Fibrous Glass Research Articles

Investigation of contact vacuuming for remediation of fungally contaminated duct materials

Environmental fungi become a potential Indoor Air Quality (IAQ) problem when adequate moisture and nutrients are present in building materials. Because of their potential to rapidly spread contamination throughout a building, ventilation system materials are of particular significance as potential microbial contamination sources. Current recommendations are to discard fibrous glass insulation that appears to be wet or moldy. Unfortunately, this advice is not always followed. Instead, cleaning is sometimes being used in buildings to remediate fibrous glass duct liner that is already contaminated with microbial growth. The objectives of this research program were to: 1) determine, under dynamic test conditions, whether fungal spore levels on heating, ventilating, and air-conditioning (HVAC) duct material surfaces could be substantially reduced by thorough vacuum cleaning, 2) evaluate whether subsequent fungal growth could be limited or contained by mechanical cleaning, and 3) provide data concerning the advisability of cleaning duct materials. The constant high relative humidity (RH) environment to which the test materials were exposed during this study was selected as a favorable growth environment that is frequently found in Southeastern United States HVAC systems. The results showed that, following cleaning, the levels of the two test fungi, A. versicolor and P. chrysogenum, recovered to preclean levels within 6 weeks. Therefore, mechanical cleaning by contact vacuuming alone was able to only temporarily reduce the surface fungal load. The current guidelines to discard contaminated materials should be followed.

Enhancement by bFGF of osteogenesis induced by rhBMP-2 in rats.

Subcutaneous implantation of bone morphogenetic protein (BMP) combined with a fibrous glass membrane (FGM) induces cartilage formation in the entire inner area of the membrane within 2 wk. It has been hypothesized that a tight FGM network (1 microm exclusion size) provides immature cells with spaces for penetrating into the membrane, but not for vascular formation, at least until 2 wk. To test this hypothesis, basic fibroblast growth factor (bFGF), known to be a potent stimulant of capillary formation, was applied to the implant. BMP was combined with FGM in the presence or absence of bFGF, and then implanted subcutaneously into the backs of rats. The bFGF-supplemented implant caused 1.3 times higher alkaline phosphatase activity and 3 times higher calcium contents at 2 wk, whereas type II collagen contents decreased, thus indicating that bFGF enhances bone formation in BMP/FGM implants. These results suggest that bFGF induces faster and stronger invasion of capillaries into the FGM and destroys its tight network, resulting in acceleration of the ossification process.

Thermal conductivity of fibrous glass board by guarded hot plates and heat flow meters: An international round-robin

In the early 1980s, an international round-robin was held in which the apparent thermal conductivity of specimens of fibrous glass insulation board was measured by users of guarded hot plates (GHPs) and heat-flow meters (HFMs). The round-robin was performed over a period of several years by laboratories in Europe, North America, Australia, and the Far East. Participants in this round-robin were organized into 12 “loops.” 8 for participants with GHPs and 4 for those with HFMs. Each loop included laboratories located in the same region of the world and sharing the same set of specimens. In an attempt to obtain insight into the accuracy of the measurements, participants were also asked to measure the thermal conductivity of a layer of air. The data submitted in this round-robin are exhibited and analyzed. The overall agreement of individual measurements with a least-squares fitted curve, as measured by one standard deviation σ, was σ=2.4% for GHPs and σ=2.7% for HFMs. Suggestions are made for conducting future round-robins of this type

BMPs induce endochondral ossification in rats when implanted ectopically within a carrier made of fibrous glass membrane.

Bone morphogenetic proteins (BMPs) replicate the process of embryonic bone formation when implanted in ectopic sites. Our previous studies have indicated that BMPs can induce intramembranous ossification, i.e., direct bone formation without preexisting cartilage when implanted in rats subcutaneously by using the fibrous collagen membrane (FCM) as a carrier for implanting BMPs (Sasano et al. 1993. Anat. Rec., 236:373-380). The present study was designed to investigate how the physicochemical property of the carrier material influences the process of bone formation induced by BMPs, using a carrier made of fibrous glass membrane (FGM). BMPs, partially purified from bovine metatarsal bones, were added to an FGM carrier and implanted subcutaneously in rats. The implants were analyzed at weekly intervals, and the osteogenic process induced by BMPs was examined by histology and immunohistochemistry for cartilage and bone formation. Neither cartilage nor bone were observed after week 1. Cartilage formation occurred within the carrier after week 2, although no bone formation was seen. The cartilage matrix showed immunoreactivity for types II, X, and I collagen. Bone was induced on the previously formed cartilage after week 3. The bone matrix stained with anti-osteocalcin antibody and with anti-type I collagen antibody. The cartilage was replaced by bone and bone marrow after week 10. BMPs cause endochondral ossification when administered with an FGM carrier. The physicochemical property of the carrier may be involved in the BMP-induced phenotype expression of bone and cartilage.

Fibrous glass insulation and cancer: Response and rebuttal

In response to our commentary on fibrous glass and cancer [Infante et al., 1994], three letters have been received by the journal. The arguments put forth in these letters do not lead us to alter our scientific view that fibrous glass insulation is carcinogenic. No information is given in the letters that has not previously been stated. Even though these letters raise the same diaphanous arguments, we believe that to preserve occupational and public health we must respond in detail to ensure that the contentions of the fibrous glass industry do not gain further acceptance. Thus, we respond to each letter in turn: The first by Weiss questions and distorts epidemiologic findings, the second by McConnell attempts to recant his past views on the carcinogenicity of fibrous glass and on the value of rodent bioassays in general, and the third by Hesterberg and Chase impugns our analyses demonstrating a positive cancer response in their study. Lastly, we have not debated every issue raised in these letters because of space limitations, and have centered our responses on what we consider the major incongruities and falsities in each letter. Likewise, we have been selective in citing only relevant literature, or those reports used by the industry or its consultants to support their views. © 1996 Wiley-Liss, Inc. 1 This article is a US Government work and, as such, is in the public domain in the United States of America.

Fibrous glass insulation and cancer: Response and rebuttal

In response to our commentary on fibrous glass and cancer [Infante et al., 1994], three letters have been received by the journal. The arguments put forth in these letters do not lead us to alter our scientific view that fibrous glass insulation is carcinogenic. No information is given in the letters that has not previously been stated. Even though these letters raise the same diaphanous arguments, we believe that to preserve occupational and public health we must respond in detail to ensure that the contentions of the fibrous glass industry do not gain further acceptance. Thus, we respond to each letter in turn: The first by Weiss questions and distorts epidemiologic findings, the second by McConnell attempts to recant his past views on the carcinogenicity of fibrous glass and on the value of rodent bioassays in general, and the third by Hesterberg and Chase impugns our analyses demonstrating a positive cancer response in their study. Lastly, we have not debated every issue raised in these three letters because of space limitations, and have centered our responses on what we consider the major incongruities and falsities in each letter. Likewise, we have been selective in citing only relevant literature, or those reports used by the industry or its consultants to support their views.

Use of Lung Toxicity and Lung Particle Clearance to Estimate the Maximum Tolerated Dose (MTD) for a Fiber Glass Chronic Inhalation Study in the Rat

Short-term toxicity and lung clearance were assessed in rats exposed by inhalation to size-selected fibrous glass (FG) for 13 weeks. Results from this study and from a recent FG chronic inhalation study are presented here as guidelines for the selection of a maximum tolerated dose (MTD) for chronic inhalation studies of fibers. Fischer 344 rats were exposed using nose-only inhalation chambers, 6 hr/day, 5 days/week, for 13 weeks to one of five concentrations of FG (36, 206, 316, 552, or 714 fibers/cc; expressed gravimetrically, 3, 16, 30, 45, or 60 mg/m3) or to filtered air. Rats were then held for an additional 10 weeks of postexposure recovery. Test fiber was size-selected from glass wool having a chemical composition representative of building insulation. Rats were terminated at 7, 13, 19, and 23 weeks after the onset of exposure to evaluate pulmonary pathology, lung epithelium cell proliferation, lung fiber burden, and lung lavage cells and chemistry. The effect of fiber inhalation on lung clearance of innocuous microspheres was also evaluated: following fiber exposure, six rats/group were exposed to85Sr-labeled 3.0-μm polystyrene microspheres by intratracheal inhalation and then monitored for whole-body radioactivity during the 10-week recovery period. Data from the short-term study support the choice of 30 mg/m3as the MTD for the previous chronic FG study and also provide indicators of long-term lung toxicity and functional impairment that can be used to estimate the MTD for future chronic fiber inhalation studies.

Commentary on ?fibrous glass and lung cancer?

Commentary on ?fibrous glass and lung cancer?

Commentary on ?fibrous glass and lung cancer?

Commentary on ?fibrous glass and lung cancer?

Commentary on “fibrous glass and lung cancer”

Commentary on “fibrous glass and lung cancer”

Fibrous glass insulation and cancer: Response and rebuttal

Fibrous glass insulation and cancer: Response and rebuttal

An Outbreak of Pruritic Skin Lesions in a Group of Laboratory Workers A Case Report

In May 1993, an outbreak of pruritic skin lesions occurred among a group of employees located in four laboratories in the basement of an office building. Medical interviews with the affected workers were performed and an industrial hygiene survey of the site was conducted. Workers commonly reported a pricking sensation on exposed skin. Four of the workers had small (< 5mm) erythematous papules on their forearms. Just prior to the outbreak, the installation of fibrous glass insulation had commenced in the mechanical rooms which provided air to the basement of the building. Because of the nature of the symptoms and the temporal relationship with the nearby insulation work, direct skin contact with fibrous glass fibres was thought to be the cause of the outbreak. The poorly maintained air handling unit supplying air to the laboratories probably contributed to this outbreak by inefficient filtering of the circulating air.

Crystallization of Al&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt;-SiO&lt;sub&gt;2&lt;/sub&gt; Glass Fiber and Effect of ZrO&lt;sub&gt;2&lt;/sub&gt; and Cr&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; Additions on the Crystallization

Crystallization of Al2O3-SiO2 glass fiber (AS) and the effect of ZrO2 and Cr2O3 addition on the crystallization were investigated by PTA, XRD and density measurement. Mullite crystallized in the AS at 995°C. The mullite crystal grew and its amount increased with rising temperature. Cristobalite crystallized in the AS at 1450°C and above. Mullite crystallized at 1015°C with t-ZrO2 and spinel phase in fibrous glass containing ZrO2 (ASZ). The mullite crystal grew and its amount increased with rising temperature. At 1500°C, cristobalite crystallized and the t-ZrO2 partly transformed into m-ZrO2. The amount of cristobalite in this fibers was larger than that in the AS. Only spinel phase crystallized at 990°C in fibrous glass containing Cr2O3 (ASC). The amount of spinel phase increased up to 1100°C, but slightly decreased at 1200°C and disappeared at 1300°C. Mullite appeared from 1100°C and increased with rising temperature. Cr2O3 dissolved in the mullite and suppressed the crystallization rate and grain growth. The addition of Cr2O3 raised the temperature at which the amount of mullite reached the calculated value by 105°C compared to that of the AS. Although the amount was smaller than that of the AS, cristobalite also crystallized in the ASC by firing at 1500°C.

Assessment of fungal (Penicillium chrysogenum) growth on three HVAC duct materials

Many building investigators have documented fungal biocontamination in heating, ventilating, and air-conditioning (HVAC) ducts. It has been suggested that emissions of spores and volatile organic compounds from the growing fungi may contribute to poor indoor air quality and result in adverse health effects. Laboratory experiments were conducted to evaluate the susceptibility of three types of ventilation duct materials (fibrous glass ductboard, galvanized steel, and insulated flexible duct) to fungal ( P. chrysogenum) growth. Each sample was inoculated with spores of P. chrysogenum and incubated in a static chamber controlled at 97% relative humidity (RH) and 21°C for six weeks. Culturable spores on each sample were enumerated before and after incubation to determine the extent of fungal amplification. The results indicated that, of the newly purchased duct materials, only the flexible duct supported moderate growth of P. chrysogenum. No fungal growth was detected on the fibrous glass and galvanized steel. The number of culturable spores on galvanized steel even decreased during the test period. Wetting the clean duct samples with sterile water did not increase amplification of the P. chrysogenum over the level seen without the wetting. Soiling the samples with dust collected from residential heating and air-conditioning systems enhanced the susceptibility of all three duct materials to fungal growth; however, at different levels of soiling. At a moderate level (0.4–0.7 mg cm −2) of soiling, growth occurred on the fibrous glass ductboard and the flexible duct, but not the galvanized steel. At a markedly higher level (9–18 mg cm −2) of soiling, growth was seen on the galvanized steel as well. The results of these experiments suggest that dust accumulation and/or high humidity should be properly controlled in any HVAC duct to prevent the growth of P. chrysogenum.

Thermal performance evaluation of a prefabricated fiber-reinforced plastic building envelope system

Fiber-reinforced plastic (FRP) materials are extensively used in building construction, primarily due to their superior structural performance characteristics. Recently, a newly-developed concept consisting of a prefabricated, interlocking fiberglass composite panel system has been adopted for use in the construction of building envelope systems. The structural characteristics of these panels allow, among other things, expeditious construction. Other performance advantages include corrosion resistance, reduced maintenance, electric insulation characteristics, and electromagnetic transparency. Since little information is available on the thermal performance characteristics of such a panel system, a testing program was developed to investigate the thermal insulation characteristics of FRP panels that are commercially available at the present. Two full-scale 1.2 m by 1.2 m (4 ft by 4 ft) FRP panels were tested. Two panel thicknesses were considered: 25 mm (1 in.) and 75 mm (3 in.). The thermal characteristics of the panels were measured including the effects of the presence of the joints between the panels. A temperature-controlled test plate, calibrated with fibrous glass board material of known thermal conductivity, was used with heat flow sensors to determine the thermal resistance of the FRP panels at the mid-sections of panels and at the interfaces (i.e. joints) between two adjoining panels. Two conditions were simulated; ‘dry joint’ which includes only mechanical interlocking at the joints, and ‘sealed joint’ in which the joints were sealed with a commercially available sealant. The R values of the tested panels were approximately 5% to 46% higher in the sealed-joint condition. Sealed joints decrease heat exchange across the envelope system, thereby increasing the thermal resistance values of the panel system. The relatively high R value of the 75 mm panel system (2.0 (m 2 K)/W (11.36 (h ft 2 °F)/Btu)) is encouraging, and makes this envelope system a potential candidate for wider use in energy-conscious commercial buildings.

Chronic Inhalation Studies of Man-Made Vitreous Fibres: Characterization of Fibres in the Exposure Aerosol and Lungs

Inhalation studies were conducted to determine the chronic biological effects in rodents of respirable fractions of different man-made vitreous fibres (MMVFs), including refractory ceramic fibre (RCF), fibrous glass, rock (stone) wool and slag wool. Animals were exposed nose-only, 6 h per day, 5 days per week, for 18 months (hamsters) or 24 months (rats). Exposure to 10 mg m−3 of crocidolite or chrysotile asbestos induced pulmonary fibrosis, lung tumours and mesothelioma in rats, thus validating the inhalation model with known human carcinogenic fibres. Exposure of rats to 30 mg m−3 of refractory ceramic fibres (RCF) also resulted in pulmonary fibrosis as well as significant increases in lung tumours and mesothelioma. In hamsters, 30mg m−3 of RCF induced a 41% incidence of mesotheliomas. Exposure of rats to 30 mg m−3 of fibre glasses (MMVF 10 or 11) or of slag wool (MMVF 22) was associated with an inflammatory response, but no mesotheliomas or significant increase in the lung tumours were observed. Rock wool (stone wool: MMVF 21) at the same exposure level resulted in minimal lung fibrosis, but no mesotheliomas or significant increase in the lung tumours were observed. Fibre numbers (WHO fibres) and dimensions in the aerosols and lungs of exposed animals were comparable in this series of inhalation studies. Differences in lung fibre burdens and lung clearance rates could not explain the differences observed in the toxicologie effects of the MMVFs. These findings indicate that dose, dimension and durability may not be the only determinants of fibre toxicity. Chemical composition and the surface physico-chemical properties of the fibres may also play an important role.

Chronic inhalation studies of man-made vitreous fibres: Characterization of fibres in the exposure aerosol and lungs

Inhalation studies were conducted to determine the chronic biological effects in rodents of respirable fractions of different man-made vitreous fibres (MMVFs), including refractory ceramic fibre (RCF), fibrous glass, rock (stone) wool and slag wool. Animals were exposed nose-only, 6 h per day, 5 days per week, for 18 months (hamsters) or 24 months (rats). Exposure to 10 mg m−3 of crocidolite or chrysotile asbestos induced pulmonary fibrosis, lung tumours and mesothelioma in rats, thus validating the inhalation model with known human carcinogenic fibres. Exposure of rats to 30 mg m−3 of refractory ceramic fibres (RCF) also resulted in pulmonary fibrosis as well as significant increases in lung tumours and mesothelioma. In hamsters, 30 mg m−3 of RCF induced a 41% incidence of mesotheliomas. Exposure of rats to 30 mg m−3 of fibre glasses (MMVF 10 or 11) or of slag wool (MMVF 22) was associated with an inflammatory response, but no mesotheliomas or significant increase in the lung tumours were observed. Rock wool (stone wool: MMVF 21) at the same exposure level resulted in minimal lung fibrosis, but no mesotheliomas or significant increase in the lung tumours were observed. Fibre numbers (WHO fibres) and dimensions in the aerosols and lungs of exposed animals were comparable in this series of inhalation studies. Differences in lung fibre burdens and lung clearance rates could not explain the differences observed in the toxicologic effects of the MMVFs. These findings indicate that dose, dimension and durability may not be the only determinants of fibre toxicity. Chemical composition and the surface physico-chemical properties of the fibres may also play an important role.

Adjustment for the confounding effect of cigarette smoking in an historical cohort mortality study of workers in a fiberglass manufacturing facility.

In 1986 a statistically significant lung cancer SMR based on U.S. white male national mortality rates was reported for male fibrous glass workers for follow-up through 1982 of a cohort of U.S. man-made mineral fiber workers. The Newark, Ohio, plant of Owens-Corning, which comprised 38% of the fibrous glass workers in that cohort, also exhibited a statistically significant lung cancer standardized mortality ratio based on U.S. white male mortality rates. A case-control study of the Newark workers demonstrated that a history of cigarette smoking and not exposure to respirable glass is the most important factor in lung cancer risk for workers at the Newark plant. We provide an estimate of the extent of confounding by cigarette smoking for the Newark plant nationally based lung cancer standardized mortality ratio with data not previously available and which suggests that adjusting for the confounding effect of cigarette smoking could reduce the lung cancer standardized mortality ratio to a non-statistically significant level.

Weight of scientific evidence approach shows fibrous glass presents little public health risk

To date, several scientific research studies have been published discussing the health effects of exposure to fibrous glass. Although the majority of these studies have failed to demonstrate any causal association between exposure to fibrous glass and adverse health effects, the material has nevertheless been classified/labeled as a ‘‘possible carcinogen.’’ This paper discusses the basis for this classification/label as well as a more realistic ‘‘weight of the evidence’’ approach to evaluating the scientific data on fiberglass. Using such an approach and integrating the substantial toxicological, epidemiological, exposure, and chemical data accumulated on fibrous glass over the past 50 years, one is led to the conclusion that the material poses little, if any, risk to the public health under normal conditions of use.

Two distinctive BMP-carriers induce zonal chondrogenesis and membranous ossification, respectively; geometrical factors of matrices for cell-differentiation.

A partially purified BMP preparation was combined with a fibrous glass membrane (FGM) or porous particles of hydroxyapatite (PPHAP), and then implanted subcutaneously into the backs of rats. As a control of these new carriers, a conventional carrier of insoluble bone matrix (IBM) was also used. These new geometrically different solid-state carriers induced tissues in quite different manners. FGM/BMP implants induced cartilage formation within the entire inner area of the membrane accompanied by a small amount of bone formation on the surface of the membrane. In contrast, PPHAP/BMP implants induced only bone within the pores of PPHAP without any detectable cartilage formation. Enzyme-linked immunosorbent assay revealed that the type II collagen content in FGM/BMP was six times higher than that in IBM/BMP, while there was no detectable type II collagen in PPHAP/BMP. The results were explained by the geometric properties of the two distinctive carriers.