Gasoline vapor exposures at a high volume service station

Gasoline vapor concentrations were measured at a high volume service station for one week in May, 1983, for service station attendants, self-service customers and for various area locations. To facilitate the retention of highly volatile, low-molecular weight gasoline vapor components, 100/50 mg charcoal adsorption tubes were used with flow rates of 100 cc/min for long-term exposure samples and 900 cc/min for short-term exposures. Methylene chloride was selected as the desorption solvent. Desorbed hydrocarbons were analyzed and quantitated by capillary column gas chromatography using a flame ionization detector and a 0-100 degrees C temperature program. The data proved that the predominant ambient air hydrocarbons are those of C4 and C5 compounds. Monitoring results showed that the total gasoline vapor TWA exposures for service station attendants ranged from 0.6 to 4.8 ppm with a geometric mean of 1.5 ppm. Short-term personal samples collected while refueling ranged from not detectable to 38.8 ppm with a geometric mean of 5.8 ppm.     

Gasoline vapor exposures. Part II. Evaluation of the nephrotoxicity of the major C4/C5 hydrocarbon components

Analysis of workplace exposures to gasoline vapors revealed that C4 and C5 hydrocarbons constitute anywhere from 67 to 74% by weight of a typical vapor. Furthermore, it was found that n-butane, isobutane, n-pentane, and isopentane together comprise greater than 90% of all the C4/C5 vapor components and approximately 61 to 67% by weight of the total vapor. Accordingly, a 21-day inhalation toxicity study of a blend consisting of 25% (w/w) each of these four hydrocarbons was conducted using rats to assess the potential for these major gasoline vapor components to induce kidney damage. No evidence of the kidney lesions typically associated with hydrocarbon-induced nephropathy was observed in rats exposed at up to 11 800 mg/m3 (4437 ppm) of the blend.     

Gasoline and vapor exposures in service station and leaking underground storage tank scenarios.

Exposure to gasoline and gasoline vapors from service station operations and leaking underground storage tanks is a major health concern. Six scenarios for human exposure were examined, based primarily on measured air and water concentrations of total hydrocarbons, benzene, xylenes, and toluene. Calculated mean and upper limit lifetime exposures provide a tool for assisting public health officials in assessing and managing gasoline-related health risks.     

Characterization of exposures among cemented tungsten carbide workers. Part I: Size-fractionated exposures to airborne cobalt and tungsten particles

As many as 30,000 workers in the United States of America are exposed to cemented tungsten carbides (CTC), alloys composed primarily of tungsten carbide and cobalt, which are used in cutting tools. Inhalation of cobalt-containing particles may be sufficient for the development of occupational asthma, whereas tungsten carbide particles in association with cobalt particles are associated with the development of hard metal disease (HMD) and lung cancer. Historical epidemiology and exposure studies of CTC workers often rely only on measures of total airborne cobalt mass concentration. In this study, we characterized cobalt- and tungsten-containing aerosols generated during the production of CTC with emphasis on (1) aerosol "total" mass (n=252 closed-face 37 mm cassette samples) and particle size-selective mass concentrations (n=108 eight-stage cascade impactor samples); (2) particle size distributions; and (3) comparison of exposures obtained using personal cassette and impactor samplers. Total cobalt and tungsten exposures were highest in work areas that handled powders (e.g., powder mixing) and lowest in areas that handled finished product (e.g., grinding). Inhalable, thoracic, and respirable cobalt and tungsten exposures were observed in all work areas, indicating potential for co-exposures to particles capable of getting deposited in the upper airways and alveolar region of the lung. Understanding the risk of CTC-induced adverse health effects may require two exposure regimes: one for asthma and the other for HMD and lung cancer. All sizes of cobalt-containing particles that deposit in the lung and airways have potential to cause asthma, thus a thoracic exposure metric is likely biologically appropriate. Cobalt-tungsten mixtures that deposit in the alveolar region of the lung may potentially cause HMD and lung cancer, thus a respirable exposure metric for both metals is likely biologically appropriate. By characterizing size-selective and co-exposures as well as multiple exposure pathways, this series of papers offer an approach for developing biologically meaningful exposure metrics for use in epidemiology.     

Size-separated sampling and analysis of isocyanates in workplace aerosols. Part I. Denuder--cascade impactor sampler

Isocyanates in the workplace atmosphere are typically present both in gas and particle phase. The health effects of exposure to isocyanates in gas phase and different particle size fractions are likely to be different due to their ability to reach different parts in the respiratory system. To reveal more details regarding the exposure to isocyanate aerosols, a denuder-impactor (DI) sampler for airborne isocyanates was designed. The sampler consists of a channel-plate denuder for collection of gaseous isocyanates, in series with three-cascade impactor stages with cut-off diameters (d(50)) of 2.5, 1.0 and 0.5 mum. An end filter was connected in series after the impactor for collection of particles smaller than 0.5 mum. The denuder, impactor plates and the end filter were impregnated with a mixture of di-n-butylamine (DBA) and acetic acid for derivatization of the isocyanates. During sampling, the reagent on the impactor plates and the end filter is continuously refreshed, due to the DBA release from the impregnated denuder plates. This secures efficient derivatization of all isocyanate particles. The airflow through the sampler was 5 l min(-1). After sampling, the samples containing the different size fractions were analyzed using liquid chromatography-mass spectrometry (LC-MS)/MS. The DBA impregnation was stable in the sampler for at least 1 week. After sampling, the DBA derivatives were stable for at least 3 weeks. Air sampling was performed in a test chamber (300 l). Isocyanate aerosols studied were thermal degradation products of different polyurethane polymers, spraying of isocyanate coating compounds and pure gas-phase isocyanates. Sampling with impinger flasks, containing DBA in toluene, with a glass fiber filter in series was used as a reference method. The DI sampler showed good compliance with the reference method, regarding total air levels. For the different aerosols studied, vast differences were revealed in the distribution of isocyanate in gas and different particle size fractions. The opportunity to obtain detailed information regarding the distribution of isocyanates in aerosols in addition to the total air levels make the DI sampler a valuable tool for studies of possible health effects in the different parts of the airways.     

A conceptual model for take-home workplace exposures

The boundary between occupational and environmental exposures is often artificial, as occupational hazards can readily escape the workplace. One way that this occurs is when workers “take-home” occupational hazards, exposing family members. While take-home exposures have long been recognized, there is no comprehensive framework describing the pathways by which workers bring home workplace hazards. In this article, we provide such a conceptual model that includes three pathways for take-home exposures: external contamination, internal dose, and behavior change of workers. This conceptual model should help to describe the problems of take-home exposures more comprehensively in future research.     

Formaldehyde vapor exposures in anatomy laboratories

This study examined formaldehyde vapor exposures that occurred in the gross anatomy laboratories of a major medical school during a 12-week study period. Formaldehyde samples were collected using personal sampling pumps to draw air through midget impingers containing a 0.1% solution of sodium bisulfite dissolved in deionized water as the absorbing medium. Breathing zone and ambient air samples were collected and analyzed from 8 laboratories on a rotating basis. Analysis was via the chromotropic acid method recommended by the National Institute for Occupational Safety and Health. It was found that 44% of all breathing zone samples were greater than the 1.0 ppm ceiling value for occupational exposure recently recommended by the American Conference of Governmental Industrial Hygienists. Only 11% of ambient air samples were in excess of 1.0 ppm.     

A strategy for assessing workplace exposures to nanomaterials

This article describes a highly tailorable exposure assessment strategy for nanomaterials that enables effective and efficient exposure management (i.e., a strategy that can identify jobs or tasks that have clearly unacceptable exposures), while simultaneously requiring only a modest level of resources to conduct. The strategy is based on strategy general framework from AIHA? that is adapted for nanomaterials and seeks to ensure that the risks to workers handling nanomaterials are being managed properly. The strategy relies on a general framework as the basic foundation while building and elaborating on elements essential to an effective and efficient strategy to arrive at decisions based on collecting and interpreting available information. This article provides useful guidance on conducting workplace characterization; understanding exposure potential to nanomaterials; accounting methods for background aerosols; constructing SEGs; and selecting appropriate instrumentation for monitoring, providing appropriate choice of exposure limits, and describing criteria by which exposure management decisions should be made. The article is intended to be a practical guide for industrial hygienists for managing engineered nanomaterial risks in their workplaces.     

Gasoline vapor exposure during bulk handling operations

The survey evaluated gasoline vapor concentrations in the employees, breathing zone at five bulk handling facilities. Charcoal tube samples were analyzed by a special GLC/flame ionization/flasher technique which coupled with a computer program identified up to 142 constituents. A time-weighted limit of 240 ppm/10-hour day was only exceeded for five percent of the time at one location.     

Characterization of exposures among cemented tungsten carbide workers. Part II: Assessment of surface contamination and skin exposures to cobalt, chromium and nickel

Cobalt, chromium and nickel are among the most commonly encountered contact allergens in the workplace, all used in the production of cemented tungsten carbides (CTC). Exposures to these metal-containing dusts are frequently associated with skin sensitization and/or development of occupational asthma. The objectives of this study were to assess the levels of cobalt, chromium and nickel on work surfaces and on workers' skin in three CTC production facilities. At least one worker in each of 26 work areas (among all facilities) provided hand and neck wipe samples. Wipe samples were also collected from work surfaces frequently contacted by the 41 participating workers. Results indicated that all surfaces in all work areas were contaminated with cobalt and nickel, with geometric means (GMs) ranging from 4.1 to 3057 microg/100 cm(2) and 1.1-185 microg/100 cm(2), respectively; most surfaces were contaminated with chromium (GM=0.36-67 microg/100 cm(2)). The highest GM levels of all metals were found on control panels, containers and hand tools, whereas lowest levels were on office and telecommunication equipment. The highest GM levels of cobalt and nickel on skin were observed among workers in the powder-handling facility (hands: 388 and 24 microg; necks: 55 and 6 microg, respectively). Levels of chromium on workers' skin were generally low among all facilities. Geometric standard deviations associated with surface and skin wipe measurements among work areas were highly variable. Exposure assessment indicated widespread contamination of multiple sensitizing metals in these three facilities, suggesting potential transfer of contaminants from surfaces to skin. Specific action, including improved housekeeping and training workers on appropriate use and care of personal protective equipment, should be implemented to reduce pathways of skin exposure. Epidemiologic studies of associated adverse health effects will likely require more biologically relevant exposure metrics to improve the ability to detect exposure-response relationships.     

Assessing total exposures to gasoline vapor using the source exposure model.

Recent developments in source apportionment modeling of volatile organic compounds (VOCs) include receptor modeling (RM) applications to "total" (indoor and outdoor) exposure assessment for source of VOC. Source fingerprints are available for major VOC sources such as gasoline vapor, automobile exhaust, refinery emissions, cleaning solvent vapors, printing inks, and waste-water treatment facilities. The relative proportion of each VOC species in the source fingerprint enables the RM method, through a least squares analysis, to identify each source's presence and quantify its contribution to ambient air concentrations. Sampling periods and locations may be selected to represent microenvironmental exposures. Receptor modeling has direct applicability to determining the relative contribution of gasoline vapors to VOC exposures in the general population.     

Estimation of the diesel exhaust exposures of railroad workers: I. Current exposures

As a part of a series of epidemiological studies of railroad workers, measurements were made to characterize workers' exposures to diesel exhaust. Since diesel exhaust is not a single compound, an exposure marker was sought. The personal exposures to respirable particulate matter (RPM) of over 530 workers in 39 common jobs were measured in four U.S. railroads over a three-year period. Significant amounts of cigarette smoke (20–90%) were found in many of these samples. Therefore, the respirable particulate concentration, adjusted to remove the fraction of cigarette smoke (ARP), was chosen as a marker of diesel exhaust exposures. The geometric mean exposures to ARP ranged from 17 μg/m³ for clerks to 134 μg/m³ for locomotive shop workers. Significant interrailroad variations were observed in some job groups indicating that the different facilities, equipment, and work practices found among the railroads can affect a worker's exposure to diesel exhaust. Climate was also found to have a significant effect on exposure in some job groups.     

Odor and chemesthesis from exposures to glutaraldehyde vapor

Objectives Assessment of olfactory and chemesthetic sensitivity (feel, sensory irritation) to vapor of glutaraldehyde in young adult females. For chemesthetic sensitivity, assessment included the variable of duration, with focus on whether concentrations initially too low to evoke feel in the eye or upper airway might do so in exposures up to 15 min. Methods Experiment 1 probed sensitivity with forced-choice testing of detection over ranges of concentrations appropriate to three endpoints: odor, feel in the eye, and feel in the nose. A subject participated in hours of testing per endpoint to yield enough data to erect a psychometric (concentration-response) function. Exposure in Experiment 1 entailed use of a vapor-delivery system that stimulated sites of interest separately. Exposure in Experiment 2 occurred in the ambient environment of a chamber, with the sites stimulated simultaneously. In that case, subjects rated confidence by the minute that they felt the presence of vapor in the eyes, nose, and throat during exposures of 15 minutes to 35, 50, 75, and 100 ppb, a blank, and an odor control of mild heptane. Results In Experiment 1, the typical subject achieved 50% detection (threshold) of odor at 0.3 ppb. The typical subject achieved 50% detection of feel in the eye and nose at 390 and 470 ppb, respectively. Psychometric functions for feel showed much sharper dependence on concentration than those for odor. In Experiment 2, confidence in detection of feel migrated progressively away from no—with certainty toward the zone of uncertainty, with bigger change when the exposures contained any glutaraldehyde. The ratings of confidence failed, however, to show distinguish among these concentrations. Conclusions Glutaraldehyde has much higher odor potency than previously thought. Its green-apple odor should signal presence of the vapor at levels more than a 100-fold below any that might evoke sensory irritation in brief exposures. Exposures that start decidedly below irritating (100 ppb and below) seem unlikely to turn irritating over time. Although the effects from these concentrations differentiated themselves from those of air and an odor control, they exhibited none of the concentration dependence seen for sensations of feel. They seemed likely driven by the penetrating odor of glutaraldehyde.     

Hard metal exposures. Part 2: Prospective exposure assessment

Hard metal exposures may precipitate lung disease in exposed workers. This article reports on a project investigating the relationship between local exhaust hood air flow levels and workplace hard metal exposures. Airborne cobalt, chromium, and cadmium exposure concentrations, and ventilation system function were monitored for three consecutive days prior to installation of three new ventilation systems, and then were followed monthly for one year. Work activities included wet and dry grinding of saw blades, brazing, welding, and setup. Work task exposures were highly variable over the period of the study. Ventilation air flows failed to meet design goals due to low total air volume and poor distribution; however, worker exposures to metals were controlled in most cases. Hood design, worker acceptance, and use of the hoods were as important in controlling exposures as were exhaust hood air flow levels.     

Expanding control banding for workplace silica exposures throughout the Americas

Abstract

Background: Silicosis, a lung disease caused by inhaling respirable crystalline silica dust, is an occupational illness affecting millions of workers worldwide. The National Institute for Occupational Safety and Health (NIOSH) has partnered with the World Health Organization, the International Labour Organization, and multiple agencies in the Americas to implement the program “The Elimination of Silicosis in the Americas”.

Objectives: One component of this program is control banding, a qualitative risk assessment and management strategy that allows non-experts to use task-based hazard data and potential exposure information to determine appropriate controls.

Results: From 2005 to the present, NIOSH occupational health researchers have worked with experts in Chile, Peru, Colombia, and Brazil to assess, implement, and provide tools to evaluate the use of control banding methodology.