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.

Critique of 1985 ACGIH report on particle size-selective sampling in the workplace.

The criteria recently proposed by ACGIH for judging the acceptability of respirable and other dust fraction samplers are analyzed. Implications on the sampling of workplace aerosol are determined. With the consideration of both bias and imprecision, the overall accuracy limited by the criteria is estimated for the sampling of coal mine dust as characterized by various researchers. The accuracy limits thus found appear to be excessively broad. As an example with actual workplace dust distributions in the sampling of a single aerosol (mass median diameter = 18.6 micrometers and geometric standard deviation = 2.3) with respirable dust concentration near 2 mg/m3, two samplers acceptable according to the proposed criteria could be found giving respirable dust measurements equal to 0.71 mg/m3 and 4.3 mg/m3 (even after excluding 5% of the low and high measurements from each sampler, respectively). Large variation in samplers acceptable according to the criteria is found for many other distributions as well; this indicates that tighter requirements are necessary. Seldom attained are both the single-sample +/- 25% accuracy at the 95% confidence level required of sampling/analytical methods endorsed by the National Institute for Occupational Safety and Health (NIOSH) and the tighter ISO dust fraction measurement requirement that 67% of the measurements of a sampled dust fall within 10% of a true value. Suggestions are given for sharpening the criteria without eliminating all samplers from acceptability.

A modified impinger for personal sampling.

The performance of a modified impinger is described. Laboratory and limited field studies found that the modification made the device relatively spill-proof. In addition, the collection efficiency of the spill-proof impinger was compared to the standard midget impinger. For particles larger than 0.8 micrometer equivalent aerodynamic diameter, the impaction efficiencies of the two devices were found to be identical. However, the capture efficiencies of the two devices were not always found to be equivalent. In three tests, the modified impinger collected proportionately more material than the midget impinger. In three other tests, the capture efficiencies of the two devices were found to be equivalent.

A solid sorbent personal sampling method for the simultaneous collection of nitrogen dioxide and nitric oxide in air.

A sampling method is described for the collection of air samples containing both nitrogen dioxide (NO2) and nitric oxide (NO) in the range of 0.5 to 5 ppm NO2 and 9 to 50 ppm NO. These two gases are trapped on a solid sorbent sampling tube which employs the collection of the NO2 on a triethanol-amine (TEA)-impregnated molecular sieve surface; the oxidation of NO to NO2 by a solid oxidizer; and the collection of the converted NO on another section of TEA sorbent. The trapped NO/NO2 on each TEA section is desorbed and the concentrations are determined spectrophotometrically. At all concentrations tested, the collection efficiency for NO2 averaged approximately 96%. The collection efficiencies for NO were as follows: at 9 ppm, 97%; at 11 ppm, 106%; at 24 ppm, 84%; and at 50 ppm, 67%.

Performance characteristics of the 10 mm respirable mass sampler: Part II--coal dust studies.

The 10 mm cyclone respirable mass sampler was evaluated to determine the flow rate which best matched the BMRC and the LASL-ACGIH criteria, and to determine effects of pulsating flow, particle charge, mass loading, and sampler orientation. Part II, this paper, presents the work with coal dust. There is no significant difference between results obtained, for normal ranges of airborne dust concentration and size distribution, due to particle charge, sampler orientation or position (except upside down, which was not investigated), dust concentration, and ambient air velocity.

Performance characteristics of the 10 mm cyclone respirable mass sampler: part I--monodisperse studies.

The 10 mm cyclone respirable mass sampler was evaluated to determine the flow rate which best matched the BMRC and the LASL-ACGIH criteria and to determine effects of pulsating flow, particle charge, mass loading and sampler orientation. Part 1, this paper, describes the work with monodisperse aerosol. The best match for BMRC was 1.4 lpm; for LASL, 1.7 lpm. The two separate criteria should be merged. The 10 mm cyclone is two separate criteria should be merged. The 10 mm cyclone is better for sampling logistics than the BMRC horizontal elutriator.