Biomedical subjects

R P Garrison

Publications and source records attributed to R P Garrison.

11 recordsLinked to original sources

PubMed1994

A case-control study of chronic neuropsychiatric disease and organic solvent exposure in automobile assembly plant workers.

A case-control study of chronic neurological and psychiatric disease and occupational exposure to solvents was carried out in eight automobile assembly plants. Cases included 299 subjects who were granted medical disability retirement in 1980-8. Two control groups were selected, the first from those granted retirement in the same period because of medical disability from causes unrelated to solvent exposure. The second included hourly employees from the plant population. In these facilities, solvent exposures tended to be short term and low level, although common: the average duration of exposure was 2.3 years; about 41% experienced at least one day of exposure. Of those exposed, 46% had less than one year of exposure. Results for all psychiatric disease combined (273 cases) suggested that cases had lower exposures than either control group, regardless of how exposure was expressed. Results could not be explained by conventional confounding exposures or characteristics or by usual manifestations of the healthy worker effect. By contrast, chronic neurological disease, and multiple sclerosis in particular, seemed to be associated with exposure, although few cases were identified and observed increases in risk were not statistically significant.

Adult↗

PubMed1991

Development of a field method for determining the service lives of respirator cartridges--Part IV: Results of field validation trials.

Results of a fourth study on the use of small, carbon-filled glass tubes, referred to as respirator carbon tubes (RCTs), for predicting the service lives of organic vapor respirator cartridges are presented. Organic vapors are drawn through the RCT by using a personal sampling pump until breakthrough is detected. This breakthrough time is then used in conjunction with a bed-residence adsorption model to predict the breakthrough time of a cartridge containing carbon identical to that in the RCT. Previous laboratory work demonstrated that accurate prediction of cartridge breakthrough time was possible for exposure to carbon tetrachloride in atmospheres containing 5-94% relative humidity (RH) with both dry and prehumidified carbon beds and with n-hexane, pyridine, and binary mixtures of each with carbon tetrachloride. This report examines the performance of the RCT method in a workplace environment where carbon tetrachloride concentrations varied from 101 to 855 ppm, pyridine levels varied from 0 to 29 ppm, temperatures ranged from 28 to 39 degrees C, and RH varied from 19% to 49%. The RCT method predicted cartridge breakthrough times to an accuracy of +/- 8 at the 95% confidence level, which equaled or exceeded results of previously reported laboratory studies. Actual breakthrough times averaged within +/- 5% of times predicted with previous laboratory data. A plot of bed-residence time versus breakthrough time yielded a coefficient of determination of 0.71 when ambient concentrations were standardized.

Air Pollutants, Occupational↗

PubMed1991

Contaminant reduction by ventilation in a confined space model--toxic concentrations versus oxygen deficiency.

Airborne contaminants can create hazardous conditions in confined spaces (CS) across a broad range of concentrations, e.g., from relatively low, potentially toxic levels (ppm) to much higher levels (%) causing oxygen deficiency. This study investigated ventilation characteristics for isobutylene (IBE) at relatively low concentrations, simulating toxic levels. Experimental data were compared to results from previous studies of oxygen deficiency. Data were obtained at several locations in a cubical CS model, with several variable test parameters: ventilation mode (exhaust and supply), volume flow rate ("air changes" per hour), and ventilation inlet/outlet elevation (% of model height). Findings indicated similar ventilation characteristics, in general, for simulated toxic (IBE) levels compared to oxygen deficiency. Both IBE and O2 deficiency data have shown that supply ventilation is typically more effective than exhaust and that CS locations aligned with supply outlets experience much more rapid contaminant reduction than do other locations. The data suggest that highly accurate predictions of ventilation characteristics cannot be expected for all cases with widely different contaminants and concentrations. Findings from this study indicate that ventilation guidelines for one range of contaminant concentration (e.g., causing oxygen deficiency) can be extended reasonably to encompass a broader range of concentration (e.g., to include toxic or flammable atmospheres).

Air Pollutants, Occupational↗

PubMed1990

Multicellular model for contaminant dispersion and ventilation effectiveness with application for oxygen deficiency in a confined space.

Multicellular models were developed to predict contaminant dispersion in a three-dimensional (3-D) space. The method utilized in this study was patterned after models which have been developed for water pollution in lakes and streams. This approach involved (1) design of cell structures to accommodate the geometry and mass flow characteristics of the 3-D space and (2) approximation of dispersion coefficients to describe contaminant transport in addition to that resulting from mass flow between cells. The dispersion model utilized a mass balance equation to predict contaminant dispersion as a function of time. The computer model was evaluated against experimental data for oxygen deficiency inside a ventilated confined space (CS) model. Eight test cases of ventilation design for the CS model were tested for each of three contaminant release (nitrogen to cause oxygen deficiency) characteristics: (1) purging (oxygen recovery from an initial deficiency); (2) steady state; and (3) variable rate. The dispersion model did a reasonably good job of predicting oxygen concentrations for different locations (cells) in the CS model. The primary limitations of this multicellular method are associated with experimental approximations of flow patterns and dispersion coefficients.

Air Pollutants↗

PubMed1989

Development of a field method for evaluating the service life of organic vapor cartridges: results of laboratory testing using carbon tetrachloride.

A new method for determining the service life of respirator cartridges has been developed and tested in a laboratory setting. The method involves using small respirator carbon tubes (RCTs) packed with sorbent obtained from a respirator cartridge of interest. The tubes may be taken into an industrial setting and used to evaluate the work environment. A sample tube is placed directly behind the RCT and periodically replaced. This tube acts as a backup section to the RCT. The sample tube can be brought back to a laboratory and analyzed for the contaminant of interest using validated sampling methods specific for the contaminant. Alternatively, a direct-reading instrument can be placed at the exit end of the RCT to obtain "real-time" breakthrough information. The results, when combined with existing sorbent theories, can be used to predict the service life of a respirator cartridge. The advantage of using RCTs is that, unlike respirator cartridges, they can be taken into the field and used with traditional high-flow air sampling pumps. This method is designed to be able to determine the service life of respirator cartridges even when multiple contaminants are present in the workplace. Results of initial laboratory studies, using carbon tetrachloride as a challenge agent, indicated that RCTs were capable of predicting cartridge service life within an accuracy of +/- 15%.

Carbon Tetrachloride↗

PubMed1986

Confined spaces--a case for ventilation.

Many exposures, some leading to deaths and injuries, in confined spaces could have been prevented by ventilating the space prior to and during the entry. Current standards and guidelines generally do not require ventilation. Nor do they sufficiently emphasize the need for ventilation or provide guidance on how to ventilate confined spaces. Mechanical ventilation is a positive engineering control action that can usually be taken and that will reduce the hazards of adverse atmospheric conditions inside a confined space. Natural ventilation usually is not sufficiently reliable to serve as a primary means of control. Unfortunately, very little specific information is available for designing and implementing ventilation strategies for confined spaces. More published information is needed, such as examples of effective policy and procedures in use by industry and findings from research on confined space ventilation. Basic and applied research can help to demonstrate effective ventilation actions and develop useful design guidelines. Additional published information should increase hazard awareness and reduce the likelihood of accidents.

Industry↗

PubMed1985

Health examination and air monitoring evaluation for workers exposed to 2-nitropropane.

Comprehensive employee health examinations along with work-place area and personal monitoring were conducted to evaluate potential exposure to 2-nitropropane. The employee cross section included in the study consisted of nearly all workers at the plant. The entire workforce was represented, including those who did not have contact with 2-nitropropane. No adverse health effects were found which could be connected with work experience. Body systems evaluated included: lungs, liver, kidney, blood, skin and cardiovascular. Work area levels at specific locations sometimes exceeded 25 ppm, but personal time-weighted average levels generally were below 25 ppm.

Air Pollutants, Occupational↗

PubMed1984

Odor threshold determination for 2-nitropropane.

The odor threshold of 2-nitropropane (2-NP) has been characterized as not capable of providing warning that air concentrations possibly exceed acceptable guidelines. However, recent testing indicates that the odor threshold is significantly lower than previously thought. In particular, the odor threshold has been indicated by this study to be below the current TLV for 2-NP.

Alkanes↗

PubMed1980

Noise characteristics of circular nozzles for high velocity/low volume exhaust ventilation.

Noise characteristics of circular exhaust nozzles were studied for average face velocities ranging 25-175 m/sec (5000-35 000 fpm). Experimental parameters were examined for nozzle design variations consisting of: (a) seven profile shapes having 2.54 cm (1.0 inch) inside diameter, and (b) five plain profiles of different size, 1.27-3.81 cm (0.50-1.50 inch) inside diameter. All nozzles exhibited a "peaking" characteristic in which the maximum noise level was reached at less than the maximum face velocity. As maximum face velocity (flowrate) was achieved, noise spectra exhibited a pronounced drop in high frequency noise, with a shift in peak frequency from 4000 Hz to 2000 Hz. Both of these characteristics indicated the onset of aerodynamic "choking", as sonic velocity was established in the nozzle flow. Variations in nozzle shape and size had significant effects upon noise levels propagated into the "workspace".

Equipment and Supplies↗

PubMed1980

Static pressure and velocity characteristics of circular nozzles for high velocity/low volume exhaust ventilation.

Static pressure and velocity characteristics of circular exhaust nozzles were studied for average face velocities ranging 50-125 m/sec (10 000-25 000 fpm). Experimental nozzle variations included: (a) seven profile shapes having 2.54 cm (1.0 inch) inside diameter, and (b) five plain profiles of different size, 1.27-3.81 cm (0.50-1.50 inch) inside diameter. Plain and flanged nozzles experienced formation of pronounced vena contracta; flared and rounded nozzles did not. Nondimensional centerline velocity gradients were affected strongly by variations in nozzle shape, but were insensitive to changes in nozzle size and face velocity. Profile shape and size variations significantly affected overall nozzle static pressure loss, with the most pronounced effects for wedge-shaped inlets. Empirical representations were determined for velocity and static pressure loss data to permit calculations for nozzle design.

Equipment and Supplies↗

PubMed1980

Statis pressure, velocity, and noise characteristics of rectangular nozzles for high velocity/low volume exhaust ventilation.

Static pressure, velocity, and noise characteristics of rectangular exhaust nozzles were studied for average face velocities (V0) ranging 25-150 m/sec (5000-30 000 fpm). Experimental nozzle variations included plain and flanged profile shapes having width-to-length ratios (WLR) of 1.0, 0.50, 0.25, and 0.10. Centerline static pressures for all nozzles indicated formation of pronounced vena contracta in post-entry airflow. Empirical representations were determined for the centerline velocity gradient into the nozzles, which became more gradual with decreasing WLR. Nozzle noise levels varied with V0, exhibiting a "peaking" characteristic indicative of aerodynamic "choking". Flanges were found to have significant effects upon nozzle performance.

Air Pollutants↗