[Comparison of two methods for fiber count concentration determination].

Area of Science:

• Occupational Health and Safety
• Environmental Science
• Industrial Hygiene

Background:

• Accurate determination of fiber number concentration is crucial for assessing occupational exposure risks.
• Existing methodologies, such as those from the World Health Organization (WHO) and China, may differ in their counting rules and application.
• Understanding these differences is vital for consistent and reliable exposure monitoring in manufacturing environments.

Purpose of the Study:

• To compare the fiber number concentration determination methods established by China and the WHO.
• To evaluate the statistical differences and correlations between the two methodologies.
• To identify potential reasons for discrepancies in fiber counting results.

Main Methods:

• Individual fiber air samplings were performed in a refractory ceramic fiber (RCF) manufacturing enterprise.
• Samples were prepared using acetone-triacetin, and fiber counting was conducted according to both Chinese and WHO counting rules.
• Statistical analysis included paired sign-rank tests for differences and Spearman rank correlation for association.

Main Results:

• The WHO counting method consistently yielded higher fiber number concentrations compared to the Chinese method, with ratios ranging from 1.88 to 3.70.
• Statistically significant differences (P<0.01) were observed between the results of the two methods.
• A strong positive correlation (Spearman's rank coefficient 0.621–0.975, P<0.01) was found between the counting results of both methods.

Conclusions:

• The WHO fiber counting method provides higher estimates of fiber number concentration than the Chinese method.
• Despite quantitative differences, a high degree of correlation exists between the two methods, suggesting comparability under certain conditions.
• Discrepancies may stem from differences in fiber morphology (asbestos vs. man-made mineral fibers) and specific counting rule interpretations.