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Human Exposure and Atmospheric Sciences Division Publications: 2007
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This page lists publication titles, citations and abstracts produced by NERL's Human Exposure and Atmospheric Sciences Division for the year 2007, organized by Publication Type. Your search has returned
62 Matching Entries.
See also Human Exposure and Atmospheric Sciences Division citations with abstracts:
1999,
2000,
2001,
2002,
2003,
2004,
2005,
2006,
2007,
2008
Technical Information Manager: Liz Hope - (919) 541-2785 or hope.elizabeth@epa.gov
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Exposure Related Dose Estimating Model (Erdem) |
06/20/2007
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BLANCATO, J. N., F. W. POWER, A. RUIZ, A. TSANG, M. S. OKINO, J. C. JOHNSON, C. C. DARY, N. HERAVI, R. N. BROWN, AND L. S. SHELDON. Exposure Related Dose Estimating Model (Erdem). U.S. Environmental Protection Agency, Washington, DC, EPA/600/C-07/010, 2007.
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ERDEM is a physiologically-based pharmacokinetic (PBPK) model with a graphical user interface (GUI) front end. Such a mathematical model was needed to make reliable estimates of the chemical dose to organs of animals or humans because of uncertainties of making route-to route, low-to-high exposure, and species-to-species extrapolations when there are exposures to one, or to multiple chemicals.
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An Environmental Technology Verification (Etv) Testing of Three Immunoassay Test Kits for Anthrax, Botulinum Toxin and Ricin |
01/09/2007
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BATTELLE MEMORIAL INSTITUTE, M. SCHROCK, R. JAMES, A. DINDAL, Z. WILLENBURG, AND K. RIGGS. An Environmental Technology Verification (Etv) Testing of Three Immunoassay Test Kits for Anthrax, Botulinum Toxin and Ricin. U.S. Environmental Protection Agency, Washington, DC, EPA/600/R-06/147 (NTIS PB2007-105370), 2006.
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Immunoassay test kits are based on immunoassay methods, where specific antibodies are used to detect and measure the contaminants of interest. Immunoassay test kits rely on the reaction of a contaminant or antigen with a selective antibody to give a product that can be measures. Many types of technologies involved enzymes, fluorescence, phosphorescence, electrochemiluminescence, and chemiluminescence, have been used for quantifying the assay. The sample concentration can be either directly or inversely proportional to color intensity, depending on the technology. Results from these methods can be qualitative or quantitative. While there are several types of immunoassays, enzyme-linked immunoabsorbent assays are most common.
Of the three test kit technologies tested in the verification test, the QTL Biosystems, LLC's QTL Biosensor technology uses an immunomagnetic technique which produces a magnetic and a fluorescent component, while the PharmaLeads's EzyBot uses a fluorescence quenching technology. The BioVeris Corporation's BioVerify test kit uses an electrochemical stimulated technology. These three technologies do not all that the capabilities to detect all three of the tested contaminants.
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An Environmental Technology Verification (Etv) Testing of Four Mercury Emission Sampling Systems |
05/07/2007
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BATTELLE MEMORIAL INSTITUTE, T. KELLY, J. SATOLA, Z. WILLENBERG, AND A. DINDAL. An Environmental Technology Verification (Etv) Testing of Four Mercury Emission Sampling Systems. U.S. Environmental Protection Agency, Washington, DC, EPA/600/R-07/052 (NTIS PB2007-108680), 2007.
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CEMs - Tekran Instrument Corp. Series 3300 and Thermo Electron's Mercury Freedom System Continuous Emission Monitors (CEMs) for mercury are designed to determine total and/or chemically speciated vapor-phase mercury in combustion emissions. Performance for mercury CEMs are contained in Chapter 40 of the Code of Federal Regulations, Part 75 and Part 60 (40 CFR Parts 75 and 60) and require assessment of the performance of newly installed mercury CEMs only for their determination of HgT. This total is the sum of vapor-phase mercury in all chemical forms in the combustion gas, including Hg0 and HgOX. The CEMs tested claim to measure HgT, Hg0, and HgOX. They both use atomic fluorescence for detection. Sorbent-based Sampling System-Apex Instruments and Environmental Supply Co.HG-324K Appendix K of 40CFR Part 75 established sorbent-based sampling systems as an acceptable approach for determining mercury in the stack of utility generating stations. Sorbent-based systems collect integrated samples of mercury from stack gas onto selected sorbent material over an extended time period (from a few hours to several days). The collected mercury samples are then analyzed and the stack gas mercury concentrations are then calculated. Appendix K defines procedures for use of such systems to collect total vapor-phase mercury in combustion source emissions and require the use of multi-stage sorbent traps pre-spiked with mercury as a quality assurance measure. Apex used atomic absorption for final analysis, while ESC uses cold vapor atomic fluorescence spectrometry.
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An Environmental Technology Verification (Etv) Testing of a Ballast Exchange Assurance Meter (Beam) 100 |
10/23/2007
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BATTELLE MEMORIAL INSTITUTE, M. Schrock, W. Ivancic, C. Hunt, Z. Willenburg, AND A. Dindal. An Environmental Technology Verification (Etv) Testing of a Ballast Exchange Assurance Meter (Beam) 100. U.S. Environmental Protection Agency, Washington, DC, EPA/600/R-07/134 (NTIS PB-2008-106040), 2007.
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Mid-ocean ballast water exchange (BWE) is mandatory for all vessels entering U.S. waters from outside the 200-mile exclusive economic zone. To support such regulation, accurate and portable verification tools are needed for determining that BWE has taken place. One parameter proposed as a means of distinguishing between coastal and open ocean water content in ballast water is CDOM. CDOM refers to the fraction of colored dissolved organic matter that absorbs light and fluoresces in the UV and visible regions of the spectrum. This BWE technology provides a portable, quick measurement of CDOM. The technologies function by measuring the amount of fluorescent CDOM in ballast water and with the results reported via a digital display or electronic output signal. The technology verified with this testing was a Ballast Exchange Assurance Monitor -100 (Dakota, Inc.)
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Spatial Analysis of Volatile Organic Compounds from a Community-Based Air Toxics Monitoring Network in Deer Park, Texas, USA |
05/01/2007
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SMITH, L. A., T. H. STOCK, K. CHUNG, S. MUKERJEE, X. L. LIAO, C. STALLINGS, AND M. AFSHAR. Spatial Analysis of Volatile Organic Compounds from a Community-Based Air Toxics Monitoring Network in Deer Park, Texas, USA. ENVIRONMENTAL MONITORING AND ASSESSMENT. Springer, New York, NY, 128(1-3):369-379, (2007).
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This RARE Project with EPA Region 6 was a spatial analysis study of select volatile organic compounds (VOC) collected using passive air monitors at outdoor residential locations in the Deer Park, Texas area near the Houston Ship Channel. Correlation analysis of VOC species confirmed transportation and other petroleum-dominated sources and possible process-related (industrial) influences. As shown in other spatial studies, wind direction relative to source location had an effect on VOC concentrations.
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A Fluorescence-Based Screening Assay for Dna Damage Induced By Genotoxic Industrial Chemicals |
01/01/2007
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KAILASAM, S. AND K. R. ROGERS. A Fluorescence-Based Screening Assay for Dna Damage Induced By Genotoxic Industrial Chemicals. CHEMOSPHERE. Elsevier Science Ltd, New York, NY, 66(1):165-171, (2007).
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The possibility of deliberate or accidental release of toxic chemicals in industrial, commercial or residential settings has indicated a need for rapid, cost-effective and versatile monitoring methods to prevent exposures to humans and ecosystems. Because many toxic industrial chemicals are not only acutely toxic but genotoxic as well, there is a need for simple and rapid screening techniques to measure these genotoxins.
A rapid screening assay to detect chemically-induced DNA damage resulting from exposure of surrogate DNA to genotoxic compounds is reported.
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Pesticides and Their Metabolites in the Homes and Urine of Farmworker Children Living in the Salinas Valley, Ca |
07/01/2007
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BRADMAN, A., D. A. WHITAKER, L. QUIROS, R. CASTORINA, B. C. HENN, M. NISHIOKA, J. N. MORGAN, D. B. BARR, M. HARNLY, J. A. BRISBIN, L. S. SHELDON, T. MCKONE, AND B. ESKENAZI. Pesticides and Their Metabolites in the Homes and Urine of Farmworker Children Living in the Salinas Valley, Ca. JOURNAL OF EXPOSURE ANALYSIS AND ENVIRONMENTAL EPIDEMIOLOGY. Nature Publishing Group, London, Uk, 17(4):331-349, (2007).
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This paper describes a study to test field methods for characterizing pesticide exposures to 20 farmworker children aged 5-27 months old living in the Salinas Valley of Monterey County, California. Methods for collecting house dust, indoor and outdoor air, dislodgeable residues from surfaces and toys, residues on clothing (sock and union suits), food, as well as spot and overnight diaper urine samples were tested. Twenty-nine common agricultural and home use pesticides were measured in multiple exposure media samples. A subset of organophosphorus (OP), organochlorine (OC) and pyrethroid pesticides were measured in food. Urine samples were analyzed for OP pesticide metabolites. Four field-based exposure assessment instruments: a questionnaire; food diary; home inspection; and a self-administered child activity timeline were administered.
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A Pilot Study Using An Accelerometer to Evaluate a Caregiver's Interpretation of An Infant or Toddler's Activity Level as Recorded in a Time Activity Diary |
09/01/2007
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TULVE, N. S., P. A. JONES, T. R. MCCURDY, AND C. W. CROGHAN. A Pilot Study Using An Accelerometer to Evaluate a Caregiver's Interpretation of An Infant or Toddler's Activity Level as Recorded in a Time Activity Diary. Research Quarterly for Exercise and Sport. American Alliance for Health, Physical Education, Recreation & Dance, Reston, VA, 78(4):375-383, (2007).
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Linking a young child's activity pattern data with samples that are collected during an exposure assessment is important in evaluating uptake dose rates associated with environmental contaminant exposures. A pilot study (N=9) was performed to test how well categorical activity-level data for young children (≤ 24 months old) collected from paper time activity diaries normally used in exposure studies compared with objective activity-level information (i.e., counts) obtained using an accelerometer. The infants and toddlers wore an accelerometer for up to 4 days, while their primary caregiver simultaneously completed a time activity diary and intermittently videotaped them engaged in eating, quiet play, and active play type activities. Our findings indicate that infants and toddlers tolerate wearing an accelerometer for multiple days of data collection and that caregiver compliance was good on completing all study components. Statistical analyses showed a relatively strong positive relationship between diary entries and accelerometer output (Spearman r=0.42; p<0.0001). When the diary entries and accelerometer data were classified categorically, the classifications were identical for 70% of all entries for the entire cohort during the monitoring period. Gender and age were not significant predictors of variability in activity levels, but this was probably due to the small sample size and narrow age range of study participants.
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Exposure Reconstruction for Reducing Uncertainty in Risk Assessment: Example Using Mtbe Biomarkers and Simple Pharmacokinetic Model |
07/01/2007
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PLEIL, J. D., D. KIM, J. D. PRAH, AND S. M. RAPPAPORT. Exposure Reconstruction for Reducing Uncertainty in Risk Assessment: Example Using Mtbe Biomarkers and Simple Pharmacokinetic Model. BIOMARKERS. Taylor & Francis, Inc., Philadelphia, PA, 12(4):331-348, (2006).
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Adverse health risks from environmental agents are generally related to average (long term) exposures. We used results from a series of controlled human exposure tests and classical first order rate kinetics calculations to estimate how well spot measurements of methyl tertiary butyl ether (MTBE) and the primary metabolite, tertiary-butyl alcohol (TBA), can be expected to predict different hypothetical scenarios of previous exposures. We concluded that individual biomarker measurements are a valuable tool in reconstruction of previous exposures and that a simple pharmacokinetic model can limit the time frames over which a particular exposure - biomarker pair of compounds is useful.
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Coarse Particulate Matter Concentrations from Residential Outdoor Sites Associated With the North Carolina Asthma and Children's Environment Studies (Nc Aces) |
02/01/2007
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CHEN, F., R. W. WILLIAMS, E. R. SVENDSEN, K. YEATTS, J. P. CREASON, J. W. SCOTT, D. TERRELL, AND M. W. CASE. Coarse Particulate Matter Concentrations from Residential Outdoor Sites Associated With the North Carolina Asthma and Children's Environment Studies (Nc Aces). ATMOSPHERIC ENVIRONMENT. Elsevier Science Ltd, New York, NY, 41(6):1200-1208, (2007).
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Residential outdoor monitoring was performed at 26 homes in the RTP area of NC from September 2003 to June 2004. PM10-2.5 values were estimated using the differential between independent PM10 and PM2.5 collocated MiniVol measurements. The dichotomous sampler was used as the central site PM monitor and located on a roof of the EPA/HSF in Chapel Hill, NC. The results show that while PM10-2.5 mass concentration can be highly correlated across areas as large as 40 km, poor correlation can result at much shorts distances. The PM10-2.5 differential method evaluated in the study was observed to be highly associated with a direct dichotomous measurement and holds potential for use in other PM10-2.5 research applications.
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A Meta-Analysis of Children's Hand-to-Mouth Frequency Data for Estimating Non-Dietary Ingestion Exposure |
04/01/2007
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XUE, J., V. G. ZARTARIAN-MORRISON, J. MOYA, N. C. FREEMAN, P. BEAMER, K. BLACK, N. S. TULVE, AND S. L. SHALAT. A Meta-Analysis of Children's Hand-to-Mouth Frequency Data for Estimating Non-Dietary Ingestion Exposure. RISK ANALYSIS. Blackwell Publishing, Malden, MA, 27(2):411-420, (2007).
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Because of their mouthing behaviors, children have a higher potential for exposure to available chemicals through the non-dietary ingestion route; thus, frequency of hand-to-mouth activity is an important variable for exposure assessments. Such data are limited and difficult to collect. Few published studies report such information, and the studies that have been conducted used different data collection approaches (e.g., videography versus real-time observation), data analysis and reporting methods, ages of children, locations, and even definitions of mouthing. For this paper, hand-to-mouth frequency data were gathered from 9 available studies representing 429 subjects and more than 2000 hours of behavior observation. A meta-analysis was conducted to study differences in hand-to-mouth frequency based on study, age group, gender, and location (indoor vs. outdoor), to fit variability and uncertainty distributions that can be used in probabilistic exposure assessments, and to identify any data gaps.
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RESPONSE TO LETTER TO EDITOR OF RISK ANALYSIS ON ZARTARIAN ET AL., 2006 , "A PROBABILISTIC ARSENIC EXPOSURE ASSESSMENT FOR CHILDREN WHO CONTACT CCA-TREATED PLAYSETS AND DECKS, PART 1: MODEL METHODOLOGY, VARIABILITY RESULTS, AND MODEL EVALUATION |
02/01/2007
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ZARTARIAN-MORRISON, V. G. AND J. XUE. RESPONSE TO LETTER TO EDITOR OF RISK ANALYSIS ON ZARTARIAN ET AL., 2006 , "A PROBABILISTIC ARSENIC EXPOSURE ASSESSMENT FOR CHILDREN WHO CONTACT CCA-TREATED PLAYSETS AND DECKS, PART 1: MODEL METHODOLOGY, VARIABILITY RESULTS, AND MODEL EVALUATION. RISK ANALYSIS. Blackwell Publishing, Malden, MA, 27(1):1-5, (2007).
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Product is a letter to the editor of the Risk Analysis journal in reply to an industry's letter to the editor regarding a CCA paper published earlier this year.
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An Observational Study of the Potential Exposures of Preschool Children to Pentachlorophenol, Bisphenol-a, and Nonylphenol at Home and Daycare |
01/01/2007
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WILSON, N. K., J. C. CHUANG, M. K. MORGAN, B. LORDO, AND L. S. SHELDON. An Observational Study of the Potential Exposures of Preschool Children to Pentachlorophenol, Bisphenol-a, and Nonylphenol at Home and Daycare. ENVIRONMENTAL RESEARCH. Academic Press Incorporated, Orlando, FL, 103(1):9-20, (2007).
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The Children's Total Exposure to Persistent Pesticides and Other Persistent Organic Pollutants (CTEPP) study investigated the potential exposures of 257 preschool children, ages 1 1/2 to 5 yr, and their primary adult caregivers to more than 50 anthropogenic chemicals. Field sampling took place in selected counties in North Carolina (NC) and Ohio (OH) in 2000-2001. Over a 48-h period in each child's daycare center and/or home, food, beverages, indoor air, outdoor air, house dust, soil, participants' hand surfaces and urine were sampled. Additional samples - transferable residues, food preparation surface wipes, and hard floor surface wipes - were collected in the approximately 13% of the homes that had pesticide applications within the seven days prior to field sampling.
Three phenols were among the measured chemicals: pentachlorophenol, bisphenol A [2,2 bis(4-hydroxyphenyl)propane], and nonylphenol (4-n-nonylphenol). Nonylphenol was detected in less than 11% of the samples in any medium. Among samples that were collected at all participants' homes and daycare centers, pentachlorophenol was detected in >50% of indoor air, outdoor air, house dust, and urine samples; bisphenol A was detected in >50% of indoor air, hand wipe, solid food, and liquid food samples.
The concentrations of the phenols in the sampled media were measured, and estimates of the children's potential exposures and potential absorbed doses resulting from intake through the inhalation, dietary ingestion, and indirect ingestion routes of exposure were estimated. The children's potential exposures to pentachlorophenol were predominantly through inhalation: 78% in NC and 90% in OH. In contrast, their potential exposures to bisphenol-A were predominantly through dietary ingestion: 99%, for children in both states. The children's estimated exposures to pentachlorophenol, calculated from the amounts excreted in their urine, exceeded their estimated maximum potential intake, calculated from the multimedia pentachlorophenol concentrations, by a factor greater than 10. This inconsistency for pentachlorophenol highlights the need for further research on the environmental pathways and routes of pentachlorophenol exposure, investigation of possible exposures to other compounds that could be metabolized to pentachlorophenol, and on the human absorption, metabolism, and excretion of this phenol over time periods longer than 48 hours.
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An Observational Study of 127 Preschool Children at Their Homes and Daycare Centers in Ohio: Environmental Pathways to Cis-and Trans-Permethrin Exposure |
06/01/2007
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MORGAN, M. K., L. S. SHELDON, C. W. CROGHAN, P. A. JONES, J. C. CHUANG, AND N. K. WILSON. An Observational Study of 127 Preschool Children at Their Homes and Daycare Centers in Ohio: Environmental Pathways to Cis-and Trans-Permethrin Exposure. ENVIRONMENTAL RESEARCH. Academic Press Incorporated, Orlando, FL, 104(2):266-274, (2007).
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The potential exposures of 127 preschool children to the pyrethroid insecticides, cis- and trans-permethrin, in their everyday environments were examined. Participants were recruited randomly from 127 homes and 16 daycare centers in six Ohio (OH) counties. Monitoring was performed over a 48-h period at the children's homes and/or daycare centers. Samples collected included soil, carpet dust, indoor air, outdoor air, diet, hand wipes, surface wipes, transferable residues, and urine. The environmental samples were analyzed for the cis and trans isomers of permethrin, and the urine samples were analyzed for the pyrethroid urinary metabolite, 3-phenoxybenzoic acid (3-PBA), by gas chromatography/mass spectrometry. The isomers were detected most often in the dust (100%) and hand wipe (>78%) samples collected at both homes and daycare centers. The median levels of cis-permethrin (470 and 1,010 ng/g) were higher than the median levels of trans-permethrin (344 and 544 ng/g) in the dust samples at both the children's homes and daycare centers, respectively. In the children's hand wipe samples, the median levels of cis- and trans-permethrin were similar, ranging from 0.03 - 0.04 ng/cm2, at both locations. The urinary metabolite 3-PBA was detected in 67% of the children's urine samples. The median urinary 3-PBA concentration for the children was 0.3 ng/mL, and the maximum value for one child was 33.8 ng/mL. The primary route of the children's exposure to the combined isomers was through dietary ingestion, followed by indirect ingestion. In addition, our calculated aggregate absorbed doses of permethrin accounted for about 60% of the excreted amounts of 3-PBA found in the children's urine. In conclusion, these children were potentially exposed to low levels of permethrin from several sources, and through several pathways and routes.
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The Dry Deposition of Speciated Mercury to the Florida Everglades: Measurements and Modeling |
01/01/2007
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MARSIK, F. J., G. J. KEELER, AND M. S. LANDIS. The Dry Deposition of Speciated Mercury to the Florida Everglades: Measurements and Modeling. ATMOSPHERIC ENVIRONMENT. Elsevier Science Ltd, New York, NY, 41(1):136-149, (2007).
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The Florida Everglades Dry-Deposition Study (FEDDS) was designed to test the viability of using new and existing measurement techniques in the estimation of the dry-depositional loading of speciated mercury (elemental gaseous, reactive gaseous and particulate) to a mixed sawgrass (Cladium jamaicense) and cattail (Typha domingensis)stand within the Florida Everglades.
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Comparing Field Performances of Denuder Techniques in the High Arctic |
03/01/2007
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IANNIELLO, A., H. J. BEINE, M. S. LANDIS, R. K. STEVENS, G. ESPOSITO, A. AMOROSO, AND I. ALLEGRINI. Comparing Field Performances of Denuder Techniques in the High Arctic. ATMOSPHERIC ENVIRONMENT. Elsevier Science Ltd, New York, NY, 41(8):1604-2625, (2007).
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A field evaluation between two annular denuder system configurations was conducted during the spring of 2003 in the marine Arctic (Ny-Ålesund, Svalbard). The IIA annular denuder system (ADS) employs a series of five single channel annular denuders, a cyclone and a filter pack to discriminate between gas and aerosol species, while the deployed EPA-Versatile Air Pollution Sampler (VAPS) configuration employs a single multichannel annular denuder to protect the integrity of PM2.5 sample filters by collecting acidic gases. The concentrations of gaseous nitric acid (HNO3), nitrous acid (HONO), sulfur dioxide (SO2) and hydrochloric acid (HCl) determined using the IIA-ADS denuder system were compared to those measured with the EPA-VAPS denuder system. Results for HNO3 and SO2 suggested losses of gas phase species within the EPA-VAPS inlet surfaces due to low temperatures, high relative humidities, and coarse particle sea salt deposition to the VAPS inlet during sampling. The difference in HNO3 concentration (55%) between the EPA-VAPS and IIA-ADS data might also be due to the reaction between HNO3 and NaCl on inlet surfaces within the EPA-VAPS system. Furthermore, we detected the release of HCl from marine aerosol particles in the EPA-VAPS inlet during sampling that contributed to higher observed concentration values. Based on this work we present recommendations on the application of denuder sampling techniques for low concentration gaseous species in Arctic and remote marine locations to minimize sampling errors. We suggest an annular denuder technique without a large surface area inlet device in order to minimize adsorption, absorption, and/or production of gaseous atmospheric pollutants during sampling.
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Development and Application of Immunoaffinity Column Chromatography as a Cleanup Method for the Determination of Atrazine in Complex Environmental Sample Media |
01/30/2007
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CHUANG, J. C., J. M. VAN EMON, R. JONES, J. DURNFORD, AND B. LORDO. Development and Application of Immunoaffinity Column Chromatography as a Cleanup Method for the Determination of Atrazine in Complex Environmental Sample Media. ANALYTICA CHIMICA ACTA. Elsevier Science Ltd, New York, NY, 583(1):32-39, (2007).
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A rabbit antibody immunoaffinity (IA) column procedure was evaluated as a cleanup method for the determination of atrazine in soil, sediment, and food. Four IA columns were prepared by immobilizing a polyclonal rabbit anti-atrazine antibody solution to HiTrap Sepharose columns. Atrazine effectively bound to the IA columns with loading solvents of either 100% water, 2% acetonitrile in water, or 10% methanol in phosphate buffer. Quantitative removal of atrazine from the IA columns was achieved with elution solvents of either 70% ethanol in water, 70% methanol in water, or 100% methanol. One control column was prepared using nonspecific rabbit IgG antibody. This control column did not retain any applied atrazine indicating the compound did not bind indiscriminately to protein or the Sepharose support. The four IA columns showed reproducible coupling efficiency for the immobilization of the atrazine antibody and consistent binding and releasing of atrazine. The coupling efficiency (4.25 mg of antibody in 1 mL of resin bed) for the four IA columns ranged from 93 to 97% with an average of 96±2% (2.1%). Recoveries of the 500, 50, and 5 ng mL-1 atrazine standard solutions from the four IA columns were 107±7%(6.5%), 122±14% (12%), and 114±9% (8.0%) respectively, based on enzyme-linked immunosorbent assay (ELISA) data. The maximum loading was approximately 700 ng of atrazine for each IA column (~0.16 micro g of atrazine per mg of antibody). The IA columns could withstand 100% methanol as the elution solvent and be reused more than 50 times with no change in performance. The IA columns were challenged with real-world soil, sediment, and duplicate-diet food samples and effectively removed interferences from these various matrices for subsequent gas chromatography/mass spectrometry (GC/MS) and ELISA analysis. The log-transformed ELISA and GC/MS data were significantly correlated for soil, sediment and food samples although the ELISA values were slightly higher than those obtained by GC/MS. The IA column cleanup procedure coupled with ELISA analysis could be used as an alternative effective analytical method for the determination of atrazine in complex sample media such as soil, sediment, and food samples.
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Investigation of a Systematic Offset in the Measurement of Organic Carbon With a Semi-Continuous Analyzer |
05/01/2007
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OFFENBERG, J. H., M. LEWANDOWSKI, M. JAOUI, E. O. EDNEY, AND T. E. KLEINDIENST. Investigation of a Systematic Offset in the Measurement of Organic Carbon With a Semi-Continuous Analyzer. JOURNAL OF AIR AND WASTE MANAGEMENT. Air & Waste Management Association, Pittsburgh, PA, 57(5):596-599, (2007).
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Organic carbon was measured semi-continuously in laboratory experiments of steady-state secondary organic aerosol formed by hydrocarbon + NOx irradiations. Examination of the mass of carbon measured on the filter for various sample volumes reveals a systematic offset that is not observed when performing an instrumental blank. These findings suggest that simple subtraction of instrumental blanks determined as the standard analysis without sample collection (i.e. by cycling the pump and valves yet filtering zero liters of air followed by routine chemical analysis) from measured concentrations may be inadequate. This may be especially true for samples collected through the filtration of small air volumes wherein the influence of the systematic offset is greatest. All experiments show that filtering a larger volume of air minimizes the influence of contributions from the systematic offset. Application of these results to measurements of ambient concentrations of carbonaceous aerosol suggests a need for collection of sufficient carbon mass to minimize the relative influence of the offset signal.
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Exploring Relationships Between Outdoor Air Particulate-Associated Polycyclic Aromatic Hydrocarbon and PM2.5: A Case Study of Benzo(a)PYRENE in California Metropolitan Regions |
09/01/2007
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LOBSCHEID, A. B., T. MCKONE, AND D. A. VALLERO. Exploring Relationships Between Outdoor Air Particulate-Associated Polycyclic Aromatic Hydrocarbon and PM2.5: A Case Study of Benzo(a)PYRENE in California Metropolitan Regions. ATMOSPHERIC ENVIRONMENT. Elsevier Science Ltd, New York, NY, 41(27):5659-5672, (2007).
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Polycyclic aromatic hydrocarbons (PAHs) and particulate matter (PM) are co-pollutants emitted as by-products of combustion processes. Convincing evidence exists for PAHs as a primary toxic component of fine PM (PM2.5). Because PM2.5 is listed by the US EPA as a "Criteria Pollutant", it is monitored regularly at sites nationwide. In contrast, very limited data is available on measured ambient air concentrations of PAHs. However, between 1999-2001, ambient air concentrations of PM2.5 and benzo(a)pyrene (BaP) are available for California locations. We use multivariate linear regression models (MLRMs) to predict ambient air levels of BaP in four air basins based on reported PM2.5 concentrations and spatial, temporal and meteorological variables as variates. We obtain an R2 ranging from 0.57-0.72 among these basins. Significant variables (p<0.05) include the average daily PM2.5 concentration, wind speed, temperature and relative humidity, and the coastal distance as well as season, and holiday or weekend. Combining the data from all sites and using only these variables to estimate ambient BaP levels, we obtain an R2 of 0.55. These R2-values, combined with analysis of the residual error and cross validation using the PRESS-statistic, demonstrate the potential of our method to estimate reported outdoor air PAH exposure levels in metropolitan regions. These MLRMs provide a first step towards relating outdoor ambient PM2.5 and PAH concentrations for epidemiological studies when PAH measurements are unavailable, or limited in spatial coverage, based on publicly available meteorological and PM2.5 data.
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Composition of PM 2.5 During the Summer of 2003 in Research Triangle Park, Nc |
06/01/2007
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LEWANDOWSKI, M., M. JAOUI, T. E. KLEINDIENST, J. H. OFFENBERG, AND E. O. EDNEY. Composition of PM 2.5 During the Summer of 2003 in Research Triangle Park, Nc. ATMOSPHERIC ENVIRONMENT. Elsevier Science Ltd, New York, NY, 41(19):4073-4083, (2007).
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A field study was carried out during the summer of 2003 to examine the overall composition of fine particulate matter (PM2.5) in Research Triangle Park, North Carolina, USA, with particular emphasis on polar compounds from secondary organic aerosol (SOA). Collected samples were examined for gravimetric mass, organic and elemental carbon concentrations, inorganic ion concentrations, and detailed organic composition. On average, the ambient PM2.5 was found to consist of 41% organic matter, 2% elemental carbon, 12% ammonium, 37% sulfate, and less than 1% nitrate and oxalate. Mass concentrations ranged from 6.4 to 31.4 µg m-3. The acidity of the aerosol was also estimated, and higher PM2.5 and organic mass concentrations were generally observed under acidic conditions. A suite of chemical derivatization methods was used in conjunction with gas chromatography-mass spectrometry (GC-MS) to identify and quantify 29 polar organic compounds. Most of these compounds have been previously identified in laboratory photooxidation studies from hydrocarbon precursors, including isoprene, monoterpenes, ß-caryophyllene, and toluene. From laboratory studies, several of these polar compounds have been proposed as tracers for SOA, and concentrations measured in this study indicate the contributions of the precursor hydrocarbons to ambient SOA could be important. Some of the organic tracers, particularly those associated with isoprene SOA, represented a greater fraction of the organic carbon when the aerosol was acidic.
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| JOURNAL |
Evidence for Organosulfates in Secondary Organic Aerosol |
01/15/2007
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SURRATT, J. D., J. H. KROLL, T. E. KLEINDIENST, E. O. EDNEY, M. CLAEYS, A. SOROOSHIAN, N. L. NG, J. H. OFFENBERG, M. LEWANDOWSKI, M. JAOUI, R. FLAGAN, AND J. SEINFELD. Evidence for Organosulfates in Secondary Organic Aerosol. ENVIRONMENTAL SCIENCE & TECHNOLOGY. American Chemical Society, Washington, DC, 41(2):517-527, (2007).
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| Abstract:
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Recent work has shown that particle-phase reactions contribute to the formation of secondary organic aerosol (SOA), with enhancements of SOA yields in the presence of acidic seed aerosol. In this study, the chemical composition of SOA from the photooxidations of α-pinene and isoprene, in the presence or absence of sulfate seed aerosol, is investigated through a series of controlled chamber experiments in two separate laboratories. By using electrospray ionization - mass spectrometry, sulfate esters in SOA produced in laboratory photooxidation experiments are identified for the first time. Sulfate esters are found to account for a larger fraction of the SOA mass when the acidity of seed aerosol is increased, a result consistent with aerosol acidity increasing SOA formation. Many of the isoprene and α-pinene sulfate esters identified in these chamber experiments are also found in ambient aerosol collected at several locations in the southeastern U.S. It is likely that this pathway is important for other biogenic terpenes, and may be important in the formation of humic-like substances (HULIS) in ambient aerosol.
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| JOURNAL |
Ozone-Isoprene Reaction: Re-Examination of the Formation of Secondary Organic Aerosol |
01/05/2007
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KLEINDIENST, T. E., M. LEWANDOWSKI, J. H. OFFENBERG, M. JAOUI, AND E. O. EDNEY. Ozone-Isoprene Reaction: Re-Examination of the Formation of Secondary Organic Aerosol. GEOPHYSICAL RESEARCH LETTERS. American Geophysical Union, Washington, DC, 34(1):01/05/07, (2007).
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| Abstract:
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The reaction of ozone and isoprene has been studied to examine physical and chemical characteristics of the secondary organic aerosol formed. Using a scanning mobility particle sizer, the volume distribution of the aerosol was found in the range 0.05 - 0.2 µm. The aerosol yield was estimated to be 0.01, a value which is a factor of 5 - 10 higher than previous reports. The aerosol formation is complicated by the presence of minor impurities in the isoprene and the fact that OH-radicals produced in the ozonolysis can react with isoprene to produce organic aerosol. Without an OH-radical scavenger present, up to 50% of the observed aerosol comes from the OH channel. A GC-MS analysis of the products of the composite aerosol showed that two methyl tetrols and 2-methylglyceric acid are formed which can be attributed to the OH reaction channel. A measurement of the effective enthalpy of vaporization using a volatility differential mobility analyzer found the aerosol to have ΔHeff of -42 kJ mol-1, a value at the upper end of the range of organic aerosols previously studied. Even with the increased yield found in this study, the ozonolysis reaction probably remains a minor contributor to secondary organic aerosol in PM2.5 from the atmospheric oxidation of isoprene.
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| JOURNAL |
Ss-Caryophyllinic Acid: An Atmospheric Tracer for Ss-Caryophyllene Secondary Organic Aerosol |
03/10/2007
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JAOUI, M., M. LEWANDOWSKI, T. E. KLEINDIENST, J. H. OFFENBERG, AND E. O. EDNEY. Ss-Caryophyllinic Acid: An Atmospheric Tracer for Ss-Caryophyllene Secondary Organic Aerosol. GEOPHYSICAL RESEARCH LETTERS. American Geophysical Union, Washington, DC, 34(5):L05816 1-4, (2007).
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| Abstract:
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The chemical compositions of ambient PM2.5 samples, collected in Research Triangle Park, North Carolina, USA, and a sample of secondary organic aerosol, formed by irradiating a mixture of the sesquiterpene, ß-caryophyllene, and oxides of nitrogen in a smog chamber, were chemically analyzed using derivative-based GC-MS methods. The analyses showed the presence of an oxidized compound, tentatively identified as ß-caryophyllinic acid, in both the ambient PM2.5 field samples and in the smog chamber sample. The seasonal concentrations of ß-caryophyllinic acid in the ambient PM2.5 samples were 0.5, 0.9, 7.0, and 0.5 ng m-3 during the winter, spring, summer and fall respectively. To our knowledge, this is the first time that an oxidation product of a sesquiterpene, a hydrocarbon with high secondary organic aerosol yields and emitted from plants and trees in significant quantities, has been detected in ambient PM2.5 samples.
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| JOURNAL |
Making Sense of Human Biomonitoring Data: Findings and Recommendations of a Workshop |
07/01/2007
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BAHADORI, T., R. PHILLIPS, C. MONEY, J. J. QUACKENBOSS, H. J. CLEWELL, J. BUS, S. ROBISON, C. HUMPHRIS, A. PAREKH, K. OSBORN, AND R. KAUFFMAN. Making Sense of Human Biomonitoring Data: Findings and Recommendations of a Workshop. Journal of Exposure Science and Environmental Epidemiology . Nature Publishing Group, London, Uk, 17(4):308-313, (2007).
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| Abstract:
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The ability to measure chemicals in humans (often termed biomonitoring) is far outpacing the ability to reliably interpret these data for public health purposes, creating a major knowledge gap. Until this gap is filled, the great promise of routinely using biomonitoring data to support decisions to protect public health cannot be realized. Research is needed to link biomonitoring data quantitatively to the potential for adverse health risks, either through association with health outcomes or using information on the concentration and duration of exposure, which can then be linked to health guidelines. Developing such linkages in the risk assessment paradigm is one of the primary goals of the International Council of Chemical Associations' (ICCA) Long-Range Research Initiative (LRI) program in the area of biomonitoring. Therefore, ICCA sponsored a workshop to facilitate development of a coordinated agenda for research to enable an improved interpretation of human biomonitoring data. Discussions addressed three main topics: (1) exploration of the link between exposure, dose, and human biomonitoring data, (2) the use of computational tools to interpret biomonitoring data, and (3) the relevance of human biomonitoring data to the design of toxicological studies.
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| JOURNAL |
Recognition of Pyrene Using Molecularly-Imprinted Electrochemically-Deposited Poly (2-Mercaptobenzimidazole) or Poly(resorcinol) on Gold Electrodes |
10/01/2007
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LUO, N., D. W. HATCHETT, AND K. R. ROGERS. Recognition of Pyrene Using Molecularly-Imprinted Electrochemically-Deposited Poly (2-Mercaptobenzimidazole) or Poly(resorcinol) on Gold Electrodes. ELECTROANALYSIS. John Wiley & Sons, Ltd., Indianapolis, IN, 19(19-20):2117-2124, (2007).
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| Abstract:
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The feasibility of using thiol chemistry to form molecularly imprinted polymer-coated gold electrodes to measure pyrene is reported. For the first approach, poly(2-mercaptoimidazole) (2-MBI) was electrochemically deposited on gold electrodes in the presence or absence of the template pyrene. For the second approach, the pyrene derivative N-(1-pyrenyl)maleimide was covalently bound to 1,3-propane thiol that had been previously self-assembled on a cleaned gold surface. Resorcinol was then electrochemically polymerized onto the electrode followed by electrochemical stripping of the thiolated pyrene from the polymer-coated electrode. For both electrode configurations, the binding of pyrene to the MIP-coated electrode was detected indirectly through pyrene-dependent access of a ferricyanide probe to the electrode surface as measured using squarewave voltammetry.
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| JOURNAL |
Bayesian Hierarchical Modeling of Personal Exposure to Particulate Matter |
09/01/2007
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MCBRIDE, S. J., R. W. WILLIAMS, AND J. P. CREASON. Bayesian Hierarchical Modeling of Personal Exposure to Particulate Matter. ATMOSPHERIC ENVIRONMENT. Elsevier Science Ltd, New York, NY, 41(29):6143-6155, (2007).
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| Abstract:
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In the US EPA's 1998 Baltimore Epidemiology-Exposure Panel Study, a group of 21 residents of a single building retirement community wore personal monitors recording personal fine particulate air pollution concentrations (PM2.5) for 27 days, while other monitors recorded concurrent apartment, central indoor, outdoor and ambient site PM2.5 concentrations. Using the Baltimore panel study data, we develop a Bayesian hierarchical model to characterize the relationship between personal exposure and concentrations of PM2.5indoors and outdoors. Personal exposure is expressed as a linear combination of time spent in microenvironments and associated microenvironmental concentrations. The model incorporates all available monitoring data and accounts for missing data and sources of uncertainty such as measurement error and individual differences in exposure. We discuss the implications of using personal versus ambient PM2.5 measurements in characterization of personal exposure to PM2.5.
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| JOURNAL |
Refined PBPK Model of Aggregate Exposure to Methyl Tertiary-Butyl Ether |
03/30/2007
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KIM, D., M. E. ANDERSEN, J. D. PLEIL, L. A. NYLANDER-FRENCH, AND J. D. PRAH. Refined PBPK Model of Aggregate Exposure to Methyl Tertiary-Butyl Ether. TOXICOLOGY LETTERS. Elsevier Science Ltd, New York, NY, 169(3):222-235, (2007).
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| Abstract:
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Aggregate (multiple pathway) exposures to methyl tertiary-butyl ether (MTBE) in air and water occur via dermal, inhalation, and oral routes. Previously, physiologically-based pharmacokinetic (PBPK) models have been used to quantify the kinetic behavior of MTBE and its primary metabolite, tertiary-butyl alcohol (TBA), from inhalation exposures. However, the contribution of dermal and oral exposures to the internal dose of MTBE and TBA were not characterized well. The model was based entirely on blood MTBE and TBA measurements from controlled human exposures. The PBPK model consists of seven primary compartments representing the lung, skin, fat, kidney, liver, rapidly perfused tissue, and slowly perfused tissue. The MTBE and TBA models are linked by a single metabolic pathway. Although the general structure of the model is similar to previously published models of volatile organic compounds, we have now developed a detailed mathematical description of the lung, skin, and gastrointestinal tract. This PBPK model represents the most comprehensive and accurate description of MTBE and TBA pharmacokinetics in humans to date. The aggregate exposure model application for MTBE can be generalized to other environmental chemicals under this framework given appropriate empirical measurement data.
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| JOURNAL |
Effect of Acidity on Secondary Organic Aerosol Formation from Isoprene |
08/01/2007
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SURRATT, J. D., M. LEWANDOWSKI, J. H. OFFENBERG, M. JAOUI, T. E. KLEINDIENST, E. O. EDNEY, AND J. SEINFELD. Effect of Acidity on Secondary Organic Aerosol Formation from Isoprene. ENVIRONMENTAL SCIENCE & TECHNOLOGY. American Chemical Society, Washington, DC, 41(15):5363-5369, (2007).
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| Abstract:
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The effect of particle-phase acidity on secondary organic aerosol (SOA) formation from isoprene is investigated in a laboratory chamber study, in which the acidity of the inorganic seed aerosol was controlled systematically. The observed enhancement in SOA mass concentration is closely correlated with increasing aerosol acidity (R2 = 0.979). Direct chemical evidence for acid-catalyzed particle-phase reactions was obtained from the SOA chemical analyses. Aerosol mass concentrations for the 2-methyltetrols, as well as the newly identified sulfate esters, both of which serve as tracers for isoprene SOA in ambient aerosols, increased significantly with enhanced
aerosol acidity. Aerosol acidities, as measured in nmol H+ m-3, employed in the present
study are in the same range as those observed in tropospheric aerosol collected from the eastern U.S.
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| JOURNAL |
Perfluorinated Compounds in the Cape Fear Drainage Basin in North Carolina |
07/04/2007
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NAKAYAMA, S., M. J. STRYNAR, L. HELFANT, P. P. EGEGHY, X. YE, AND A. B. LINDSTROM. Perfluorinated Compounds in the Cape Fear Drainage Basin in North Carolina. ENVIRONMENTAL SCIENCE AND TECHNOLOGY. John Wiley & Sons, Ltd., Indianapolis, IN, 41(15):5271-5276, (2007).
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| Abstract:
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Concern over perfluorinated organic compounds (PFCs), e.g., perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA), is due to a number of recent studies which show that the PFCs are persistent, bioaccumulative, and toxic. Despite sustained interest
in this topic, little information is available concerning the environmental distributions of the compounds. In this study, a new method was developed for the analysis of 10 target PFCs and its performance was examined in a systematic evaluation of the Cape Fear River Basin in North Carolina, USA. One hundred samples from 80 different locations were collected during the spring of 2006. Detectable levels of the target PFCs were found in all samples, with maximum PFOS at 132 ng/L, PFOA at 287 ng/L, perfluorononanoic acid (C9) at 194 ng/L, and perfluoroheptanoic acid (C7) at 329 ng/L. In general, the
lowest concentrations of the PFCs were found in the smallest tributaries while the highest levels were found in middle reaches of the Drainage Basin. Variability of PFC
concentrations suggests a series of source inputs throughout the Basin. Seventeen sample sites (22%) had PFOS concentrations greater than 43 ng/L, a conservative safe water concentration estimated to be protective of avian life. In addition, a total of 26 sites (32%) had PFOA concentrations above 40 ng/L.
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| JOURNAL |
Performance of a New Diffusive Sampler for Hg0 Determination in the Troposphere |
04/17/2007
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SKOV, H., B. T. SORENSEN, M. S. LANDIS, M. S. JOHNSON, P. SACCO, M. E. GOODSITE, C. LOHSE, AND K. S. CHRISTIANSEN. Performance of a New Diffusive Sampler for Hg0 Determination in the Troposphere. ENVIRONMENTAL CHEMISTRY. CSIRO Publishing, Collingwood Victoria, Australia, 4(2):75-80, (2007).
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| Abstract:
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Mercury behaves uniquely in the atmosphere due to its volatility and long lifetime. The existing methods for measuring atmospheric mercury are either expensive or labour intensive. The present paper presents a new measurement technique, the diffusive sampler, that is portable, inexpensive, easy to use, and does not need a power supply. The sampler is sufficiently sensitive that it can measure Hg at low ambient levels with an exposure time of 1 to 3 days. The sampler is based on the Radiello diffusive sampler. The sampler is a modified version of the original design, where it was used to collect volatile organic compounds. In the present paper the method is validated under controlled laboratory conditions. The uptake rate of the Radiello diffusive sampler is determined using known concentrations of GEM, and is measured as a function of wind speed, relative humidity and temperature. The Radiello sampler has a detection limit of 0.14 ng m-3 for 1 day of exposure and thus can be used to measure mercury concentrations at the low levels found in ambient air. The Radiello sampler is therefore useful for mapping concentrations close to sources and sinks, in addition to ambient concentrations. For example the sampler can be used to describe the geographical extent of Arctic mercury depletion episodes where GEM is removed and stays close to zero ng m-3 for days, and it can be a powerful tool for mapping gradients around e.g. point sources.
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| JOURNAL |
Pesticide Exposure and Chiral Chemistry: the Pyrethroid Family |
09/01/2007
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ULRICH, E. M. Pesticide Exposure and Chiral Chemistry: the Pyrethroid Family. Chimica Oggi (Chemistry Today). TEKNOSCIENZE, Milano, Italy, 25(5):37-39, (2007).
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| Abstract:
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Advances in chiral chromatography significantly advanced
the ability to analyze individual enantiomers of chiral
compounds. These techniques are being employed at the
U.S. EPA for human exposure and ecological research studies. Enantiomer fractions (EFs) were measured for cispermethrin, a pyrethroid insecticide. Nonracemic EFs in some environmental samples indicate that some nantioselective biological degradation has occurred, either in the indoor environment or prior to translocation
indoors. These results highlight the importance of chiral methods because some degradation pathways can change the
distribution of enantiomers in the environment and may lead
to differential exposure. The toxicity of enantiomers can also vary. When these two factors are combined, a differential risk to humans and other organisms may be revealed.
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| JOURNAL |
Contributions of Toluene and Α-Pinene to Soa Formed in An Irradiated Toluene/Α-Pinene/Nox/Air Mixture: Comparison of Results Using 14c Content and Soa Organic Tracer Methods |
05/04/2007
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OFFENBERG, J. H., C. W. LEWIS, M. LEWANDOWSKI, M. JAOUI, T. E. KLEINDIENST, AND E. O. EDNEY. Contributions of Toluene and Α-Pinene to Soa Formed in An Irradiated Toluene/Α-Pinene/Nox/Air Mixture: Comparison of Results Using 14c Content and Soa Organic Tracer Methods. ENVIRONMENTAL SCIENCE AND TECHNOLOGY. John Wiley & Sons, Ltd., Indianapolis, IN, 41(11):3972-3976, (2007).
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| Abstract:
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An organic tracer method, recently proposed for estimating individual contributions of toluene and α-pinene to secondary organic aerosol (SOA) formation, was evaluated by conducting a laboratory study where a binary hydrocarbon mixture, containing the anthropogenic aromatic hydrocarbon, toluene, and the biogenic monoterpene, α-pinene, was irradiated in air in the presence of NOx to form SOA. The contributions of toluene and α-pinene to the total SOA concentration, calculated using the organic tracer method, were compared with those obtained with a more direct 14C content method. In the study, SOA to SOC ratios of 2.07 ± 0.08 and 1.41 ± 0.04 were measured for toluene and α-pinene SOA, respectively. The individual tracer-based SOA contributions of 156 µg m-3 for toluene and 198 µg m-3 for α-pinene, which together accounted for 82% of the gravimetrically determined total SOA concentration, compared well with the 14C values of 182 and 230 µg m-3 measured for the respective SOA precursors. While there are uncertainties associated with the organic tracer method, largely due to the chemical complexity of SOA forming chemical mechanisms, the results of this study suggest the organic tracer method may serve as a useful tool for determining whether a precursor hydrocarbon is a major SOA contributor.
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| JOURNAL |
Hydroxydicarboxylic Acids: Markers for Secondary Organic Aerosol from the Photooxidation of a-Pinene |
03/01/2007
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Claeys, M., R. Szmigielski, I. Kourtchev, P. Van der Veken, R. Vermeylen, W. Maenhaut, M. JAOUI, T. E. KLEINDIENST, M. LEWANDOWSKI, J. H. OFFENBERG, AND E. O. EDNEY. Hydroxydicarboxylic Acids: Markers for Secondary Organic Aerosol from the Photooxidation of a-Pinene. ENVIRONMENTAL SCIENCE AND TECHNOLOGY. John Wiley & Sons, Ltd., Indianapolis, IN, 41(5):1628-1634, (2007).
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| Abstract:
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Detailed organic analysis of fine (PM 2.5) rural aerosol collected during summer at K-puszta, Hungary, a mixed deciduous/coniferous forest site, shows the presence of polar oxygenated compounds that are also formed in laboratory irradiated a-pinene/NOx/air mixtures. In the present work, two major photooxidation products of a-pinene were characterized as the hydroxydicarboxylic acids, 3-hydroxyglutaric acid and 2-hydroxy-4-isopropyladipic acid, on the basis of chemical, chromatographic and mass spectral data. Different types of volatile derivatives, including trimcthylsilyl ester/elher, metbyl ester trimethylsilyl ether, and ethyl ester trimethylsilyl ether derivatives were measured by gas chromatographY/mass spectrometry (GCIMS), and their electron ionization (EI) spectra were interpreted in detail. The proposed structure of the hydroxydicarboxylic acids were confirmed or supported with reference compounds. 2-Hydroxy-4-isopropyladipic acid formally corresponds to a further reaction product of pinic acid involving addition of a molecule of watcr and opening of the dimethylcyclobutane ring; this proposal is supported by a laboratory irradiatjon experiment with a-pinene/NOx/air. In addition, we report the presence of a structurally related minor a-pinene photooxidation product, which was tentatively identified as the C7 homolog of 3-hydroxyglutaric acid, 3-hydroxy-4,4-dimethylglutaric acid. The detection of 2-hydroxy-4-isopropyladipic acid in ambient aerosol provides an explanation for the relatively low atmospheric concentrations of pinic acid found during daytime in forest environments.
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| PRESENTATION |
Exposure Assessment for the National Children's Study: Integrating Biomonitoring With Environmental Measures and Questionnaire/Diary/Observational Information |
07/26/2007
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QUACKENBOSS, J. J., L. L. NEEDHAM, W. GALKE, S. VIET, AND B. OBRIEN. Exposure Assessment for the National Children's Study: Integrating Biomonitoring With Environmental Measures and Questionnaire/Diary/Observational Information. Presented at International Council of Chemical Associations Workshop, Minneapolis, MN, July 26 - 27, 2006.
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| Abstract:
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The National Children's Study (NCS) is proposed to be the largest and most ambitious study of the health and development of children ever to be undertaken in the United States. The Study is led by the U.S. Department of Health and Human Services - through the National Institutes of Health and the Centers for Disease Control and Prevention - and by the U.S. Environmental Protection Agency. The Study plans to enroll a representative sample of America's children (approximately 100,000 from more than 100 locations throughout the U.S.) and their families, and follow them longitudinally from either before conception or early in pregnancy until age 21 years to better understand the multiple factors which influence the physical and mental health and development of children.
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| PRESENTATION |
A Physiologically Based Pharmacokinetic/Pharmacodynamic (PBPK/Pd) Model for Estimation of Cumulative Risk from Exposure to Three N-Methyl Carbamates: Carbaryl, Aldicarb, and Carbofuran |
03/25/2007
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XIAOFEI, Z., M. S. OKINO, J. B. KNAAK, A. M. TSANG, F. W. POWER, J. XUE, L. S. HARRISON, C. B. THOMPSON, AND C. C. DARY. A Physiologically Based Pharmacokinetic/Pharmacodynamic (PBPK/Pd) Model for Estimation of Cumulative Risk from Exposure to Three N-Methyl Carbamates: Carbaryl, Aldicarb, and Carbofuran. Presented at 2007 Society of Toxicology Annual Meeting, Charlotte , NC, March 25 - 29, 2007.
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| Abstract:
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A physiologically-based pharmacokinetic (PBPK) model for a mixture of N-methyl carbamate pesticides was developed based on single chemical models. The model was used to compare urinary metabolite concentrations to levels from National Health and Nutrition Examination Survey (NHANES III) based on inputs from the Stochastic Human Exposure Dose Simulation (SHEDS) model.
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| PRESENTATION |
The Potential for Human Exposures to Pet-Borne Diazinon Residues Following Residential Lawn Applications |
03/25/2007
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MORGAN, M. K., D. M. STOUT, AND P. P. EGEGHY. The Potential for Human Exposures to Pet-Borne Diazinon Residues Following Residential Lawn Applications. Presented at American Chemical Society,Spring National Meeting, Chicago, IL, March 25 - 29, 2007.
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| Abstract:
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This observational study examined the potential for indoor/outdoor pet dogs to be an important pathway for transporting diazinon residues into homes and onto occupants following residential lawn applications. The primary objective was to investigate the potential exposures of children and their pet dogs to diazinon after a lawn application at their homes.
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| PRESENTATION |
Issues in the Measurement and Assessment of Environmental Exposures for a Large Prospective Cohort Study |
07/29/2007
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QUACKENBOSS, J. J., W. GALKE, S. VIET, AND D. MARKER. Issues in the Measurement and Assessment of Environmental Exposures for a Large Prospective Cohort Study. Presented at 2007 Joint Statistical Meetings, Salt Lake City, UT, July 29 - August 02, 2007.
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| Abstract:
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The National Children's Study (NCS) is a large-scale, multi-agency effort (lead by NIH, EPA, and CDC) to evaluate relationships among multiple exposures and changes in susceptibility over life stages, and subsequent health and developmental outcomes. In an invited presentation to the American Statistical Society's Joint Statistical Meetings, both statistical and logistical considerations for exposure assessment designs and approaches in the NCS will be discussed.
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| PRESENTATION |
American Healthy Homes Survey: A National Study of Residential Pesticides Measured from Floor Wipes |
03/25/2007
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STOUT, D. M., K. D. BRADHAM, R. HIGHSMITH, P. A. JONES, C. W. CROGHAN, W. FREIDMAN, E. PINZER, D. COX, AND G. DEWALT. American Healthy Homes Survey: A National Study of Residential Pesticides Measured from Floor Wipes. Presented at American Chemical Society, Chicago, IL, March 25 - 29, 2007.
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| Abstract:
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The US Environmental Protection Agency and the US Department of Housing and Urban Development conducted the American Healthy Homes Survey (AHHS) in 2006 to assess environmental concentrations of lead, allergens, mold, pesticides, and arsenic in and around U.S. residences.
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| PRESENTATION |
Pharmacokinetic/Pharmacodynamic Modeling of Permethrin in the Rat |
03/25/2007
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TORNERO-VELEZ, R., E. SCOLLON, J. M. STARR, M. F. HUGHES, M. J. DEVITO, AND C. C. DARY. Pharmacokinetic/Pharmacodynamic Modeling of Permethrin in the Rat. Presented at 2007 Society of Toxicology Annual Meeting, Charlotte, NC, March 25 - 29, 2007.
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| Abstract:
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A physiologically-based pharmacokinetic (PBPK) model was used to describe pharmacokinetics of permethrin and calibrated using experimental data on the concentration time-course of cis- and trans-permethrin in rat blood and brain tissues following oral administration.
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| PRESENTATION |
Sample Extraction and Gc-MS Analysis for Polar Volatile Organic Compounds (Pvocs) in Liquid Biological Media |
02/06/2007
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PLEIL, J. D., J. R. SOBUS, H. HUBBARD, AND M. C. MADDEN. Sample Extraction and Gc-MS Analysis for Polar Volatile Organic Compounds (Pvocs) in Liquid Biological Media. Presented at Environmental Analysis Conference 2007, Wellington, NEW ZEALAND, February 06 - 09, 2007.
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| Abstract:
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Current approaches for assessing the cumulative exposures and effects from broad classes of environmental stressors incorporate the measurement of specific groups of endogenous compounds in human biological fluids. Recent focus has been on interpreting patterns of differentially expressed proteins and large molecule adducts (e.g hemoglobin, albumin, DNA) which are difficult to measure. In contrast, this work exploits classes of simple polar volatile organic compounds (PVOCs) that are abundant and ubiquitous products of human metabolism and can be found in non-invasively collected breath or urine samples. Methodology for measuring metabolic PVOCs is presented using standard laboratory tools and modest gas chromatography/mass spectrometry equipment.
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| PRESENTATION |
Immunoassays for Biomarkers and Neutraceuticals/Pharmaceuticals |
02/25/2007
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VAN EMON, J. M. AND J. C. CHUANG. Immunoassays for Biomarkers and Neutraceuticals/Pharmaceuticals. Presented at PITTICON, Chicago, IL, February 25 - March 02, 2007.
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| Abstract:
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Product is an abstract for an invited oral platform presentation to be given at the Pittsburgh Conference to be held February 25 - March 2, 2007 in Chicago, Ilinois. The presentation will describe methods research for the development of bioanalytical methods to measure biomarkers and neautraceutical/pharmaceuticals to support monitoring studies. One method developed was an immunoassay to detect 2,4-D in urine with a detection limit of 30 ng/mL which favorably compared to a GC/MS procedure.
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| PRESENTATION |
Ecologic Study of Mesoscale Environments With Excess Disease Prevalence |
02/01/2007
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SHEPPARD, P. R., J. D. PLEIL, R. J. SPEAKMAN, G. RIDENOUR, AND M. L. WITTEN. Ecologic Study of Mesoscale Environments With Excess Disease Prevalence. Presented at NCSE-2007 , Washington, DC, February 01 - 02, 2007.
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| Abstract:
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This work employs an ecologic epidemiological approach to assess the relationship between environmental stressors and excess disease prevalence in small communities. Specifically, the childhood leukemia cluster in Fallon Nevada is used as an example; heavy metals (tungsten and cobalt) exposures are contrasted with disease prevalence in Fallon, control communities, and pristine desert. Further biomedical research is suggested as a follow-up
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| PRESENTATION |
Planned Integration of Measurement and Survey Data from the Dears With Local and Regional Research Efforts: Preliminary Data Findings and Observations |
09/27/2007
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WILLIAMS, R. W., A. F. VETTE, C. W. CROGHAN, C. D. STEVENS, T. M. BARZYK, P. A. JONES, D. A. WHITAKER, S. R. MCDOW, G. A. NORRIS, S. MUKERJEE, J. M. BURKE, B. J. GEORGE, AND M. HEINDORF. Planned Integration of Measurement and Survey Data from the Dears With Local and Regional Research Efforts: Preliminary Data Findings and Observations. Presented at Canada-US Border Air Quality Studies Workshop, Windsor, ON, CANADA, September 27, 2007.
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The Canadian-US Border Air Quality Studies represent collaborative research being performed by both parties. This abstract details the efforts of the Detroit Exposure and Aerosol Research Study (DEARS) to work collaboratively in this regards. A discussion of the collaborations is provided along with select data findings and observations from the ongoing study.
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| PRESENTATION |
An Observational Study on the Potential Exposures of 111 Preschool Children to Phthalates in Their Everyday Environments |
11/03/2007
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FIGUEROA, Z., M. K. MORGAN, P. A. JONES, C. W. CROGHAN, L. S. SHELDON, AND A. M. CALAFAT. An Observational Study on the Potential Exposures of 111 Preschool Children to Phthalates in Their Everyday Environments. Presented at American Public Health Association Annual Conference, Washington, DC, November 03 - 07, 2007.
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The purpose of this work was to identify potential sources and routes of preschool children exposures to two phthalate diesters used in household and personal care products and building materials. Exposure and biomonitoring data was reviewed. The abstract included the preliminary conncentration results found in the collected media. Urine samples were analyzed for two main metabolites of interest in collaboration with CDC.
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| PRESENTATION |
Source Apportionment of Particulate Matter in the U.S. and Associations With in Vivo and in Vitro Lung Inflammatory Markers |
09/24/2007
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DUVALL, R. M., G. A. NORRIS, J. M. BURKE, J. K. MCGEE, M. I. GILMOUR, AND R. B. DEVLIN. Source Apportionment of Particulate Matter in the U.S. and Associations With in Vivo and in Vitro Lung Inflammatory Markers. Presented at 29th NATO/SPS International Technical Meeting, Aveiro, PORTUGAL, September 24 - 28, 2007.
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This is an abstract submitted to the 29th NATO International Technical Meeting on Air Pollution Modelling and its Application. In this research, sources of particulate matter were determined in cities across the U.S. using the chemical mass balance receptor model. The sources were then compared to in vivo and in vitro lung inflammatory markers to examine links between sources and health effects.
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| PRESENTATION |
Meta-Analysis of the Life Style Factors Relevant to Environmental Hazards for the Aging Population |
11/03/2007
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CHAO, Y., T. R. MCCURDY, K. W. THOMAS, AND N. S. TULVE. Meta-Analysis of the Life Style Factors Relevant to Environmental Hazards for the Aging Population. Presented at American Public Health Association Annual Meeting, Washington, DC, November 03 - 07, 2007.
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The goal of this U.S. Environmental Protection Agency (EPA) study is to characterize activity patterns, physiological changes, and environmental exposures for the aging population. Meta analysis was performed on more than 2000 reviewed articles to evaluate the lifestyle factors most relevant to environmental hazards for the aging population, and to develop statistical distributions of inputs to EPA's time series exposure models. In addition, these data should provide age-specific information for EPA's Exposure Factors Handbook.
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| PRESENTATION |
Ord Best Practices for Observational Human Exposure Measurement Studies |
03/27/2007
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FORTMANN, R. C. Ord Best Practices for Observational Human Exposure Measurement Studies. Presented at 2007 Society of Toxicology Annual Meeting, Charlotte, NC, March 25 - 29, 2007.
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This abstract describes a presentation for the 2007 Society of Toxicology Annual Meeting in Charlotte, NC on March 27, 2007. It will be included in a special Issues Session titled "Scientific and Ethical Considerations in Human Exposure Studies." The presentation describes scientific and ethical approaches for observational exposure studies. It discusses issues to be addressed in the design and implementation of observational exposure studies, the state of the science for these approaches, and information sources available to researchers conducting observational studies.
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| PRESENTATION |
A Multi-Residue Method for the Analysis of Insecticides Collected on Cotton Surface Wipes |
06/03/2007
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CLIFTON, M. AND D. M. STOUT. A Multi-Residue Method for the Analysis of Insecticides Collected on Cotton Surface Wipes. Presented at ASMS Conference on Mass Spectrometry, Indianapolis, IN, June 03 - 07, 2007.
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A method was developed for the extraction, clean-up, and analysis of multiple pesticides from cotton wipe media used in human exposure studies to collect residues from residential hard surfaces. Measurements of pesticides are critical for estimating dermal and indirect ingestion exposure, particularly for children. Methods used previously for multi-residue analysis of cotton wipes have been difficult to use for routine analysis at trace levels due to extensive problems with matrix effects from the cotton media and the hard surfaces being sampled. This method incorporates a multi-stage SPE clean-up procedure to remove extraneous compounds. An effective approach to correct for extraction efficiency and matrix effects based primarily on response enhancement on the GC/MS system is described.
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| PRESENTATION |
Asbestos Exposure Research Air, Soil and Bulk Material Scenarios |
03/17/2007
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VALLERO, D. A. Asbestos Exposure Research Air, Soil and Bulk Material Scenarios. Presented at 24th Annual Conference and Exposition of the Environmental Information Association, Charlotte, NC, March 17 - 21, 2007.
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Presently, asbestos and other mineral fibers are monitored in the workplace and in the environment using several basic analytical techniques, based primarily upon observing the fiber by either optical or electron microscopy. EPA is conducting research to determine which sampling and analytical approaches best support these analyses. In two surveys conducted in 2004, EPA asbestos coordinators identified the highest priority exposure research needs to be improvements to analytical procedures and counting rules for asbestos detection and quantitation in bulk samples, air, settled dust, and soil for field monitoring and risk analysis in various exposure scenarios.
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| PRESENTATION |
Indoor-Outdoor Characterization of the Elemental Components of PM 2.5 |
09/05/2007
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STEVENS, C. D., R. W. WILLIAMS, A. F. VETTE, AND P. A. JONES. Indoor-Outdoor Characterization of the Elemental Components of PM 2.5. Presented at ISEE Conference, Mexico City, MEXICO, September 05 - 09, 2007.
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This presentation is based on analyses of outdoor PM2.5 mass concentration, composition and the infiltration associated with indoor PM2.5.
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| PRESENTATION |
Human Exposure Air Monitoring: Examples from the National Exposure Research Laboratory |
03/20/2007
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WILLIAMS, R. W. Human Exposure Air Monitoring: Examples from the National Exposure Research Laboratory. Presented at US EPA-NCCU Cross Pollination Workshop, Durham, NC, March 20, 2007.
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The US-EPA and North Carolina Central University (NCCU) have a cross-pollination agenda to help share research opportunities between the two institutions. This presentation provides NCCU with an understanding of current air monitoring research the US EPA is involved in and some of the approaches used in that effort.
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| PRESENTATION |
The Impact of Passive Sampling Methodologies Used in the Dears |
08/19/2007
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WILLIAMS, R. W., A. F. VETTE, D. A. WHITAKER, C. W. CROGHAN, P. A. JONES, H. DAUGHTREY, K. OLIVER, H. JACUMIN, D. D. WILLIAMS, C. E. RODES, J. W. THORNBURG, J. S. HERRINGTON, AND J. ZHANG. The Impact of Passive Sampling Methodologies Used in the Dears. Presented at 2007 National Environmental Monitoring Conference, Cambridge, MA, August 19 - 23, 2007.
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This abstract details the use of passive sampling methodologies in the Detroit Exposure and Aerosol Research Study (DEARS). A discussion about the utility of various gas-phase passive samplers used in the study will be described along with examples of field data measurements employing the technology.
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| PRESENTATION |
Field Collection Methods Used in the EPA National Exposure Research Laboratory Human Exposure Measurement Program to Evaluate Children's Aggregate Exposure to Pesticides: A Tutorial |
03/22/2007
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TULVE, N. S. Field Collection Methods Used in the EPA National Exposure Research Laboratory Human Exposure Measurement Program to Evaluate Children's Aggregate Exposure to Pesticides: A Tutorial. Presented at OPP Health Effects Division (HED) Risk Assessment Training Program, Washington, DC, March 22, 2007.
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A tutorial on the field sampling equipment used to collect multimedia samples.
We conduct observational human exposure measurement studies in order to understand what chemicals people come into contact with, at what levels, what the sources of those chemicals are, and where, when, how often, and why people come into contact with those chemicals in their everyday environments.
A discussion of the other types of ancillary data collected, the algorithms, and example data will be shown.
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| PRESENTATION |
Application of Pscf to Pmf-Modeled Sources of PM2.5 in Riverside Using 1-Hr Averaged Data |
06/26/2007
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EATOUGH, D. J., B. GROVER, W. WOOLWINE, R. FARBER, AND W. F. CHRISTENSEN. Application of Pscf to Pmf-Modeled Sources of PM2.5 in Riverside Using 1-Hr Averaged Data. Presented at Air and Waste Management Association Annual Conference, Pittsburgh, PA, June 26 - 29, 2007.
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Data from semi-continuous instruments employed during a sampling campaign in Riverside, CA in July-August 2005 was used in a PMF2 analysis and sixteen sources were identified. Factors attributed to being primarily from local automobile emissions, local diesel emissions, wood combustion and local secondary photochemical associated sources were found. Several transport attributed factors were also identified, including, transported nonvolatile material, transported secondary ammonium nitrate, and transported secondary organic material. The PMF2 results were combined with hourly averaged back-trajectory data from HYSPLIT to identify factors associated with specific meteorological transport conditions.
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| PRESENTATION |
Measurement of Polycyclic Aromatic Hydrocarbons (PAHs) Associated With Fine Particulate Matter to Estimate Statewide Cumulative Exposures in North Carolina |
03/26/2007
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FUNK, W. E., S. M. RAPPAPORT, M. CLARK, AND J. D. PLEIL. Measurement of Polycyclic Aromatic Hydrocarbons (PAHs) Associated With Fine Particulate Matter to Estimate Statewide Cumulative Exposures in North Carolina. Presented at Society of Toxicology Annual Meeting, Charlotte, NC, March 25 - 29, 2007.
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Airborne particulate matter (PM) is routinely collected at over a thousand air monitoring stations across the nation using Teflon filters. After they are weighed to measure the amount of PM in the air, the filters are stored in refrigerators and, after a year, are thrown away. Three years ago, scientists at the U.S. Environmental Protection Agency (EPA) and the university of North Carolina jointly developed a method for using these stored filters for the additional job of measuring the levels of several carcinogenic polyaromatic hydrocarbons (PAHs) that are bound to the particles. We have now used archived filters from the state of North Carolina to start to assess the potential incremental cancer risk from the cumulative exposures from PAHs across the state. This methodology can be easily and cost effectively implemented in other states across the country using such archived filters.
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| PRESENTATION |
(California) Meta-Analysis of the Life Style Factors Relevant to Environmental Hazards for the Aging Population |
11/16/2007
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CHAO, E., T. R. MCCURDY, K. W. THOMAS, AND N. S. TULVE. (California) Meta-Analysis of the Life Style Factors Relevant to Environmental Hazards for the Aging Population. Presented at The Gerontological Society of America Scientific Meeting, San Francisco, CA, November 16 - 20, 2007.
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The goal of this U.S. Environmental Protection Agency (EPA) Aging Initiative study is to characterize activity patterns, physiological changes, and environmental exposures for the aging population. Meta-analysis was performed on more than 2000 reviewed articles to evaluate the lifestyle factors most relevant to environmental hazards for the aging population, and to develop statistical distributions of inputs to EPA's time series exposure models. In addition, these data should provide age-specific information for EPA's Exposure Factors Handbook.
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| PRESENTATION |
(Portugal)THE Detroit Exposure and Aerosol Research Study |
09/24/2007
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WILLIAMS, R. W., A. F. VETTE, J. M. BURKE, G. A. NORRIS, K. WESSON, M. STRUM, T. FOX, AND T. H. WATKINS. (Portugal)THE Detroit Exposure and Aerosol Research Study. Presented at International Technical Meeting on Air Pollution Modeling, Aveiro, PORTUGAL, September 24 - 28, 2007.
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The Detroit Exposure and Aerosol Research Study (DEARS) represents an intensive examination of personal, residential and community-based particulate matter and related co-pollutant measurements in Detroit, Michigan. Data from the DEARS will be used as inputs into air quality, land use regression and pollutant-specific modeling. This presentation describes data collected in the DEARS and the planned modeling component of the study.
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| PRESENTATION |
Exposure Assessment Tools for Cumulative Risk Assessment: Measurement of Endogenous Biomarkers |
03/14/2007
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HUBBARD, H., J. D. PLEIL, AND M. C. MADDEN. Exposure Assessment Tools for Cumulative Risk Assessment: Measurement of Endogenous Biomarkers. Presented at Society of Environmental Toxicology and Chemistry, Chicago, IL, March 14 - 16, 2007.
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Direct assessment of cumulative risks is a difficult task due to combinations of multiple chemicals, exposure pathways, and concentration profiles using suites of environmental measurements. We are investigating the use of endogenous compounds commonly present in biological media and their changes in response to environmental stressors to indicate preclinical effects of complex exposures on metabolite expression.
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| PUBLISHED REPORT |
Important Exposure Factors for Children An Analysis of Laboratory and Observational Field Data Characterizing Cumulative Exposure to Pesticides |
03/23/2007
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EGEGHY, P. P., L. S. SHELDON, D. M. STOUT, E. A. COHEN-HUBAL, N. S. TULVE, L. J. MELNYK, M. K. MORGAN, R. C. FORTMANN, D. A. WHITAKER, C. W. CROGHAN, P. A. JONES, AND A. COAN. Important Exposure Factors for Children An Analysis of Laboratory and Observational Field Data Characterizing Cumulative Exposure to Pesticides. U.S. Environmental Protection Agency, Washington, DC, EPA/600/R-07/013 (NTIS PB2007-106980), 2007.
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In an effort to facilitate more realistic risk assessments that take into account unique childhood vulnerabilities to environmental toxicants, the U.S. EPA's National Exposure Research Laboratory (NERL) developed a framework for systematically identifying and addressing the most important sources, routes, and pathways of children's exposure to pesticides. Four priority research areas were identified as representing critical data gaps in our understanding of environmental risks to children. Several targeted studies were conducted under NERL's children's exposure research program to specifically address these priority research needs. This document is a comprehensive summary report of data collected in these studies to address the priority research needs and is intended for an audience of exposure scientists, exposure modelers, and risk assessors. The parameters measured and the measurement methods are described. Data on representative organophosphate and pyrethroid pesticides are compared across studies and across compounds with the primary purpose of identifying or evaluating important factors influencing exposures along each relevant pathway. Summary statistics, comparative analyses, and spatial and temporal patterns are presented to address previously identified data gaps. Results are compared across studies in order to identify trends that might provide a better understanding of the factors affecting children's exposures. While highlights of the results of individual studies are presented, the focus is on presenting insights gleaned from the analysis of the aggregated data from several studies. By examining relationships among application patterns, exposures, and biomarkers for multiple compounds from different classes of pesticides, this report strives to help produce more reliable approaches for assessing cumulative exposure.
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| PUBLISHED REPORT |
Malathion Exposure During Lice Treatment: Use of Exposure Related Dose Estimating Model (Erdem) and Factors Relating to the Evaluation of Risk |
03/02/2007
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POWER, F. W., C. C. DARY, J. B. KNAAK, R. TORNERO-VELEZ, AND J. N. BLANCATO. Malathion Exposure During Lice Treatment: Use of Exposure Related Dose Estimating Model (Erdem) and Factors Relating to the Evaluation of Risk. U.S. Environmental Protection Agency, Washington, DC, EPA/600/R-07/023 (NTIS PB2007-106971), 2007.
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This report is a product of this collaboration as it relates to the exposure assessment of organophosphorus (OP) insecticide, malathion, (O,O-dimethyl phosphorodithioate diethyl mercaptosuccinate; CAS 121-75-5) labeled for use as a pediculicide.
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| PUBLISHED REPORT |
EPA Unmix 6.0 User Guide |
07/11/2007
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NORRIS, G. A., R. VEDANTHAM, AND R. M. DUVALL. EPA Unmix 6.0 User Guide. U.S. Environmental Protection Agency, Washington, DC, EPA/600/R-07/089 (NTIS PB2007-112630), 2007.
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The underlying philosophy of Unmix is to let the data speak for itself. Unmix seeks to solve the general mixture problem where the data are assumed to be a linear combination of an unknown number of sources of unknown composition, which contribute an unknown amount to each sample. Unmix also assumes that the compositions and contributions of the sources are all positive. Unmix
assumes that for each source there are some samples that contain little or no contribution from that source. Using concentration data for a given selection of species, Unmix estimates the number of sources, source compositions, and
source contributions to each sample.
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| PUBLISHED REPORT |
The Optimization of Thermal Optical Analysis for the Measurement of Black Carbon in Regional PM2.5: A Chemometric Approach Report |
09/27/2007
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U.S. EPA, AND J. M. Conny. The Optimization of Thermal Optical Analysis for the Measurement of Black Carbon in Regional PM2.5: A Chemometric Approach Report. U.S. Environmental Protection Agency, Washington, DC, EPA/600/R-07/119 (NTIS PB2007-114771), 2007.
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In thermal-optical analysis (TOA), particulate organic carbon (OC) as well as black carbon (BC) must be quantified. Both the BC that is native to the filter and instrument-produced OC char are products of incomplete combustion and have similar optical as well as chemical properties.
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