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Society For Risk Analysis Annual Meeting 2007
Risk 007: Agents of Analysis
Session Schedule & Abstracts
* Disclaimer: All presentations represent the views of the authors, and not the organizations that support their research. Please apply the standard disclaimer that any opinions, findings, and conclusions or recommendations in abstracts, posters, and presentations at the meeting are those of the authors and do not necessarily reflect the views of any other organization or agency. Meeting attendees and authors should be aware that this disclaimer is intended to apply to all abstracts contained in this document. Authors who wish to emphasize this disclaimer should do so in their presentation or poster. In an effort to make the abstracts as concise as possible and easy for meeting participants to read, the abstracts have been formatted such that they exclude references to papers, affiliations, and/or funding sources. Authors who wish to provide attendees with this information should do so in their presentation or poster.
Common abbreviations
M4-D |
| Chair(s): Sean Hays |
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M4-D.1 16:00 Biomonitoring Equivalents: Ground Rules for Derivation. Pyatt DW*, Hays SM, Aylward LA; Summit Toxicology, L.L.P., University of Colorado dpyatt@summittoxicology.com Abstract: Biomonitoring Equivalents (BEs) are defined as the concentration of a chemical (or metabolite) in a biological medium (blood, urine, human milk, etc.) expected at a defined exposure level, such as a Reference Dose , Reference Concentration in humans or a No Observed Effect Level in laboratory animals. The utility of the BE is to provide a screening tool for putting biomonitoring data into a health risk context. A panel of experts at the Workshop on the Derivation and Communication of Biomonitoring Equivalents discussed the various technical issues associated with calculating BEs and developed a set of guidelines for use in the derivation of BEs. Issues addressed include the appropriate application of human and animal kinetic data and models, approaches to urinary data, and relevance of mode of action to technical choices in kinetic modeling. The findings from this expert panel workshop will be presented. |
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M4-D.2 16:20 Biomonitoring Equivalents: Ground rules for communication. LaKind JS*; LaKind Associates, LLC lakindassoc@comcast.net Abstract: The development of BEs brings to the public a new concept in the field of environmental chemical exposures and health risks. A new challenge for environmental risk communication accompanies this development. A risk communication scholarship exists which can be drawn upon to inform the current issues related to communication of information surrounding the development of BEs. To a great extent, however, new ground must be broken as one delves into discussions of risk in the context of body burden, rather than exposure. Issues of personal health will justifiably be perceived as more personal, because BEs present guidance for human exposures that are measured internally, and are not based on hypothetical exposures to chemicals in the environment. Emotionally charged expressions such as “chemical trespass and body “burden” have been used to describe the presence of chemicals in the body, making communication of scientific information on risk and safety more difficult. The National Research Council refers to the “We do not know how to convey the biomarker-presence-does-not-indicate-health-effects message effectively” problem. With the development of BEs, a first step can be taken to directly address this problem. A careful description of the extent to which BEs relate to “health effects” is needed. Information from the deliberations and ground rules developed by the expert panel at the Workshop on the Derivation and Communication of BEs will be described. |
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M4-D.3 16:40 Biomonitoring Equivalents Case Studies: Putting Chemical-Specific Biomonitoring Data in a Public Health Risk Context. Hays SM*, Aylward LA, LaKind JS; Summit Toxicology shays@summittoxicology.com Abstract: Biomonitoring equivalents (BEs) are estimates of the concentration of a chemical in blood or urine that is consistent with exposure at an existing exposure guideline or toxicity value that is considered to represent a tolerable exposure (for example, a reference dose or reference concentration [RfD or RfC]} in humans or a level observed in laboratory animals associated with exposures at a point of departure or No Observed Effect Level (NOEL). This talk presents case studies of the derivation and communication of BEs for four chemicals: toluene, 2,4-D, acrylamide, and cadmium. These chemicals encompass a range of toxicologic issues (carcinogens vs. non-carcinogens, active parent vs. active metabolite) and pharmacokinetic properties (short-lived volatile compounds, metals, extensive metabolism vs. unchanged elimination, etc.). These chemicals also have a range of available pharmacokinetic data and models including data from human volunteer and occupational studies, simple one-compartment models, and human and animal PBPK models. Issues encountered in the evaluation and incorporation of the available data and models into the derivation of BE values for these compounds include evaluation of variability and uncertainty; disparities between BE values estimated for oral vs. inhalation exposure guidelines and among exposure guidelines derived by different agencies; appropriate consideration of uncertainty factors; and appropriate approaches for quantitative assessment of urinary excretion (creatinine-adjusted vs. volume basis). Challenges in communication of biomonitoring data in the context of the resulting BE values for these compounds will be discussed. |
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M4-D.4 17:00 PHYSIOLOGICALLY BASED PHARMACOKINETIC MODEL FOR MONOBUTYL PHTHALATE: INTERPRETING BIOMONITORING DATA TO ASSESS HUMAN EXPOSURE AND RISK. Campbell, Jr. JL*, Tan Y-M, Clewell RA, Clewell, III HJ; The Hamner Institutes for Health Sciences jcampbell@thehamner.org Abstract: Phthalate esters have been widely used as plasticizers and in cosmetics. In rodents, several phthalate isomers, including di-n-butyl phthalate, have been shown to disrupt normal male reproductive development at high exposure levels. Epidemiological studies attest to phthalate exposure in humans based on serum and urine measurements from samplings representative of the US population. Physiologically based pharmacokinetic (PBPK) modeling can be employed to increase our comprehension of the correlation between this biomonitoring data and environmental exposure. Extrapolation of an existing rodent PBPK model for n-dibutyl phthalate (DBP) and the primary metabolite (n-monobutyl phthalate, MBP) to humans was carried out in order to estimate the intake of DBP based on measured urinary excretion data for MBP. The predictive ability of the model was tested against published data for a single dose of labeled DBP followed by collection of a 24 h urine sample. The percent free MBP vs. conjugated MBP in urine was compared to a sub-sample of urine data collected as part of the NHANES study (CDC). The model adequately described both the amount of MBP excreted in a 24 h urine sample after a single exposure to DBP and the percent free MBP in urine. Parameter sensitivity and Monte Carlo analyses were performed to investigate sources of variability in model output. The variability in exposure (e.g., timing of meals) and time of sample collection after the last exposure to DBP were shown to contribute more to the uncertainty in model predictions than variations in pharmacokinetic parameters (e.g., body weight). The model was then applied to reconstruct daily dose for DBP based on the variability in concentrations of MBP measured in human urine from biomonitoring studies conducted by the CDC. |
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M4-D.5 17:20 Choosing chemicals to biomonitor in Californians. Dunn AJ*, Sandy MS, Zeise L; California Environmental Protection Agency adunn@oehha.ca.gov Abstract: By directly measuring levels of contaminants in the body, biomonitoring produces important information that traditional air, water and soil monitoring cannot provide. A program to measure chemicals in bodies of Californians, the California Environmental Contaminant Biomonitoring Program (CECBP), was signed into law in 2006. The CECBP will collect and analyze blood and other human biological specimens from a representative sample of Californians. The California program’s findings will be used to determine baseline levels and time trends of the sampled chemicals, and to assess the effectiveness of related public health and environmental regulatory programs. The assessment of effectiveness and actions that biomonitoring results can inform depend upon the chemicals measured. A panel of external scientists will assist the program in determining which chemicals to measure. Criteria for choosing the chemicals to biomonitor, specified in the law, include: the degree of exposure to the public or specific subgroups, the likelihood that the chemical causes cancer or other health effects, the availability of adequate laboratory methodology, and incremental cost. In this presentation, we consider chemicals that may be of interest for biomonitoring in relation to the specified criteria and the extent of data available to evaluate them. Chemicals considered include those sampled by the National Biomonitoring Program of the U.S. Centers for Disease Control and Prevention. These results may be useful not only for the CECBP, but also to other state or local agencies considering similar programs. |
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