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Paustenbach D.J.,ChemRisk LLC | Tvermoes B.E.,ChemRisk LLC | Unice K.M.,ChemRisk LLC | Finley B.L.,ChemRisk LLC | Kerger B.D.,ChemRisk LLC
Critical Reviews in Toxicology | Year: 2013

Cobalt (Co) is an essential element with ubiquitous dietary exposure and possible incremental exposure due to dietary supplements, occupation and medical devices. Adverse health effects, such as cardiomyopathy and vision or hearing impairment, were reported at peak blood Co concentrations typically over 700 g/L (8-40 weeks), while reversible hypothyroidism and polycythemia were reported in humans at ∼300 g/L and higher (2 weeks). Lung cancer risks associated with certain inhalation exposures have not been observed following Co ingestion and Co alloy implants. The mode of action for systemic toxicity relates directly to free Co(II) ion interactions with various receptors, ion channels and biomolecules resulting in generally reversible effects. Certain dose-response anomalies for Co toxicity likely relate to rare disease states known to reduce systemic Co(II)-ion binding to blood proteins. Based on the available information, most people with clearly elevated serum Co, like supplement users and hip implant patients, have >90% of Co as albumin-bound, with considerable excess binding capacity to sequester Co(II) ions. This paper reviews the scientific literature regarding the chemistry, pharmacokinetics and systemic toxicology of Co, and the likely role of free Co(II) ions to explain dose-response relationships. Based on currently available data, it might be useful to monitor implant patients for signs of hypothyroidism and polycythemia starting at blood or serum Co concentrations above 100 g/L. This concentration is derived by applying an uncertainty factor of 3 to the 300 g/L point of departure and this should adequately account for the fact that persons in the various studies were exposed for less than one year. A higher uncertainty factor could be warranted but Co has a relatively fast elimination, and many of the populations studied were of children and those with kidney problems. Closer follow-up of patients who also exhibit chronic disease states leading to clinically important hypoalbuminemia and/or severe ischemia modified albumin (IMA) elevations should be considered. © 2013 Informa UK Ltd.

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.

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.

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.

Lewis R.C.,ChemRisk LLC | Gaffney S.H.,ChemRisk LLC | Le M.H.,ChemRisk LLC | Unice K.M.,ChemRisk LLC | Paustenbach D.J.,ChemRisk LLC
International Journal of Hygiene and Environmental Health | Year: 2012

Workers handle catalysts extensively at petroleum refineries throughout the world each year; however, little information is available regarding the airborne concentrations and plausible exposures during this type of work. In this paper, we evaluated the airborne concentrations of 15 metals and total dust generated during solid catalyst loading and unloading operations at one of the largest petroleum refineries in the world using historical industrial hygiene samples collected between 1989 and 2006. The total dust and metals, which included aluminum, cadmium, chromium, cobalt, copper, iron, lead, manganese, molybdenum, nickel, platinum, silicon, silver, vanadium, and zinc, were evaluated in relation to the handling of four different types of solid catalysts associated with three major types of catalytic processes. Consideration was given to the known components of the solid catalysts and any metals that were likely deposited onto them during use. A total of 180 analytical results were included in this analysis, representing 13 personal and 54 area samples. Of the long-term personal samples, airborne concentrations of metals ranged from <0.001 to 2.9mg/m 3, and, in all but one case, resulted in concentrations below the current U.S. Occupational Safety and Health Administration's Permissible Exposure Limits and the American Conference of Governmental Industrial Hygienists' Threshold Limit Values. The arithmetic mean total dust concentration resulting from long-term personal samples was 0.31mg/m 3. The data presented here are the most complete set of its kind in the open literature, and are useful for understanding the potential exposures during solid catalyst handling activities at this petroleum refinery and perhaps other modern refineries during the timeframe examined. © 2011 Elsevier GmbH.

Panko J.M.,ChemRisk LLC | Chu J.,ChemRisk LLC | Kreider M.L.,ChemRisk LLC | Unice K.M.,ChemRisk LLC
Atmospheric Environment | Year: 2013

In addition to industrial facilities, fuel combustion, forest fires and dust erosion, exhaust and non-exhaust vehicle emissions are an important source of ambient air respirable particulate matter (PM10). Non-exhaust vehicle emissions are formed from wear particles of vehicle components such as brakes, clutches, chassis and tires. Although the non-exhaust particles are relatively minor contributors to the overall ambient air particulate load, reliable exposure estimates are few. In this study, a global sampling program was conducted to quantify tire and road wear particles (TRWP) in the ambient air in order to understand potential human exposures and the overall contribution of these particles to the PM10. The sampling was conducted in Europe, the United States and Japan and the sampling locations were selected to represent a variety of settings including both rural and urban core; and within each residential, commercial and recreational receptors. The air samples were analyzed using validated chemical markers for rubber polymer based on a pyrolysis technique. Results indicated that TRWP concentrations in the PM10 fraction were low with averages ranging from 0.05 to 0.70 μg m-3, representing an average PM10 contribution of 0.84%. The TRWP concentration in air was associated with traffic load and population density, but the trend was not statistically significant. Further, significant differences across days were not observed. This study provides a robust dataset to understand potential human exposures to airborne TRWP. © 2013 Elsevier Ltd.

Kreider M.L.,ChemRisk Inc. | Panko J.M.,ChemRisk Inc. | McAtee B.L.,ChemRisk Inc. | Sweet L.I.,ChemRisk Inc. | Finley B.L.,ChemRisk Inc.
Science of the Total Environment | Year: 2010

The purpose of this study was to characterize the physical and chemical properties of particles generated from the interaction of tires and road surfaces. Morphology, size distribution, and chemical composition were compared between particles generated using different methods, including on-road collection, laboratory generation under simulated driving conditions, and cryogenic breaking of tread rubber. Both on-road collected and laboratory generated particles exhibited the elongated shape typical of tire wear particles, whereas tread particles were more angular. Despite similar morphology for the on-road collected and the laboratory generated particles, the former were smaller on average. It is not clear at this stage if the difference is significant to the physical and chemical behavior of the particles. The chemical composition of the particles differed, with on-road generated particles containing chemical contributions from sources other than tires, such as pavement or particulates generated from other traffic-related sources. Understanding the differences between these particles is essential in apportioning contaminant contributions to the environment between tires, roadways, and other sources, and evaluating the representativeness of toxicity studies using different types of particulate generated. © 2009 Elsevier B.V. All rights reserved.

Finley B.L.,ChemRisk LLC | Monnot A.D.,ChemRisk LLC | Gaffney S.H.,ChemRisk LLC | Paustenbach D.J.,ChemRisk LLC
Journal of Toxicology and Environmental Health - Part B: Critical Reviews | Year: 2012

Cobalt (Co) is an essential component of vitamin B12. As with all metals, at sufficiently high doses, Co may exert detrimental effects on different organ systems, and adverse responses have been observed in animals, patients undergoing Co therapy, and workers exposed to respirable Co particulates. Although blood Co concentrations are postulated to be the most accurate indicator of ongoing Co exposure, little is known regarding the dose-response relationships between blood Co concentrations and adverse health effects in various organ systems. In this analysis, the animal toxicology and epidemiology literature were evaluated to identify blood Co concentrations at which effects have, and have not, been reported. Where necessary, a biokinetic model was used to convert oral doses to blood Co concentrations. Our results indicated that blood Co concentrations of 300 μg/L and less have not been associated with adverse responses of any type in humans. Concentrations of 300 μg/L and higher were associated with certain hematological and reversible endocrine responses, including polycythemia and reduced iodide uptake. Blood Co concentrations of 700-800 μg Co/L and higher may pose a risk of more serious neurological, reproductive, or cardiac effects. These blood concentrations should be useful to clinicians and toxicologists who are attempting to interpret blood Co concentrations in exposed individuals. Copyright © Taylor & Francis Group, LLC.

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.

Finley B.L.,ChemRisk LLC | Monnot A.D.,ChemRisk LLC | Paustenbach D.J.,ChemRisk LLC | Gaffney S.H.,ChemRisk LLC
Regulatory Toxicology and Pharmacology | Year: 2012

Cobalt (Co) is an essential element in humans as a component of vitamin B12. However, at high levels Co exposure has been shown to have detrimental effects. This study was designed to identify a chronic oral reference dose (RfD) for Co. Currently available data indicate that non-cancer health effects associated with Co exposure may include hematological, neurological, immunological, reproductive, cardiovascular, and endocrine responses. This analysis employs the standard US EPA risk assessment methodology for establishing a chronic RfD. In this analysis, the Jaimet and Thode (1955) 10-week, multiple dose human study of thyroid effects (decreased iodine uptake) in children was determined to be the most robust and sensitive study for identifying a potential point of departure dose (POD). A dose of 0.9. mg. Co/kg-day was chosen as the POD. Consistent with the US EPA's previous derivation of the perchlorate RfD, which is also based on decreased iodine uptake in humans, we considered several uncertainly factors (UFs), and determined that a factor of 10 for human variability was appropriate, as well as a factor of three for database adequacy. Applying an aggregate uncertainty factor of 30 to the POD yields a chronic oral RfD of 0.03. mg/kg-day. We believe this value would be protective of non-cancer health effects in the general population for a lifetime of daily exposure to Co. © 2012 Elsevier Inc.

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