Patrick J. Callahan

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 µg/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 (µg/g or µg/m2) and dermal wipes (Pearson=0.055 µg/g and 0.015 µg/m2; Spearman=0.644 µg/g and 0.578 µg/m2). These data suggest the importance of dermal penetration of semi-volatiles as a route of residential human exposure.

Monitoring methods for polycyclic aromatic hydrocarbons and their distribution in house dust and track-in soil

An analytical method was developed and employed to determine polycyclic aromatic hydrocarbons (PAH) in house dust and soil. The method was applied to the analysis of samples collected in an eight-home pilot study that was conducted in Columbus, OH, before and after the 1992/1993 heating season. The purpose of the study was to obtain concentration profiles of PAH in house dust and track-in soil, and to determine whether the track-in of outdoor soil contributes to PAH in house dust. A total of 19 PAH, ranging from naphthalene (2-ring) to coronene (7-ring), were monitored. The sums of concentrations of the 19 PAH ranged from 16 to 580 ppm (w/w) in house dust, from 58 to 5500 ppm in entryway soil, from 0.58 to 1200 ppm in pathway soil, and from 0.63 to 63 ppm in foundation soil. In general, the concentration trend was as follows : entryway soil > house dust > pathway soil > foundation soil. PAH levels in house dust and track-in soil were of the same order of magnitude before and after the heating season. In house dust samples, levels of most 4- to 6-ring PAH, the sums of the 19 PAH, and the sums of the PAH that are probable carcinogens correlated well (r > 0.90 at p < 0.001) with the corresponding levels in the entryway soil samples.

Design and performance of a high-volume compound annular denuder

Abstract A laminar flow model incorporating variable collisional reaction efficiency is developed and applied for the design of annular denuders. Efficiencies predicted with the model show excellent agreement with published empirical data for annular denuders that are used for collection of SO 2 , but point to potential errors in extending the empirical data to different chemical systems. The design and construction of a compound annular denuder for collection of polynuclear aromatic hydrocarbon (PAH) vapor are described. This denuder, which consists of a nested set of cylindrical tubes, is shown to operate efficiently at sampling rates of up to 3.33 l s −1 while maintaining essentially 100 per cent transmission of micron-sized particulate matter.

Efficiency of silicone-grease-coated denuders for collection of polynuclear aromatic hydrocarbons

Abstract The overall efficiency of silicone-grease-coated denuders was determined for the collection of selected 3- and 4-ring polynuclear aromatic hydrocarbons (PAH). PAH studied were fluorene, phenanthrene, anthracene, acenaphthene and pyrene. Fluorene was subsequently eliminated from consideration because of analytical problems caused by the reactivity of this compound. Results are interpreted in terms of the collisional reaction efficiencies (γ) for these compounds. An analysis of the effects of uncertainties in diffusion coefficients and γ values for these compounds on overall phase distributions derived from experimental data suggests that the consequences of these uncertainties are less significant than normal variations due to sampling and analysis effects.

Direct Sampling and Analysis of Volatile Organic Compounds in Air by Membrane Introduction and Glow Discharge Ion Trap Mass Spectrometry with Filtered Noise Fields

Two direct air sampling interfaces have been evaluated in the laboratory for monitoring toxic air pollutants in real time by ion trap mass spectrometry in both single mass spectrometry and tandem mass spectrometry (MS/MS) modes. The mass spectrometer is the research-grade Finnigan MAT ion trap (ITMSTM) equipped with the Teledyne filtered noise field (FNF) module to eject unwanted ions and isolate only ions of interest. This results in enhanced sensitivity and selectivity for analyte ions of interest. MS/MS operation, for characterization of individual compounds with high sensitivity and specificity, is achieved by applying a supplementary RF signal to the end-caps of the ion trap. The direct air sampling interfaces are a semi-permeable helium-purged tubular membrane and an atmospheric sampling glow discharge ionization (ASGDI) source. Nonpolar and polar volatile organic compounds (VOCs) are measured at trace levels in air, using an environmental test chamber as the source of the target compound mixtures at known concentrations. Experiments conducted with the combination systems permit a comparison of the two direct air sampling interfaces for monitoring VOCs continuously in real time and illustrate the power of the FNF method to isolate ions with unit mass resolution and to perform MS/MS measurements.

Design and Evaluation of a Breath-Analysis System for Biological Monitoring of Volatile Compounds

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 faci...