Design and evaluation of a breath-analysis system for biological monitoring of volatile compound.

To ensure the health and safety of workers, integrated industrial hygiene methodologies often include biological monitoring of the workers to help understand their exposure to chemicals. To this end, a field-portable breath-analysis system was developed and tested to measure selected solvents in exhaled air. The exhaled breath data were evaluated using a physiologically based pharmacokinetic (PBPK) model to relate exposure to tissue dose. The system was designed to monitor workers every time they entered or left a work environment--a vast improvement over current 8-hour integrated monitoring strategies. The system combines (1) chemical dosimeters to measure airborne contaminant levels (analyzed in the field/ workplace); (2) real-time breath analysis to quantitate exposure; and 3) PBPK models to estimate internal target tissue dose. To evaluate the system, field tests were conducted at two locations: (1) at an incinerator in Tennessee monitoring benzene and toluene exposures; and (2) a waste repackaging facility in Washington State where hexane, trimethylbenzene, and methylene chloride was monitored. Exhaled breath was sampled and analyzed before and after each specific job task, which ranged from 15 min to 8 hours in duration. In both field studies several volunteers had posttask breath levels higher than pretask levels. The greatest increase corresponded to 573 ppb for methylene chloride and 60 ppb for toluene. Compared with breath analysis, the chemical dosimeters underpredicted the dosimetry, particularly for longer sampling intervals when the volume of air sampled may have diluted exposures. The results of the field studies illustrate the utility of monitoring workers for exposures throughout the day, particularly when job-specific tasks may indicate a potential for exposure.

Effect of water temperature on dermal exposure to chloroform.

We have developed and applied a new measurement methodology to investigate dermal absorption of chloroform while bathing. Ten subjects bathed in chlorinated water while breathing pure air through a face mask. Their exhaled breath was delivered to a glow discharge source/ion trap mass spectrometer for continuous real-time measurement of chloroform in the breath. This new method provides abundant data compared to previous discrete time-integrated breath sampling methods. The method is particularly well suited to studying dermal exposure because the full face mask eliminates exposure to contaminated air. Seven of the 10 subjects bathed in water at two or three different temperatures between 30 degrees C and 40 degrees C. Subjects at the highest temperatures exhaled about 30 times more chloroform than the same subjects at the lowest temperatures. This probably results from a decline in blood flow to the skin at the lower temperatures as the body seeks to conserve heat forcing the chloroform to diffuse over a much greater path length before encountering the blood. These results suggest that pharmacokinetic models need to employ temperature-dependent parameters. Two existing models predict quite different times of about 12 min and 29 min for chloroform flux through the stratum corneum to reach equilibrium. At 40 degrees C, the time for the flux to reach a near steady-state value is 6-9 min. Although uptake and decay processes involve several body compartments, the complicating effect of the stratum corneum lag time made it difficult to fit multiexponential curves to the data; however, a single-compartment model gave a satisfactory fit.

Extraction of lignite coal fly ash for polynuclear aromatic hydrocarbons: modified and unmodified supercritical fluid extraction, enhanced-fluidity solvents, and accelerated solvent extraction.

A comparison among modified and unmodified supercritical fluid extraction (SFE), enhanced-fluidity liquid extraction, and accelerated solvent extraction (ASE) techniques was made for the extraction of polynuclear aromatic hydrocarbons (PAHs) from an aged, spiked lignite coal fly ash. All of the attempted extraction conditions allowed the extraction of the PAHs to some degree, but no single extraction technique proved to be superior for all of the PAHs used. Three groups of PAHs with similar extraction efficiencies were identified. The group with the lowest molecular weights was best recovered using a 90% CO2-10% methanol mixture at 70 degrees C and 238 atm. The group of medium-molecular-weight PAHs was recovered equally well using any of three extraction conditions: SFE (100% CO2, 90 degrees C, and 238 atm), enhanced-fluidity liquid mixture (60% CO2-40% methanol, 70 degrees C, and 238 atm), and a methanol ASE mixture. The group of high-molecular-weight PAHs seemed to be equally well recovered with all of the attempted extraction conditions, but the enhanced-fluidity conditions (60% CO2-40% methanol, 70 degrees C, and 238 atm) had extraction recoveries (> 85%) with the lowest standard deviations (approximately 5%).

Extraction of bituminous coal fly ash for polynuclear aromatic hydrocarbons: evaluation of modified and unmodified supercritical fluid extraction, enhanced fluidity solvents, and accelerated solvent extraction.

A comparison among supercritical fluid extraction (SFE), modified SFE, enhanced-fluidity extraction, and accelerated solvent extraction (ASE) techniques was made for the extraction of polynuclear aromatic hydrocarbons (PAHs) from an aged, spiked bituminous coal fly ash. Non-ASE extraction techniques used in this study could not recover PAHs with molecular weights greater than that of pyrene. ASE techniques using methylene chloride (with and without a static step) and toluene were able to recover most of the PAHs studied. None of the ASE techniques could quantitatively extract the low-molecular-weight PAHs from the bituminous fly ash. The medium-molecular-weight PAHs were best recovered with toluene ASE. The high-molecular-weight PAHs were best recovered with the toluene ASE technique (> 80%), but the overall precision of these measurements was low. Methylene chloride ASE with a static step recovered the high-molecular-weight PAHs with the next highest efficiency (approximately 55%) and had standard deviations less than 10% (longer extraction times [> 30 min] with the methylene chloride would increase the recoveries of these analytes.) A comparison of the results from this study with those of a previous study using lignite coal fly ash illustrates the difficulty in developing and adapting analyte-specific extraction methods for analytes that are adsorbed on different matrices.

APCI low energy collision-induced dissociation fragmentation of protonated ortho silicates: mclafferty or ion-neutral complex rearrangement?

The fragmentation mechanism of tetraethyl ortho silicate and tetrapropyl ortho silicate was studied to determine if the consecutive alkene losses observed in their MS/MS daughter ion spectra were produced via a McLafferty rearrangement or by ion-neutral rearrangement mechanisms. The experiments were carried out using atmospheric pressure chemical ionization and low energy collision-induced dissociation. Deuterium labeling of the γ-position provided evidence mat the rearrangement mechanism of the successive alkene losses proceeds predominantly via the ion-neutral complex mechanism. Because the energies imparted to the ions in this experiment are of the same order of magnitude as solution phase reactions, this mechanism may shed light on the formation of silica gels (e.g., aerogels) in that similar structures have been proposed as reaction intermediates in the polymerization of SiO2.

Transformations, lifetimes, and sources of NO2, HONO, and HNO3 in indoor environments.

Recent research has demonstrated that nitrogen oxides are transformed to nitrogen acids in indoor environments, and that significant concentrations of nitrous acid are present in indoor air. The purpose of the study reported in this paper has been to investigate the sources, chemical transformations and lifetimes of nitrogen oxides and nitrogen acids under the conditions existing in buildings. An unoccupied single family residence was instrumented for monitoring of NO, NO2, NOy, HONO, HNO3, CO, temperature, relative humidity, and air exchange rate. For some experiments, NO2 and HONO were injected into the house to determine their removal rates and lifetimes. Other experiments investigated the emissions and transformations of nitrogen species from unvented natural gas appliances. We determined that HONO is formed by both direct emissions from combustion processes and reaction of NO2 with surfaces present indoors. Equilibrium considerations influence the relative contributions of these two sources to the indoor burden of HONO. We determined that the lifetimes of trace nitrogen species varied in the order NO approximately HONO > NO2 > HNO3. The lifetimes with respect to reactive processes are on the order of hours for NO and HONO, about an hour for NO2, and 30 minutes or less for HNO3. The rapid removal of NO2 and long lifetime of HONO suggest that HONO may represent a significant fraction of the oxidized nitrogen burden in indoor air.