This research investigated the efficacy of machine enclosures in reducing employee exposures to metalworking fluid mist. Four hundred fifty-five personal samples from automotive machining and grinding operations collected over six years were divided into three groups based on the type and extent of enclosure and local exhaust ventilation. The sample groups were (1) machining equipment with original equipment manufacturer (OEM) total enclosures and local exhaust ventilation, (2) machining equipment with partial or retrofit enclosures and local exhaust ventilation, and (3) machining equipment with little or no enclosure. The results of the Mann Whitney U test of the three data sets indicated that the employees operating equipment with OEM enclosures had significantly lower exposures than employees operating equipment that had either of the other two control methods. There was no difference between the exposures of operators of equipment with retrofit enclosures compared to operators of equipment without enclosures. The median exposure for operators of equipment with OEM enclosures was 0.21 mg/m3, about half that found with the other two control methods. Each of the data sets was compared to exposure criteria; 100% of the exposures associated with OEM enclosures were below 1.0 mg/m3, and 90% of the exposures were below 0.5 mg/m3. The other two methods were not as effective as OEM in reducing exposure to below these criteria. These results indicate that OEM enclosures provide the most effective control of metalworking fluid mist exposure.
Dogs have been bred for different sizes and functions, which can affect their locomotor biomechanics. As quadrupeds, dogs must distribute their mass between fore and hind legs when standing. The mass distribution in dogs was studied to determine if the proportion of supported mass on each limb couplet is dependent on body size. A total of 552 dogs from 123 breeds ranging in size from Chihuahua to Mastiff were examined. Each dog was weighed on a digital scale while standing, alternating foreleg, and hind leg support. The overall “grand” mean proportion of mass on the forelegs to the total mass was 60.4% (range: 47.6–74.4%). The data set indicated no significant change in the ratio with total mass but there was a significant difference by sex. When separated into American Kennel Club categories, no group was notably different from the grand mean or from each other, but when sex was also considered, there was a significant difference that was not specifically discerned by post hoc analysis. The mean for female Hounds was notably below the grand mean. For clades based on genetics, the mean for European origin mastiffs was notably greater than the grand mean and significantly different from UK origin herders and coursers. The mass of the head, chest, and musculature for propulsion could explain the mass support differential. Mass distribution and terrestrial locomotion in dogs shows substantial variation among breeds.
Three studies were performed to assess the effectiveness of various techniques to control metalworking fluid (MWF) mist. The studies consisted of a detailed main study that determined the effect of degree of enclosure on personal exposures and area concentrations of MWF mist on two machining transfer lines. One ancillary study was conducted to determine the effect of shutting off MWF delivery during down time; the second ancillary study investigated the effectiveness of improved retrofitted enclosure. In the main study, the two operations were identical except for degree of enclosure. Personal and area sampling results for the new line were about half those found in the old line. Measurements at the new operation exhibited significantly less variability. Personal exposures and area concentrations were significantly less at the new operation than at the older, less enclosed operation, demonstrating that the total enclosure in the new operation provides better and more consistent control of the mist. The first ancillary study was conducted to determine if shutting off MWF delivery to the parts being machined reduced area MWF mist concentration during downtime at a partially enclosed transfer machining line. A significant reduction in concentration of 80% was measured with machining off/MWF off. Mist concentrations measured with machining off/MWF on were not significantly different from mist levels measured during machining on/MWF on. The second ancillary study investigated the reduction of mist concentration achieved through improved enclosure of an existing set of machines. Area mist concentrations were measured at a machining operation before and after the installation of an improved enclosure. Area mist concentrations were reduced by 87% with the improved enclosure.
Two prototype cyclones were the subjects of a comparative research campaign with a diesel particulate matter sampler (DPMS) that consists of a respirable cyclone combined with a downstream impactor. The DPMS is currently used in mining environments to separate dust from the diesel particulate matter and to avoid interferences in the analysis of integrated samples and direct-reading monitoring in occupational environments. The sampling characteristics of all three devices were compared using ammonium fluorescein, diesel, and coal dust aerosols. With solid spherical test aerosols at low particle loadings, the aerodynamic size-selection characteristics of all three devices were found to be similar, with 50% penetration efficiencies (d50) close to the design value of 0.8 µm, as required by the US Mine Safety and Health Administration for monitoring occupational exposure to diesel particulate matter in US mining operations. The prototype cyclones were shown to have ‘sharp cut’ size-selection characteristics that equaled or exceeded the sharpness of the DPMS. The penetration of diesel aerosols was optimal for all three samplers, while the results of the tests with coal dust induced the exclusion of one of the prototypes from subsequent testing. The sampling characteristics of the remaining prototype sharp cut cyclone (SCC) and the DPMS were tested with different loading of coal dust. While the characteristics of the SCC remained constant, the deposited respirable coal dust particles altered the size-selection performance of the currently used sampler. This study demonstrates that the SCC performed better overall than the DPMS.
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