A Longitudinal Study of Chest Radiographic Changes of Workers in the Refractory Ceramic Fiber Industry

doi:10.1378/chest.121.6.2044

Chest

Volume 121, Issue 6, June 2002, Pages 2044-2051

https://doi.org/10.1378/chest.121.6.2044 Get rights and content

Study objective

This industry-wide longitudinal study examines chest radiographic changes of workers manufacturing refractory ceramic fibers (RCF).

Design

Chest radiographs were obtained every 3 years and were interpreted using the 1980 International Labour Organization classification for pneumoconiosis. Three exposure metrics were calculated: duration and latency in a production job, and cumulative exposure (fiber-months per cubic centimeter).

Participants

The radiographic survey included 625 current workers at five manufacturing sites and 383 former workers at two of the five sites.

Measurements and results

Pleural changes were seen in 27 workers (2.7%). Of workers with > 20 years of latency from initial production job or 20 years of duration in a production job, 16 workers (8.0%) and 5 workers (8.1%) demonstrated pleural changes, respectively. Results from the cumulative exposure analysis (> 135 fiber-months per cubic centimeter) demonstrated a significant elevated odds ratio (OR) of 6.0 (95% confidence interval [CI], 1.4 to 31.0). The incidence of irregular opacities at profusion categories ≥ 1/0 was similar to other nonspecified dust-exposed worker populations at 1.0%, and showed a nonsignificant elevated OR in regard to cumulative fiber exposure of 4.7 (95% CI, 0.97 to 23.5).

Conclusions

RCF are significantly associated with pleural changes that were predominantly pleural plaques, but have not resulted in a statistically significant increase in interstitial changes.

Section snippets

Subjects

A prospective industry-wide health study was initiated in 1987 with current workers at three facilities and with current and former workers at two facilities where RCF and RCF products are produced.^6,⁷ Additional details of subject recruitment and data collection are reported elsewhere.^8,^9,¹⁰ Eligible workers had a minimum of 1 year of employment between 1953 (commencement of RCF production) and December 31, 1996. Female clerical employees who left work prior to study initiation in June 1987

Radiography

As described in Table 1, there were 1,008 workers from five manufacturing locations; most were white (81%), male (85%), and had an average age of 46.6 years at time of the last chest radiograph. Approximately 20% of workers were in nonproduction jobs, approximately 36% had > 10 years of duration in RCF production jobs, and the average latency period between first production job and last chest radiograph was 16.4 years. On average, the workers had 2.7 separate radiographic evaluations over the

Pleural Changes

The vast majority of cases of pleural plaques in the general population are related to previous occupational and/or environmental exposure to asbestos, and occurs most commonly > 15 to 20 years after initial exposure. Castellan and colleagues²² demonstrated a 0.21% rate of pleural abnormalities in blue-collar workers with minimal history of exposure to respiratory hazards. A population in Sweden studied by Hillerdal²³ demonstrated a background prevalence of bilateral pleural plaques of 0.3% for

ACKNOWLEDGMENT

The authors thank the participants in this study, and the participating radiologists: Ralph Shipley, MD; Harold Spitz, MD; and Jerome Wiot, MD. They also thank the Refractory Ceramic Fiber Coalition: Paul Epstein, MD; Edward Horvath, Jr., MD, MPH; Mark Utell, MD; and Alec Walker, MD, for their review and insights. The authors are grateful to their staff and to their administrative assistant, Connie Thrasher.

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Cited by (33)

Refractory ceramic fibers: Fiber characteristics, potential health effects and clinical observations
2018, Toxicology and Applied Pharmacology
Citation Excerpt :
9.1, 95% CI 2.5–33.6) for all subjects and for those with no potential asbestos exposure, respectively. This compared to an earlier report were pleural changes were seen in 27 workers (2.7%) (Lockey et al., 2002) The increase in pleural plaques with time is not surprising as the presence of plaques is likely to be related to increasing latency. Prevalence among recent hires (after 1985) was similar to the background.
Refractory ceramic fibers (RCFs) are amorphous fibers that belong to a class of materials termed synthetic vitreous fibers (SVFs), also called man-made mineral fibers (MMMFs), which includes alkaline earth silicate wool, glass wool, rock (stone) wool, slag wool, and special-purpose glass fibers. RCFs are more durable and biopersistent than several other SVFs, although very much less biopersistent than either amosite or crocidolite asbestos. Chronic inhalation studies indicated that rats and hamsters exposed to RCF fibers developed fibrosis and tumors. Epidemiological studies at the University of Cincinnati funded by the Industry indicated that exposed workers; (1) exhibited symptoms (e.g., dyspnea) similar to those reported in other dust-exposed populations, (2) developed statistically, but not clinically, significant deficits in certain measures of pulmonary function in a cross sectional study, but no excessive decline in a longitudinal study, and (3) a dose related increase in pleural plaques, but no interstitial fibrosis. The 2003 mortality study indicated no incremental lung cancer and no cases of mesothelioma. RCF producers developed a comprehensive industry wide product stewardship program (PSP) beginning in the late 1980s. In conjunction with the PSP, there has been a progressive decrease in the TWA concentration of fibers by manufacturers and end-users. The research program has successfully produced more soluble fibers and undertaken efforts to develop larger diameter fibers. The results of the ongoing epidemiology studies confirm that occupational exposure to RCF is associated with the development of pleural plaques and minor decrements in lung function, but no interstitial fibrosis or incremental lung cancer.
The different pleuro-pulmonary pathologies related to asbestos: Definitions, epidemiology and evolution
2012, Revue des Maladies Respiratoires
Les plaques pleurales (fibrose de la plèvre pariétale), sont parfois observées après des expositions faibles. Leur prévalence peut atteindre 70 % dans des populations fortement exposées. La fibrose de la plèvre viscérale est beaucoup moins fréquente. Elle n’est pas spécifique de l’amiante. L’incidence de l’asbestose (fibrose du poumon induite par l’exposition à l’amiante) est en diminution en France. Selon les données du Programme national de surveillance du mésothéliome pour la période 1998–2003, le nombre annuel de cas incidents de mésothéliomes pleuraux varie de 646 à 800. Les cancers bronchopulmonaires primitifs (CBP), dus à l’amiante, n’ont pas de spécificité clinique, radiologique ou anatomopathologique. L’INVS a estimé entre 2086 et 4172 le nombre de CBP attribuables à l’amiante en 1999. Un rapport (2007) de l’Académie nationale de médecine, de l’Académie des sciences et du Centre international de recherche sur le cancer, a pour sa part évalué l’incidence du CBP attribuable à l’amiante à 969 cas chez l’homme et 133 cas chez la femme en 2000. Le risque de CBP est augmenté dans des populations exposées à l’amiante, même en l’absence de signes radiographiques de fibrose pulmonaire. À exposition cumulée identique, l’asbestose majore le risque de CBP. Sur la base d’études radiographiques, les plaques pleurales sont associées à un risque accru de CBP et de mésothéliome. À exposition cumulée identique à l’amiante, il n’est pas établi que la présence de plaques pleurales confère un risque majoré de développer un cancer thoracique.
Pleural plaques (fibrosis of the parietal pleura) are sometimes seen following light exposure. Their prevalence may reach 70% in heavily exposed populations. Fibrosis of the visceral pleura is much less common and it is not specifically related to asbestos. The incidence of asbestosis (pulmonary fibrosis induced by asbestos exposure) is diminishing in France. According to the data of the National Programme for the Surveillance of Mesothelioma, the annual number of cases of pleural mesothelioma varied from 646 to 800 for the period 1998–2003. Primary lung cancer due to asbestos does not have specific clinical, radiological or anatomical-pathological features. The number of cases attributable to asbestos has been estimated as between 2086 and 4172 for 1999. A report of the National Academy of Medicine, the Academy of Sciences and the International Centre of Cancer Research has calculated the incidence of primary lung cancer due to asbestos in 2000 as 969 for men and 133 for women. The risk of primary lung cancer is increased in populations exposed to asbestos even in the absence of radiological signs of pulmonary fibrosis. For an identical total exposure, asbestosis increases the risk of primary lung cancer. On the basis of radiological studies, pleural plaques are associated with an increased risk of lung cancer and mesothelioma. For identical levels of total asbestos exposure, it has not been established that the presence of pleural plaques increases the risk of developing thoracic cancer.
Man-Made Mineral Fibers and The Respiratory Tract
2012, Archivos de Bronconeumologia
Citation Excerpt :
In another follow-up study, no reduction was observed in carbon monoxide diffusion capacity (DLCO) related with exposure.65 As for radiological studies, Lockey et al.66 completed a longitudinal, radiological follow-up study in 1008 workers who worked in RCF manufacturing. They found pleural changes in 2.7% of the workers, mainly pleural plaques, and they observed an association between the level of accumulated exposure and the appearance of pleural plaques.
Man-made mineral fibers are produced using inorganic materials and are widely used as thermal and acoustic insulation. These basically include continuous fiberglass filaments, glass wool (fiberglass insulation), stone wool, slag wool and refractory ceramic fibers. Likewise, in the last 2 decades nanoscale fibers have also been developed, among these being carbon nanotubes with their high electrical conductivity, mechanical resistance and thermal stability. Both man-made mineral fibers and carbon nanotubes have properties that make them inhalable and potentially harmful, which have led to studies to assess their pathogenicity. The aim of this review is to analyze the knowledge that currently exists about the ability of these fibers to produce respiratory diseases.
Las fibras minerales artificiales son fibras producidas por el hombre usando materia inorgánica que se emplean ampliamente como aislantes térmicos y acústicos. Incluyen básicamente el filamento continuo de fibra de vidrio, las lanas de vidrio, de roca y de escoria, y las fibras cerámicas refractarias. Así mismo, en las últimas 2 décadas también se han desarrollado fibras a nivel de nanoescala, entre las que destacan los nanotubos de carbono por su gran conductividad eléctrica, resistencia mecánica y estabilidad térmica. Tanto las fibras minerales artificiales como los nanotubos de carbono tienen propiedades que los hacen respirables y potencialmente nocivos, lo que ha conducido a la realización de estudios para valorar su patogenicidad. El objetivo de esta revisión es analizar los conocimientos que existen actualmente sobre la capacidad que tienen estas fibras de producir enfermedad respiratoria.
Refractory ceramic fibres: A human health hazard? A literature review
2010, Archives des Maladies Professionnelles et de l'Environnement
Les fibres céramiques réfractaires (FCR) sont des fibres minérales artificielles amorphes utilisées pour des applications d’isolation à haute température. Elles sont moins biopersistantes que l’amiante amphibole mais plus durables que d’autres fibres vitreuses telles que les laines de verre. Leur biopersistance est équivalente à celle de la laine de roche et inférieure à celle des verres E et 475. Une fraction des fibres contenues dans les produits FCR est respirable. Les autorités sanitaires européennes ont classé les FCR comme étant « des substances potentiellement cancérogènes pour l’Homme ». Ainsi, en France, près de 70 % des FCR ont été remplacés par des fibres produites à partir de silicates alcalinoterreux dites Alkaline Earth Silicate (AES) dont les propriétés physiques seraient avantageuses dans l’isolation thermique haute température avec cependant peu ou pas de risque sanitaire associé. La règlementation de l’utilisation des FCR faisant intervenir les valeur limite d’exposition professionnelle (VLEP) prévoit d’abaisser le seuil limite d’exposition à 0,1 f/cm³ à compter du 1^er juillet 2009 (décret n^o 2007-1539 du 26 octobre 2007).
L’objectif principal de ce travail est de déterminer les risques sanitaires associés aux FCR ; l’objectif secondaire est de rapporter les principales données sur les FCR.
Des études toxicologiques menées sur des rongeurs et appliquant plusieurs méthodes d’exposition ont rapporté des mésothéliomes et des carcinomes pulmonaires. Ces derniers ont été après analyse, attribués à un phénomène de surcharge pulmonaire. Les études épidémiologiques sur les professionnels européens et américains de l’industrie de production des FCR rapportaient comme signes fonctionnels dyspnée et douleurs thoraciques récidivantes, comme données spirométriques une baisse du volume expiré maximum en une seconde et de la capacité vitale chez les fumeurs seulement, occupant un poste à la production (uniquement pendant la première décennie des années 1980) et enfin comme donnée radiologique une majoration de la prévalence des plaques pleurales. La prévalence moyenne des plaques pleurales des travailleurs exposés (2,7 %) ne dépassait pas toutefois les valeurs rencontrées dans les populations non exposées. Il n’existait aucune mise en évidence de mésothéliomes, de carcinomes bronchiques ni de pathologie infiltrative diffuse. Les études de mortalité étaient négatives en ce qui concernait les pathologies pulmonaires. Par ailleurs, l’exposition aux fibres céramiques ne concerne que le milieu professionnel et non pas le grand public.
Refractory ceramic fibres (RCF) are amorphous man-made mineral fibres used for high-temperature insulation applications. RCF are less biopersistent than amphibole asbestos, but more durable than other vitreous fibres such as glass-wools. Their biopersistance is equivalent to that of rock wools and less than that of E glass fibres and 475 glass fibres. As produced, some RCF are breathable. European and North American health authorities have classified RCF as “potentially carcinogenic in humans”. As a result, in France, about 70% of RCF have been replaced by fibres produced from Alkaline Earth Silicate (AES) whose physical properties were considered to be advantageous for heat insulation at high temperature, with little or no related health risk. In the regulations governing the use of RCF based on occupational exposure limit values (OEL), it has been planned to lower the exposure threshold to 0.1 f/cm³ as from July 1, 2009 (Decree 2007-1539 of October 26, 2007).
The principal aim of this work is to determine the health risks associated with RCF and then to report main data about these fibres.
Toxicological studies conducted on rodents using several exposure methods reported lung carcinoma and mesothelioma. After analysis, they were attributed to lung overloading Epidemiological studies on European and American professionals in the RCF production industry reported symptoms of dyspnea and recurrent chest pain, spirometric data showing a fall in the maximum expired volume in one second and lower vital capacity among smokers assigned to a production job position (only in the 1980s), and radiological data showing an increased prevalence of pleural plaques. The average prevalence of pleural plaques of exposed workers (2.7%) did not however exceed the values noted in the nonexposed population. No evidence of mesothelioma, bronchial carcinoma or diffuse infiltration pathology was shown. Mortality study results were negative as far as lung pathologies were concerned. Furthermore, the exposure to ceramic fibres concerns only the occupational environment and not the public at large.
Diseases of the Lung and Pleura
2005, Textbook of Clinical Occupational and Environmental Medicine
Mortality of workers employed in refractory ceramic fiber manufacturing: An update
2022, Journal of Applied Toxicology

View all citing articles on Scopus

: This study was supported by the Refractory Ceramic Fiber Coalition and National Institute of Environmental Health Sciences grant No. 5-P30-ES06096–09.

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Chest

Occupational and Environmental Lung DiseaseA Longitudinal Study of Chest Radiographic Changes of Workers in the Refractory Ceramic Fiber Industry

Study objective

Design

Participants

Measurements and results

Conclusions

Section snippets

Subjects

Radiography

Pleural Changes

ACKNOWLEDGMENT

Reg Toxicol Pharmacol

Environ Res

Chest

Health and safety aspects of man-made vitreous fibers: part IV

Recent studies of man-made vitreous fibers

J Occup Med

Studies on the chronic toxicity (inhalation) of four types of refractory ceramic fiber in male Fischer 344 rats

Inhal Toxicol

Multiple-dose chronic inhalation toxicity study of size-separated kaolin refractory ceramic fiber in male Fischer rats

Inhal Toxicol

Chronic inhalation toxicity of a kaolin-based refractory ceramic fiber in Syrian golden hamsters

Inhal Toxicol

Radiographic changes among workers manufacturing refractory ceramic fibre and products

Ann Occup Hyg

Refractory ceramic fiber exposure and pleural plaques

Am J Respir Crit Care Med

Longitudinal estimates of pulmonary function in refractory ceramic fiber manufacturing workers

Am J Respir Crit Care Med

An industry-wide pulmonary study of men and women manufacturing refractory ceramic fibers

Am J Epidemiol

Assessment of current fibre and silica exposure in the U.S. refractory ceramic fibre manufacturing industry

Ann Occup Hyg

Guidelines for the use of ILO international classification of radiographs of pneumoconiosis

Selection of measures of exposure for epidemiology studies

Appl Occup Environ Hyg

Time-weighted averages, peaks and other indices of exposure in occupational epidemiology

Am J Indust Med

Occupational and Environmental Lung Disease
A Longitudinal Study of Chest Radiographic Changes of Workers in the Refractory Ceramic Fiber Industry