Hexavalent chromium exposures and exposure-control technologies in American enterprise: results of a NIOSH field research study.

The National Institute for Occupational Safety and Health (NIOSH) conducted 21 field surveys in selected industries to characterize workers' exposures to hexavalent chromium-containing airborne particulate and to evaluate existing technologies for controlling these exposures. Hexavalent chromium Cr(VI) is a respiratory irritant and chronic inhalation may cause lung cancer. Primary evaluation methods included collection of full work shift, personal breathing-zone (PBZ) air samples for Cr(VI), measurement of ventilation system parameters, and documentation of processes and work practices. This study emphasized evaluation of engineering exposure control measures, so PBZ exposures were measured on the outside of personal protective equipment, for example, respirators. Field surveys were conducted in two chromium electroplating facilities, including one where full-shift PBZ exposures to Cr(VI) ranged from 3.0 to 16 times the 1 micro g/m(3)NIOSH recommended exposure limit (REL) despite several engineering controls on the plating tanks. At a painting and coating facility that used Cr(VI)-containing products, full-shift exposures of painters and helpers (2.4 to 55 micro g/m(3)) exceeded the REL, but LEV effectiveness was limited. Other operations evaluated included welding in construction; metal cutting operations on chromium-containing materials in ship breaking; chromate-paint removal with abrasive blasting; atomized alloy-spray coating; foundry operations; printing; and the manufacture of refractory brick, colored glass, prefabricated concrete products, and treated wood products. NIOSH researchers concluded that, in many of the evaluated processes, Cr(VI) exposures at or below the current NIOSH REL are achievable. However, for some processes, it is unclear whether controlling exposures to this range is consistently achievable without respirator use. Some operations involving the application of coatings and finishes may be among those most difficult to control to this range. Most operations judged to be moderately difficult to control to this range involve joining and cutting metals with relatively high chromium content. Nonetheless, exposures in a wide variety of other processes were judged more easily controllable to the current REL or below, or were found to be minimal, including some operations meeting the general descriptions named above but with different specific operating parameters producing lower Cr(VI) exposures.

Electromyographic and discomfort analysis of confined-space shipyard welding processes.

This study examined muscle fatigue and discomfort in a confined-space welding operation at a shipyard. Surface electromyography (SEMG) was recorded from seven upper extremity and torso muscles of welders welding in a mock-up of the work environment. Following spectral transform of the SEMG data the percentage of the total signal power in the 10-30 Hz frequency band was compared over time during welding. For the conventional stick electrode welding process (SMAW) several muscles exhibited an increase in the percent of the total signal power in the low-frequency band. Fewer muscles exhibited this fatigue-related spectral density shift with a wire welding process (FCAW) the shipyard has considered adopting. This finding suggests that localized muscle fatigue may be reduced by a change to the wire welding process. Subjectively reported discomfort was generally low for both processes, but confirmed the finding that discomfort in the low back and shoulder regions is experienced in this welding operation.

Summary of the NIOSH guidelines for air sampling and analytical method development and evaluation.

Suggested guidelines for the development and evaluation of sampling and analytical methods for industrial hygiene monitoring have recently been published in a NIOSH technical report. These guidelines are based in part on various published approaches for method development and evaluation and serve as an attempt at a more unified experimental approach. This paper presents some salient features of this unified approach for method development and evaluation. The basic goal of the approach is to determine if the method under study meets the criterion to produce a result that fell within 25% of the true value 95 times out of 100 on average, although other factors of method performance are evaluated. The experiments proposed for the evaluation of method performance include determination of analytical recovery from the sampler, sampler capacity, storage stability of samples and effect of environmental factors. Evaluation criteria for the experimental data and procedures for the calculation of method bias, precision and accuracy are also included.

Phase contrast microscopy asbestos fiber counting performance in the Proficiency Analytical Testing program.

This report evaluates 20 years (1972-1992) of asbestos fiber count reporting for the Proficiency Analytical Testing (PAT) program, which is operated by the American Industrial Hygiene Association (AIHA) in cooperation with the National Institute for Occupational Safety and Health (NIOSH). Estimates were obtained for total, intracounter, and intercounter variability. Results show that total variability of counting chrysotile asbestos fibers improved by approximately 35% in recent years when compared with the variability found during 1975-1977, at the lowest filter fiber densities used in the PAT program. Total, intercounter, and intracounter variability for counting amosite and chrysotile asbestos fibers also were compared over a six-year period starting in 1986. PAT program laboratories achieved about one-quarter lower intracounter variability and about one-third lower total and intercounter variability when counting amosite fibers versus chrysotile fibers. In addition, amosite intercounter variability improved by about one-third, with large improvements occurring in the first year that amosite was included in the program. Factors affecting performance, such as changes in phase contrast microscope fiber counting methods, PAT participation, the AIHA Laboratory Accreditation Program, and PAT sample production, are discussed as possible factors affecting variability.

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.

Comparison of three sampling and analytical methods for measuring m-xylene in expired air of exposed humans.

Three breath sampling and analytical methods were tested following exposure of 12 subjects for 4 hr to 75 ppm m-xylene in a controlled environmental chamber. Mixed-expired breath was sampled for m-xylene from all 12 subjects with a new stainless steel device that permits continuous mainstream or sidestream sampling of the solvents present. The m-xylene was sampled from the mainstream using charcoal cloth and from the sidestream using Tenax TA. Alveolar breath also was sampled for m-xylene from 6 of these subjects using bags. The carbon dioxide concentrations of the mixed and alveolar samples, obtained from these 6 subjects, were also determined and used to assess the accuracy of the mixed-expired sampling and analytical procedures. Breath sampling was conducted over the immediate 240-min postexposure period. All m-xylene samples were analyzed using gas chromatography with flame ionization detection. Carbon dioxide concentrations were determined with an infrared analyzer. Nonlinear regression analysis was used to model the desaturation of m-xylene via the breath. Overall, the desaturation of m-xylene from all subjects by all methods was best described using three-compartment pharmacokinetic models. The precision of each sampling and analytical method, estimated from the residual variabilities of the desaturation curves were 0.13 for alveolar sampling, 0.14 for mainstream-mixed sampling (12 subjects), and 0.23 for sidestream-mixed sampling (12 subjects). For all 12 subjects, the breath m-xylene concentrations determined by sidestream-mixed sampling averaged 83% of those determined by mainstream-mixed sampling; this bias was significant. For the 6 subjects from whom both mixed-expired and alveolar breath samples were obtained, the average m-xylene desaturation rates determined by both mainstream-mixed and alveolar sampling were comparable but substantially different from those determined by sidestream-mixed sampling. For these subjects, comparison of the average and individual mixed to alveolar ratios of m-xylene and carbon dioxide showed that mainstream-mixed sampling was accurate and that sidestream-mixed sampling was not.

Performance of asbestos fiber counting laboratories in the NIOSH proficiency analytical testing (PAT) program.

Asbestos fiber counting data reported in the NIOSH Proficiency Analytical Testing (PAT) Program are used in this study to evaluate the analytical performance of participating laboratories and to determine if overall performance has improved during a ten-year period. PAT laboratories have achieved intralaboratory precision of 0.18 to 0.28 relative standard deviation (RSD), and interlaboratory precision of 0.33 to 0.44 RSD. In addition, there was higher variability between PAT laboratories from 1974 to 1978, when the program underwent considerable change and growth than the variability found during previous or subsequent time periods. The improvements in interlaboratory precision by approximately one-third since 1974 and the tendency of laboratories with little PAT experience to have poorer interlaboratory precision than more experienced laboratories raises a concern that interlaboratory precision may deteriorate as large numbers of new laboratories start to enroll in the PAT Program with the increased emphasis on asbestos removal in public buildings.

Methylphenidate therapy for aggression in a man with ring 22 chromosome. Report and literature review.

A 28-year-old mentally retarded man with ring 22 chromosome [r(22)] had deterioration of mood and behavior, decreased speech, bradykinesia, and decline of fine motor skills over a three-year period, which were further exacerbated by treatment with phenothiazines. A trial of methylphenidate hydrochloride resulted in rapid improvement of mood, behavior, and to a small extent, motor function. This finding suggests that dopamine depletion may play a role in the behavioral deterioration seen in this disorder. The possibility that genes that control dopamine metabolism may be present on chromosome 22 is raised. The phenotype of this patient is compared with the 25 reported cases of r(22).

Control of styrene vapor in a large fiberglass boat manufacturing operation.

An evaluation of a control system for worker protection from styrene vapor was performed at a manufacturer of large fiberglass reinforced plastic yachts. The manufacturing operations included five tiltable boat hull mold stations. Each station had a floor air slot located beneath the mold which was exhausting about 17 000 CFM. The building had an overall ventilation rate of 10-15 air changes per hour. An attempt was made to improve the performance of this control system by blowing air into the hull mold and by blocking air flow from the back of the mold to induce greater flow from the front of the mold. Consecutive short term breathing zone samples were collected in an effort to show the effect of different job tasks and work modes on exposures. ANOVA was performed to determine levels of significance of several variables. A significant exposure difference was found between right and left tilts of the 46-foot hull mold. The TWA styrene exposure values for the 3-day period of the 4 hull lamination workers were low, ranging from 17 ppm to 25 ppm, and demonstrating that styrene levels can be effectively controlled by means of strategically located high volume exhaust vents for the process studied.

Arteriohepatic dysplasia (Alagille syndrome): extreme variability among affected family members.

We describe a three-generation family in which five individuals have arteriohepatic dysplasia (Alagille syndrome) with striking differences in the degree of severity. Two sisters presented with neonatal jaundice, peripheral pulmonic stenosis, and characteristic facial appearance including a broad forehead, deep-set eyes, prominent nose, and pointed chin. One died at 5 years of cirrhosis with portal hypertension and the other at 18 months of congestive heart failure. Their asymptomatic 32-year-old mother and 35-year-old maternal aunt have a similar facial appearance, pulmonic stenosis, skeletal anomalies, and bilateral posterior embryotoxon. Neither has evidence of clinical liver disease. The maternal grandfather, who refused evaluation, has a similar appearance, a history of liver disease, and a heart murmur. Extreme intrafamilial variability has not been reported previously and most affected individuals described in the past have followed a benign course. The pattern of severity in this family suggests the possibility of a maternal factor augmenting the clinical expression in affected offspring. The skeletal anomalies and posterior embryotoxon are valuable signs in detecting asymptomatic but affected individuals who are at risk for having offspring with this potentially lethal condition.

Identification and counting of asbestos fibers.

A combined analytical electron microscopic/optical count method for the determination of airborne asbestos fibers was tested for precision and bias. A modified phase contrast microscopic count method (NIOSH Method 7400) was used to determine total fiber content. The analytical electron microscope (AEM) procedure was added to identify the fraction of amosite asbestos fibers in airborne, laboratory-generated samples containing amosite and wollastonite fibers. Then this fraction was applied to the routine optical counts of all the samples in the set to estimate the asbestos fiber concentration. The effects of sample to sample, wedge to wedge, within wedge and between and counter variability were examined. In addition, the variabilities of the elemental ratio within a fiber and between fibers was also determined to find their possible influence on the ability to identify the fiber as amosite in the presence of other silicate fibers. A precision of 20.1% relative standard deviation (RSD) and a bias of -9.1% for the AEM count method compared with the optical count procedure were found for these mixed fiber samples.