ABSTRACT
<p><b>OBJECTIVE</b>To compare the determination methods of fiber number concentration between China and WHO.</p><p><b>METHODS</b>Individual fiber samplings were conducted at a RCF manufacturing enterprise for 40 types of work. Flow rate was set as 2 L/min and lasted 2 to 4 hours. We used acetone-triacetin to prepare samples. The rules of two methods were used to count fibers for each sample respectively. The differences between the results of two methods were compared using the sign-rank test, and the correlation between the two methods' counting results were evaluated by the Spearsman rank correlation analysis.</p><p><b>RESULTS</b>The results of WHO counting rule were higher than those of Chinese counting rule for the same sample. The ratios of WHO method to Chinese method ranged from 1.88 to 3.70. Paired sign-rank test found the statistically significant differences of the results between the two methods (P<0.01). The rank correlation coefficient of the results by two rules counting ranged between 0.621 to 0.975, suggested positive correlation (P<0.01). The possible reasons of the difference between the two methods included the difference between the shapes of asbestos fiber and man-made mineral fiber, and counting rules of two methods.</p><p><b>CONCLUSION</b>The results of WHO counting method is higher than those of Chinese counting method. High correlations between the results of the two methods were observed.</p>