Airborne Fiber Research Articles

Malignant Mesothelioma due to Environmental Exposure to Asbestos: Follow-Up of a Turkish Cohort Living in a Rural Area

This study examines the incidence of malignant pleural mesothelioma (MPM) in a rural population of Turkey with environmental exposure to asbestos-contaminated soil mixtures (white soil).A field-based epidemiologic study.A cohort of villagers (the "Eskisehir" cohort) from 11 villages around Eskisehir in central Anatolia, who had been environmentally exposed to asbestos due to the use of white soil.The mineral content and asbestos contamination of the white soil used in these villages was determined, as well as airborne fiber concentrations. Cohort members' details of age, sex, ambient exposure data, duration of residence in the villages, and hospital records, including pathologic diagnosis, were recorded.The Eskisehir cohort consisted of 1,886 villagers. During the observation time, 377 deaths occurred and 24 MPM cases were diagnosed. Average annual mesothelioma incidence rates were 114.8/100,000 for men and 159.8/100,000 for women.These data indicate that the risk of mesothelioma is 88.3 times greater in men and 799 times greater in women, respectively, in comparison to world background incidence rates.

Airborne Fiber Exposure Assessment of Dry Asbestos-Containing Gaskets and Packings Found in Intact Industrial and Maritime Fittings

Airborne Fiber Exposure Assessment of Dry Asbestos-Containing Gaskets and Packings Found in Intact Industrial and Maritime Fittings

Airborne fiber exposure assessment of dry asbestos-containing gaskets and packings found in intact industrial and maritime fittings.

This study assessed airborne fiber exposures from intact asbestos-containing gaskets and packings while activities representative of historical work practices were performed. The study design eliminated analytical interferences while systematically capturing information related to activity variables. A series of gasket and packing activities was conducted according to traditional methods while sampling was performed to determine the 8-hour time-weighted average (TWA). The fittings used during this study were obtained intact from a decommissioned industrial power plant and U.S. Navy destroyers. The activities tested included flat blade scraping, hand wire brushing, power wire brushing, making gaskets with a ball-peen hammer, and stem packing removal and replacement. All activities were performed dry. Results for every area and personal sample showed the 8-hour TWAs were well below the current Occupational Safety and Health Administration permissible exposure limit of 0.1 f/cc. A database of more than 400 points was developed to analyze information from variable factors related to the tests. These factors included, for example, type of gasket, composition of the gasket, percentage of gasket adhering to a flange surface, gasket surface area, and minutes elapsed for removal. The results demonstrate a very low rate of fiber exposure from routine activities associated with asbestos-containing elastomeric gaskets and impregnated packing.

Sol-gel alumina fibre mats for high-temperature applications

Polycrystalline, high-alumina fibre mats (with 4 wt.% SiO 2), for application as high-temperature thermal insulation materials having a web-like structure, were fabricated in situ by a single-step sol-gel spinning technique using a multi-orifice spinneret. Strong and resilient fibres with diameters in the range 3–10 μm were obtained from spinnable alumina–silica sols devoid of organics as the binder aid. Incorporation of 4 wt.% SiO 2 as an additive increased the stability of the metastable transition alumina phases, which helped to increase the strength of the fibre mats. The mats exhibited a small linear shrinkage of about 2.75% at 1600 °C. Disintegration of the mats was also found to be negligible (about 2.25 wt.%) at 1600 °C. The health hazard involved with airborne fibres was drastically minimised in the developed fibre mats by applying sol-gel coatings on their surfaces and subsequent calcination at 1200 °C. The oxide-coated fibres exhibited coherent coatings by anchoring loose surface fibres in a network of alumina.

Developments in the RICE asbestos fibre counting scheme, 1992-2000. Regular Interlaboratory Counting Exchanges.

The UK's Regular Interlaboratory Counting Exchanges (RICE) scheme provides proficiency testing for laboratories counting asbestos fibres by phase contrast optical microscopy, as in the method for measurement of airborne fibre concentrations. From 1984 to 1992, the scheme used circulations of industrial samples containing mostly chrysotile, and reference values were obtained from fibre counts by automated image analysis. In 1992, lower density (< 100 fibres/mm2) samples from asbestos clearance operations were added and the new reference values were medians of the laboratories' determinations. In extensive data from 28 recent rounds of sample exchanges, the new reference values are shown to be more reliable than the old. Average counting levels have changed, with different trends according to fibre density. In low density samples, after initial increases, the levels appear to have stabilized. Counting levels on the higher density samples show a continuing trend of approximately 0.5% decrease per round. Widening the density range may have reduced the influence of counters' preconceptions of what values are expected and so their counts on the reference samples may now better reflect their routine counting. The implications of these findings and of other new developments, such as expected new counting rules, are discussed.

Electron microscopy study of refractory ceramic fibers.

In epidemiological studies designed to identify potential health risks of exposures to synthetic vitreous fibers, the characterization of airborne fiber dimensions may be essential for assessing mechanisms of fiber toxicity. Toward this end, air sampling was conducted as part of an industry-wide study of workers potentially exposed to airborne fibrous dusts during the manufacture of refractory ceramic fibers (RCF) and RCF products. Analyses of a subset of samples obtained on the sample filter as well as on the conductive sampling cowl were performed using both scanning electron microscopy (SEM) and transmission electron microscopy (TEM) to characterize dimensions of airborne fibers. Comparison was made of bivariate fiber size distributions (length and diameter) from air samples analyzed by SEM and by TEM techniques. Results of the analyses indicate that RCF size distributions include fibers small enough in diameter (< 0.25 microm) to be unresolved by SEM. However, longer fibers (> 60 microm) may go undetected by TEM, as evidenced by the proportion of fibers in this category for TEM and SEM analyses (1% and 5%, respectively). Limitations of the microscopic techniques and differences in fiber-sizing rules for each method are believed to have contributed to the variation among fiber-sizing results. It was concluded from these data that further attempts to characterize RCF exposure in manufacturing and related operations should include analysis by TEM and SEM, since the smallest diameter fibers are not resolved with SEM and the fibers of longer length are not sized by TEM.

Spontaneous polymerisation on amphibole asbestos: relevance to asbestos removal.

Taking advantage of the spontaneous polymerisation of eugenol to lignin-like species catalysed by the surface of crocidolite fibres, a procedure is proposed, possibly useful in asbestos removal and disposal, where the polymer avoids the release of airborne fibres and also scavenges ROS (reactive oxygen species).

Characterization of Airborne Fibers via Fraunhofer Theory: Examination of the Validity of Fraunhofer Theory Using the Exact Scattering Theory MMP

Owing to the health hazard of respirable airborne fibers, there is great interest in detectors able to monitor fibers online. This paper features such an optical fiber detector which is based on Fraunhofer theory for the estimation of fiber size. Because Fraunhofer theory is not an exact theory and does not take into account the three-dimensional shape of fibers and their material properties, comparative computations with an exact theory, the multiple multipole method (MMP), a variant of the generalized multipole technique, were performed. For small fiber diameters these simulations showed differences between diffraction patterns calculated via Fraunhofer theory and scattering patterns computed with MMP. The differences were strongly dependent on the optical properties of the fiber material.

Characterization of Airborne Fibers via Fraunhofer Theory: Examination of the Validity of Fraunhofer Theory Using the Exact Scattering Theory MMP

Characterization of Airborne Fibers via Fraunhofer Theory: Examination of the Validity of Fraunhofer Theory Using the Exact Scattering Theory MMP

Dustiness of Different High-Temperature Insulation Wools and Refractory Ceramic Fibres

Recent regulations are encouraging the replacement of older types of man-made mineral fibre by more soluble and, thus, less biopersistent compositions. In order for there to be any health benefits from this policy and to gain maximum benefit from such substitutions, the use of the new materials should not increase exposure. The work reported here was undertaken to investigate the use of new high-temperature glass insulation wools in place of refractory ceramic fibres (RCF). Airborne fibre levels occurring during the manufacture of both RCF and calcium magnesium silicate wools (CMS) were compared using measurements of genuine workplace exposure from a routine monitoring operation on the same plant. Exposures during use were compared in one customer facility where RCF and CMS blankets were used for the same task. Further comparisons were made in a laboratory test of dustiness using a "shaking box test". For some manufacturing tasks there are only a few workplace samples and there are few opportunities for genuine comparisons with both RCF and CMS in identical uses. However, both materials produced very similar exposure levels during manufacture, use and in the laboratory test. The novel magnesium silicate fibre was significantly dustier in the laboratory test.

Dustiness of different high-temperature insulation wools and refractory ceramic fibres

Recent regulations are encouraging the replacement of older types of man-made mineral fibre by more soluble and, thus, less biopersistent compositions. In order for there to be any health benefits from this policy and to gain maximum benefit from such substitutions, the use of the new materials should not increase exposure. The work reported here was undertaken to investigate the use of new high-temperature glass insulation wools in place of refractory ceramic fibres (RCF). Airborne fibre levels occurring during the manufacture of both RCF and calcium magnesium silicate wools (CMS) were compared using measurements of genuine workplace exposure from a routine monitoring operation on the same plant. Exposures during use were compared in one customer facility where RCF and CMS blankets were used for the same task. Further comparisons were made in a laboratory test of dustiness using a “shaking box test”. For some manufacturing tasks there are only a few workplace samples and there are few opportunities for genuine comparisons with both RCF and CMS in identical uses. However, both materials produced very similar exposure levels during manufacture, use and in the laboratory test. The novel magnesium silicate fibre was significantly dustier in the laboratory test.

Review : Mineral Fibres and Health

The use of inorganic fibrous materials is a comparatively new phenomenon and was uncommon before the Indus trial Revolution. Humans evolved in a comparatively fibre-free environment and consequently never fully de veloped the defence mechanisms needed to deal with the consequences of inhaling fibres. However, the urban environment now has an airborne fibre concentration of around 1 f.I -1, which is a tenfold increase on the natural background. Any sample of ambient air collected in doors or outdoors will probably contain some mineral fibres, but there is little evidence that these pose any risk to human health. They come from asbestos used in brakes, glass and mineral wools used as insulation and fire proofing of buildings, gypsum from plaster and a variety of types from many sources. Few of these have the potential to do any harm. Asbestos is the only fibre of note but urban levels are insignificant compared to occu pational exposures. When the health of cohorts occupa tionally exposed to the several types of asbestos is stud ied the problem can be put into perspective. Studies of workers in the chrysotile industry exposed to much high er dust levels than in a factory today show no excess lung cancer or mesothelioma. By comparison those liv ing near crocidolite mines, let alone working in them, may develop asbestos-related disease. As always, dose is the critical factor. Chrysotile is cleared from the lungs very efficiently, only the amphiboles are well retained. The only real health problem comes from the earlier use of asbestos products that may now be old, friable and damaged and made from amphibole or mixed fibre. If, though, these are still in good condition, they do not pose a health problem. Asbestos-related diseases are very rare in those not occupationally exposed. Where they exist exposure has nearly always been to croci dolite.

Zirconia fibre mats prepared by a sol-gel spinning technique

Abstract Fine grained, polycrystalline, stabilized zirconia (with 10 wt.% Y 2 O 3 ) fibre mats having a web-like structure were fabricated directly during synthesis by a sol-gel spinning technique using a multi-orifice spinneret. Points of fusion in gel fibre mats helped in the formation of a web-like fibrous body having reasonable strength and very little dust formation after calcination. Strong and resilient fibres with diameters in the range 3–10 micron were obtained by a single-step sol-gel method from spinnable acetate sols devoid of organics as the binder aid. The Y 2 O 3 additive in the fibre mats helped to retain the tetragonal phase even at 1600°C by inhibiting grain growth. The health hazard involved with airborne fibres was significantly minimized in the developed zirconia mats by applying sol-gel coatings on their surfaces followed by calcination. The resulting samples exhibited reasonably coherent coatings by anchoring loose surface fibres in a network of zirconia.

Measurement of airborne fibers: a review.

Current fiber measurement techniques arose primarily due to health concerns over asbestos exposure. Fiber toxicity appears to be primarily a function of fiber concentration, dimensions and durability in the lungs. There are two basic approaches to fiber measurement. Fibers can be collected on filters and counted or analyzed by light or electron microscopy; alternatively, fibers can be detected directly using a combination of fiber alignment and light scattering techniques. All of these measurement approaches work best when the fibers are simple rod-shaped particles. However, most fibers can exist as curved rods, complex bundles of fibrils, and agglomerates of fibers and compact particles. These non-ideal shapes contribute to measurement bias and variability.

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.

Respirable airborne fibers in the home environment in upper silesia, Poland, compared with Davis, California

Respirable airborne fibers in the home environment in upper silesia, Poland, compared with Davis, California

A Study of Area and Personal Airborne Asbestos Samples during Abatement in a Crawl Space

Air sample data were collected during asbestos abatement of two buildings using area and personal sampling methods. Abatement involved removal of pipe insulation from crawl spaces. The two sampling methods were compared to determine if there was a relationship between them. A relationship was observed between area and personal airborne samples in building 2 as determined by correlation and regression but is most likely due to chance. One major outlier was detected for both area and personal measurement sample data sets in building 2. It was concluded that any relationship between area and personal sample measurements must be viewed with caution. Concentrations measured from personal sampling were statistically higher than those from area sampling. Also, the distributions of concentrations in the samples were calculated to be nonnormal (logarithmic form). It is proposed that area sampling under-estimates worker exposure compared to personal measurements and is not applicable for exposure and hazard assessment. It is suggested that area and personal samples measure two different population concentrations of airborne fibers. Use of area samples in lieu of personal measurements should only be employed with caution.

A Study of Area and Personal Airborne Asbestos Samples during Abatement in a Crawl Space

Air sample data were collected during asbestos abate ment of two buildings using area and personal sampling methods. Abatement involved removal of pipe insula tion from crawl spaces. The two sampling methods were compared to determine if there was a relationship be tween them. A relationship was observed between area and personal airborne samples in building 2 as deter mined by correlation and regression but is most likely due to chance. One major outlier was detected for both area and personal measurement sample data sets in building 2. It was concluded that any relationship be tween area and personal sample measurements must be viewed with caution. Concentrations measured from personal sampling were statistically higher than those from area sampling. Also, the distributions of concentra tions in the samples were calculated to be nonnormal (logarithmic form). It is proposed that area sampling under-estimates worker exposure compared to personal measurements and is not applicable for exposure and hazard assessment. It is suggested that area and person al samples measure two different population concentra tions of airborne fibers. Use of area samples in lieu of personal measurements should only be employed with caution.

A Novel Approach for the In-Situ Chemical Elimination of Chrysotile from Asbestos-Containing Fireproofing Materials

We report here the development of a method for the chemical digestion of chrysotile asbestos in asbestos-containing fireproofing to levels lower than the regulatory threshold. The resulting fireproofing, no longer defined as asbestos-containing, can remain in place with properties intact. In the process, chrysotile fibers are digested without generating excessive gaseous byproducts, and the foam-based delivery system essentially eliminates release of airborne fibers. New X-ray diffraction methods quantified chrysotile levels with far greater precision than standard optical microscopic methods. Full-scale field testing confirmed the laboratory phase of the project. Fire testing of the treated fireproofing showed that the treated material functions as well as the original fireproofing.

Multi-parameter observation of environmental asbestos pollution at the Institut de Physique du Globe de Paris (Jussieu Campus, France)

An original multi-parameter system has been used to study the nature of dust in the ambient air, particularly the total fibers and asbestos fibers, in eight areas of the Institut de Physique de Globe de Paris (France). These analyses provide a detailed case study of environmental pollution by asbestos fibers at low levels. The levels of total fibers with a length greater than 3 μm, measured with a real time fiber analyser monitor (FAM), give a baseline of 2.5 fibers per l., throughout the duration of sampling. The same levels, calculated during periods of effective presence of staff, are smaller than 10 fb per l. During these periods, the instantaneous value can show high peaks, reaching a maximum of 60 fb per l., but more often of about 5 to 10 fb per l. A direct cause and effect relationship exists between fiber concentrations and the presence of people, and indirectly with the variation of the other environmental parameters (temperature, humidity, air velocity). The baseline concentration of asbestos fibers, determined by analytical transmission electron microscopy (ATEM), is about 10−1 fb per l., with a mean value during the presence of people always less than 1.5 fb per l. The low levels of asbestos fibers do not allow us to establish a precise correlation between the concentration of total fibers and the asbestos concentration, but a rough estimate suggests that asbestos could represent 10–20% of the airborne fibers monitored with the FAM. The statistical study of fiber sizes shows that 70 and 55% of analyzed chrysotile and amosite fibers respectively are smaller than 5 μm. These numbers are 40 and 35% for fibers smaller than 3 μm, which are undetected by the FAM. Amosite, which characterizes most of the asbestos-containing materials (ACM) in the analyzed areas, is detected in the ambient air in quantities ten times less important than chrysotile. The low asbestos levels and the difference between the nature of building asbestos and airborne fibers, show that the mean measured asbestos contents in the ambient air represent the geochemical background of chrysotile asbestos fibers in the Parisian air.