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Banerjee S.,University of Minnesota | Ramachandran G.,University of Minnesota | Vadali M.,University of Minnesota | Sahmel J.,ChemRisk LLC
Annals of Occupational Hygiene | Year: 2014

A hierarchical Bayesian framework has been developed for exposure assessment that makes use of statistical sampling-based techniques to estimate the posterior probability of the 95th percentile or arithmetic mean of the exposure distribution being located in one of several exposure categories. The framework can synthesize professional judgment and monitoring data to yield an updated posterior exposure assignment for routine exposure management. The framework is versatile enough that it can be modified for use in epidemiological studies for classifying the arithmetic mean instead of the 95th percentile into several exposure categories. Various physico-chemical exposure models have also been incorporated in the hierarchical framework. The use of the framework in three settings has been illustrated. First, subjective judgments about exposure magnitude obtained from industrial hygienists for five tasks were treated as priors in the Bayesian framework. Monitoring data for each task were used to create a likelihood function in the hierarchical framework and the posterior was predicted in terms of the 95th percentile being located in each of the four AIHA exposure categories. The accuracy of the exposure judgments was then evaluated. Second, we illustrate the use of exposure models to develop priors in this framework and compare with monitoring data in an iron foundry. Finally, we illustrate the use of this approach for retrospective exposure assessment in a chemical manufacturing facility, to categorize exposures based on arithmetic mean instead of 95th percentile. © 2014 The Author. Source


Tvermoes B.E.,ChemRisk LLC
Food and chemical toxicology : an international journal published for the British Industrial Biological Research Association | Year: 2013

Recently, there has been an increase in the marketing and sales of dietary supplements, energy drinks, and other consumer products that may contain relatively high concentrations of essential elements. Cobalt-containing supplements are readily available in the U.S. and have been marketed to consumers as energy enhancers. However, little information is available regarding cobalt (Co) body burden and steady-state blood concentrations following the intake of Co dietary supplements. We assessed Co whole blood concentrations in four healthy adult male volunteers who ingested a commercially available Co supplement (0.4 mg Co/day) for 15 or 16 days. Pre-supplementation blood Co concentrations were less than the reporting limit of 0.5 μg/L, consistent with background concentrations reported to range between 0.1 and 0.4 μg/L. The mean whole blood Co concentration in the volunteers after 15 or 16 days of dosing was 3.6 μg Co/L and ranged from 1.8 to 5.1 μg Co/L. The mean observed concentration in the study group was approximately 9-36 times greater than background concentrations. Further studies of Co whole blood concentrations following supplementation over longer time periods with additional monitoring of physiological parameters may provide useful information for evaluating the health of persons who take various doses of Co. Copyright © 2012 Elsevier Ltd. All rights reserved. Source


Franke K.,ChemRisk LLC | Paustenbach D.,Second Street
Inhalation Toxicology | Year: 2011

We evaluated dozens of published and unpublished documents describing the knowledge and awareness of both the scientific community and governmental entities, particularly the US Navy, regarding the health hazards associated with asbestos over time. We divided our analysis into specific blocks of time: 19001929, 19301959, and 19601970. By 1930, it was clear that high occupational exposure to asbestos caused a unique disease (asbestosis). Between about 1938 and 1965, a considerable amount of exposure and epidemiology data were collected by various scientific and government organizations. Between 1960 and 1970, mesothelioma was clearly linked to exposure to amphibole asbestos. Nonetheless, the Navy continued to require the use of asbestos-containing materials on ships, but also recommended that proper precautions be taken when handling asbestos. We concluded that the Navy was arguably one of the most knowledgeable organizations in the world regarding the health hazards of asbestos, and that it attempted to implement procedures that would minimize the opportunity for adverse effects on both servicemen and civilians. Finally, it is apparent from our research that through at least 1970, neither the military nor the private sector believed that the myriad of asbestos-containing products considered "encapsulated" (e.g. gaskets, brakes, Bakelite) posed a health hazard to those working with them. © 2011 Informa Healthcare USA, Inc. Source


Paustenbach D.J.,ChemRisk LLC | Kerger B.D.,ChemRisk LLC
Chemosphere | Year: 2013

The University of Michigan Dioxin Exposure Study provides extensive data on elevated residential soil and house dust concentrations of polychlorinated dioxins and dibenzofurans (PCDD/Fs) and adult body burdens among residents near a chemical manufacturing plant in Midland, Michigan. Recent reports found no significant contribution of residential soil/dust concentrations to serum lipid PCDD/Fs in adults. Although child body burdens were not studied by the University of Michigan, internal dose modeling that incorporates recent findings on demonstrated shorter elimination half life of PCDD/Fs in children (1-2. year half life in children vs. ∼7. years in older adults) can be applied to assess this important issue. The model examines children (ages 0-7. years) with background dietary intake and exposure to residential soils at selected concentrations (10, 100 and 1000. pg/g 2,3,7,8-tetrachlorodibenzo-p-dioxin toxic equivalents, TEQ) using the congener patterns observed in Midland. Model predictions assuming 50th percentile TEQ uptake from soil/dust-related dermal and ingestion exposures indicate no measurable changes in serum lipid TEQ concentrations up to 1000. pg/g in soil/dust. Assuming 95th percentile uptake, the model shows no measurable serum lipid TEQ change up to 100. pg/g in soil/dust, but serum lipid TEQ levels rose ∼2. pg/g at 1000. pg/g in soil/dust. Since the vast majority of soil/dust data were below 100. pg/g, Michigan children exposed to such soil/dust TEQ concentrations are not reasonably expected to exhibit measurable changes in serum lipid TEQ concentrations when compared to typical background dietary exposures. With adequate data, this approach can be applied to evaluate child dose and risk for other persistent chemicals. © 2013 Elsevier Ltd. Source


Unice K.M.,ChemRisk LLC | Kreider M.L.,ChemRisk LLC | Panko J.M.,ChemRisk LLC
International Journal of Environmental Research and Public Health | Year: 2012

Pyrolysis(Pyr)-GC/MS analysis of characteristic thermal decomposition fragments has been previously used for qualitative fingerprinting of organic sources in environmental samples. A quantitative pyr-GC/MS method based on characteristic tire polymer pyrolysis products was developed for tread particle quantification in environmental matrices including soil, sediment, and air. The feasibility of quantitative pyr-GC/MS analysis of tread was confirmed in a method evaluation study using artificial soil spiked with known amounts of cryogenically generated tread. Tread concentration determined by blinded analyses was highly correlated (r2 ≥ 0.88) with the known tread spike concentration. Two critical refinements to the initial pyrolysis protocol were identified including use of an internal standard and quantification by the dimeric markers vinylcyclohexene and dipentene, which have good specificity for rubber polymer with no other appreciable environmental sources. A novel use of deuterated internal standards of similar polymeric structure was developed to correct the variable analyte recovery caused by sample size, matrix effects, and ion source variability. The resultant quantitative pyr-GC/MS protocol is reliable and transferable between laboratories. ©2012 by the authors; licensee MDPI, Basel, Switzerland. Source

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