Martin T. Abell

A Sampling and Analytical Method for the Simultaneous Determination of Multiple Organophosphorus Pesticides in Air

A sampling and analytical method for organophosphorus pesticides using a combined filter/XAD-2 sorbent sampler and gas chromatography (GC)-flame photometric detection (FPD) was developed. The method was evaluated for 19 organophosphorus pesticides based on the joint Occupational Safety and Health Administration/National Institute for Occupational Safety and Health Standards Completion Program methods evaluation protocol. The evaluation addressed analyte recovery, sampler capacity, sample stability, and precision and accuracy. Additional experiments addressed long-term sample stability (30-day storage), short-term exposure limits, limits of detection, and concentration levels down to 0.1 times an exposure limit value. Samples were stable for 30 days of storage under either ambient or refrigerated conditions. Based on this research, all 19 compounds studied can be successfully determined simultaneously using one method with an accuracy of +/- 25% of the true value 95 times out of 100.

Performance of laboratories measuring silica in the Proficiency Analytical Testing program.

A statistical study was performed on the results reported by laboratories analyzing silica samples in the first 101 rounds of the Proficiency Analytical Testing (PAT) program. Five laboratories participated in the first round of the PAT program in 1972, and participation grew to 130 laboratories before falling to 105 in Round 101. The laboratories use all three of the major methods of analysis: colorimetry, x-ray diffractometry, and infrared spectroscopy. The objectives of the study were to determine bias between methods, the variability associated with the methods, and any changes in bias or variability caused by a number of factors. The colorimetric method has consistently given the lowest results, particularly at higher loadings. X-ray diffractometry results were biased higher than infrared spectroscopy results during one period but not in the following period. Between the two periods, the procedures and materials used to prepare PAT samples changed in a number of ways, but the switch to quartz dust with a smaller particle size is a likely explanation for the bias difference. Generally, silica analyses have improved in precision over time, and this improvement has taken place for all three of the methods. The colorimetric method has shown the poorest precision of the three methods, but, unlike the differences in bias, the differences in precision have diminished considerably over time. Precision estimates from other studies were compared to those from this study to learn more about sources of variability. The largest source of variability, the differences between laboratories, was large even when laboratories used the same method, as they did in a collaborative study of silica methods.

An Ion Chromatographic Method for Insoluble Chromates in Paint Aerosol

Potential exposure to Cr(VI) extends to over a million U.S. workers in the plating, paint, steel, tanning and chrome ore processing industries. Historically, Cr(VI) exposure has been monitored using a colorimetric method. This colorimetric method requires acidification of the sample for color development, a step that could cause reduction of Cr(VI) to Cr(III), thus underestimating the Cr(VI) content of the sample. A new method of analysis has been developed that uses ion chromatography (IC) for the measurement and which does not require acidification of the sample. In this method, the same extraction solution of hot 2% NaOH and 3% Na2CO3 as used in the earlier methods is used to dissolve both soluble and insoluble chromates (e.g., PbCrO4, ZnCrO4 and BaCrO4), but it can be carried through the method with only a dilution step before sample injection. Therefore, this method has the advantage of minimizing the potential for Cr(VI) loss by reduction. Another advantage is provided by the IC measurement step, which is not interfered with by colored samples that may affect the colorimetric method. The new method was tested with filter samples of paint aerosol containing PbCrO4 and ZnCrO4. Complete extraction of Cr(VI) from the filter samples was verified by comparison to an independent method in which the filter was completely ashed and analyzed by inductively coupled plasma-atomic emission spectroscopy method. Nothing in the paint samples interfered with the Cr(VI) measurement, nor did five common anions used in a separate test. The method had the sensitivity needed for monitoring at the ACGIH TLV of 0.05 mg Cr(VI)/m3.

A Simple Reliable Method for the Determination of Airborne Hexavalent Chromium

A method is presented to determine airborne hexavalent chromium concentrations. Samples collected on poly vinyl chloride membrane filters have good long term stability and are easily washed clean so that a colorimetric determination with diphenylcarba-zide can be performed up to two weeks after the time the sample was originally collected.

The Quality of Fiber Count Data

Abstract Optical fiber counts are used to determine asbestos exposure, so it is important to assess, control, and document the quality of those counts. These functions are the responsibility of the quality assurance (QA) coordinator in each laboratory. The QA coordinator must recognize that, compared to the analytical results for other substances, fiber count data are much more variable and have different statistical properties. These data, therefore, warrant special treatment. This article discusses the need to recount some samples, the procedures for determining bias and variability from these recount data, and the use of these statistics to test analytical results or assign confidence limits to them. Three kinds of bias and variability must be considered: intracounter, intra-laboratory, and interlaboratory. As data pairs (count and recount) are obtained, the first consideration is whether bias is present. If bias is detected in a set of data, that data should not be used for any purpose until the sourc...

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.

Research Recommendations of the NORA Exposure Assessment Methods Team

The National Occupational Research Agenda (NORA) is a framework to guide occupationalsafety and health research into the next decade. This framework is beingbuilt by National Institute for Occupational Safety and Health (NIOSH) and its partners in industry, academia, and labor. Over 500 individuals and organizations from outside of NIOSH partnered to develop the NORA concept. The process embodies 20 partnership teams addressing 21 priority research areas. Each partnership team includes members from NIOSH, other government agencies, academia, labor, and industry. The team that is the focus of this presentation is the exposure assessment methods (EAM) team. The goals of the EAM team include:

A Computer Program to Promote Understanding of the Monitoring Method Evaluation Guidelines Used at NIOSH

A computer-based training program has been devised to promote better understanding of the recently revised National Institute for Occupational Safety and Health (NIOSH) test guidelines applicable to methods requiring on-site sample collection and laboratory sample analysis of airborne toxic substances. A statistics section explains the basis of the NIOSH accuracy criterion (NAC); an experiments section provides details on the evaluation experiments; and a calculations section calculates method statistics based on data entered by the user. The statistics section graphically explains concepts such as the NAC and limit of detection, allowing the user to experiment with some parameters to see how the results are affected. This section also provides background material to show how some of the performance criteria evolved. The experiments section provides a summary of the experiments used to generate the data for method evaluation. The calculations section has several screens that work like customized spreadsheets for the entry of data collected during the laboratory evaluation of a method. A separate screen then calculates the precision (relative standard deviation) of analytical results at each of four concentrations, tests to see if the precision values are statistically homogeneous, and combines the homogeneous data for calculation of the relative standard deviation. It does the same for bias, and combines the precision with method bias to arrive at an estimate of method accuracy. Other screens in the calculations section facilitate the determination of method limit of detection and sample storage stability.

Benefits of a Nickel-Cadmium Battery Cycler

Abstract A battery cycler that could prolong the life of nickel-cadmium batteries used in personal sampling pumps was described several years ago in the industrial hygiene literature. Cycling involves discharging a battery to a predetermined voltage level, then recharging at a fixed rate for a timed interval. The cycler evaluated here was fashioned after that earlier cycler, but has an improved recharge timer. Current capacity measurements of batteries during discharge have shown that cycling can improve the capacity of older batteries. Measurements on 17 used battery packs gave the following results: 5 improved substantially, 2 improved slightly, 9 were unchanged, and 1 actually deteriorated. Measurements on newer, unused battery packs showed there is no benefit to cycling them. Kovein, R. J.; Abell, M. T. Benefits of a nickel-cadmium battery cycler.

Personal Pump Reliability Tester

Abstract A test instrument has been built that measures, displays, and records the flow rate of up to 15 personal sampling pumps. The “Pump Tester” is typically run for eight hours with five or six pumps of one type and displays a graph of flow rate over time for each pump. The flow record for each pump contains up to 240 data points and, although not continuous, provides a useful record of pump performance over long test periods. The numerical flow data can be printed and saved to disk. At the end of the test, the flow-rate graph for each pump is printed. The flow-rate graph can be added to the maintenance and calibration record for the pump to document its performance. Occasionally, erratic pump performance is documented that would not have been detected by flow-rate checks at the beginning and end of an eight-hour period. The Pump Tester can also be used for more formal studies to demonstrate the relative performance of different kinds of pumps under different conditions.