chrysotile. If a relation of fiber burden-causality of mesothelioma is accepted, mesothelioma would be likely caused by amphibole contamination of the plant in 2/12 cases and by the mineral fibers (tremolite and chrysotile) from the mine site in the 10 other cases.     

Asbestos concentration and fiber size in lungs of the urban residents]

Asbestos fiber concentrations and fiber size distribution in lung tissues of 53 urban residents (males: 34, female: 19) were analyzed by low temperature ashing-analytical transmission electronmicroscopy. The following findings were obtained. 1. Pulmonary asbestos fibers were found in 51 out of 53 patients. The types of asbestos fibers were chrysotile, amosite, crocidolite, actinolite and tremolite. 2. Thirty-six of 53 patients had no history of occupational asbestos exposure, and their geometric mean concentration of asbestos fibers was 1.67 x 10(6) fibers/g dry lung. Most of these asbestos fibers are probably attributable to general environmental contamination. Thirteen patients who had a history of occupational asbestos exposure showed a geometric mean of their pulmonary asbestos concentrations (5.82 x 10(6) fibers/g dry lung) which was significantly higher than that of patients without occupational asbestos exposure (p less than 0.01). 3. The geometric mean concentration of asbestos fiber in males (2.70 x 10(6)) was higher than in females (1.59 x 10(6)), probably due to a difference in the occupational asbestos exposure between males and females. 4. Regardless of the patient's sex, the geometric mean concentration of asbestos fibers in patients without a history of smoking (male: 4.91 x 10(6), female: 1.78 x 10(6)) was higher than that in patients with a smoking history (male: 2.76 x 10(6), female: 1.37 x 10(6)). The difference, however, was not statistically significant, and no correlation was seen between the concentration of asbestos fibers and smoking history. 5. Although most asbestos fiber utilized in Japan is chrysotile, the geometric mean concentration of chrysotile (0.87 x 10(6)) was almost identical to that of amphibole asbestos fiber (0.90 x 10(6)). 6. Of the asbestos fibers observed, 95% of chrysotile and 85% of amphibole asbestos were less than 5 microns in length and 93% of the total asbestos fibers were too small to be visible by light microscopy.     

Mineral phases and some reexamined characteristics of the international union against cancer standard asbestos samples

Standard asbestos samples to be used for biomedical research were first prepared by the International Union Against Cancer (UICC) in 1966 in the United Kingdom and South Africa. Using modern techniques, X-ray diffractometry, analytical transmission electron microscopy, and thermal analysis, we have now analyzed these UICC samples to determine the mineral compositions (mineral phases) and their respective quantities. UICC chrysotile A (from Zimbabwe) contains 2% fibrous anthophyllite as impurity; chrysotile B (from Canada) does not contain any fibrous impurities, only non-fibrous minerals. UICC amosite and crocidolite are almost pure. UICC anthophyllite has 20–30% talc as impurity. The chemical compositions and fiber size distributions of the UICC asbestos samples have also been determined. The mean widths of the fibers of chrysotile A and B are smaller than those of the amphibole fibers. This agrees well with the earlier results which showed the two chrysotile samples to have a larger respirable fraction than the amphiboles. © 1996 Wiley-Liss, Inc.     

Carcinoma of the colon in asbestos-exposed workers: analysis of asbestos content in colon tissue.

Epidemiological studies have indicated an increased incidence of carcinoma of the colon in asbestos workers. The present study evaluated the colon tissue asbestos burden, by light and electron microscopic analytic techniques, in patients with a history of occupational asbestos exposure and colon cancer. Asbestos fibers and/or asbestos bodies were present in colon tissue from 14 of 44 (31.8%) asbestos workers with colon carcinoma (range 142,199 to 15,231, 543 fibers/g/wet weight, mean 2,517,823). Chrysotile was identified in 9 patients and amosite in 3 patients. Both amosite and chrysotile were found in the colonic wall in one individual. Other forms of asbestos (e.g., crocidolite, tremolite, or anthophyllite) were not found. Asbestos fibers and asbestos bodies were not found in colon tissue from 20 control patients (colon carcinoma and no asbestos exposure). Asbestos fibers frequently enter and reside in the wall of the colon and are often intimately associated with tumor tissue at the site of colon carcinoma in workers with asbestos exposure and colon carcinoma.     

Occupational exposure to asbestos and urinary bladder cancer.

By the use of transmission electron microscopy (TEM) and energy dispersion spectrometry the amount (mean value mean = 191 +/- 94 fibers/mg of tissue) and the type (chrysotile and tremolite) of asbestos fibers have been determined in tissue samples of four bladder cancer patients affected by pulmonary asbestosis, working in the same plant producing asbestos-cement pipes and boards. Similar measurements were carried out on samples of bladder cancers of eight control patients not professionally exposed to asbestos. Only five of them also revealed chrysotile fibers (mean = 151 +/- 196 fibers/mg of tissue). The paucity of the study and control cases and the small quantitative difference between them regarding the presence of infraneoplastic asbestos fibers does not consent us to hypothesize a causal relationship between tumor and occupational exposure.     

Inferences on the kinetics of asbestos deposition and clearance among chrysotile miners and millers

BACKGROUND: The health effects of asbestos are intimately related to the fate of inhaled fibers in the lungs. The kinetics of asbestos fibers have been studied primarily in rodents. The objective of this study was to explore the application of these kinetic models to human autopsy data. METHODS: We analyzed the asbestos fiber content of the lungs of 72 Quebec chrysotile miners and millers and 49 control subjects using analytical transmission electron microscopy. Statistical methods included standard multivariate linear regression and locally weighted regression methods. RESULTS: The lung burdens of asbestos bodies and chrysotile and tremolite fibers were correlated, as were the concentrations of short, medium, and long fibers of each asbestos variety. There were significant associations between the duration of occupational exposure and the burdens of chrysotile and tremolite. The concentration of chrysotile decreased with the time since last exposure but the concentration of tremolite did not. The clearance rate varied inversely with the length of chrysotile fibers. For fibers greater than 10 mu in length the clearance half-time was estimated to be 8 years. CONCLUSIONS: The patterns in our data are compatible with both of the hypotheses suggested from rodent experiments; the existence of a long-term sequestration compartment and overload of clearance mechanisms in this compartment.     

Tremolite and mesothelioma

BACKGROUND: Exposure to chrysotile dust has been associated with the development of mesothelioma and recent studies have implicated contaminating tremolite fibers as the likely etiological factor. Tremolite also contaminates talc, the most common non-asbestos mineral fiber in our control cases. METHODS: We examined 312 cases of mesothelioma for which fiber burden analyses of lung parenchyma had been performed by means of scanning electron microscopy to determine the content of tremolite, non-commercial amphiboles, talc and chrysotile. The vast majority of these patients were exposed to dust from products containing asbestos. RESULTS: Tremolite was identified in 166 of 312 cases (53%) and was increased above background levels in 81 cases (26%). Fibrous talc was identified in 193 cases (62%) and correlated strongly with the tremolite content (P < 0.0001). Chrysotile was identified in only 32 cases (10%), but still correlated strongly with the tremolite content (P < 0.0001). Talc levels explained less of the tremolite deviance for cases with an increased tremolite level than for cases with a normal range tremolite level (22 versus 42%). In 14 cases (4.5%) non-commercial amphibole fibers (tremolite, actinolite and/or anthophyllite) were the only fiber types found above background. CONCLUSIONS: We conclude that tremolite in lung tissue samples from mesothelioma victims derives from both talc and chrysotile and that tremolite accounts for a considerable fraction of the excess fiber burden in end-users of asbestos products.     

Asbestos bodies in bronchoalveolar lavage fluids of brake lining and asbestos cement workers.

Asbestos body (AB) concentrations in bronchoalveolar lavage samples of 15 brake lining (BL) workers exposed only to chrysotile have been determined and compared with those from 44 asbestos cement (AC) workers extensively exposed to amphiboles. The mean AB concentrations (263 +/- 802 and 842 +/- 2086 AB/ml respectively) for those groups did not differ significantly but were much higher than those found in control groups. Analytical electron microscopy of asbestos body cores showed that in the BL group 95.6% were chrysotile fibres whereas in the AC group amphiboles accounted for 93.1%. The size characteristics of the central fibres differed for chrysotile and amphibole AB, the former being shorter and thinner. Examination of repeated bronchoalveolar lavage samples showed that the mechanisms of clearance of chrysotile fibres do not affect AB concentration for at least 10 months after cessation of exposure. It thus appears that routine counting of ABs in BAL allows the assessment of current or recent occupational exposures to asbestos. Exposures to chrysotile lead to AB concentrations comparable with those encountered in exposures to amphiboles.     

Occupational asbestos exposure among respiratory cancer patients in Lithuania

BACKGROUND: Despite intensive use of asbestos, no cancer case has ever been diagnosed as asbestos related in Lithuania. This paper attempts to estimate the proportion of those occupationally exposed to asbestos among respiratory cancer patients. MATERIAL AND METHODS: Occupational exposure to asbestos was assessed retrospectively for 298 lung cancer and four mesothelioma patients, admitted to the Institute of Oncology, Vilnius. The evaluation was based on personal interview data using an internationally established questionnaire covering most likely activities of asbestos exposure at the workplace. Cumulative exposure to asbestos at work was estimated in fiber years. Lung tissue asbestos fiber burden analysis was conducted by scanning transmission electron microscopy on 23 samples. RESULTS: A cumulative asbestos exposure of > or =25 fiber years was found for 10 lung cancer patients (3.4%). They worked in foundries, construction, installation, shipyard, power plant, railway, asbestos cement, glass and chemical industry. In a further 56 lung cancer patients (18.8%) and for one (25%) mesothelioma patient, a cumulative exposure from 5 to 24.9 fiber years was assessed. Asbestos fibers were detected in 18 cases, the burden ranged from 0.1 to 4.1 million fibers/g dry lung tissue; concentrations exceeding 1 million f/g dry lung tissue were found in four cases. All fibers were chrysotile. CONCLUSIONS: Findings indicate that a fraction (3.4%) of the lung cancer cases could be attributed to heavy occupational exposure to asbestos using the Helsinki criterion of > or =25 fiber years. Therefore, approximately 50 lung cancer cases per year in Lithuania could be asbestos-related compensable occupational diseases.     

Asbestos bodies in bronchoalveolar lavage fluids of brake lining and asbestos cement workers

Asbestos body (AB) concentrations in bronchoalveolar lavage samples of 15 brake lining (BL) workers exposed only to chrysotile have been determined and compared with those from 44 asbestos cement (AC) workers extensively exposed to amphiboles. The mean AB concentrations (263 +/- 802 and 842 +/- 2086 AB/ml respectively) for those groups did not differ significantly but were much higher than those found in control groups. Analytical electron microscopy of asbestos body cores showed that in the BL group 95.6% were chrysotile fibres whereas in the AC group amphiboles accounted for 93.1%. The size characteristics of the central fibres differed for chrysotile and amphibole AB, the former being shorter and thinner. Examination of repeated bronchoalveolar lavage samples showed that the mechanisms of clearance of chrysotile fibres do not affect AB concentration for at least 10 months after cessation of exposure. It thus appears that routine counting of ABs in BAL allows the assessment of current or recent occupational exposures to asbestos. Exposures to chrysotile lead to AB concentrations comparable with those encountered in exposures to amphiboles.     

Retention patterns of asbestos fibres in lung tissue among asbestos cement workers.

Retention patterns in lung tissue (determined by transmission electron microscopy and energy dispersive spectrometry) of chrysotile, tremolite, and crocidolite fibres were analysed in 69 dead asbestos cement workers and 96 referents. There was an accumulation of tremolite with time of employment. Among workers who died within three years of the end of exposure, the 13 with high tremolite concentrations had a significantly longer duration of exposure than seven in a low to intermediate category (medians 32 v 20 years; p = 0.018, one sided). Crocidolite showed similar patterns of accumulation. In workers who died more than three years after the end of exposure, there were no correlations between concentrations of amphibole fibres and time between the end of exposure and death. Chrysotile concentrations among workers who died shortly after the end of exposure were higher than among the referents (median difference in concentrations 13 million fibres (f)/g dry weight; p = 0.033, one sided). No quantitative differences in exposure (duration or intensity) could be shown between workers with high and low to intermediate concentrations. Interestingly, all seven workers who had had a high intensity at the end of exposure (> 2.5 f/ml), had low to intermediate chrysotile concentrations at death, whereas those with low exposure were evenly distributed (31 subjects in both concentration categories); hence, there was a dependence between last intensity of exposure and chrysotile concentration (p = 0.014). Among 14 workers with a high average intensity of exposure, both those (n = 5) with high tissue concentrations of chrysotile and those (n = 10) with high tissue concentrations of tremolite fibres had more pronounced fibrosis than those with low to intermediate concentrations (median fibrosis grades for chrysotile: 2 v 1, p = 0.021; for tremolite: 2 v 0.5, p = 0.012). Additionally, workers who died shortly after the end of exposure with high concentrations of chrysotile and crocidolite had smoked more than those with low intermediate concentrations (medians for chrysotile 35 v 15 pack-years, p = 0.030; for crocidolite 37 v 15 pack-years, p = 0.012). The present data indicate that chrysotile has a relatively rapid turnover in human lungs, whereas the amphiboles, tremolite and crocidolite, have a slower turnover. Further, chrysotile retention may be dependent on dose rate. Chrysotile and crocidolite deposition and retention may be increased by tobacco smoking; chrysotile and tremolite by fibrosis.     

Airborne fiber concentration and size distribution of mineral fibers in area with serpentinite outcrops in Aichi prefecture, Japan

Airborne fiber concentrations and size distributions of both asbestos and nonasbestos fibers were determined at property boundaries of 4 serpentinite quarries producing crushed stone (quarry property boundary), 10 sites within 10 km of the area with serpentinite outcrops (serpentinite area), and 2 sites in a reference area. The asbestos was identified in 7 rock and 3 soil samples collected in the serpentinite area. The geometric means of airborne concentrations of asbestos and nonasbestos fibers longer than 0.2 microm in length were: 384 and 447 fibers/liter (f/L) in the quarry property boundary (in operation), 12 and 124 f/L in the quarry property boundary (in closed), 5 and 103 fibers/liter in the serpentinite area, and less than 2 and 59 fibers/liter in the reference area, respectively. There was a significant difference in airborne concentrations of both asbestos and nonasbestos fibers among the areas. Ttremolite/actinolite were found with chrysotile in the stones. Airborne concentrations of tremolite/actinolite were higher than those of chrysotile at the quarry property boundary and in the serpentinite area. Tremolite/actinolite were also found in the soils. There was no significant difference among the areas in the arithmetic means of fiber size distribution of both asbestos and nonasbestos fibers.     

Early response of gastric mucosa to ingested asbestos dust and the dissolution of nickel

The gastric response evoked by asbestos fibers (chrysotile, tremolite, anthophyllite, and amosite) was studied in guinea pigs 6 hours after oral administration. Substantial amounts of nickel were leached from the dusts into the gastric juice, the maximum being with chrysotile. Histopathological examination of stomach and biochemical analysis for total acidity, peptic activity, and the contents of mucin did not reveal any alterations of significance.     

Assessment of airborne asbestos fiber concentrations in urban area of Tehran, Iran

Air quality in ambient outdoor air has seldom been evaluated in Iran. Accordingly, we evaluated airborne asbestos fiber concentrations in the urban environment of Tehran, Iran between January 2006 and March 2007. The airborne fiber concentrations of 80 air samples collected from 40 different sites in five areas of Tehran were analyzed by energy-dispersive X-ray analysis in combination with phase-contrast optical microscopy (PCM) and scanning electron microscopy (SEM). The geometric means of the airborne asbestos fiber concentrations were 3.4 × 10⁻³ PCM f/ml (0.1 SEM f/ml) and 3.3 × 10⁻³ PCM f/ml (0.20 SEM f/ml) according to areas and seasons, respectively. There were significant differences in the asbestos fiber concentrations between the areas and seasons (p = 0.02; p = 0.04), respectively. In the areas, the average concentration was 3.4 × 10 ⁻³ PCM f/ml (0.1 SEM f/ml), which is considerably higher than those reported for the levels of asbestos in outdoor air in the USA and the urban environment of the Europe. The SEM analyses revealed that the fibrous particles consisted, approximately, of chrysotile (60%), tremolite (10%), anthophyllite (10%), and non-asbestos fibers (20%). We conclude that the high volume of traffic, industrial consumption of asbestos, and geographical and climate conditions are responsible for the high airborne asbestos levels in non-occupational environments in Tehran. Thus, it is to be expected that inhabitants of Tehran will suffer negative health effects due to exposure to asbestos airborne fibers.