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The OSHA final rule on respirable crystalline silica (RCS) will require hydraulic fracturing companies to implement engineering controls to limit workers' exposure to RCS. RCS is generated by pneumatic transfer of quartz-containing sand during hydraulic fracturing operations. Chronic inhalation of RCS can lead to serious disease, including silicosis and lung cancer. NIOSH research identified at least seven sources where RCS aerosols were generated at hydraulic fracturing sites. NIOSH researchers developed an engineering control to address one of the largest sources of RCS aerosol generation, RCS escaping from thief hatches on the top of sand movers. The control, the NIOSH Mini-Baghouse Retrofit Assembly (NMBRA), mounts on the thief hatches. Unlike most commercially available engineering controls, the NMBRA has no moving parts and requires no power source. This article details the results of an evaluation of generation 3 of the NMBRA at a sand mine in Arkansas from May 19-21, 2015. During the evaluation, 168 area air samples were collected at 12 locations on and around a sand mover with and without the NMBRA installed. Analytical results for respirable dust and RCS indicated the use of the NMBRA effectively reduced concentrations of both respirable dust and RCS downwind of the thief hatches. Reductions of airborne respirable dust were estimated at 99+%; reductions in airborne RCS ranged from 98-99%. Analysis of bulk samples of the dust showed the likely presence of freshly fractured quartz, a particularly hazardous form of RCS. Use of an improved filter fabric and a larger area of filter cloth led to substantial improvements in filtration and pressures during these trials, as compared to the generation 2 NMBRA. Planned future design enhancements, including a weather cover, will increase the performance and durability of the NMBRA. Future trials are planned to evaluate the long-term operability of the technology.

This article describes the evaluation of the generation rate of respirable dust (GAPS, defined as the mass of respirable dust generated per unit linear length cut) from cutting fiber cement siding using different tools in a laboratory testing system. We used an aerodynamic particle sizer spectrometer (APS) to continuously monitor the real-time size distributions of the dust throughout cutting tests when using a variety of tools, and calculated the generation rate of respirable dust for each testing condition using the size distribution data. The test result verifies that power shears provided an almost dust-free operation with a GAPS of 0.006 gram meter−1 (g m−1) at the testing condition. For the same power saws, the cuts using saw blades with more teeth generated more respirable dusts. Using the same blade for all four miter saws tested in this study, a positive linear correlation was found between the saws’ blade rotating speed and its dust generation rate. In addition, a circular saw running at the highest blade rotating speed of 9068 RPM generated the greatest amount of dust. All the miter saws generated less dust in the ‘chopping mode’ than in the ‘chopping and sliding’ mode. For the tested saws, GAPS consistently decreased with the increases of the saw cutting feed rate and the number of board in the stack. All the test results point out that fewer cutting interactions between the saw blade’s teeth and the siding board for a unit linear length of cut tend to result in a lower generation rate of respirable dust. These results may help guide optimal operation in practice and future tool development aimed at minimizing dust generation while producing a satisfactory cut.

Inhalation of respirable crystalline silica (RCS) is a significant risk to worker health during well completions operations (which include hydraulic fracturing) at conventional and unconventional oil and gas extraction sites. RCS is generated by pneumatic transfer of quartz-containing sand during hydraulic fracturing operations. National Institute for Occupational Safety and Health (NIOSH) researchers identified concentrations of RCS at hydraulic fracturing sites that exceed 10 times the Occupational Safety and Health Administration (OSHA) Permissible Exposure Limit (PEL) and up to 50 times the NIOSH Recommended Exposure Limit (REL). NIOSH research identified at least seven point sources of dust release at contemporary oil and gas extraction sites where RCS aerosols were generated. NIOSH researchers recommend the use of engineering controls wherever they can be implemented to limit the RCS released. A control developed to address one of the largest sources of RCS aerosol generation is the NIOSH mini-baghouse assembly, mounted on the thief hatches on top of the sand mover. This article details the results of a trial of the NIOSH mini-baghouse at a sand mine in Arkansas from November 18-21, 2013. During the trial, area air samples were collected at 12 locations on and around a sand mover with and without the mini-baghouse control installed. Analytical results for respirable dust and RCS indicate the use of the mini-baghouse effectively reduced both respirable dust and RCS downwind of the thief hatches. Reduction of airborne respirable dust ranged from 85-98%; reductions in airborne RCS ranged from 79-99%. A bulk sample of dust collected by the baghouse assembly showed the likely presence of freshly fractured quartz, a particularly hazardous form of RCS. Planned future design enhancements will increase the performance and durability of the mini-baghouse, including an improved bag clamp mechanism and upgraded filter fabric with a modified air-to-cloth ratio. Future trials are planned to determine additional respirable dust and RCS concentration reductions achieved through these design changes.

Airborne formaldehyde concentrations can be measured using several different techniques, including laboratory-based methods and direct-reading instruments. Two commercially available direct-reading instruments, an RKI Instruments Model FP-30 and a PPM Technology Formaldemeter htV, were compared with National Institute for Occupational Safety and Health Method 2016 in different test environments to determine if these direct-reading instruments can provide comparable results. The methods yielded the following mean concentrations for 47 samples: NIOSH Method 2016, 0.37 ppm; FP-30, 0.29 ppm; and htV, 0.34 ppm. Results from both of the direct-reading instruments were correlated with the laboratory-based method (R² = 0.78 for FP-30, and 0.902 for htV). Comparison of the means of the three methods showed that on average the FP-30 instrument (p0.001) differed statistically from NIOSH Method 2016, whereas the htV (p = 0.15) was not statistically different from the NIOSH method. Sensitivity and specificity tests demonstrated that the FP-30 had sensitivity above 60% to detect formaldehyde concentrations at all the cutoff levels tested, whereas the htV appeared to have greater sensitivity above 88% for the levels evaluated.

A laboratory testing system was developed to systematically characterize the dust generation rate and size-dependent crystalline silica content when cutting or shaping silica containing materials. The tests of cutting fiber cement siding in this system verify that it provides high test repeatability, making it suitable for the targeted characterizations. The mass-based size distributions obtained from a gravimetric-based instrument and a direct reading instrument both show bimodal lognormal distributions with a larger mode around 13 µm and another mode smaller than 5 µm for the dusts from cutting four different brands of fiber cement siding. The generation rates of respirable dust obtained from the two instruments are comparable, and the results from each instrument are similar for the four brands. The silica content in the airborne dusts, however, strongly depends on the amount of silica used in the respective product. It is also observed that the silica content in the airborne dust from cutting the four brands of fiber cement siding showed the same trend of an increase with the aerodynamic diameter of the dust, approaching the silica content levels found in their respective bulk samples. Combining the results for both the dust size distribution and size-dependent silica content, it is found that most of the respirable crystalline silica (RCS) resides in the dust about 2.5 µm in aerodynamic diameter. These results would help guide the development of specific engineering control measures targeted at lowering workers’ exposure to RCS while cutting fiber cement siding. With the high repeatability using the laboratory testing system, the dust generation rate could then be characterized under different operating conditions, and with the deployment of various engineering control measures. This would greatly facilitate the systematic evaluation of the control effectiveness and the selection of the optimal control solutions for field trials.

Small businesses frequently have inadequate in-house expertise to solve a variety of safety and health problems. The National Institute for Occupational Safety and Health (NIOSH) has therefore conducted a demonstration project in the commercial lithographic printing industry, which consists largely of small companies, in an effort to establish suitable control technology for airborne solvent vapors released primarily during press cleaning operations. These solvent vapors have a number of potential adverse health effects, including narcosis, kidney and liver damage, and cancer. Also, airborne anti-offset powder is a potential allergic sensitizer and cause of occupational asthma. As a means of controlling worker exposures to the vapors and dust, a local exhaust inlet was attached to the side of the press adjacent to the paper delivery point. Tempered outside air was introduced through ceiling outlets installed to make up for the exhausted air. Measurements of press operator exposure and area concentrations of solvent vapors and area concentration of anti-offset powder were made before and after installation of the new ventilation controls. Vapor concentrations were reduced by 73 percent for the press operators. Area concentrations of the vapors were reduced by 86 percent and dust concentration by 67 percent. The ventilation system was found to be suitable for vapor and dust control, although substitution of a cleaning solution containing non-carcinogenic solvents for solutions containing carcinogens was recommended.

A study was conducted to evaluate the effectiveness of a local exhaust ventilation system for a foundry casting-cleaning operation in which a worker cleaned gray iron castings using a variety of handheld chipping and grinding tools. The operation originally had an exhaust system consisting only of an exhaust duct terminating approximately 1 m (3 ft) above the floor and 2 m (6 ft) from the casting-cleaning workstation. An earlier evaluation of this original control system found time-weighted average exposures to respirable silica ranging from 124 to 160 micrograms/m3. The local exhaust ventilation system evaluated in this present study consisted of a downdraft booth outfitted with a turntable for manipulating the castings. The modified local exhaust ventilation system was installed at this facility and connected to the existing plant exhaust ventilation system through the original ductwork. A direct-reading instrument was used to measure the operator's respirable aerosol exposure concentrations during a single day both before and after the installation of the new workstation. The same worker was sampled both times. The operator's activities were recorded on videotape so that the exposures associated with the various tools could be determined. While day-to-day variability could not be accounted for, depending on the type of tool used the local exhaust ventilation system reduced exposures by 59 to 79% during casting cleaning by the sampled worker when compared with the original configuration. These reductions were statistically significant.

A patient who had photorefractive keratectomy for low myopia 6 years earlier had an enhancement by hyperopic laser in situ keratomileusis (LASIK). Moderate reticular corneal haze developed after LASIK. An attempted flap lift 4 months after LASIK resulted in a flap tear at the edge of the zone of corneal haze. Because haze can indicate an area of exuberant wound healing that can result in flap adhesion to the bed, recutting a LASIK flap may be safer than lifting it in the presence of haze.

To maximize the 8 kilobyte memory of the Rustrak Ranger data logger, a patented technique called adaptive storage was used. With adaptive storage, the data logger predicts the value of an incoming reading. Based on previously stored readings, the data logger predicts the next reading to be constant, linear, or exponential. If the reading falls outside a window surrounding the predictions, it is stored; otherwise, it is discarded. The size of the window affects the rate at which the readings are stored, and thus is adjusted so data can be collected for the specified sampling time. If the windows are made too large, there is a resultant loss in the resolution of the data. The characteristics of the instrument and the contaminant or physical agent being measured (i.e., air contaminant versus noise) also affect data resolution. In this evaluation, previously collected exposure data (air monitoring) were sent by a computer to the Rustrak Ranger for recording. To determine the effect of the sampling time on resolution, the recorded data were analyzed using two different methods. Sampling times varied from 2 to 120 minutes. These tests showed poor resolution for sampling times as short as 30 minutes, indicating that the Rustrak Ranger may not be suitable for certain types of sampling schemes. However, if used within its limitations, this data logger is a valuable tool for recording real-time industrial hygiene data.

Researchers from the National Institute for Occupational Safety and Health (NIOSH) applied Hazard and Operability (HAZOP) analysis to examine hazards during the use of anhydrous ammonia by farmers. This analysis evaluated the storage, transfer, and application of anhydrous ammonia, identifying credible hazard scenarios, practical solutions, and research needs. Ninety-five findings were developed that are of use to farmers, distributors of ammonia and application equipment, and manufacturers of application equipment. The findings generally involve training, equipment design changes, preventive maintenance, and material compatibilities. The HAZOP team found that additional safety features need to be developed or implemented. The study also pointed out where correct operator procedure and preventive maintenance can prevent inadvertent releases. Other inadvertent releases are caused by incompatible materials, or by using equipment in ways other than intended. Several examples of the findings are given to emphasize the HAZOP technique and the high-risk scenarios. Strategies for dissemination to the agricultural community are presented.

The focus of this exposure assessment and control technology study was a brass foundry and the lead exposures of workers involved in the transportation and pouring of metal. Controls in place at the foundry included ventilation systems at the furnace and along the continuous and stationary pouring lines. Real-time measurements were made to determine which tasks were the primary exposure sources, and a hand-held aerosol monitor was used to measure real-time aerosol exposures (as a surrogate for lead) in the workers' breathing zones. Data were collected over two 30-min sampling periods while worker activities were monitored using a video camera. Analysis of the data showed that the greatest aerosol exposures occurred during the transportation of an unventilated, full ladle, resulting in an average concentration of at least twice that of the other tasks. The study concluded that the addition of exhaust ventilation such as a moveable hood and duct system during the ladle transport and pouring tasks, and the implementation of a side draft hood at the pigging area, could result in a reduction of worker exposure to aerosols during the continuous pouring operation by up to 40%. The controls and techniques suggested in this study could be applied to pouring operations throughout the industry to reduce worker exposure to metal fumes.

Conventional sampling with pumps and sampling media can be used to determine whether exposures to air contaminants are excessive. Unfortunately, such results provide few insights into the reasons for the excessive exposures. However, Video Exposure Monitoring can be used to identify the sources causing these excessive exposures. Any movable instrument that has an analog or digital output can potentially be used for Video Exposure Monitoring. The instrument should be light enough to mount on a worker, be specific for the chemical interest, and have a short time constant. Although most existing direct-reading instruments do not simultaneously meet all these requirements, currently available instruments, such as aerosol photometers, photoionization detectors, and portable infrared analyzers have been used effectively. The analog or digital output from direct-reading instruments can be recorded by data-logging devices. The data-logging devices transfer the exposure data to a personal computer for sto...

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 ...

Previous studies have found that formaldehyde exposures to embalmers during the embalming process exceeded current occupational health criteria and standards. There are currently just over 20,000 mortuaries in the United States, employing 75,000 people. Mortuaries, as small businesses, typically do not have access to the occupational health and safety expertise that larger companies do. Therefore, a research study was conducted to develop and evaluate a local exhaust ventilation system to control formaldehyde exposures. The control design that was developed consisted of a pair of 6-ft-long slot hoods placed on each side of the embalming table. Through a series of laboratory tests, an optimum flow rate (20 m3/min) was determined for the local exhaust ventilation system. The final design was field tested at a college of mortuary science to determine its effectiveness. A series of 16 tests were conducted with a variety of different embalming procedures. For each test, two personal and three area sam...

A variety of tasks are performed during the brief time required to open and empty a bag of powdered material. Each task creates a potential source of dust exposure for the workers performing these tasks. In this study, 50-pound bags of powdered lead chromate were emptied at a ventilated bag-dumping station. Continuous, real-time measurements of dust exposure were recorded, and the worker's actions were videotaped while emptying 65 bags in a 24-minute period. Using a computer program, a representation of the instantaneous dust exposure was overlaid onto the videotape of the worker's actions. Study of this videotape identified seven specific tasks and the relative contribution of each to the worker's overall dust exposure. It was found that pushing empty bags into barrels for subsequent disposal was the major dust source; cutting open bags and lifting them to the emptying shelf of the dump station were lesser but significant dust sources. It was also observed that the bag disposal unit within the d...

Process hazards review (PHR) techniques have generally been applied by large, sophisticated companies in the nuclear, aerospace, and chemical process industries. There remains, however, a large population of smaller distributors and consumers of hazardous materials which could benefit equally from the application of PHR. These consumers unfortunately are generally less sophisticated and individually lack the necessary resources required to apply such state-of-the-art safety techniques. Where common processes can be identified, it is possible to conduct a more generic PHR that will provide a sound technical basis for recognizing and preventing the development of hazards wherever these processes are used. Some facility-specific issues will always need to be considered, but the existence of the generic PHR should make the conduct of a PHR by each facility considerably easier and less costly. Researchers from the National Institute for Occupational Safety and Health (NIOSH) contracted with DNV Technica Inc. to lead a hazard and operability study (HAZOP) of agricultural handling of anhydrous ammonia, from the receipt of ammonia at the retail distribution centre to the application of the ammonia by farmers to the fields. The multidisciplinary HAZOP team consisted of representatives from NIOSH, an agricultural chemical trade association, an ammonia producer, state ammonia facility inspectors, a retail distributor, and an equipment manufacturer. Several participants were part-time farmers with ammonia application experience. Some specific aspects of applying the HAZOP technique in the context of this study, the findings obtained, and the plans to disseminate the important safety information developed during the course of the PHR are discussed. Finally, it is suggested that this approach could prove to be a useful addition to the product stewardship activities of chemical producers.

Effective, economical control of metalworking fluid mists at the source is important, because exposure to these mists may cause adverse health effects. This study investigated performance changes over time for industrial collectors that removed metalworking fluid mist in the laboratory and in a transmission plant. Aerosizers were used to measure the efficiency of each stage in several multistage collectors as a function of mist droplet diameter, for up to one year of continuous operation. Metal-mesh, first-stage filters operated at low pressure drops and were effective at removing droplets larger than 3 to 5 microns in diameter. Some second-stage filters worked better than others. Both "65 percent" and "95 percent" cartridge filters failed after only a few weeks; their efficiencies decreased substantially over that time. Pocket filters and cylindrical cartridges used as second-stage filters also decreased in efficiency for submicron droplets. Whereas filters for solid particles load continuously to form a dust cake that increases efficiency, mist filters form no cake and load only to the point where collection equals drainage. As a mist filter loads, the interstitial gas velocity increases, so that efficiency decreases for small droplets that collect by diffusion. Although a third-stage 95 percent DOP filter showed important decreases in efficiency over time for submicron droplets, third-stage HEPA filters operated with efficiencies that consistently approaches 100 percent for droplets of all sizes, even after one year of operation. These results suggest that the performance of second-stage filters can be improved if they can be made to drain collected liquid more effectively. For high efficiency, mist collectors should use a HEPA filter as a final stage.

Researchers from the National Institute for Occupational Safety and Health (NIOSH) conducted a joint survey with the New Jersey Department of Health (NJDOH) to measure crystalline silica exposures and evaluate the adequacy of the existing control measures for reducing these exposures at a sanitary ware pottery. This survey found that 95% of the personal and area samples from the Slip House, Casting, Glaze Spray, and Glaze Preparation Departments exceeded the NIOSH Recommended Exposure Level (87% exceeded the Occupational Safety and Health Administration Permissible Exposure Level) for crystalline silica. Three years later, a follow-up survey found statistically significant reductions in respirable crystalline silica exposures in two of four plant departments, and statistically significant reductions in area concentrations in all four plant departments. These reductions were accomplished through a combination of automating and enclosing the batching system in the Slip House and by replacing the mold parting compound with a nonsilica material, altering the method of dry sweeping, cleaning of castings while damp, improving exhaust ventilation at the spray booths, and improved housekeeping.

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.

Since the 1985 release of methyl isocyanate in Bhopal, India, which killed thousands, the chemical industry has begun to use process hazard analysis techniques more widely to protect the public from catastrophic chemical releases. These techniques can provide a systematic method for evaluating a system design to ensure that it operates as intended, help identify process areas that may result in the release of a hazardous chemical, and help suggest modifications to improve process safety. Eight different techniques are discussed, with some simple examples of how they might be applied. These techniques include checklists, "what if" analysis, safety audits and reviews, preliminary hazard analysis (PHA), failure modes and effect analysis (FMEA), fault tree analysis (FTA), event tree analysis (ETA), and hazard and operability studies (HAZOP). The techniques vary in sophistication and scope, and no single one will always be the best. These techniques can also provide the industrial hygienist with the tools needed to protect both workers and the community from both major and small-scale chemical releases. A typical industrial hygiene evaluation of a facility would normally include air sampling. If the air sampling does detect a specific hazardous substance, the source will probably be a routine or continuous emission. However, air sampling will not be able to identify or predict the location of a nonroutine emission reliably. By incorporating these techniques with typical evaluations, however, industrial hygienists can proactively help reduce the hazards to the workers they serve.

As an engineer practicing in the area of engineering controls for the reduction of occupational exposures to hazardous agents, the Intervention Research Workshop studies appeared to be effective for the studied situations, yet the models may not be applicable across a wide range of intervention possibilities. A more generic model might be more appropriate, perhaps a business model. Dr. W. Edwards Deming has proposed a model for the production of goods and services. If we can view interventions as products which need to be sold to potential customers, perhaps this type of model would be more effective across a wide range of intervention strategies.

Response Team investigators from the US Centres for Disease Control and Prevention (CDC), National Institute for Occupational Safety and Health (NIOSH), recognised the potential for Bacillus anthracis (B. anthracis) cross-contamination during recent emergency response activities in the Capitol area. The three case studies presented offer the opportunity to examine procedural response practices related to bioterrorism events, and consider the "lessons learned". An examination of the actions, practices and environmental sampling results from the Capitol response effort compelled investigators to develop six recommendations that, if implemented, should reduce the potential for cross-contamination in future national and international emergency response activities.

Ninety-five patients (104 eyes) were enrolled in a pilot study of subconjunctival 5-fluorouracil (5-FU) injections after filtering surgery in eyes with poor surgical prognoses. At least a six-month follow-up was available on 84 patients, of whom four were excluded from the analysis of surgical outcome because they suffered retinal detachments within six months of their filtering surgery. The initial 5-FU procedures on the remaining 80 patients were successful (no further glaucoma surgical procedures were either performed or recommended, and the intraocular pressures [IOPs] were either 21 mmHg or lower with ocular hypotensive medication[s] or 25 mmHg or lower without ocular hypotensive medication) in 33 (68%) of the 48 aphakic eyes with non-neovascular glaucomas, 13 (81 %) of the 16 phakic eyes with non-neovascular glaucomas after unsuccessful filtering surgery, and 12 (75%) of the 16 eyes with neovascular glaucoma (NVG). The follow-up on the successful eyes ranged from 6 to 34 months (mean ± SD=18.5 ± 7.5). The visual acuities remained within one line of their preoperative levels or improved in 38 (79%) of the 48 aphakic eyes with non-neovascular glaucoma, 11 (69%) of the 16 phakic eyes with nonneovascular glaucoma after unsuccessful filtering surgery, and 12 (75%) of the 16 eyes with NVG. The initial 5-FU procedures on the 104 eyes were complicated by the following: corneal epithelial defects (50%); conjunctival wound and suture tract leaks (36%; 2% underwent surgical repair); suprachoroidal hemorrhages (9%); retinal detachments (3%); subepithelial corneal scarring (3%); endophthalmitis (2%); and malignant glaucoma (1 %). It is the authors' impression that postoperative subconjuctival 5-FU increases the likelihood of achieving IOP control after filtering surgery in eyes with poor surgical prognoses; however, a randomized clinical trial is necessary to confirm this impression.

Past studies have shown that ventilation does not always provide complete dust control during the manual weigh-out and transfer of powders. However, these studies have not shown where the dust emission sources are located. A field study was conducted in a plastics manufacturing plant to evaluate factors affecting worker dust exposure at a ventilated booth which was used for the weigh-out and transfer of powdered materials. A unique study plan was formulated utilizing real-time air sampling and short-term air sampling in conjunction with an ergonomic evaluation to determine activities or factors associated with dust exposure. The factors and activities evaluated were depth of scooping, cleanliness of the workers' clothing, worker anthropometry, and work practices. Realtime air sampling and work cycle evaluation showed that dust concentrations were highest when the worker was scooping material out of the drum, and these levels increased dramatically when the worker placed his breathing zone inside ...

• Eight cases of delayed nonexpulsive suprachoroidal hemorrhage occurred after filtering operations in aphakic eyes. Sustained hypotonia resulting in serous choroidal detachments, scleral infolding, or both was observed prior to the hemorrhage in seven of the eight eyes. The prognosis was related to the extent of the hemorrhage and possibly to whether or not surgical drainage was performed. Only one of the five patients with massive hemorrhages recovered visual acuity better than hand motions; that patient had undergone prompt surgical drainage of the suprachoroidal blood.

The effect of light scattering by ocular media opacities on OCTOPUS and Humphrey perimeter threshold measurements was simulated with randomly ordered sequences of six ground-glass diffusers in the right eyes of five subjects. Threshold measurements were performed at 0 degrees, 5 degrees, 10 degrees, 15 degrees, 20 degrees, and 25 degrees nasally along the 180 degrees meridian with the F4 program on an OCTOPUS perimeter, and with twice-repeated profiles on a Humphrey perimeter. The reduction in differential light sensitivity correlated well with the 2.7-dB to 16.7-dB reduction in stimulus intensity caused by the 46% to 98% scattering of incident light by the diffusers. Contrast sensitivity in the presence of a glare source (Miller-Nadler glare test) was also affected by the diffusers, such that a 75% contrast target was not visible through the strongest diffuser whereas a 5% contrast target was visible without a diffuser. Conversely, the diffusers had very little effect on visual acuity measurements that were performed with projected high-contrast targets in a darkened room. Our data suggest that even minimal light scattering, such as might be caused by a cataract that has a relatively insignificant effect on visual acuity, may influence threshold measurements.

A computerized data acquisition system, utilizing real-time instrumentation and a video taping system, can provide the information necessary to identify the sources or activities which most affect worker exposure levels. Integrated workplace samplers, such as pumps with filters or charcoal tubes, may indicate a certain level of exposure. However, due to the complexity of the process or work cycle, an evaluation of activities affecting exposure patterns may be difficult. Such a system, utilizing a computer, real-time instrumentation, and video taping, has been used successfully in three different NIOSH studies. In the first, a study of manual weigh-out and transfer of powders, the data acquisition system identified the scooping operation as the component of the work cycle which most affected the worker dust exposures. Because of the short work cycle, typically 30 seconds or less, filter sampling could not isolate this work element as the major cause of worker dust exposure. In the second study, an...

Failure of a glaucoma filtering procedure commonly results from scarring at the surgical site. Fibroblasts play an important role in the scarring process. 5-fluorouracil is an antimetabolite capable of inhibiting fibroblast proliferation. We tested the ability of 5-fluorouracil to inhibit cicatrization at the filtering site in an experimental model. Posterior lip sclerectomies were performed in each eye of ten normal owl monkeys. Postoperatively, one eye of each animal received subconjunctival injections of fluorouracil and the fellow eye received saline injections in a randomized, masked fashion. Two animals died of undetermined causes. None of the control eyes developed blebs, but six of the eight treated eyes in surviving animals developed blebs. The difference between intraocular pressures in fluorouracil-treated and control eyes was statistically significant (P less than 0.05). Signs of ocular toxicity included persistent corneal epithelial defects and delayed healing of the conjunctival incision. These results are considerably more favorable than those previously reported with experimental filtering procedures in non-human primates. Pharmacologic modulation of wound healing may decrease the risk of failure of filtering operations.

Ventilated booth workstations often do not provide complete dust control during the manual transfer and weigh out of chemical powders. In a typical process, a worker removes powder from the bulk material drum with a scoop, weighs the powder into a paper bag, and then places the full bag into a second drum. A previous study identified points of exposure in a ventilated weigh-out operation at a plastics manufacturing plant. Eddies in front of the worker and inside the weigh-out drum hindered dust control. The depth of the powder in the weigh-out drum also contributed to increased exposures. This follow-up study sought to apply and evaluate three different control modifications of the weigh-out station. The first control was the modification of the worktable to streamline the process. The second control was a local exhaust hood placed at the lip of the bulk material drum. This hood controlled the eddy in the bulk material drum. The last control was an air shower, i.e., a low-velocity, fresh air supp...

This study characterized the emissions generated during the pouring, cooling, and shakeout of castings made with the evaporative pattern casting (EPC) process. In addition, emissions from molds produced using conventional green sand technology were determined as a basis for comparison. Tests were performed under pilot-scale foundry conditions for production of both aluminum and gray iron water pump castings using an enclosing hood with a sampling stack. Sampling was conducted during pouring, cooling, and casting removal. Gas chromatographic/mass spectrometric (GC/MS) techniques and real-time instrumentation were used to identify the contaminants produced, to quantify the major contaminants, and to determine the temporal nature of these emissions. Major gaseous contaminants were identified as styrene, benzene, toluene, and ethyl benzene. Analysis of the real-time data indicated that the EPC molds produced more carbon soot and hydrocarbons during pouring than the green sand for both iron and alumin...

The effect of refraction accuracy on the differential light threshold of a Goldmann size III (0.43 degrees diameter) stimulus was evaluated in the right eyes of five normal subjects with randomly ordered sequence of plano, +1.00-, +2.00-, +3.00-, +4.00-, +5.00-, and +6.00-diopter (D) spherical overcorrections. Threshold measurements were performed at 0 degree, 5 degrees, 10 degrees, 15 degrees, 20 degrees, and 25 degrees eccentricity nasally along the 180 degrees meridian with the F4 program on the Octopus 201 perimeter. The +1.00- through +6.00-D overcorrections decreased the threshold values by an average of 1.4, 2.9, 4.2, 5.6, 6.7, and 7.6 dB, respectively, compared with the plano overcorrection. The depression of the differential light threshold was of similar magnitude at all eccentricities within the central 25 degrees.

A life-table analysis of surgical outcomes was performed on the first eye of 155 patients who were enrolled in a pilot study of glaucoma filtering surgery with postoperative subconjunctival 5-fluorouracil (5-FU) injections. The success rates at 1-, 2-, and 3-year intervals were 68, 63, and 63%, respectively, for 88 patients with non-neovascular glaucoma in aphakia; 82, 75, and 75% for 39 patients with non-neovascular glaucoma after unsuccessful filtering surgery; and 68% at each yearly interval for 28 patients with neovascular glaucoma. Complications which resulted from filtering surgery and the 5-FU injections included corneal epithelial defects (55.5%), conjunctival wound leaks (36.8%), suprachoroidal hemorrhage (5.8%), rhegmatogenous retinal detachment (2.6%), endophthalmitis and phthisis (1.9% each), and corneal scarring, late bleb leak, malignant glaucoma, and traction retinal detachment (1.3% each). A Cox Model regression analysis failed to demonstrate a correlation between surgical success and age, race, type of filtering procedure, or total dose of 5-FU received. Postoperative subconjunctival 5-FU may increase the operative success rate for selected patients with a high risk for failure after glaucoma filtering surgery.

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 worker's 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...

5-Fluorouracil (5-FU) was injected subconjunctivally after glaucoma filtering surgery in a pilot study of eyes with poor surgical prognoses. Twenty-seven (79%) of the 34 aphakic eyes with glaucoma achieved an intraocular pressure (IOP) of less than or equal to 21 mmHg (range of follow-up on nonreoperated eyes, 91 -468 days). Nine (69%) of 13 eyes with neovascular glaucoma achieved an IOP of less than or equal to 21 mmHg (range of follow-up on nonreoperated eyes, 120-379 days). Eight (89%) of nine phakic eyes with glaucoma following unsuccessful filtering procedures achieved an IOP of less than or equal to 21 mmHg (range of follow-up on nonreoperated eyes, 134-394 days). Visual acuities remained within one line of their preoperative levels or improved in 32 (94%) of the 34 aphakic eyes with glaucoma, eight (62%) of the 13 eyes with neovascular glaucoma, and six (67%) of the nine phakic eyes with glaucoma following unsuccessful filtering procedures. Postoperative corneal epithelial defects occurred in 45% of the cases. Conjunctival wound and conjunctival needle tract leaks were observed in 41% of the cases, but only one eye required wound revision. No other serious side effects that we attributed to 5-FU were observed. It seems that postoperative subconjunctival 5-FU increases the likelihood of achieving IOP control following filtering surgery in eyes with poor surgical prognoses; however, a randomized clinical trial is necessary to confirm this.

Postoperative subconjunctival fluorouracil injections may be a useful adjunct to standard glaucoma filtering surgery in eyes that are at high risk of failure. Topical administration would be preferable to subconjunctival administration; however, there are no data on the ocular penetration of topically applied fluorouracil. Consequently, we investigated the pharmacokinetics of topically administered fluorouracil labeled with carbon 14 in normal rabbit eyes. One drop (approximately 2.4 mg) of fluorouracil resulted in the following concentrations at 0.5 and six hours, respectively: 17.3 and 0.9 micrograms/g of conjunctiva; 24.3 and 1.3 micrograms/g of cornea; 14.6 and 0.2 micrograms/mL of aqueous; 0.8 and 0.5 microgram/g of lens; 1.1 and 0.3 microgram/g of vitreous; and 0.2 and less than 0.1 microgram/mL of serum. Three drops (approximately 7.2 mg) of fluorouracil resulted in the following concentrations at 0.5 and eight hours, respectively: 589.8 and 1.3 micrograms/g of conjunctiva; 502.9 and 1.8 micrograms/g of cornea; 199.6 and 0.8 micrograms/mL of aqueous; 6.2 and 0.5 micrograms/g of lens; 6.8 and 0.5 micrograms/g of vitreous; and 1.3 and 0.2 microgram/mL of serum. Since a fluorouracil concentration of 0.2 microgram/mL inhibits rabbit conjunctival fibroblast proliferation in cell culture by 50%, these data suggest that topically applied fluorouracil achieves sufficient levels in the ocular compartments and tissues to have potential therapeutic applications.

• Unilateral posterior lip sclerectomies were performed in ten owl monkeys. Five milligrams of fluorouracil was injected subconjunctivally in each operated eye immediately after surgery. Three drops (approximately 2.4 mg/drop) of fluorouracil were instilled ten minutes apart in each operated eye twice daily on postoperative days 1 through 7 and once daily on postoperative days 8 through 15, 17, 19, and 21. One monkey died on the seventh postoperative day; its death could not be attributed to systemic fluorouracil toxicity. All of the operated eyes had filtering blebs after the full course of fluorouracil, but seven also had corneal epithelial defects. By the seventh postoperative week, two of the operated eyes manifested moderately severe corneal opacification. Ten weeks postoperatively, the electroretinographic a- and b-wave amplitudes averaged 17% and 12% less, respectively, in the seven operated eyes without clinically significant corneal opacification than in the unoperated fellow eyes. Only two eyes had blebs after the 12th postoperative week. Histopathologic examination was performed on five eyes, of which only two revealed patent sclerostomies. Although topical fluorouracil appears to delay bleb scarring, the corneal findings suggest that it may be more toxic than subconjunctival fluorouracil.

Decreased retinal illumination (such as can be caused by pupillary constriction or light absorption by ocular media opacities) was simulated with a randomly ordered series of neutral density filters in front of the right eyes of five subjects with dilated pupils. Threshold measurements were performed on Humphrey and Octopus perimeters at 0, 5, 10, 15, 20, and 25 degrees nasally along the 180-degree meridian. A 0.6-log unit neutral density filter, which reduces retinal illumination the equivalent of halving the pupillary diameter, decreased the mean Humphrey thresholds by 1.1 +/- 0.8 decibels (dB) (mean +/- standard deviation) and the mean Octopus thresholds by 1.7 +/- 1.4 dB. Statistically significant (P less than or equal to .05, Dunnett's test) threshold depressions were observed at all eccentricities with a 1.5-log unit neutral density filter on the Humphrey perimeter (-4.5 +/- 0.7 dB) and with a 1.0-log unit neutral density filter on the Octopus perimeter (-3.5 +/- 1.0 dB).

The absorbing, scattering, and blurring effects of media opacities on Octopus 201 perimeter and/or Humphrey Field Analyzer threshold measurements were simulated in the right eyes of five subjects with randomly-ordered series of neutral density filters (NDFs), diffusers, and spherical plus overcorrections. Threshold measurements were performed 0°, 5°, 10°, 15°, 20°, and 25° nasally along the 180° meridian with the F4 program on the Octopus 201 perimeter and with twice-repeated profiles on the Humphrey Field Analyzer.

• We performed posterior lip sclerectomies in 29 owl monkey eyes to determine the natural history of wound healing after filtering surgery without adjunctive antimetabolite therapy. We noted three phases of wound healing during clinical and histologic examination: early healing (days 2 to 6), intermediate healing (days 7 to 9), and late healing (days 10 to 14). In the early healing phase, all limbal fistulas except one remained open gonioscopically, but by day 6, fibroblasts had proliferated along the walls of the opening. Proliferation and migration of fibroblasts continued during the intermediate healing phase to completely occlude four and to partially occlude two of the ten fistulas in the eyes studied during this time. In the late healing phase, the limbal fistula was completely closed by granulation tissue in four of five eyes and was slitlike open in one eye. In this model of filtering surgery, wound healing at the sclerectomy site with obliteration of the limbal opening by proliferating fibroblasts occurred within the first 14 postoperative days. We believe that the short-term effects of newer treatments designed to alter wound healing after filtering surgery may be assessed in this model, which is characterized by predictable and prompt wound healing.