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Developing and evaluating distributions for probabilistic human exposure assessments

Description: This report describes research carried out at the Lawrence Berkeley National Laboratory (LBNL) to assist the U. S. Environmental Protection Agency (EPA) in developing a consistent yet flexible approach for evaluating the inputs to probabilistic risk assessments. The U.S. EPA Office of Emergency and Remedial Response (OERR) recently released Volume 3 Part A of Risk Assessment Guidance for Superfund (RAGS), as an update to the existing two-volume set of RAGS. The update provides policy and technical guidance on performing probabilistic risk assessment (PRA). Consequently, EPA risk managers and decision-makers need to review and evaluate the adequacy of PRAs for supporting regulatory decisions. A critical part of evaluating a PRA is the problem of evaluating or judging the adequacy of input distributions PRA. Although the overarching theme of this report is the need to improve the ease and consistency of the regulatory review process, the specific objectives are presented in two parts. The objective of Part 1 is to develop a consistent yet flexible process for evaluating distributions in a PRA by identifying the critical attributes of an exposure factor distribution and discussing how these attributes relate to the task-specific adequacy of the input. This objective is carried out with emphasis on the perspective of a risk manager or decision-maker. The proposed evaluation procedure provides consistency to the review process without a loss of flexibility. As a result, the approach described in Part 1 provides an opportunity to apply a single review framework for all EPA regions and yet provide the regional risk manager with the flexibility to deal with site- and case-specific issues in the PRA process. However, as the number of inputs to a PRA increases, so does the complexity of the process for calculating, communicating and managing risk. As a result, there is increasing effort required of both ...
Date: August 1, 2002
Creator: Maddalena, Randy L. & McKone, Thomas E.
Partner: UNT Libraries Government Documents Department


Description: The effect of temperature and humidity on formaldehyde emissions from samples collected from temporary housing units (THUs) was studied. The THUs were supplied by the U.S Federal Emergency Management Administration (FEMA) to families that lost their homes in Louisiana and Mississippi during the Hurricane Katrina and Rita disasters. Based on a previous study 1, 2, four of the composite wood surface materials that dominated contributions to indoor formaldehyde were selected to analyze the effects of temperature and humidity on the emission factors. Humidity equilibration experiments were carried out on two of the samples to determine how long the samples take to equilibrate with the surrounding environmental conditions. Small chamber experiments were then conducted to measure emission factors for the four surface materials at various temperature and humidity conditions. The samples were analyzed for formaldehyde via high performance liquid chromatography. The experiments showed that increases in temperature or humidity contributed to an increase in emission factors. A linear regression model was built using natural log of percentage relative humidity (RH) and inverse of temperature (in K) as predictor variables, and natural log of emission factors as the target variable. The coefficients of both inverse temperature and log relative humidity with log emission factor were found to be statistically significant for all the samples at the 95percent confidence level. This study should assist to retrospectively estimate indoor formaldehyde exposures of occupants of temporary housing units (THUs).
Date: April 1, 2010
Creator: Parthasarathy, Srinandini; Maddalena, Randy L.; Russell, Marion L. & Apte, Michael G.
Partner: UNT Libraries Government Documents Department

Plant Uptake of Organic Pollutants from Soil: A Critical Review of Bioconcentration Estimates Based on Modelsand Experiments

Description: The role of terrestrial vegetation in transferring chemicals from soil and air into specific plant tissues (stems, leaves, roots, etc.) is still not well characterized. We provide here a critical review of plant-to-soil bioconcentration ratio (BCR) estimates based on models and experimental data. This review includes the conceptual and theoretical formulations of the bioconcentration ratio, constructing and calibrating empirical and mathematical algorithms to describe this ratio and the experimental data used to quantify BCRs and calibrate the model performance. We first evaluate the theoretical basis for the BCR concept and BCR models and consider how lack of knowledge and data limits reliability and consistency of BCR estimates. We next consider alternate modeling strategies for BCR. A key focus of this evaluation is the relative contributions to overall uncertainty from model uncertainty versus variability in the experimental data used to develop and test the models. As a case study, we consider a single chemical, hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), and focus on variability of bioconcentration measurements obtained from 81 experiments with different plant species, different plant tissues, different experimental conditions, and different methods for reporting concentrations in the soil and plant tissues. We use these observations to evaluate both the magnitude of experimental variability in plant bioconcentration and compare this to model uncertainty. Among these 81 measurements, the variation of the plant/soil BCR has a geometric standard deviation (GSD) of 3.5 and a coefficient of variability (CV-ratio of arithmetic standard deviation to mean) of 1.7. These variations are significant but low relative to model uncertainties--which have an estimated GSD of 10 with a corresponding CV of 14.
Date: January 1, 2007
Creator: McKone, Thomas E. & Maddalena, Randy L.
Partner: UNT Libraries Government Documents Department

Field Derived Emission Factors For Formaldehyde and other Volatile Organic Compounds in FEMA Temporary Housing Units

Description: Sixteen previously occupied temporary housing units (THUs) were studied to assess emissions of volatile organic compounds. The whole trailer emission factors wereevaluated for 36 VOCs including formaldehyde. Indoor sampling was carried out in the THUs located in Purvis staging yard in Mississippi, USA. Indoor temperature andrelative humidity (RH) were also measured in all the trailers during sampling. Indoor temperatures were varied (increased or decreased) in a selection of THUs using theheating, ventilation and air conditioning (HVAC) systems. Indoor temperatures during sampling ranged from 14o C to 33o C, and relative humidity (RH) varied between 35percentand 74percent. Ventilation rates were increased in some trailers using bathroom fans and vents during some of the sampling events. Ventilation rates measured during some aselection of sampling events varied from 0.14 to 4.3 h-1. Steady state indoor formaldehyde concentrations ranged from 10 mu g-m-3 to 1000 mu g-m-3. The formaldehyde concentrations in the trailers were of toxicological significance. The effects of temperature, humidity and ventilation rates were also studied. A linearregression model was built using log of percentage relative humidity, inverse of temperature (in K-1), and inverse log ACH as continuous independent variables, trailermanufacturer as a categorical independent variable, and log of the chemical emission factors as the dependent variable. The coefficients of inverse temperature, log relativehumidity, log inverse ACH with log emission factor were found to be statistically significant for all the samples at the 95percent confidence level. The regression model wasfound to explain about 84percent of the variation in the dependent variable. Most VOC concentrations measured indoors in the Purvis THUs were mostly found to be belowvalues reported in earlier studies by Maddalena et al.,1,2 Hodgson et al.,3 and Hippelein4. Emissions of TMPB-DIB (a plasticizer found in vinyl products) were found to be higher than values reported in comparable housing by Hodgson et ...
Date: October 1, 2010
Creator: Parthasarathy, Srinandini; Maddalena, Randy L.; Russell, Marion L. & Apte, Michael G.
Partner: UNT Libraries Government Documents Department

Rapid and sensitive gas chromatography ion-trap mass spectrometry method for the determination of tobacco specific N-nitrosamines in secondhand smoke

Description: Tobacco-specific nitrosamines (TSNAs) are some of the most potent carcinogens in tobacco and cigarette smoke. Accurate quantification of these chemicals is needed to help assess public health risks. We developed and validated a specific and sensitive method to measure four TSNAs in both the gas- and particle-phase of secondhand smoke (SHS) using gas chromatography and ion-trap tandem mass spectrometry,. A smoking machine in an 18-m3 room-sized chamber generated relevant concentrations of SHS that were actively sampled on Teflon coated fiber glass (TCFG) filters, and passively sampled on cellulose substrates. A simple solid-liquid extraction protocol using methanol as solvent was successfully applied to both filters with high recoveries ranging from 85 to 115percent. Tandem MS parameters were optimized to obtain the best sensitivity in terms of signal to-noise ratio (S/N) for the target compounds. For each TSNA, the major fragmentation pathways as well as ion structures were elucidated and compared with previously published data. The method showed excellent performances with a linear dynamic range between 2 and 1000 ng mL-1, low detection limits (S/N> 3) of 30-300 pg.ml-1 and precision with experimental errors below 10percent for all compounds. Moreover, no interfering peaks were observed indicating a high selectivity of MS/MS without the need for a sample clean up step. The sampling and analysis method provides a sensitive and accurate tool to detect and quantify traces of TSNA in SHS polluted indoor environments.
Date: July 1, 2009
Creator: SLEIMAN, Mohamad; MADDALENA, Randy L.; GUNDEL, Lara A. & DESTAILLATS, Hugo
Partner: UNT Libraries Government Documents Department

A Formaldehyde Exposure Assessment Tool for Occupants of FEMA Temporary Housing Units

Description: The report outlines the methodology used to develop a web-based tool to assess the formaldehyde exposure of the occupants of Federal Emergency Management Administration (FEMA) temporary housing units (THUs) after Hurricanes Katrina and Rita in 2005. Linear regression models were built using available data to retrospectively estimate the indoor temperature and relative humidity, formaldehyde emission factors and concentration, and hence the formaldehyde exposures. The interactive web-tool allows the user to define the inputs to the model to evaluate formaldehyde exposures for different scenarios.
Date: October 1, 2010
Creator: Parthasarathy, Srinandini; Spears, Michael; Maddalena, Randy L.; Russell, Marion L & Apte, Michael G.
Partner: UNT Libraries Government Documents Department

Indoor Pollutants Emitted by Electronic Office Equipment

Description: The last few decades have seen major changes in how people collect and process information at work and in their homes. More people are spending significant amounts of time in close proximity to computers, video display units, printers, fax machines and photocopiers. At the same time, efforts to improve energy efficiency in buildings by reducing leaks in building envelopes are resulting in tighter (i.e., less ventilated) indoor environments. Therefore, it is critical to understand pollutant emission rates for office equipment because even low emissions in areas that are under-ventilated or where individuals are in close proximity to the pollutant source can result in important indoor exposures. We reviewed existing literature reports on pollutant emission by office equipment, and measured emission factors of equipment with significant market share in California. We determined emission factors for a range of chemical classes including volatile and semivolatile organic compounds (VOCs and SVOCs), ozone and particulates. The measured SVOCs include phthalate esters, brominated and organophosphate flame retardants and polycyclic aromatic hydrocarbons. Measurements were carried out in large and small exposure chambers for several different categories of office equipment. Screening experiments using specific duty cycles in a large test chamber ({approx}20 m{sup 3}) allowed for the assessment of emissions for a range of pollutants. Results from the screening experiments identified pollutants and conditions that were relevant for each category of office equipment. In the second phase of the study, we used a smaller test chamber ({approx}1 m{sup 3}) to measure pollutant specific emission factors for individual devices and explored the influence of a range of environmental and operational factors on emission rates. The measured emission factors provide a data set for estimating indoor pollutant concentrations and for exploring the importance of user proximity when estimating exposure concentrations.
Date: July 1, 2008
Creator: Maddalena, Randy L.; Destaillats, Hugo; Russell, Marion L.; Hodgson, Alfred T. & McKone, Thomas E.
Partner: UNT Libraries Government Documents Department


Description: Four unoccupied FEMA temporary housing units (THUs) were studied to assess their indoor emissions of volatile organic compounds including formaldehyde. Measurement of whole-THU VOC and aldehyde emission factors (mu g h-1 per m2 of floor area) for each of the four THUs were made at FEMA's Purvis MS staging yard using a mass balance approach. Measurements were made in the morning, and again in the afternoon in each THU. Steady-state indoor formaldehyde concentrations ranged from 378 mu g m-3 (0.31ppm) to 632 mu g m-3 (0.52 ppm) in the AM, and from 433 mu g m-3 (0.35 ppm) to 926 mu g m-3 (0.78 ppm) in the PM. THU air exchange rates ranged from 0.15 h-1 to 0.39 h-1. A total of 45 small (approximately 0.025 m2) samples of surface material, 16 types, were collected directly from the four THUs and shipped to Lawrence Berkeley Laboratory. The material samples were analyzed for VOC and aldehyde emissions in small stainless steel chambers using a standard, accurate mass balance method. Quantification of VOCs was done via gas chromatography -- mass spectrometry and low molecular weight aldehydes via high performance liquid chromatography. Material specific emission factors (mu g h-1 per m2 of material) were quantified. Approximately 80 unique VOCs were tentatively identified in the THU field samples, of which forty-five were quantified either because of their toxicological significance or because their concentrations were high. Whole-trailer and material specific emission factors were calculated for 33 compounds. The THU emission factors and those from their component materials were compared against those measured from other types of housing and the materials used in their construction. Whole THU emission factors for most VOCs were typically similar to those from comparative housing. The three exceptions were exceptionally large emissions of formaldehyde and TMPD-DIB (a common plasticizer in vinyl ...
Date: May 4, 2008
Creator: Salazar, Olivia; Maddalena, Randy L.; Russell, Marion; Sullivan, Douglas P. & Apte, Michael G.
Partner: UNT Libraries Government Documents Department

Standardized approach for developing probabilistic exposure factor distributions

Description: The effectiveness of a probabilistic risk assessment (PRA) depends critically on the quality of input information that is available to the risk assessor and specifically on the probabilistic exposure factor distributions that are developed and used in the exposure and risk models. Deriving probabilistic distributions for model inputs can be time consuming and subjective. The absence of a standard approach for developing these distributions can result in PRAs that are inconsistent and difficult to review by regulatory agencies. We present an approach that reduces subjectivity in the distribution development process without limiting the flexibility needed to prepare relevant PRAs. The approach requires two steps. First, we analyze data pooled at a population scale to (1) identify the most robust demographic variables within the population for a given exposure factor, (2) partition the population data into subsets based on these variables, and (3) construct archetypal distributions for each subpopulation. Second, we sample from these archetypal distributions according to site- or scenario-specific conditions to simulate exposure factor values and use these values to construct the scenario-specific input distribution. It is envisaged that the archetypal distributions from step 1 will be generally applicable so risk assessors will not have to repeatedly collect and analyze raw data for each new assessment. We demonstrate the approach for two commonly used exposure factors--body weight (BW) and exposure duration (ED)--using data for the U.S. population. For these factors we provide a first set of subpopulation based archetypal distributions along with methodology for using these distributions to construct relevant scenario-specific probabilistic exposure factor distributions.
Date: March 2003
Creator: Maddalena, Randy L.; McKone, Thomas E. & Sohn, Michael D.
Partner: UNT Libraries Government Documents Department

Indoor pollutants emitted by office equipment: A review ofreported data and information needs

Description: There is concern that potentially harmful pollutants may be emitted from office equipment. Although office equipment has been a focal point for governmental efforts to promote energy efficiency through programs such as the US EPA's Energy Star, little is known about the relationship between office equipment use and indoor air quality, and information on pollutant emissions is sparse. In this review, we summarize available information on emission rates and/or ambient concentrations of various pollutants that are related to office equipment use. Experimental methods used in the characterization of emissions are briefly described. The office equipment evaluated in this review includes computers (desktops and notebooks), printers (laser, ink-jet and all-in-one machines) and photocopy machines. Reported emission rates of the following pollutant groups are summarized: volatile organic chemicals (VOCs), ozone, particulate matter and several semivolatile organic chemicals (SVOCs). The latter include phthalate esters, brominated flame retardants, organophosphate flame retardants and polycyclic aromatic hydrocarbons (PAHs). We also review studies reporting airborne concentrations in indoor environments where office equipment was present and thought to be a significant contributor to the total pollutant burden (offices, residences, schools, electronics recycling plants). For certain pollutants, such as organophosphate flame retardants, the link between emission by office equipment and indoor air concentrations is relatively well established. However, indoor VOCs, ozone, PAHs and phthalate esters can originate from a variety of sources, and their source apportionment is less straightforward. This literature review identifies substances of toxicological significance, with the purpose of serving as a guide to evaluate their potential importance with respect to human exposures.
Date: February 1, 2007
Creator: Destaillats, Hugo; Maddalena, Randy L.; Singer, Brett C.; Hodgson, Alfred T. & McKone, Thomas E.
Partner: UNT Libraries Government Documents Department

Indoor Air Quality Assessment of the San Francisco Federal Building

Description: An assessment of the indoor air quality (IAQ) of the San Francisco Federal Building (SFFB) was conducted on May 12 and 14, 2009 at the request of the General Services Administration (GSA). The purpose of the assessment was for a general screening of IAQ parameters typically indicative of well functioning building systems. One naturally ventilated space and one mechanically ventilated space were studied. In both zones, the levels of indoor air contaminants, including CO2, CO, particulate matter, volatile organic compounds, and aldehydes, were low, relative to reference exposure levels and air quality standards for comparable office buildings. We found slightly elevated levels of volatile organic compounds (VOCs) including two compounds often found in"green" cleaning products. In addition, we found two industrial solvents at levels higher than typically seen in office buildings, but the levels were not sufficient to be of a health concern. The ventilation rates in the two study spaces were high by any standard. Ventilation rates in the building should be further investigated and adjusted to be in line with the building design. Based on our measurements, we conclude that the IAQ is satisfactory in the zone we tested, but IAQ may need to be re-checked after the ventilation rates have been lowered.
Date: July 1, 2008
Creator: Apte, Michael; Bennett, Deborah H.; Faulkner, David; Maddalena, Randy L.; Russell, Marion L.; Spears, Michael et al.
Partner: UNT Libraries Government Documents Department

Dependence of intake fraction on release location in a multi-media framework: A case study of four contaminants in North America

Description: The extent of human exposure to persistent anthropogenic environmental contaminants is a complex function of the amount of chemical emitted, its physico-chemical properties and reactivity, the nature of the environment, and the characteristics of the pathways for human exposure, such as inhalation, intake of food and water and dermal contact. For some chemicals, the location of emissions relative to areas of high population density or intense food production may also be an important factor. The relative importance of these variables is explored using the regionally segmented BETR North America contaminant fate model and data for food production patterns and population density for North America. The model is applied to four contaminants emitted to air: benzene, carbon tetrachloride, benzo[a]pyrene and 2,3,7,8-tetrachlorodibenzo dioxin. The total continental intake fraction (iF), relating exposure quantity to emission quantity, is employed as a metric for assessing population exposure to environmental contaminants. The results show that the use of continentally averaged parameters for population density and food production provides an accurate estimate of the median of iF calculated for emissions in individual regions, however iF can range from this median by up to 3 orders of magnitude, especially for chemicals transferred to humans through the food pathway. The location of population relative to food production and emissions of chemicals are important variables that should be considered in assessing the public health implications of chemical emissions.
Date: March 1, 2003
Creator: MacLeod, Matthew; Bennett, Deborah H.; Perem, Merike; Maddalena, Randy L.; M cKone, Thomas E. & Mackay, Don
Partner: UNT Libraries Government Documents Department

Applications of contaminant fate and bioaccumulation models in assessing ecological risks of chemicals: A case study for gasoline hydrocarbons

Description: Mass balance models of chemical fate and transport can be applied in ecological risk assessments for quantitative estimation of concentrations in air, water, soil and sediment. These concentrations can, in turn, be used to estimate organism exposures and ultimately internal tissue concentrations that can be compared to mode-of-action-based critical body residues that correspond to toxic effects. From this comparison, risks to the exposed organism can be evaluated. To illustrate the practical utility of fate models in ecological risk assessments of commercial products, the EQC model and a simple screening level biouptake model including three organisms, (a bird, a mammal and a fish) is applied to gasoline. In this analysis, gasoline is divided into 24 components or ''blocks'' with similar environmental fate properties that are assumed to elicit ecotoxicity via a narcotic mode of action. Results demonstrate that differences in chemical properties and mode of entry into the environment lead to profound differences in the efficiency of transport from emission to target biota. We discuss the implications of these results and insights gained into the regional fate and ecological risks associated with gasoline. This approach is particularly suitable for assessing mixtures of components that have similar modes of action. We conclude that the model-based methodologies presented are widely applicable for screening level ecological risk assessments that support effective chemicals management.
Date: February 1, 2004
Creator: MacLeod, Matthew; McKone, Thomas E.; Foster, Karen L.; Maddalena, Randy L.; Parkerton, Thomas F. & Mackay, Don
Partner: UNT Libraries Government Documents Department