Prevalence and Severity of Specific Pneumoconiosis Lesions Among Autopsied Miners Who Worked Only Under the New Dust Regulations (n = 662) Compared With Those Who Worked Only Under the Old Dust Regulations (n = 2217), National Coal Workers' Autopsy Study, 1971-1996 (a) Pneumo- Prevalence (%)
coniosis Old New Lesion Severity Regulations (b) Regulations (c) P (d) Coal Absent 17.4 41.2 <.001 macules Mild 33.2 35.2 Moderate 34.0 18.7 Severe 15.4 4.8 Coal Absent 53.7 85.0 <.001 nodules Mild 21.4 9.4 Moderate 12.0 3.8 Severe 12.9 1.8 Silicotic Absent 71.8 92.0 <.001 nodules Mild 15.3 5.9 Moderate 6.9 0.9 Severe 6.0 1.2 PMF Absent 89.7 98.8 <.001 Present 10.3 1.2 Abbreviation: PMF, progressive massive fibrosis.