9Ballal SG, Ahmed HO, Ali BA, el al. Pulmonary effects of occupational exposure to Portland cement: a study from eastern Sandi Arabia[J]. Int J occup Environ Heahh,2004, 10(3):272-277.
10Blackford JA, Jones W, Dey RD, el al. Comparison of inducible nitric oxide synthase gene expression and lung inflammation following intratracheal instillation of silica, coal, carbony iron, or titanium dioxide in rats [J]. J Toxical Environ Health, 1997,27:203-218.