Changes Induced by Exposure of the Human Lung to Glass Fiber-Reinforced Plastic

Article excerpt

The inhalation of glass dusts mixed in resin, generally known as glass fiber-reinforced plastic (GRP), represents a little-studied occupational hazard. The few studies performed have highlighted nonspecific lung disorders in animals and in humans. In the present study we evaluated the alteration of the respiratory system and the pathogenic mechanisms causing the changes in a group of working men employed in different GRP processing operations and exposed to production dusts. The study was conducted on a sample of 29 male subjects whose mean age was 37 years and mean length of service 11 years. All of the subjects were submitted to a clinical check-up, basic tests, and bronchoalveolar lavage (BAL); microscopic studies and biochemical analysis were performed on the BAL fluid. Tests of respiratory function showed a large number of obstructive syndromes; scanning electron microscopy highlighted qualitative and quantitative alterations of the alveolar macrophages; and transmission electron microscopy revealed the presence of electron-dense cytoplasmatic inclusions indicating intense and active phlogosis (external inflammation). Biochemical analyses highlighted an increase in protein content associated with alterations of the lung oxidant/antioxidant homeostasis. Inhalation of GRP, independent of environmental concentration, causes alterations of the cellular and humoral components of pulmonary interstitium; these alterations are identified microscopically as acute alveolitis. Key words: BAL, biochemical analysis, bronchoalveolar lavage, glass fiber-reinforced plastic, lung, microscopy. Environ Health Perspect 114:1725-1729 (2006). doi:10.1289/ehp.8676 available via http://dx.doi.org/ [Online 23 June 2006]

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Glass fiber reinforced plastic (GRP) is an extremely versatile structural material composed of unsaturated polyester resin and fiberglass; objects made from it, obtained by manual or mechanical layering, are characterized by a low specific weight, high resistance to corrosives and atmospheric agents, and low thermal and electrical conductivity. Through a complex chain of events, exposure to fiberglass contributes to the development of pathologic alterations of the respiratory apparatus for which the etiopathogenesis and evolution are still unclear.

Hesterberg et al. (1993) observed that in rats the exposure to fiberglass does not cause lung fibrosis and/or the statistical increase of lung cancer and mesotheliomas; so they suggest that in humans the exposure to fiberglass dust does not represent a particularly important element in the evolution towards fibrosis and/or lung cancer. Adamson et al. (1995) and McConnell et al. (1999) reached a different conclusion: in studies conducted on animals, they found that glass fibers produced a fibrotic reaction. Dorger et al. (2000) reported a reduction of alveolar macrophage phagocytosis associated with increased production of reactive oxygen species in a study on phagocytic responses in rats and hamsters.

In studies of samples from exposed humans, Chiazze et al. (2002), Enterline et al. (1983), and Riboldi et al. (1999) found inconsistent evidence for a respiratory disease hazard related to exposure to fiberglass. In a case report, Takahashi et al. (1996) described a case of pulmonary fibrosis in a carpenter who had been exposed to glass fibers for 41 years.

Even more complex is the interpretation of the effects caused by exposure to GRP. In fact, the existing studies in the literature do not comprehensively clarify the pathogenetic mechanisms on the basis of the changes that take place (Morisset et al. 1979).

In this study we aimed to further increase the knowledge of alterations to the broncho-alveolar system induced by occupational exposure to GRP and to clarify the pathogenic mechanisms involved.

Materials and Methods

Subjects. We excluded subjects from the study based on the following criteria: heavy smokers (> 15 cigarettes/day); subjects with acute or chronic pathologies of the respiratory system; subjects reporting previous occupational exposure that might present a toxic risk for the respiratory system; and subjects with a family and/or personal history of neoplasia and/or respiratory pathologies. …