RESUMEN
<p><b>OBJECTIVE</b>To provide scientific basis data for revising the national hygiene criteria of "Classification of hazard conditions of productive dust" (GB5817-86).</p><p><b>METHODS</b>The data of the retrospective study and the field survey data were analyzed with correlation and regression analysis. The product of total dust concentration of respiratory exposure (mg/m(3)), total ventilation during exposure (m(3)/d per psrson), and level of free SiO(2) in dust (%) was the respiratory exposure dose of free SiO(2) (mg per day per person) which was used as dose criteria value of classification of hazard degree of dust.</p><p><b>RESULTS</b>Using free SiO(2) exposure dose and the dose-effect relationship, the hazard degrees of the dust were divided into 5 grades: 0, I, II, III, IV (0 - 8.0, 8.1 - 12.0, 12.1 - 16.0, > 24.1 mg per day per person).</p><p><b>CONCLUSION</b>The exposure dose of free SiO(2) is closely related to the pathogenesis of silicosis. Using the exposure dose of free SiO(2) as the classification indicator of hazard degree of dust is reliable, simple and easy to execute.</p>