Pneumoconiosis is an
occupational disease accompanied by long-term lung impairment, for which prediction of prognosis is poorly understood because of the complexity of the inhaled particles. Micro-
proton-induced X-ray emission (micro-PIXE) analysis, which is advantageous for high-sensitivity, two-dimensional
element mapping of lung tissues, was used to investigate
element-based predictive factors of prognosis in Chinese patients with welder's and
coal miner's
pneumoconiosis. Chest radiographs and lung function tests showed that most of the
coal miners deteriorated, whereas symptoms in some welders were alleviated after 5 yr, as determined by comparing percent vital capacity (%VC) and forced expiratory volume in the 1st second over forced vital capacity (FEV1.0/FVC) to values taken at the initial diagnosis. Micro-PIXE analysis suggested that the most abundant particulates in welder's
pneumoconiosis were Fe, Mn, and Ti (metallic
oxide),which were accompanied by particulates containing Si, Al, and Ca (
aluminum silicate) or only Si (SiO2); the most abundant particulates in
coal miner's
pneumoconiosis were composed of C, Si, Al, K, and Ti, which were accompanied by particulates containing Ca or Fe. Particulates containing Al, Si, S, K, Ca, and Ti (
orthoclase and
anorthite) were correlated with severity of
fibrosis. Multivariable linear regression suggested that long-term FEV1.0/FVC decrease was independently associated with Si and smoking index, whereas %VC decrease was associated with Si and Ti. A risk index comprised of these factors was developed to predict the prognosis of
pneumoconiosis. Micro-PIXE analysis is feasible for the evaluation of elemental composition and dust exposure, especially for patients whose exposure is mixed or uncertain.