Field evaluation of a portable photoionization detector for assessing exposure to solvent mixtures.

To evaluate a portable photoionization detector for assessing personal exposure to solvent mixtures, a set of 26 side-by-side, time-weighted average (TWA) personal breathing zone samples were collected during various construction painting tasks by two different sampling methods: (1) standard charcoal sorbent tubes analyzed by gas chromatography (CST/GC), and (2) a direct-reading photoionization detector coupled with an extended data-logger (PID). The TWA concentrations of the hydrocarbons detected by CST/GC analysis were summed for comparison with the TWA concentration obtained from the direct-reading PID. Based on linear regression between the log TWA concentrations of the two sampling methods, the data were highly correlated (r2 = 0.95). Since the solvents had effects that may be considered additive, threshold limit values (TLVs) for mixtures were developed using American Conference of Governmental Industrial Hygienists formulas to evaluate solvent exposure. The logs of the TLV mixture data from the sampling methods were highly correlated (r2 = 0.94). Based on the linear regression analyses, the response of the portable PID was highly correlated to the CST/GC results for hydrocarbon mixtures encountered during various painting tasks. Due to the short duration of tasks, highly fluctuating exposures, and complexity of the mixtures, the PID may provide the most cost-effective, detailed exposure assessment for solvent mixtures.

Exposures of geotechnical laboratory workers to respirable crystalline silica.

Geotechnical laboratory testing involves the determination of the physical properties of soil, rock, and other building materials for engineering purposes. Individuals working in these laboratories are exposed to airborne soil, rock, and other dusts during the preparation and testing of these materials. Crystalline silica as quartz is a common constituent of these materials and represents a potential hazard to geotechnical laboratory workers when airborne as a respirable dust. The authors conducted an examination of the potential for geotechnical laboratory workers to be exposed to respirable dust and respirable quartz during the performance of three routine laboratory tasks. A task-based exposure assessment strategy was used. Although respirable dust was generated during the performance of each of these tasks, its impact on exposures was generally overridden by the presence of respirable quartz in the dust. Quartz content in the respirable dust ranged from below the detection limit to greater than 50 percent. Mean exposure to respirable quartz, based on the duration of the task and assuming no other exposures for the rest of the 8-hour day, exceeded the National Institute for Occupational Safety and Health (NIOSH) "action level" (the exposure level at which certain actions must be taken) of 0.025 mg/m3. If exposure was assumed to continue for the rest of the 8-hour day at the measured concentration, mean exposure to respirable quartz exceeded the American Conference of Governmental Industrial Hygienists (ACGIH) Threshold Limit Value (TLV) time-weighted average (TWA), the Occupational Safety and Health Administration (OSHA) PEL, and the NIOSH REL. Seven percent of 57 individual task exposure measurements exceeded the TLV-TWA and the PEL, 18 percent exceeded the REL, and another 12 percent exceeded excursion limits as defined by ACGIH. The results of this study support the conclusion that geotechnical laboratory workers are potentially exposed to respirable crystalline silica as quartz at levels that may be harmful. Because the quartz content of the materials being tested in these laboratories is highly variable and is almost never determined prior to testing, all materials being tested in the geotechnical laboratory should be assumed to contain quartz. Appropriate controls should be used to protect workers from inhaling dusts generated from these materials.

A local exhaust ventilation system to reduce airborne ribavirin concentrations.

A local exhaust hood was designed and built to capture and contain aerosol emissions of ribavirin during drug administration. The newly designed over-the-head hood is similar to the single hood currently used to administer the drug. This new hood was surrounded by an exhaust plenum to form a compound hood configuration. The exhaust plenum was connected to a filtered local exhaust air system to remove the waste aerosol. The compound hood and local exhaust ventilation system were evaluated for leak rate and inside hood aerosol concentration as a function of exhaust flow rates. This hood reduced the leak rate from an average of 98% with the traditional head hood to an average of less than 1% with the compound hood with exhaust port. The compound hood did not perform quite as well when not in use (set aside during infant caretaking) with the nebulizer remaining on. The leak rate was found to increase from an average of less than 1% to an average of 12% when trials were conducted that used a doll as a simulated patient versus trials without a doll, respectively. As regards therapeutic dose inside the hood, the system's performance may lead to an 18% to 25% decrease in inside hood concentration of aerosol entering the hood. Optimum hood operating parameters were identified. An exhaust flow rate in the range from 1.0 Lpm below to 1.0 Lpm above inlet flow rate from the small particle aerosol generator (SPAG nebulizer) reduced the leak rate to an average of less than 1%.(ABSTRACT TRUNCATED AT 250 WORDS)

A predictive model for determining asbestos concentrations for fibers less than five micrometers in length.

The controversy of whether small asbestos fibers are biologically significant has not been resolved. The present standard method for evaluating asbestos fiber concentrations in workroom air excludes fibers less than 5 micron long even though it has been shown that small fiber concentrations dominate in a dust cloud. This research project was conducted to develop a mathematical model whereby one could predict small (less than 5 micron length) asbestos fiber concentration based on the fiber count concentration determined by phase contrast microscope analysis. Dry chrysotile asbestos was aerosolized into a chamber and sampled by membrane filtration. Segments from each filter were analyzed by both the NIOSH technique using phase contrast microscopy (PCM) and scanning electron microscopy (SEM) at 2000 X for fiber concentrations. A linear relationship was found to exist between the natural logarithm of the SEM-determined concentration and the natural logarithm of the PCM-determined concentration (r = 0.852). Using these data, a mathematical model was developed to predict SEM concentrations based on PCM counts. This model may have application in retrospective epidemiological studies for estimating small fiber exposure levels to determine if small fibers play a role in disease production. The greatest utility would be in those retrospective studies where the only exposure information available is based on PCM counts.

The determination of ambient air quality within an environmental care unit.

Various chemicals found in the environment have been suspected of initiating or contributing to conditions such as asthma, dermatitis, irritability, headaches, cardiac arrhythmias, thrombophlebitis, and vasculitis. The increasing number and variety of chemicals present in the environment has led to the hypothesis that there may also be a corresponding increase in the number of people who are sensitive to these chemicals. Sensitive individuals may be continually exposed to chemical insults in their normal environment and may be experiencing a chronic reaction; however, an exposure-response relationship is difficult to establish. An Environmental Care Unit (ECU) provides an atmosphere that minimizes exposures to potential insults so patients symptoms of reaction to chemical insult may be relieved before challenge testing. Air quality required within an ECU to achieve this symptom remission is not known; therefore, this study was designed to document and compare concentrations of six criteria pollutants (sulfur dioxide, carbon monoxide, nitrogen dioxide, hydrocarbons, total suspended particular, and ozone) and formaldehyde within the ECU, the hospital outside the ECU, and the ambient atmosphere of the neighborhood around the hospital. Air movement studies indicated that the ECU was under positive pressure with respect to the rest of the hospital and had an air supply to air exhaust ratio of approximately two. Overall, no significant differences were found for any sampled pollutant at sites within the ECU or between ECU sites and the hospital proper. With an exception of ozone, significant differences among contaminant concentrations were noted between the atmosphere of the surrounding neighborhood and the hospital proper.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of waste anesthetic gas and vapor exposure on reproductive outcome in veterinary personnel.

Elevated rates of adverse reproductive outcome among medical and dental personnel exposed to waste anesthetic gas and vapor have been noted in the literature. NIOSH issued recommended standards for occupational exposure to these agents in a criteria document published in 1977. This study was designed to investigate adverse reproductive outcome in veterinary personnel who are exposed to waste anesthetic gas and vapors at levels near the NIOSH recommended standards. This epidemiologic study employed case-control methodology using a national sample of male veterinarians, female veterinarians and female veterinary assistants. Occupational exposure to waste anesthetic gas and vapors was not found to be associated significantly with adverse reproductive outcome at the 95% confidence level for female veterinary personnel when adjustment was made for use of diagnostic x-rays. Use of diagnostic x-rays in veterinary practice was associated with a statistically significant increase in odds ratios for spontaneous abortion in female veterinarians and veterinary assistants.

Aerosol sampling efficiency of 37 mm filter cassettes.

This research compared the sampling efficiencies of open- and closed-face 37 mm filter cassettes and an experimental cassette with a tapered inlet. The experiment involved challenging the cassettes with various aerosol sizes up to 24 micron Mass Median Aerodynamic Diameter (MMAD) in a wind tunnel operated at 100 cm/sec. Sampling efficiencies were determined by comparing cassette mass concentration measurements to paired isokinetic samples. It was found that sampling efficiencies dropped with increasing particle size and that the cassette with the tapered entry offered no improvement to sampling efficiency. Sampling efficiency appeared to be improved by placing cassettes on a manikin to simulate personal sampling.

Characterization of particleboard aerosol--size distribution and formaldehyde content.

Health hazards unique to particleboard include the generation of urea-formaldehyde resin bound in wood aerosol and release of formaldehyde gas that can be inhaled by the worker. A particleboard aerosol was generated by a sanding process and collected under laboratory conditions that determined the particle size distribution and formaldehyde content. Three side-by-side Marple 296 personal cascade impactors with midget impingers attached downstream collected particleboard aerosol and gaseous formaldehyde for ten sample runs. Gravimetric analysis quantified the collected aerosol mass, and chromotropic acid/spectrophotometric analytical methods were employed for formaldehyde content in particleboard aerosol and gaseous formaldehyde liberated from sanded particleboard. Significant variations (p less than .005) were observed for the particleboard mass and gaseous formaldehyde collected between sample runs. No significant differences (alpha = .05) were observed for the aerosol size distribution determined and formaldehyde content in particleboard aerosol per unit mass for sampling trials. The overall MMAD of particleboard aerosol was 8.26 microns AED with a sigma g of 2.01. A predictive model was derived for determining the expected formaldehyde content (microgram) by particleboard aerosol mass (mg) collected and particulate size (micron AED).

Airborne asbestos in Colorado public schools.

Levels of airborne asbestos for six Colorado public school facilities with sprayed-on asbestos materials were documented using three analytical techniques. Phase contrast microscopy showed levels up to the thousandths of a fiber per cubic centimeter (f/cc), scanning electron microscopy (SEM) up to the hundredths of a f/cc, and transmission electron microscopy coupled to selected area electron diffraction and energy dispersive X-ray analysis (TEM-SAED-EDXA) up to the tenths of an asbestos f/cc. Phase contrast microscopy was found to be an inadequate analytical technique for documenting the levels of airborne asbestos fibers in the schools: only large fibers which were not embedded in the filter were counted, and asbestos fibers were not distinguished from nonasbestos.

The accreditation of academic programs in industrial hygiene.

The American Academy of Industrial Hygiene has initiated a program to accredit academic programs in industrial hygiene. Guidelines, criteria, and procedures to be employed by the Accreditation Committee are summarized, along with a status report of activities currently underway.

Development of a mathematical model for predicting concentrations of small asbestos fibers.

The standard method of asbestos sample analysis by phase-contrast microscopy excludes fibers which are below the resolution limits of the light microscope. Electron microscopic studies revealed that fibers in these small size ranges comprise the majority of fibers in asbestos dust. This research was conducted to determine if the development of a mathematical model for predicting concentrations of small fibers (less than 5 microns length) based on phase-contrast concentrations was feasible. The model presented in this paper was evaluated for its practical utility and was determined to be of minimal value; however, it was felt that the development of a reasonably accurate model can be arrived at through continued research.

Asbestos in Colorado schools.

Forty-one public schools in Colorado were drawn at random and surveyed for asbestos-containing materials. After bulk samples of possible asbestos materials from the schools were collected and analyzed, the K2 asbestos screening test was used to eliminate samples that did not contain asbestos. Samples with positive results on the K2 test were analyzed by an outside laboratory by polarized light microscopy. The risk of potential exposure presented by these materials was then assessed for each site from which a sample was taken. Of 113 samples collected, results were negative for asbestos for only 10.6 percent by the K2 test. Of the 101 samples for which results were positive, 56 actually contained 1 or more forms of asbestos. Twelve of these 56 samples were from sprayed material; the remaining 44 were from other materials containing asbestos. Of the 41 schools sampled, 31 had asbestos materials in one of more locations. The potential exposure values for these materials ranged from very low to very high, but the majority had high-exposure potentials. Estimates based on the survey of the 41 schools indicated that 63 to 89 percent of the public schools in Colorado have asbestos materials that present potentially serious hazards, not only to the children, teachers, and staff, but also to members of the community who use the school buildings after regular school hours.

Characterization of the aerosol in turkey rearing confinements.

A study was conducted to characterize the aerosol found in turkey rearing confinements, to study biological response to inhalation of the aerosol, and to evaluate a water spray, dust suppression system in one confinement as compared to a control barn. A significant reduction in aerosol concentration in the "sprayed" barn was inferred by many environmental and biological sampling parameters. Similarity of physical and biological factors in both study populations, with the exception of the dust suppression system, implied that a mortality rate increase of 1.74 of control versus "sprayed" barn was directly related to aerosol concentration.

Waste anesthetic gas exposures to veterinarians and animal technicians.

A survey of veterinarians was conducted in an 11-county region of eastern Colorado to determine the extent of usage of inhalation anesthetics and to measure exposures of veterinarians and their assistants to waste anesthetic gases. The survey indicated that inhalation anesthetics were used in 80.8% of the 210 practices. Exposures to waste anesthetics in veterinary practices were far less than reported in human hospitals. Waste anesthetic concentrations were affected by size of the patient, type of breathing system, and use of scavenging systems. Dilution ventilation had no effect on breathing zone concentrations. The endotracheal tube and occasionally the anesthetic machine were the major sources of leakage of anesthetic gases.

A comparison of aerosol sampling techniques: "open" versus "closed-face" filter cassettes.

Accepted practice by most professional industrial hygienists in government and industry is to use "closed-face" filter cassette techniques as standard sampling procedures for the majority of aerosols. A two-phase, field study was conducted to determine whether a gravimetric bias exists between "open" and "closed-face" sampling methods. Phase I involved an in-depth analysis of the potential gravimetric viability as it applies to an industrial paint spray mist, and Phase II was a series of pilot studies, of small sample base, to determine if this phenomena exists over a range of aerosol types. Dusts of wood, grain, cellulose, Portland cement and perlite, welding fumes, and chromic acid mist were sampled in Phase II. Paired breathing zone samples, "open" and "closed-face", 37 mm, 3-piece filter cassettes were utilized in both phases of the study. In both phases of the study, "open-face" concentrations were consistently higher than "closed-face" concentrations, with the exception of cellulose dust. Based on the concentration for both sampling techniques, the data suggests that "closed-face" sampling techniques (4.0 mm inlet diameter) might be size selective against large particles. This could lead to an underestimation of a worker's total aerosol exposure.

Carbon monoxide: Dosimetry in occupational exposures in Denver, Colorado.

The occupational carbon monoxide (CO) exposure of Denver traffic control personnel was evaluated during 8-hr workshifts using three parameters: (1) 98, 8-hr time-weighted average breathing zone air samples (personal dosimetry); (2) before- and after-workshift CO breath samples; and (3) 8-hr moving average, ambient CO levels during the fall and winter months. Different shifts and work experiences were taken into consideration. The data revealed greater CO exposure in subjects working on the street than controls working inside downtown buildings with respect to breath CO concentration and breathing zone air samples. The CO concentrations in the after-workshift breath samples were closely associated with the 8-hr time-weighted average CO levels. The greatest source of CO to the sample population was cigarette smoking, followed by occupational-related sources, and finally, the ambient background CO levels.

Waste anesthetic gas and vapor exposures in veterinary hospitals and clinics.

A survey of veterinary hospitals and clinics was conducted to determine the extent of usage of inhalation anesthetics and measure exposures of veterinarians and their assistants to waste anesthetic gases and vapors. A questionnaire survey indicated 80.8 percent of practices in the study area used inhalation of anesthetics, with a wide range noted between types of practices. Exposures to waste anesthetics were less in veterinary hospitals than reported in human hospitals. Mean methoxyflurane concentrations were 1.9 ppm and 1.7 ppm in breathing zones of small animal veterinarians and animal technicians, respectively. Waste methoxyflurane concentrations were significantly affected by size of patient, type of breathing system, and use of scavenging systems. Dilution ventilation had no significant effect on breathing zone concentrations of waste methoxyflurane.