PULMONARY RETENTION OF CERAMIC FIBERS IN SILICON-CARBIDE (SIC) WORKERS

The fibrous inorganic content of post-mortem lung material obtained fr om 15 men who worked in the primary silicon carbide (SiC) industry was evaluated, Five men had neither lung fibrosis nor lung cancer (NFNC) sin had lung fibrosis(LF), and four had lung fibrosis and lung cancer (LFLC). The workers had 23 to 32 years of exposure. Mean duration of e xposure was 23.4 (SD 6.9) years in the NFNC group, 28.8 (SD 5.5) in th e LF, and 32.3 (SD 9.0) in the LFLC group. Concentrations of SIC ceram ic fibers and other fibrous minerals and angular particles were determ ined by transmission electron microscopy and energy dispersive spectro scopy. The geometric mean and geometric standard deviation lung concen trations of SiC ceramic fibers < 5 mu m were not statistically differe nt for the three groups (Mann-Whitney, p > 0.1). Pulmonary retention o f SiC fibers greater than or equal to 5 mu m showed art excess in LF a nd LFLC cases combined versus NFNC that approached statistical signifi cance (Mann-Whitney, p = 0.06). There was a somewhat greater differenc e for lung retention of ferruginous bodies between NFNC and either LF or LFLC cases (Mann-Whitney, p = 0.02). SiC fibers greater than or equ al to 5 mu m and angular particles containing Si and especially ferrug inous bodies were found at higher concentrations in LF and LFLC than i n NFNC cases.