Complicated silicosis refers to the development of progressive massive fibrosis (PMF) in which pulmonary nodules (typically 2-6 mm in diameter) coalesce into larger conglomerations. PMF has been observed to develop in a small percentage of patients with simple chronic silicosis and a large percentage of patients with accelerated silicosis. Accelerated silicosis is similar to simple silicosis, but the disease develops after a heavier exposure over a shorter time period. The latency is 2 to 5 years for accelerated silicosis, versus greater than 10 years for simple silicosis. Accelerated silicosis follows a course of increasing dyspnea. [LaDou, p. 378-80] The prevalence of accelerated silicosis was 29% in a cross-sectional study of 574 Chinese gold miners (rock drillers) exposed for an average of 5.6 years. [PMID 17948247
] "In 2012, there were more than 50,000 surface coal miners in the United States--44.3% of the coal mining workforce. . . . Surface coal mining has generally been considered less dusty than underground mining; however, highwall drills at surface mining operations can generate large quantities of respirable dust containing significant levels of crystalline silica. . . . Pneumoconiosis was found among 2.0% of the 2328 screened miners with at least 1 year of mining tenure. Twelve miners had radiographic changes consistent with PMF." [PMID 25563541
]Silicosis is associated with an increased risk of autoimmune diseases. [PMID 16691610
] [PMID 11811933
] and [PMID 17036363
] "Silicosis mortality declined steadily in the US during the second half of the 20th century, with about 30 deaths occurring annually between 1995-2004." [PMID 30448860
] See "Silicosis, simple" and "Silicosis, acute."