Marilyn F. Hallock

Mortality studies of machining fluid exposure in the automobile industry. V: A case-control study of pancreatic cancer.

Results are presented from a case-control study of 97 cases of pancreatic cancer nested in a cohort of workers from three automobile manufacturing plants. Risk was examined for lifetime exposure to straight, soluble, and synthetic metalworking fluids, as used in specific machining or grinding operations, as well as for constituents of the fluids. Pancreatic cancer was associated with exposure to synthetic fluids in grinding operations, with an odds ratio of 3.0 (95% CI: 1.2-7.5) among those with more than 1.4 mg/m3-years of exposure. We were unable to examine synthetic exposure in the absence of grinding because there was virtually no exposure to synthetics in machining operations in this study population. Although a disproportionately high percent of the cases were black, no black workers had any exposure to synthetic fluids, and no other measured exposure was found to be related to risk. Thus, the previously documented excess risk of pancreatic cancer among blacks in this cohort remains unexplained.

Characterization of exposures to nanoscale particles and fibers during solid core drilling of hybrid carbon nanotube advanced composites.

Abstract This work investigated exposures to nanoparticles and nanofibers during solid core drilling of two types of advanced carbon nanotube (CNT)-hybrid composites: (1) reinforced plastic hybrid laminates (alumina fibers and CNT); and (2) graphite-epoxy composites (carbon fibers and CNT). Multiple real-time instruments were used to characterize the size distribution (5.6 nm to 20 μm), number and mass concentration, particle-bound polyaromatic hydrocarbons (b-PAHs), and surface area of airborne particles at the source and breathing zone. Time-integrated samples included grids for electron microscopy characterization of particle morphology and size resolved (2 nm to 20 μm) samples for the quantification of metals. Several new important findings herein include generation of airborne clusters of CNTs not seen during saw-cutting of similar composites, fewer nanofibers and respirable fibers released, similarly high exposures to nanoparticles with less dependence on the composite thickness, and ultrafine (< 5 nm) aerosol originating from thermal degradation of the composite material.

A case-control study of cancer mortality at a transformer-assembly facility

SummaryTo address earlier reports of excess cancer mortality associated with employment at a large transformer manufacturing plant, each plant operation was rated for seven exposures: Pyranol (a mixture of poly chlorinated biphenyls and trichlorobenzene), trichloroethylene, benzene, mixed solvents, asbestos, synthetic resins, and machining fluids. Site-specific cancer deaths among active or retired employees were cases; controls were selected from deaths (primarily cardiovascular deaths) presumed to be unassociated with any of the study exposures. Using job records, we then computed person-years of exposure for each subject. All subjects were white males. The only unequivocal association was that of resin systems with lung cancer (odds ratio = 2.2 at 16.6 years of exposure, P = 0.001, in a multiple logistic regression including asbestos, age, year of death, and year of hire). Certain other odds ratios appeared larger, but no other association was so robust and remained as distinct after considering the multiplicity of comparisons. Study power was very limited for most associations, and several biases may have affected our results. Nevertheless, further investigation of synthetic resin systems of the type used in the study plant appears warranted.

Summary of the Findings from the Exposure Assessments for Metalworking Fluid Mortality and Morbidity Studies

Since 1985, a number of North American researchers have evaluated the association between worker exposure to metalworking fluids (MWFs) and cancer mortality or respiratory morbidity. The studies have used different methods to measure the MWF aerosol concentration and to evaluate the exposures to the specific components of the MWF aerosol (bacteria, endotoxin, elements, metals, ethanolamines, polyaromatic hydrocarbons). This diversity of approaches makes comparison of study results difficult and has impeded the development of an occupational exposure limit (OEL) for metalworking fluids. This article summarizes the exposures measured in these North American epidemiologic studies by estimating their thoracic and inhalable MWF particulate levels. In addition, issues that must be resolved before a universal sampling and analysis method for MWF can be recommended are reviewed, including: the use of gravimetric versus extractable analysis; whether the analytical limit of detection can support a lower occupational exposure limit; if the volatile components of mineral oils should also be collected; and whether there are components of specific concern in MWFs that should be regulated separately. Finally, recommendations for future directions in MWF exposure assessment and control are suggested.

Mortality studies of metalworking fluid exposure in the automobile industry : VI. A case-control study of esophageal cancer

BACKGROUND Results are reported from a nested case-control study of 60 esophageal cancer deaths among 46,384 automobile manufacturing workers potentially exposed to metalworking fluids (MWF) in machining and grinding operations. METHODS By using incidence-density sampling, controls were selected with a sampling ratio of 20:1 from among co-workers who remained at risk by the age of death of the case, matched on race, gender, plant, and year of birth. Conditional logistic regression was used to evaluate the risk associated with cumulative exposure (mg/m3-years) to each of three types of metalworking fluid (straight, soluble, and synthetic MWF), as well as with years of exposure to selected components of MWF, including nitrosamines, sulfur, biocides, and several metals. RESULTS Esophageal cancer was found to be significantly associated with exposure to both soluble and synthetic MWF in grinding operations. The odds ratios (ORs) for grinding with soluble MWF were elevated at 2.5 or greater in all categories of cumulative exposure, although the exposure-response trend was statistically significant only when exposure was measured as duration. Those with 12 or more years exposure to soluble MWF in grinding operations experienced a 9.3-fold relative risk of esophageal cancer mortality (95% CI = 2.1-42.1). The OR for ever grinding with synthetic MWF was 4.1 (95% CI = 1.1-15.0). Elevated risk was also associated with two agents found in both synthetic and soluble fluids, nitrosamines, and biocides. For exposure to nitrosamines, the OR was 5.4 (95% CI = 1.5-19.9); for biocides the OR was 3.8 (95% CI = 0.8-18.9). However, because the same workers were exposed to grinding with synthetics, nitrosamines and biocides, it was not possible to separate the specific risks associated with these components.

Exposure Assessment for Epidemiology: Characteristics of Exposure

Abstract Estimation of past exposures to potential health hazards is one of the most difficult problems for industrial hygiene research. Although it is very difficult, it is not impossible. There are two conceptual models that can guide the hygienist in this task: the source-receptor model and the task-TWA (time-weighted average) model of full-shift exposures. The source-receptor model is a formalization of the professional decision criteria used by hygienists in their initial assessments of a workplace to identify where hazards might exist and where to sample. Thus, by performing a detailed assessment of the nature of past operations, raw materials, and job activities, it is frequently possible to identify where exposures might have occurred and what agents might have been involved. The task-TWA model is useful for developing historical estimates of full-shift exposures by integrating information on changes in job activities with limited monitoring data. It is particularly useful for extrapolating TWA ex...

The pulmonary toxicity of talc and granite dust as estimated from an in vivo hamster bioassay

A short-term animal bioassay was used to assess the toxicity of occupational dusts. We quantified pulmonary responses in hamsters exposed to granite (12% quartz) and talc (quartz and asbestos-free) dust collected from worksites. Personal samples collected on workers showed similar quartz content and particle-size distributions to the high-volume samples collected for bioassays, thus demonstrating that the particulates were representative of worker exposure. We measured biochemical and cellular indicators of injury in bronchoalveolar lavage fluid (BAL) of animals exposed to dust suspensions by intra-tracheal instillation. The assays measured release of cytoplasmic and lysosomal enzymes into the cell-free supernatant of BAL; levels of albumin and red blood cells; changes in macrophage and polymorphonuclear neutrophil cell numbers; and in situ macrophage phagocytosis. Dose-response (0.15, 0.75, and 3.75 mg/100 g body wt) and time-course (1-14 days postexposure) studies were performed. One day after exposure, both talc and granite dust resulted in elevated enzyme levels, pulmonary edema, and increased cell numbers in BAL. Macrophage phagocytosis was also inhibited. Based on earlier studies, response levels were either intermediate between nontoxic iron oxide and toxic alpha-quartz or comparable with alpha-quartz. The response to granite dust diminished fairly rapidly over time. By contrast, after talc exposure, there was a more persistent elevation in enzyme levels, and macrophage phagocytosis remained depressed. These results indicate that, when a similar mass was deposited in the lungs, talc caused more lung injury than did granite. Better estimates of exposure-dose relationships in talc and granite workers as well as longer-term animal studies are required to evaluate the harmfulness of these work environments at present-day exposure levels.

Personal fluoride and solvent exposures, and their determinants, in semiconductor manufacturing.

Personal air sampling for fluorides and solvents was done at 35 semiconductor fabrication facilities in the United States. Fluoride compounds were used in etching and cleaning operations, and solvents were used in photoresist and developing operations. All personal solvent and fluoride levels were less than 2 percent of current Occupational Safety and Health Administration (OSHA) standards. Statistical models of the exposure determinants for the target agents found production level, as indicated by number of semiconductor wafer cassettes loaded/unloaded from the target machines or baths, was predictive of fluoride, xylene and 1-methoxy-2-propyl acetate exposures. The percent of fresh air ventilation and the percent of xylene in the photoresist were also significant determinants in the statistical model predicting personal xylene exposure levels.

Ethanolamine Exposures of Workers Using Machining Fluids in the Automotive Parts Manufacturing Industry

Abstract Ethanolamines (EAs) are present in machining and grinding fluids and have the potential to act as respiratory irritants and sensitizing agents. EA levels in bulk cutting fluids were determined and compared with information available in the material safety data sheets (MSDSs), and the exposure to EAs of workers in the auto parts manufacturing industry was characterized. Monoethanolamine (MEA), diethanolamine (DEA), and triethanolamine (TEA) were all present in bulk machining fluids at levels ranging from 1 percent to 11 percent, 4 percent to 5 percent, and 0.3 percent to 40 percent, respectively. The MSDSs provided a general guideline to the presence or absence and relative levels of alkanolamines as a class, but were not generally useful as a guide to the presence or relative amount of specific EAs. This was particularly the case with MEA. Air levels of TEA in the personal samples were generally higher for transfer operations and lowest for assembly workers, who do not use machining fluids in the...

Development of a Program for Performance Evaluation of University Specialty Local Exhaust Systems for Compliance with the OSHA Laboratory Standard

Abstract Research facilities at the university where this program was developed currently occupy about 3200 laboratories containing 900 chemical laboratory hoods. A program of annual surveys of hood performance has been in place for 30 years. In addition to chemical laboratory hoods, university laboratories also contain more than 1300 specialty local exhaust ventilation (SLEV) systems for laboratory instrumentation, engineering pilot plant operations, semiconductor fabrication clean rooms, and physical plant shops. To comply with the Occupational Safety and Health Administration Laboratory Standard 1910.1450, which requires verification that engineering controls are performing adequately, we developed a program to monitor performance of SLEV systems. Program development included: (1) survey of all laboratory spaces and identification of SLEV systems; (2) classification of systems and uses; (3) evaluation of design criteria by comparison with existing American Conference of Governmental Industrial Hyggenis...