Effect of styrene and fiber glass on small airways of mice

Non-malignant respiratory disease among workers in industries using styrene-A review of the evidence

BACKGROUND

Asthma and obliterative bronchiolitis (OB) cases have occurred among styrene-exposed workers. We aimed to investigate styrene as a risk factor for non-malignant respiratory disease (NMRD).

METHODS

From a literature review, we identified case reports and assessed cross-sectional and mortality studies for strength of evidence of positive association (i.e., strong, intermediate, suggestive, none) between styrene exposure and NMRD-related morbidity and mortality.

RESULTS

We analyzed 55 articles and two unpublished case reports. Ten OB cases and eight asthma cases were identified. Six (75%) asthma cases had abnormal styrene inhalation challenges. Thirteen (87%) of 15 cross-sectional studies and 12 (50%) of 24 mortality studies provided at least suggestive evidence that styrene was associated with NMRD-related morbidity or mortality. Six (66%) of nine mortality studies assessing chronic obstructive pulmonary disease-related mortality indicated excess mortality.

CONCLUSIONS

Available evidence suggests styrene exposure is a potential risk factor for NMRD. Additional studies of styrene-exposed workers are warranted. Am. J. Ind. Med. 60:163-180, 2017. © 2016 Wiley Periodicals, Inc.

Changes induced by exposure of the human lung to glass fiber-reinforced plastic

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.

Short-term crocidolite inhalation studies in mice: validation of an inhalation chamber

A nose-only inhalation chamber is described: this chamber being computer automated has been particularly designed for mice on which it was validated using a crocidolite aerosol at a nominal concentration of 13.6 mg/m3, 6 h/day during 5 days. A month later the mice showed typical inflammatory bronchoalveolar liquids with many polynucleated or activated macrophages and asbestos bodies. The burden of crocidolite fibers ranged from 345,000 to 1,300,000 fibers per mg of dried lung. This study demonstrates that during the month that followed a short-term mice exposure to crocidolite fibers, the inflammatory response was still persistent. These toxicological endpoints validate the nose-only inhalation chamber to be useful for common or transgenic mice.

Pulmonary response of hamsters to fibrous glass. Clearance and morphology after a single intratracheal instillation

In a one-year serial sacrifice study 10 mg glass fibres (length, 95% alpha 20 microns, 89% alpha 12 microns, 58% alpha 5 microns and 25% alpha 2 microns; diameter, 88% alpha 1.0 micron, 60% alpha 0.5 micron and 31% alpha 0.25 micron) suspended in 0.2 ml saline solution were administered to Syrian golden hamsters by a single intratracheal instillation to determine the clearance of the glass fibres from the lungs and to examine their effects on the lungs using light and electron microscopy. The clearance was rather efficient with a half-time of about 3 months. Coating and corrosion of glass fibres were sporadic findings. A violent focal acute pneumonitis was evoked by the glass fibres and was followed by excessive accumulations of alveolar macrophages often loaded with glass fibres. Thereafter, "silicotic granulomas" developed which were seen as clusters of tightly packed iron-positive macrophages containing glass fibres. These granulomas were surrounded by a layer of alveolar epithelium, and were by the end of the study the predominant lesion in otherwise normal lungs.