Filter Cassette Method for Analyzing Man-Made Vitreous Fibers Settled on Surfaces

Area of Science:

• Environmental Science
• Analytical Chemistry
• Occupational Health

Background:

• Accurate surface fiber quantification is crucial for assessing indoor environmental quality and potential health risks.
• Traditional methods like gel tape sampling have limitations in sensitivity and scope across different environments.
• Standardized methods are needed for reliable fiber analysis in diverse settings.

Purpose of the Study:

• To develop and validate a novel method for analyzing surface fiber counts using filter cassettes and scanning electron microscopy (SEM).
• To compare the performance of the new method against the traditional gel tape sampling method (ISO 16000-27).
• To evaluate the applicability of the new method across a wide range of fiber concentrations and environmental types.

Main Methods:

• Surface sampling using suction onto a cellulose filter within a filter cassette.
• Microwave digestion of filters in dilute acid, followed by filtration onto polycarbonate filters.
• Analysis of fibers using Scanning Electron Microscopy (SEM) after gilding.

Main Results:

• The filter cassette method showed comparable results to gel tape sampling between 100 and 10,000 fibers/cm².
• The new method yielded systematically higher fiber counts in high concentrations (>10,000 fibers/cm²) and in office environments (0.1-20 fibers/cm²).
• SEM analysis allows for the inclusion of a wider range of fiber sizes compared to phase contrast microscopy.

Conclusions:

• The filter cassette method is recommended for working environments with >100 fibers/cm² and office environments with <10 fibers/cm².
• New guide values may be necessary for office environments due to higher counts obtained with the filter cassette method.
• Standardization for fiber size inclusion in SEM analysis is advised to ensure consistent and relevant results.