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Frasch H.F.,U.S. National Institute for Occupational Safety and Health | Dotson G.S.,U.S. National Institute for Occupational Safety and Health | Bunge A.L.,Colorado School of Mines | Chen C.-P.,China Medical University at Taichung | And 6 more authors.
Journal of Exposure Science and Environmental Epidemiology | Year: 2014

A common dermal exposure assessment strategy estimates the systemic uptake of chemical in contact with skin using the fixed fractional absorption approach: the dermal absorbed dose is estimated as the product of exposure and the fraction of applied chemical that is absorbed, assumed constant for a given chemical. Despite the prominence of this approach there is little guidance regarding the evaluation of experiments from which fractional absorption data are measured. An analysis of these experiments is presented herein, and limitations to the fixed fractional absorption approach are discussed. The analysis provides a set of simple algebraic expressions that may be used in the evaluation of finite dose dermal absorption experiments, affording a more data-driven approach to dermal exposure assessment. Case studies are presented that demonstrate the application of these tools to the assessment of dermal absorption data. © 2014 Nature America, Inc.

Scott L.L.F.,ChemRisk | Scott L.L.F.,University of Minnesota | Nguyen L.M.,ChemRisk
International Archives of Occupational and Environmental Health | Year: 2011

Purpose: This study investigated the association between geographic region and blood lead levels (BLLs) in US children, as well as trends in this relationship, using data from the National Health and Nutrition Examination Survey (NHANES). Methods: SAS® and SUDAAN® software programs were utilized to develop linear regression models adjusted for several factors associated with BLLs. Results: The largest decline in BLLs was observed in Northeastern children, while the percentage of children with elevated blood lead levels decreased the most for the West and Northeast. Lead levels of Northeastern children were still higher than those of children living in the West. However, levels were not different among children residing in the Northeast, Midwest, and South, and the blood lead concentrations were less than 5 μg/dL for all but one subgroup of children and less than 2 μg/dL for >70% of the subgroups. More importantly, the effects of different risk factors for higher blood lead levels varied by region even after adjusting for all other covariates. Conclusions: The results of this study not only provide relevant and current blood lead levels for US children that can be used as reference values to evaluate biomonitoring data, but can also be used to help direct prevention and surveillance strategies to reduce lead in the environment of at-risk children. © 2011 Springer-Verlag.

Fillos D.,ChemRisk | Scott L.L.F.,ChemRisk | Scott L.L.F.,University of Minnesota | De Sylor M.A.,ChemRisk | And 3 more authors.
Environmental Toxicology and Chemistry | Year: 2012

Currently, environmental studies describing levels of polychlorinated biphenyls (PCBs) in imported shrimp are limited, particularly studies of aquaculture shrimp. In the present study, we measured concentrations of the 209 PCB congeners in 84 uncooked, warm-water shrimp samples from the United States and 14 other countries in three continents. Total PCB and dioxin-like PCB (DL-PCB) levels were not significantly different between wild-caught and farm-raised shrimp, and the distribution of total PCB levels did not vary considerably by country of origin although significant differences were observed in some cases. Regional trends in both total PCB and DL-PCB concentrations were observed, with the highest concentrations measured in shrimp from North America followed by Asia and then South America. The lower chlorinated homologues (i.e., mono-, di-, and tri-PCBs) generally comprised a greater fraction of the total levels measured in farm-raised shrimp and shrimp from Asia and South America whereas higher chlorinated homologues (i.e., hepta-, octa-, nona-, and deca-PCBs) contributed more to levels in wild-caught shrimp and shrimp from North America. Estimated daily intake of PCBs associated with shrimp consumption ranged from 2pg/kg/d (shrimp from South America) to 15pg/kg/d (shrimp from North America). Results from the present study were comparable to other studies conducted recently and demonstrate that exposure to PCBs from consumption of farm-raised and wild-caught shrimp imported from different regions are not likely to pose any health risks. © 2012 SETAC.

Marwood C.,ChemRisk Canada | Marwood C.,NovaTox Inc. | McAtee B.,ChemRisk | Kreider M.,ChemRisk | And 5 more authors.
Ecotoxicology | Year: 2011

Previous studies have indicated that tire tread particles are toxic to aquatic species, but few studies have evaluated the toxicity of such particles using sediment, the likely reservoir of tire wear particles in the environment. In this study, the acute toxicity of tire and road wear particles (TRWP) was assessed in Pseudokirchneriella subcapita, Daphnia magna, and Pimephales promelas using a sediment elutriate (100, 500, 1000 or 10000 mg/l TRWP). Under standard test temperature conditions, no concentration response was observed and EC/LC 50 values were greater than 10,000 mg/l. Additional tests using D. magna were performed both with and without sediment in elutriates collected under heated conditions designed to promote the release of chemicals from the rubber matrix to understand what environmental factors may influence the toxicity of TRWP. Toxicity was only observed for elutriates generated from TRWP leached under high-temperature conditions and the lowest EC/LC 50 value was 5,000 mg/l. In an effort to identify potential toxic chemical constituent(s) in the heated leachates, toxicity identification evaluation (TIE) studies and chemical analysis of the leachate were conducted. The TIE coupled with chemical analysis (liquid chromatography/mass spectrometry/mass spectrometry [LC/MS/MS] and inductively coupled plasma/mass spectrometry [ICP/MS]) of the leachate identified zinc and aniline as candidate toxicants. However, based on the high EC/LC 50 values and the limited conditions under which toxicity was observed, TRWP should be considered a low risk to aquatic ecosystems under acute exposure scenarios. © 2011 Springer Science+Business Media, LLC.

Panko J.M.,ChemRisk | Kreider M.L.,ChemRisk | McAtee B.L.,ChemRisk | Marwood C.,NovaTox Inc.
Ecotoxicology | Year: 2013

Tire and road wear particles (TRWP) consist of a complex mixture of rubber, and pavement released from tires during use on road surfaces. Subsequent transport of the TRWP into freshwater sediments has raised some concern about the potential adverse effects on aquatic organisms. Previous studies have shown some potential for toxicity for tread particles, however, toxicity studies of TRWP collected from a road simulator system revealed no acute toxicity to green algae, daphnids, or fathead minnows at concentrations up to 10,000 mg/kg under conditions representative of receiving water bodies. In this study, the chronic toxicity of TRWP was evaluated in four aquatic species. Test animals were exposed to whole sediment spiked with TRWP at concentrations up to 10,000 mg/kg sediment or elutriates from spiked sediment. Exposure to TRWP spiked sediment caused mild growth inhibition in Chironomus dilutus but had no adverse effect on growth or reproduction in Hyalella azteca. Exposure to TRWP elutriates resulted in slightly diminished survival in larval Pimephales promelas but had no adverse effect on growth or reproduction in Ceriodaphnia dubia. No other endpoints in these species were affected. These results, together with previous studies demonstrating no acute toxicity of TRWP, indicate that under typical exposure conditions TRWP in sediments pose a low risk of toxicity to aquatic organisms. © 2012 Springer Science+Business Media, LLC.

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