Monitoring the performance of occupational health laboratories.

To monitor the performance of occupational health laboratories analyzing workplace air, the American Industrial Hygiene Association (AIHA), with assistance from the National Institute for Occupational Safety and Health, has established four national quality assurance programs. They are the Proficiency Analytical Testing (PAT) Program, the AIHA Laboratory Accreditation Program, the Asbestos Analysts Registry, and the Bulk Quality Assurance Program. This paper focuses on the PAT program, a quality audit program that provides samples of asbestos, silica, metals, and solvents to laboratories quarterly. PAT data for asbestos, silica, and lead were examined for trends in precision. Simple graphs of coefficient of variation during the 18-yr history of the program provide evidence of improved agreement among laboratories performing these analyses. The improvement took place in spite of growth in the number of laboratories and decreases in the levels being analyzed. The improvement is attributed to several factors, including improved analytical methods and the very existence of the PAT and AIHA Laboratory Accreditation Programs.