Dennis M. O'brien

Metalworking Fluid Exposures in Small Machine Shops: An Overview

Sampling was conducted in 79 small machine shops to assess airborne exposures to metalworking fluids (MWFs). Measured exposures were compared with data from the literature and exposure criteria currently recommended by the National Institute for Occupational Safety and Health and the Occupational Safety and Health Administration MWF Standards Advisory Committee. Sixty-two percent of 942 personal samples collected were less than the recommended exposure limit (REL) of 0.50 mg/m3 for total particulate. However, at least 1 sample exceeded the REL in 61 of the 79 facilities studied; 100% of the samples collected in 10 shops were greater than the REL. Similar trends were found for thoracic particulate exposures where 75% of 238 samples were below the thoracic particulate REL of 0.40 mg/m3. The ratio between thoracic and total particulate for 238 paired samples was 0.55 (r2=0.73). Workers exposed to straight fluids had the highest exposures (GM=0.67 mg/m3) when compared with workers exposed to other classes of MWFs. The highest exposures were measured for grinding and hobbing (GM=0.67 and 0.60 mg/m3, respectively). Measurements using personal impactors indicated that particle size distributions of MWF aerosols had an average mass median aerodynamic diameter of 5.3 microm. Straight oils and soluble fluids tended to be associated with larger particles than were other fluid types; grinding and turning produced the largest particles, whereas hobbing resulted in the smallest. In general, exposures were similar in magnitude and particle size to those previously reported in large automotive plants. Therefore, workers in these small shops may have risks of adverse health effects similar to those demonstrated in the automotive industry.

Aerosol mapping of a facility with multiple cases of hypersensitivity pneumonitis: demonstration of mist reduction and a possible dose/response relationship.

Recent outbreaks of hypersensitivity pneumonitis (HP) have been associated with exposures to metalworking (MWF) fluid aerosols. Mycobacteria present in mismanaged fluids have been suggested as the likely culprit. In January 2001, three machinists at a machining plant were hospitalized with HP. Subsequently, additional HP cases developed as well as cases of bronchitis and occupational asthma. In October 2001, an aerosol concentration map was constructed to advise on priorities for corrective actions. In April 2002 after installation of mist collectors, a second map was generated. Mist reductions varied from about 75 percent to an increase of about 20 percent. Mist concentrations increased in the areas near an uncontrolled transfer line. Subsequent to the first mapping exercise, the exposures of 30 HP cases were classified as low, medium, and high based on job location and the map. There were 6 cases among low exposure jobs (4% of exposed), 14 cases among medium exposure jobs (19% of exposed), and 10 cases among high exposure jobs (34% of exposed), suggesting a relation between exposure to contaminated metalworking fluid mist and the development of HP. A combination of interventions (fluid management, mist control, improved fresh air ventilation, and medical surveillance/restriction) eliminated any new cases 11 months after the first diagnosis of HP.

Control of Asbestos Exposure during Brake Drum Service

Abstract An estimated 150,000 brake mechanics and garage workers in the U.S. are potentially exposed to asbestos, a known health hazard. Earlier studies of airborne asbestos exposures to mechanics during brake maintenance operations showed overexposure to asbestos fibers during brake servicing, especially brake assembly cleaning. Most brake service operations are performed by small businesses that lack resources to evaluate control devices. The results from the evaluation of five control methods for containing asbestos brake dust during brake maintenance are presented. These controls included two commercial enclosure devices with ventilation provided by high-efficiency particulate air (HEPA) filter-equipped vacuums, a HEPA filter-equipped vacuum cleaner without an enclosure, a wet brush/recycle system which recirculated the cleaning solution, and an aerosol spray for wetting the brake assembly. Detailed surveys of the controls were conducted at five separate facilities during actual brake servicing operat...

The Application of Dustiness Tests to the Prediction of Worker Dust Exposure

Laboratory bench tests, known as dustiness tests, have been used to evaluate and compare the potential of various powders to cause occupational dust exposure. Dustiness tests are used to develop products with reduced dust emissions. The correlation between dustiness test results and dust exposures was evaluated at two bag dumping and bag filling operations. At one bag dumping and one bag filling operation, there was evidence of a relationship between dustiness test results and dust exposures. In one case, regression analysis showed that dust exposures could be predicted to within nearly one order of magnitude. The variability in this prediction was caused by the inherent variability in the occupational dust exposures. In the other case, there was evidence of a correlation after the data had been adjusted for the effect of varying drop height. At the remaining two operations, no correlation between dust exposures and dustiness test results were observed. These results indicate that the relevance of dustiness tests to occupational dust exposure needs to be evaluated at each site. Because a better option does not exist, manufacturers should continue to use empirical dustiness tests to develop better products in the laboratory. The conclusions reached in the laboratory need to be validated by dust exposure measurements in the field, however.

An evaluation of short-term exposures to metalworking fluids in small machine shops

In a study of 23 small machining shops using metalworking fluids (MWFs), real-time air monitoring using an aerosol photometer was performed to investigate the temporal nature of the exposure and to examine the relationship between the instrumental measurements and traditional sampling methods. Time-weighted averages were calculated from the aerosol photometer data and the results were compared to collocated thoracic and 37-mm closed face cassette samplers. The filter samples were analyzed for total mass and the solvent extractable fraction. Depending on the averaging period used, short-term MWF concentrations exceeded 2.0 mg/m3 in 13 to 39% of the plants studied. High short-term exposures were as likely to be found in plants with average concentrations below 0.4 mg/m3 (thoracic-gravimetric) as those above. Regression analyses indicated that the aerosol photometer most closely matched the data obtained from the thoracic fraction of the total mass. In general, the aerosol photometer overestimated the levels determined using the thoracic cyclone and filter, especially when measuring concentrations of water-based fluids. Use of a calibration factor of 0.7 for straight oils or 0.5 for water-based fluids may assist in the interpretation of aerosol photometer measurements if field calibration data are not readily available. Several approaches to determining the calibration factor from field data were evaluated; more complex calibration techniques improved the accuracy of the measurements.

Acquisition and Spreadsheet Analysis of Real Time Dust Exposure Data: A Case Study

Abstract Personal sampling with a light-scattering monitor connected to a data logger has been used to evaluate the effectiveness of a high-velocity, low-volume (HVLV) sander hood used in a plant manufacturing reinforced plastics. Exposures to sanding dust were determined for two workers, one using a sander with a hood, the other using a sander with none. Both workers were partners in a two-person team sanding a truck hood and fender assembly. Side-by-side filter sampling was conducted to calibrate the aerosol monitor. Data logger output for each worker was combined into a single spreadsheet program. Simultaneous video recording allowed worker activity variables (sanding, compressed air blowing, and other) to be coded onto the spreadsheet, which permitted calculation of the contribution of each activity to each workers dose of dust. The computerized data acquisition system permitted identifying activities that change worker exposures through review of the work cycle while tracking worker exposures. Thoug...

Video Exposure Monitoring—A Means of Studying Sources of Occupational Air Contaminant Exposure, Part 2—Data Interpretation

Abstract Excessive exposures to air contaminants can be determined by conventional sampling with pumps and sampling media; however, such results do not provide insights into the reasons for the excessive exposures. The analog or digital output from direct-reading instruments can be captured by using data-logging equipment. While data are being logged from direct-reading instruments, the activities in the workplace can be recorded using a video camera. These data can be analyzed to find reasons for excessive air contaminant exposures. Three approaches have been used to quantitatively present the results of real-time sampling. First is the use of descriptive statistics to describe the data. Frequently, useful insights can be obtained from descriptive statistics and graphs. When activities in question are sufficiently separated in time, this can be a very fruitful approach. At other times, a second approach, statistical analysis, may be needed to evaluate whether a certain activity is causing an increase in ...

Size and Concentration Measurement of an Industrial Aerosol

Several real-time particle sizing instruments were evaluated for measuring the size distribution and concentration of the aerosol produced during the high speed grinding of gray iron castings. Aerosol was sampled in the airstream entrained by the motion of a spinning grinding wheel in a pilot grinding operation. Measurement methods based on differing physical principles were selected for evaluation and compared: particle inertia (aerodynamic particle sizer and quartz crystal microbalance cascade impactor); light scattering (laser aerosol spectrometer); and projected-area microscopy (scanning electron microscope). Inferences of aerodynamic diameter based on measurements by the laser aerosol spectrometer consistently undersized that determined by the aerodynamic particle sizer by a factor of 1.5. Estimates of aerodynamic diameters from projected area diameters determined by scanning electron microscopy differed from those obtained by the aerodynamic particle sizer by a factor of 2. Differences appeared to be a non-linear function of particle diameter. Estimates of respirable mass determined from mass-weighted particle size spectra varied by a factor of 6 between the largest estimate (scanning electron microscope) and the smallest estimate (laser aerosol spectrometer).

Effective Controls for Ethylene Oxide—A Case Study

Abstract The National Institute for Occupational Safety and Health (NIOSH) has studied the control of ethylene oxide (EtO) exposures associated with hospital sterilizers to determine which combinations of control measures are most effective. This case study describes the evaluation of controls at one hospital. The hospital had a gas sterilizer which used a mixture of EtO (12 percent by weight) in Freon-12[rgrave]. The sterilizer was retrofitted with the manufacturers control system consisting of a ventilated air gap, local exhaust ventilation above the sterilizer door, and cycle modifications for additional end-of-cycle air flushes. Personal and area samples for EtO were collected with charcoal tubes for laboratory analysis (NIOSH method #1607) and in gas sampling bags for on-site analysis with a portable gas chromatograph. The area in front of the sterilizer was also monitored with an infrared analyzer. All full-shift personal exposures and area concentrations were less than 0.05 ppm. Infrared monitorin...

SILICA EXPOSURE IN HAND GRINDING STEEL CASTINGS

Exposure to silica dust was studied in the grinding of castings in a steel foundry that used conventional personal sampling methods and new real-time sampling techniques developed for the identification of high-exposure tasks and tools. Approximately one-third of the personal samples exceeded the National Institute for Occupational Safety and Health recommended exposure limit for crystalline silica, a fraction similar to that identified in other studies of casting cleaning. Of five tools used to clean the castings, the tools with the largest wheels, a 6-in. grinder and a 4-in. cutoff wheel, were shown to be the major sources of dust exposure. Existing dust control consisted of the use of downdraft grinding benches. The size of the casting precluded working at a distance close enough to the grates of the downdraft benches for efficient capture of the grinding dust. In addition, measurements of air recirculated from the downdraft benches indicated that less than one-half of the respirable particles were removed from the contaminated airstream. Previous studies have shown that silica exposures in the cleaning of castings can be reduced or eliminated through the use of mold coatings, which minimize sand burn-in on the casting surface; by application of high-velocity, low-volume exhaust hoods; and by the use of a nonsilica molding aggregate such as olivine. This study concluded that all these methods would be appropriate control options.