An exploratory cross-sectional study of serum biomarkers as related to respiratory outcomes and workplace silica exposure levels in UK brick-manufacturing and stone workers.

In a cross-sectional study of UK brick and stone workers exposed to respirable crystalline silica, Club cell protein (CC16), neutrophil gelatinase-associated lipocalin, platelet-derived growth factor (PDGFββ), C-reactive protein, rheumatoid factor, antinuclear antibodies, lung surfactant proteins A & D, and monocyte chemoattractant protein 1 were measured in serum samples from 261 workers. Questionnaire data on health outcomes were also recorded, along with spirometry and a chest X-ray. Individual cumulative respirable crystalline silica exposures were calculated. Four subjects (1.5%) had silicosis, and these were characterised by evidence of small airways obstruction, reduced predicted forced expiratory volume in 1 s and noticeable increases in monocyte chemoattractant protein 1 and surfactant protein A. CC16 and surfactant protein D significantly increased with cumulative respirable crystalline silica exposure, but CC16 also independently decreased with evidence of airflow obstruction or small airways obstruction. Therefore, the interpretation of serum CC16 levels in silica-exposed populations may be complex. There was some evidence of down-regulation of the PDGFββ pathway with increasing exposure. Surfactant protein D levels were also associated with several chronic respiratory symptoms reported by workers. Serum surfactant protein A, monocyte chemoattractant protein 1, and neutrophil gelatinase-associated lipocalin showed little or no relationship to cumulative respirable crystalline silica levels. These data raise the possibility that surfactant protein D, CC16, surfactant protein A, and monocyte chemoattractant protein 1 may have a role in defining the natural history of silicosis, with the latter 2 biomarkers possibly reflecting where pathology is evidenced on imaging techniques.