Bulk asbestos laboratory programs in the United States—Seventeen years in retrospect
Quality assurance and proficiency testing programs have been available for 17 years in the United States for laboratories analyzing for asbestos in bulk building materials by polarized light microscopy. After peaking in the late 1980's, total enrollment has dropped but stabilized in the last four years to 700–750 laboratories, and participation rates currently exceed 95%. Almost 122 000 test samples have been sent worldwide by Research Triangle Institute to laboratories in four major programs. A review of nearly 113 000 analysis results reveal that a small number of bulk building materials cause the majority of difficulties in each of the programs, although error frequencies vary from program to program. Improvement has occurred in overall laboratory performance since the first programs began in the early 1980's, with a significant decline in qualitative errors and a much less dramatic decrease in errors associated with semiquantitative estimation of the amount of asbestos present.