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 I. Characterization of workplace exposures

Monitoring surveys of gasoline vapor exposures were conducted on truck drivers and terminal operators from five terminal loading facilities, on dockmen and seamen at two tanker/barge loading facilities, and on attendants at a single expressway service plaza. Results revealed wide variations in total C6+ hydrocarbon exposures for each location, with overall 8-hr time-weighted averaged (TWA) geometric means of 5.7 mg/m3 (1.4 ppm) for the terminals, and 4.0 mg/m3 (1.0 ppm) for the service plaza, respectively. The exposures ranged from 0.8 to 120.8 mg/m3 (0.2-30.1 ppm) for the terminals, and from 1.1 to 130.3 mg/m3 (0.3-32.5 ppm) for the service plaza. For the terminals, exposures were not significantly different regardless of loading method or the presence or absence of vapor recovery systems. Comprehensive chemical analyses of terminal employee exposure samples revealed that the C4 and C5 hydrocarbon components constituted 74.8 +/- 9.2% of the total exposure sample on a microgram/sample basis. The C6, C7, and C8+ components constituted 13.0 +/- 1.9, 6.2 +/- 3.0, and 5.9 +/- 7.2% of the total samples, respectively. Comprehensive analyses of the marine employee exposure samples resulted in a similar distribution of components; that is, 66.6 +/- 7.9, 17.5 +/- 4.7, 9.2 +/- 3.1, and 6.4 +/- 1.9% for the C4/C5, C6, C7, and C8+ components, respectively. The composition of the exposures, however, was weighted more toward the C5, C6 and C7 components when compared to the bulk terminal employee exposures.(ABSTRACT TRUNCATED AT 250 WORDS)     

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.     

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.     

Experimental human exposures to tetrachloroethylene vapor and elimination in breath after inhalation.

Volunteers were exposed in a controlled environment chamber and concentrations of tetrachloroethylene in alveolar air were determined. Results show a proportional relationship between the level of exposure and the alveolar concentration curve. Accordingly, tetrachloroethylene breath decay curves can be used as a method to monitor time-weighted average exposures.     

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.     

Short- and long-term responses of Daphnia spp. to propanil exposures in distinct food supply scenarios

The widespread increase of pesticides application in crops frequently leads to the contamination of vicinal freshwater lentic ecosystems. Herbicides such as propanil may impair cladoceran fitness, which is per se strongly influenced by the food availability and/or its acquisition efficiency. This work intended to evaluate the responses of Daphnia magna and three clonal lineages belonging to the Daphnia longispina complex to acute and chronic exposures of the herbicide propanil, as well as to assess whether food availability features these responses. Results showed that the agrochemical was acutely and chronically toxic to both D. magna and the D. cf. longispina clones at the same range of low concentrations, while relevant differences were depicted between the three distinct genotypes belonging to the D. longispina complex. Food-level conditioned the general fitness of the daphnids in the tests but evidences suggest that it does not interfere specifically with the toxicant mode of action.     

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.     

Stirring system for radioactive waste water storage tank.

A stirring system for 100-m(3) radioactive liquid waste tanks was constructed to unify radioactive concentrations in the tank. The stirring system is effective in certifying that the radioactive concentrations in the tanks are less than the legal limits before they are drained away as waste liquid. This system is composed of discharge units, pipe lines, and a controller. The performance of the system was assessed by comparing the calculated red ink and 32P concentrations with those monitored at six locations in the tanks. The concentration reached equilibrium after stirring 60 to 120 min with discharge units equipped with six fixed openings configured in differing directions. Residual chlorine in city water used for dilution occasionally bleached the red ink and reduced its concentration. The adsorption of 32P by slime on the walls of the tanks storing actual waste water lowered the equilibrium concentration.     

Comparison of personal diesel and biodiesel exhaust exposures in an underground mine

This study aimed to compare personal exposures to diesel fuel and a biodiesel blend exhaust in an underground mine. Personal exposure monitoring was performed in a non-operational, hard rock underground mine during use of a load-haul-dump vehicle. Eight-hour time-weighted average (TWA₈) exposure concentrations of ultra-low sulfur diesel and 75% biodiesel/25% diesel blend (B75) fuels were compared.

?Compared to diesel, use of B75 was associated with relative percent reductions of 22 and 28% in median respirable (r) diesel particulate matter (DPM) and nitrogen dioxide and 25 and 23% increases in median total DPM and nitric oxide TWA₈ exposure concentrations, respectively. Diesel was associated with a slightly greater total geometric mean mass concentration and lower mean surface area concentration.

?Although further testing is needed, B75 has the potential to reduce rDPM exposures.     

Evaluating scenarios of locations and capacities for vaccine storage in Nigeria

Many developing countries still face the prevalence of preventable childhood diseases because their vaccine supply chain systems are inadequate by design or structure to meet the needs of their populations. Currently, Nigeria is evaluating options in the redesign of the country’s vaccine supply chain. Using Nigeria as a case study, the objective is to evaluate different regional supply chain scenarios to identify the cost minimizing optimal hub locations and storage capacities for doses of different vaccines to achieve a 100% fill rate. First, we employ a shortest-path optimization routine to determine hub locations. Second, we develop a total cost minimizing routine based on stochastic optimization to determine the optimal capacities at the hubs. This model uses vaccine supply data between 2011 and 2014 provided by Nigeria’s National Primary Health Care Development Agency (NPHCDA) on Tuberculosis, Polio, Yellow Fever, Tetanus Toxoid, and Hepatitis B. We find that a two-regional system with no central hub (NC2) cut costs by 23% to achieve a 100% fill rate when compared to optimizing the existing chain of six regions with a central hub (EC6). While the government’s leading redesign alternative – no central three-hub system (Gov NC3) – reduces costs by 21% compared with the current EC6, it is more expensive than our NC2 system by 3%. In terms of capacity increases, optimizing the current system requires 42% more capacity than our NC2 system. Although the proposed Gov NC3 system requires the least increase in storage capacity, it requires the most distance to achieve a 100% coverage and about 15% more than our NC2. Overall, we find that improving the current system with a central hub and all its variants, even with optimal regional hub locations, require more storage capacities and are costlier than systems without a central hub. While this analysis prescribes the no central hub with two regions (NC2) as the least cost scenario, it is imperative to note that other configurations have benefits and comparative tradeoffs. Our approach and results offer some guidance for future vaccine supply chain redesigns in countries with similar layouts to Nigeria’s.     

The relationships between personal PM exposures for elderly populations and indoor and outdoor concentrations for three retirement center scenarios.

Personal exposures, indoor and outdoor concentrations, and questionnaire data were collected in three retirement center settings, supporting broader particulate matter (PM)--health studies of elderly populations. The studies varied geographically and temporally, with populations studied in Baltimore, MD in the summer of 1998, and Fresno, CA in the winter and spring of 1999. The sequential nature of the studies and the relatively rapid review of the mass concentration data after each segment provided the opportunity to modify the experimental designs, including the information collected from activity diary and baseline questionnaires and influencing factors (e.g., heating, ventilation, and air-conditioning (HVAC) system operation, door and window openings, air exchange rate) measurements. This paper highlights both PM2.5 and PM10 personal exposure data and interrelationships across the three retirement center settings, and identifies the most probable influencing factors. The current limited availability of questionnaire results, and chemical speciation data beyond mass concentration for these studies, provided only limited capability to estimate personal exposures from models and apportion the personal exposure collections to their sources. The mean personal PM2.5 exposures for the elderly in three retirement centers were found to be consistently higher than the paired apartment concentrations by 50% to 68%, even though different facility types and geographic locations were represented. Mean personal-to-outdoor ratios were found to 0.70, 0.82, and 1.10, and appeared to be influenced by the time doors and windows were open and aggressive particle removal by the HVAC systems. Essentially identical computed mean PM2.5 personal clouds of 3 micrograms/m3 were determined for two of the studies. The proposed significant contributing factors to these personal clouds were resuspended particles from carpeting, collection of body dander and clothing fibers, personal proximity to open doors and windows, and elevated PM levels in nonapartment indoor microenvironments.     

Health effects of gasoline refueling vapors and measured exposures at service stations

Liquid gasoline is a complex mixture of at least 150 hydrocarbons with about 60-70% alkanes (paraffins), 25-30% aromatics, and 6-9% alkenes. In order to evaluate the potential for health effects from inhaling gasoline vapors, it is essential to understand the major differences in the composition of vapors versus liquid gasoline. The small chain, low carbon-numbered components are more volatile and thus in higher percentages in the vapor phase than the larger and heavier molecules. It is noteworthy that the concentrations of aromatics (the more toxic of the gasoline components), are depleted to about 2% in the vapor phase, with the light paraffins (the less toxic) enriched to about 90%. Actual measurements of vapor exposure at service stations confirm that the vapor composition is primarily to low weight alkanes although benzene is also emitted and represents the chemical of greatest concern. A perceived health concern from inhaling gasoline vapors is the potential for carcinogenicity based on the induction of kidney tumors in male rats and liver tumors in female mice exposed to wholly-vaporized gasoline. However, the results of the animal studies are of questionable relevance for human risk assessment due to the unique mechanism operative only in the male rat and since the exposure was to wholly-vaporized gasoline rather than the gasoline vapor mixture to which humans are exposed. Recent research supports the hypothesis that branched-chain-alkanes bind to a globulin specific to make rats, alpha 2-u-globulin. The protein complex can not be degraded in the usual manner so that protein accumulation occurs in renal cells, leading to cytotoxicity, death, proliferation, and with prolonged exposure, kidney cancer. The results of epidemiology studies fail to link an increase in cancer to exposure to gasoline vapors.