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.

Residential environmental measurements in the national human exposure assessment survey (NHEXAS) pilot study in Arizona: preliminary results for pesticides and VOCs.

A major objective of the National Human Exposure Assessment Survey (NHEXAS) performed in Arizona was to conduct residential environmental and biomarker measurements of selected pesticides (chlorpyrifos, diazinon), volatile organic compounds (VOCs; benzene, toluene, trichloroethene, formaldehyde, 1,3-butadiene), and metals for total human exposure assessments. Both personal (e.g., blood, urine, dermal wipes, 24 h duplicate diet) and microenvironmental (e.g., indoor and outdoor air, house dust, foundation soil) samples were collected in each home in order to describe individual exposure via ingestion, inhalation, and dermal pathways, and to extrapolate trends to larger populations. This paper is a preliminary report of only the microenvironmental and dermal wipe data obtained for the target pesticides and VOCs, and provides comparisons with results from similar studies. Evaluations of total exposure from all sources and pathways will be addressed in future papers. The pesticides and VOCs all showed log-normal distributions of concentrations in the Arizona population sampled, and in most cases were detected with sufficient frequency to allow unequivocal description of the concentration by media at the 90th, 75th, and 50th (median) percentiles. Those combinations of pollutant and media, in which a large fraction of the measurements were below the detection limit of the analysis method used, included trichloroethene, 1,3-butadiene, and formaldehyde in outdoor air; chlorpyrifos and diazinon in outdoor air; and diazinon in dermal and window sill wipes. In general, indoor air concentrations were higher than outdoor air concentrations for all VOCs and pesticides investigated, and VOC levels were in good agreement with levels reported in other studies. In addition, the agreement obtained between co-located VOC samplers indicated that the low-cost diffusional badges used to measure concentrations are probably adequate for use in future monitoring studies. For the pesticides, the median levels found in indoor samples agreed well with other studies, although the levels corresponding to the upper 0.1-1% of the population were considerably higher than levels reported elsewhere, with indoor air levels as high as 3.3 and 20.5 microg/m3 for chlorpyrifos and diazinon, respectively. These data showed excellent correlation (Pearson and Spearman correlation coefficients of 0.998 and 0.998, respectively) between chlorpyrifos in indoor air and in the corresponding dermal wipes, and relatively poor correlation between chlorpyrifos in dust (microg/g or microg/ml) and dermal wipes (Pearson=0.055 microg/g and 0.015 microg/m2; Spearman=0.644 microg/g and 0.578 microg/m2). These data suggest the importance of dermal penetration of semi-volatiles as a route of residential human exposure.

Polycyclic aromatic hydrocarbon exposures of children in low-income families.

Children in low-income families may have high exposures to polycyclic aromatic hydrocarbons (PAH). Such exposures could result from household proximity to heavy traffic or industrial sources, environmental tobacco smoke, contaminated house dust or soil, among others. The objectives of this study were: to establish methods for measuring total PAH exposure of children in low-income families, to estimate the PAH exposures of these children, and to estimate the relative importance of the environmental pathways for PAH exposure. Analytical methods to determine PAH in air, dust, soil, and food and to determine hydroxy-PAH in urine samples were evaluated and validated. A two-home pilot study was conducted in downtown Durham, North Carolina (NC) during February 1994. One smoker's and one nonsmoker's household, which had preschool children and income at or below the official U.S. poverty level, participated. A nine-home winter and a nine-home summer study were conducted in Durham and the NC Piedmont area during February 1995 and August 1995, respectively. A summer study in four smokers' homes was also conducted. In each of these studies, multimedia samples were collected and analyzed for PAH or hydroxy-PAH. Summary statistics, Pearson correlations, and analysis of variance were performed on the combined data from these four field studies. An effective screening method was established for recruiting low-income families. The field protocol involved measurements of three homes in 2-day periods. This protocol should be suitable for large-scale studies. The results showed that indoor PAH levels were generally higher than outdoor PAH levels. Higher indoor PAH levels were observed in the smokers' homes compared to nonsmokers' homes. Higher outdoor PAH levels were found in inner city as opposed to rural areas. The relative concentration trend for PAH in dust and soil was: house dust > entryway dust > pathway soil. The PAH concentrations in adults' food samples were generally higher than those in children's food samples. Children's potential daily doses of PAH were higher than those of adults in the same household, when intakes were normalized to body weights. Inhalation is an important pathway for children's exposure to total PAH because of the high levels of naphthalene present in both indoor and outdoor air. Dietary ingestion and nondietary ingestion pathways became more important for children's exposure to the B2 PAH (ranked as probable human carcinogens, B2 by the U.S. EPA's Integrated Risk System), most of which are of low volatility. The analysis of variance results showed that inner city participants had higher total exposure to B2 PAH than did rural participants.

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.

Isolation of region-specific cosmids from chromosome 5 by hybridization with microdissection clones.

A method is described for the isolation of chromosome region specific cosmids. The 5q35 region of the long arm of human chromosome 5 was microdissected, digested with MboI, ligated to oligonucleotide adaptors, amplified by the polymerase chain reaction and cloned into a plasmid vector. Inserts which did not contain highly repetitive sequences were used to screen a chromosome 5 cosmid library by direct hybridization. There were 33 positive cosmid clones identified with 4 microclones. Individual cosmid clones were biotinylated and used as probes for fluorescence in situ hybridization to metaphase chromosomes. Of the 33 cosmids that were mapped, 29 localized to q35 and 4 to q34, demonstrating the specificity of the microdissection library and the cosmids.

Lipid mobility in the assembly and expression of the activity of the prothrombinase complex.

A phospholipid or membrane surface is a required component of the prothrombinase complex, yet little is known about the influence of the lipid on the assembly and expression of this complex. Vesicles composed of synthetic phospholipids were used to investigate the effects of membrane "fluidity" on the prothrombinase complex. All vesicle types studied were capable of supporting the prothrombinase reaction which in each case was characterized by a similar apparent Km. The binding constants for the interaction of Factor Va and prothrombin with synthetic phospholipid vesicles were not significantly affected by temperature. The rate of thrombin production, however, increased with increasing temperature. The fluidity of the vesicles was assessed by measuring the fluorescence lifetimes, steady state anisotropies, and differential phase fluorometry of diphenylhexatriene embedded in the vesicles. No correlation was observed between the fluidity of the vesicles and the steady-state rate of thrombin production, even when the enzymatic activity was monitored below and above the phase transition temperature of the lipid vesicles. A distinct correlation, however, was found between the fluidity of the vesicle and the time required to reach the maximum rate of thrombin production (pre-steady-state interval). We believe that this "lag" time corresponds to the time required for the assembly of the prothrombinase complex. Thus, although lipid fluidity does affect the assembly of the prothrombinase complex, after the complex is assembled, this property has little effect on the catalytic process itself.

Oxygen quenching of sensitized terbium luminescence in complexes of terbium with small organic ligands and proteins.

Oxygen does not quench the luminescence of either free Tb or of Tb bound to dipicolinate. However, sensitized Tb luminescence in complexes of that ion with elastase, thermolysin, and alpha-amylase is quenched by oxygen at rates that far exceed that with which the intrinsic fluorescence of the proteins is quenched. We infer that this more rapid quenching of Tb luminescence indicates a major role for energy transfer from tryptophan moieties in a triplet excited state.

1-[4-(Trimethylamino)phenyl]-6-phenylhexa-1,3,5-triene: synthesis, fluorescence properties, and use as a fluorescence probe of lipid bilayers.

1-[4-(Trimethylamino)phenyl]-6-phenylhexa-1,3,5-triene (TMA-DPH), a cationic analogue of diphenylhexatriene (DPH), has photophysical properties that are generally similar to those of DPH. In solution the fluorescence lifetime (tau) of TMA-DPH is short (less than 1.5 ns), but tau increases to approximately 7 ns when the probe is embedded in lipid bilayers at temperatures less than the thermal transition temperature (Tc) of the lipid. The cationic charge ensures that the probe is anchored at the lipid-water interface, most likely with the DPH moiety intercalated between the upper portions of the fatty acyl chains. The profiles of changes in steady-state anisotropies (rss) and limiting hindered anisotropies (r infinity) are similar for both TMA-DPH and DPH embedded in lipid bilayers, but r infinity values for TMA-DPH even at T much greater than Tc are generally greater than 0.14, e.g., at 35 degrees C in 1,2-dimyristoylglycero-3-phosphocholine (DMPC) (cf. 0.03 for DPH in DMPC at 35 degrees C). Electrostatic interactions of the cationic probe with head groups of phospholipids do not appear to significantly influence the apparent dynamics of the probe. TMA-DPH should prove useful in the study of the dynamics of phospholipid monolayers, e.g., in native or reconstituted lipoproteins.