Robert Hoke | DuPont - Academia.edu (original) (raw)

Papers by Robert Hoke

Environmental Toxicology and Chemistry, 1995

Ecotoxicology and Environmental Safety, 1993

The assessment of contaminated sediments is a difficult task due to the complex nature of the sed... more The assessment of contaminated sediments is a difficult task due to the complex nature of the sediment matrix and the potential for exposure of aquatic organisms to in-place contaminants via several routes. Differential species sensitivity also precludes the completion of a meaningful environmental assessment with only one species. Therefore, a battery of assays approach with the Microtox assay, 48 hr Daphnia magna and Ceriodaphnia dubia tests and a 10-day Chironomous tentans test was used to evaluate the toxicity of sediment pore waters and whole sediments from the Grand Calumet River-Indiana Harbor, Indiana area of concern. All toxicity tests indicated that the test fractions (pore water, whole sediment) from each study site were toxic to the test species. A toxic units (TU) approach was used to compare measured TU from each assay with calculated TU based on chemical analyses of pore waters and whole sediments and the results of reference toxicant tests. Based on the results of these analyses, ammonia, polycyclic aromatic hydrocarbons, metals, petroleum hydrocarbons, and bicarbonate ion appear to be the major contaminants of environmental significance to benthic invertebrates within the study area.

Journal of Great Lakes Research, 1990

... supernatant. Preparation of multiple ali quants of the elutriate mixture was necessary to obt... more ... supernatant. Preparation of multiple ali quants of the elutriate mixture was necessary to obtain sufficient extract for subsequent testing. ... Ohio. Giesy, JP, Rosiu, CJ, Graney, RL, Newsted, JL, Benda, A., Kreis, Jr., RG, and Horvath, FJ, 1988a. ...

Environmental Toxicology and Chemistry, Nov 24, 2010

Animals have evolved diverse protective mechanisms for responding to toxic chemicals of both natu... more Animals have evolved diverse protective mechanisms for responding to toxic chemicals of both natural and anthropogenic origin. From a governmental regulatory perspective, these protective responses complicate efforts to establish acceptable levels of chemical exposure. To explore this issue, we considered vertebrate endocrine systems as potential targets for environmental contaminants. Using the hypothalamic-pituitary-thyroid (HPT), hypothalamic-pituitary-gonad (HPG), and hypothalamic-pituitaryadrenal (HPA) axes as case examples, we identified features of these systems that allow them to accommodate and recover from chemical insults. In doing so, a distinction was made between effects on adults and those on developing organisms. This distinction was required because endocrine system disruption in early life stages may alter development of organs and organ systems, resulting in permanent changes in phenotypic expression later in life. Risk assessments of chemicals that impact highly regulated systems must consider the dynamics of these systems in relation to complex environmental exposures. A largely unanswered question is whether successful accommodation to a toxic insult exerts a fitness cost on individual animals, resulting in adverse consequences for populations. Mechanistically based mathematical models of endocrine systems provide a means for better understanding accommodation and recovery. In the short term, these models can be used to design experiments and interpret study findings. Over the long term, a set of validated models could be used to extrapolate limited in vitro and in vivo testing data to a broader range of untested chemicals, species, and exposure scenarios. With appropriate modification, Tier 2 assays developed in support of the U.S. Environmental Protection Agency's Endocrine Disruptor Screening Program could be used to assess the potential for accommodation and recovery and inform the development of mechanistically based models.

Ecotoxicology and Environmental Safety, Aug 1, 1993

Archives of Environmental Contamination and Toxicology, Jul 1, 1993

Journal of Great Lakes Research, 1989

A BSTRA CT. The rationale and conceptual basis for the use of sediment toxicity assays are discus... more A BSTRA CT. The rationale and conceptual basis for the use of sediment toxicity assays are discussed in relationship to their use in sediment evaluations employing faunal surveys, toxicity assays, and chemical analyses. The disadvantages and advantages of various species from the major classes of aquatic organisms for use as sediment toxicity assay organisms are presented. Relative sensitivities ofselected species and their ease of laboratory culture and utility as assay organisms are used to rank assays and propose a battery of assays for the rapid screening evaluation of sediment toxicity. The usefulness of a battery of assays for the screening evaluation of sediment toxicity and statistical considerations which are important in the development of study designs and the analysis of results from the battery of proposed assays are discussed. The assays recommended for inclusion in the screening battery for evaluation of sediment toxicity are MicrotoXID, an algal assay, the Chironomus tentans lO-d growth assay, and the 48-h Daphnia magna acute assay.

Chemosphere, 1994

Mutagenicity of organic solvent extracts of contaminated sediments from a Great Lakes Area of Con... more Mutagenicity of organic solvent extracts of contaminated sediments from a Great Lakes Area of Concern (AOC) was evaluated with Ames and Mutatox ® assays. Extract mutagenicity was evaluated with and without 9metabolicactivationinbothassays.H4IIEratcellhepatomaassaysalsowereconductedontheorganicsolventextractsofthesediments.LittledirectmutagenicitywasobservedineithertheAmesorMutatox®assays,however,agreaternumberofextractswereobservedtobemutagenicafter9 metabolic activation in both assays. H4IIE rat cell hepatoma assays also were conducted on the organic solvent extracts of the sediments. Little direct mutagenicity was observed in either the Ames or Mutatox ® assays, however, a greater number of extracts were observed to be mutagenic after 9metabolicactivationinbothassays.H4IIEratcellhepatomaassaysalsowereconductedontheorganicsolventextractsofthesediments.LittledirectmutagenicitywasobservedineithertheAmesorMutatoxR◯assays,however,agreaternumberofextractswereobservedtobemutagenicafter9 metabolic activation. Although numerous potentially mutagenic compounds exist in sediments from this AOC; polycyclic aromatic hydrocarbons (PAHs) appear to be the likely cause of a major fraction of the observed mutagenicity in the Ames and Mutatox ® assays. PAHs, as opposed to compounds with a mode of action similar to 2,3,7,8-TCDD, also appear responsible for the majority of the enzyme induction observed in the H4IIE assay.

Ecotoxicology and Environmental Safety, Jun 1, 1992

Microtox assays with two different methods of osmotic adjustment were used to assess the toxicity... more Microtox assays with two different methods of osmotic adjustment were used to assess the toxicity of pore waters from 13 sediment samples collected from the Fox River watershed in Wisconsin. No toxicity was observed in Microtox assays osmotically adjusted with NacI, however, 1%min ECsO values for assays osmotically adjusted with sucrose ranged from 52 to 63% pore water. Unionized ammonia accounted for a large part of the observed toxicity, but, based on a toxic units approach, did not account for all observed toxicity. Metals (Cu, Zn) and an unidentified compound(s) may potentially contribute to the observed effects in Microtox assays osmotically adjusted with sucrose. The use of alternative osmotic adjustment techniques in the Microtox assay is one potentially useful tool for elucidating several classes of compounds responsible for effects observed in toxicity assays. 0 1992 Academic press. Inc.

Environmental Toxicology and Chemistry, 2005

An expert workshop recently was convened to consider the frog embryo teratogenesis assay-Xenopus ... more An expert workshop recently was convened to consider the frog embryo teratogenesis assay-Xenopus (FETAX) as a screening method for identifying the potential developmental toxicity of single chemicals and chemical mixtures. One recommendation from the workshop was that, in order to determine the utility of FETAX for ecological risk assessments, additional consideration of how the assay is conducted is necessary. In addition, a comparative evaluation would be useful of FETAX endpoints (i.e., survival, malformations, growth) versus each other, endpoints from aquatic toxicity tests using more commonly tested species of cladocerans and fish, and tests with other amphibian species. This review provides an evaluation and critique of the current FETAX protocol from two perspectives: Practical considerations relative to conducting the test and sensitivity of the assay (and associated endpoints) compared to tests with other species. Several aspects of the current standard protocol, including test temperature, diet, loading rates, and chemical exposure options, need to be modified to ensure that the assay is robust technically. Evaluation of FETAX data from the open literature indicates that growth is the most sensitive endpoint in the assay, followed by malformations and then survival; unfortunately, the growth endpoint often is not considered or reported in the assay. Comparison of FETAX data with acute toxicity data from tests with other amphibians or traditional aquatic test species indicates FETAX is relatively insensitive. This suggests that environmental risk assessments using acute hazard data from tests with traditional aquatic test species usually would be more protective of native amphibian species than risk assessments that use hazard data from FETAX.

Environmental Toxicology and Chemistry, Nov 1, 1995

... 0730-7268(95)00150-6 Environmental Toxicology TOXICITY AND BIOACCUMULATION OF SEDIMENT-ASSOCI... more ... 0730-7268(95)00150-6 Environmental Toxicology TOXICITY AND BIOACCUMULATION OF SEDIMENT-ASSOCIATED CONTAMINANTS USING FRESHWATER INVERTEBRATES: AREVIEW OF METHODS AND APPLICATIONS ... Nickel 780 NT 12,160 Lead &amp;amp;amp;amp;amp;amp;lt;16 NT 794 ...

Bulletin of Environmental Contamination and Toxicology, Dec 1, 1984

Freshwater sediments serve an important role in the quality of freshwater communities but have of... more Freshwater sediments serve an important role in the quality of freshwater communities but have often been neglected in community assessments. Several authors have reported freshwater systems with "healthy" water quality which support depauperate benthic faunal assemblages as a result of unobtrusive perturbations within the sediments (Prater and Anderson 1977a, Lehmkuhl 1979). As a result of increased concern over toxic substances in freshwater sediments, renewed interest has been focused on the importance of sediment quality and sediment-organism, sediment-water column interactions.

Bulletin of Environmental Contamination and Toxicology, 1981

Bulletin of Environmental Contamination and Toxicology, Dec 1, 1980

Environmental Toxicology and Chemistry, Dec 1, 1996

Surficial sediments collected from Lake Michigan (N = 46) and the Virginian Province of the east ... more Surficial sediments collected from Lake Michigan (N = 46) and the Virginian Province of the east coast of the U.S. (N = 131) by the Environmental Monitoring and Assessment Program (EMAP) of the U.S. Environmental Protection Agency (EPA) were evaluated relative to a proposed approach to sediment quality criteria (SQC) for five metals (copper, cadmium, zinc, nickel, and lead). Concentrations of acid‒volatile sulfide (AVS), simultaneously extracted metals (SEM) from the AVS extraction, total metals, and total organic carbon were measured in the sediments. Interstitial pore‒water concentrations of the five metals also were measured in the freshwater sediment samples. Overall, 91% of 131 surficial marine sediments and 50% of 46 surficial freshwater sediments contained detectable AVS. In 93 of the marine sediments the concentrations of AVS were greater than total SEM (molar sum of copper, cadmium, zinc, nickel, and lead) indicating a low probability of bioavailable metal. In contrast, 91% of the surficial freshwater samples contained greater concentrations of total SEM than AVS. However, pore‒water concentrations of the five metals in the freshwater samples were uniformly low and never exceeded 0.3 toxic units based on an additive toxicity model that utilized final chronic values from EPA water quality criteria documents for the five metals. These predictions of minimal metal bioavailability in the EMAP samples were consistent with a general lack of toxicity in laboratory assays with the sediments and with the fact that they had been collected predominantly from ostensibly uncontaminated sites.

Environmental Toxicology and Chemistry, Jun 1, 1990

Environmental studies often involve the anaIysis of many samples from a limited geographic region... more Environmental studies often involve the anaIysis of many samples from a limited geographic region. The goal of these studies frequently is to compare samples from different areas within the region to determine relative levels of contamination or adverse effects. Analysis of variance (ANOVA) followed by multiple comparison tests is an often-used data analysis technique in these situations. However, ANOVA followed by the use of linear orthogonal contrasts is a more appropriate method of data analysis if obvious groups of samples for comparison can be identified a priori. The utility of the technique is demonstrated in an analysis of the growth (dry weight) of Chironomus tentans larvae during 10-d sediment toxicity assays of sediments from western Lake Erie and the Maumee River at Toledo, Ohio. The use of linear orthogonal contrasts revealed several pertinent aspects of the data set which were not apparent after ANOVA followed by multiple range tests.

Environmental Toxicology and Chemistry, Mar 1, 1995

A sediment quality database was developed for sediments from the Great Lakes and surrounding wate... more A sediment quality database was developed for sediments from the Great Lakes and surrounding watersheds Database file structure was based on commercially available database-management software and is relational in nature Database inputs include sample identification information, whole-sediment and pore-water chemical data, benthic macroinvertebrate species abundances, toxicity test results, and, when available, organism-specific chemical residue data The database functions as both a laboratory data archival system and as a source of information on the fate and effects of contaminants in freshwater sediments Database information was used to evaluate two alternative methods for developing sediment quality criteria for dieldrin, endrin, acenaphthene, fluoranthene, and phenanthrene Sediment quality criteria developed by the U S Environmental Protection Agency based on equilibrium partitioning theory were compared to sediment quality criteria or guidelines based on screening-level concentrations calculated by the Ontario Ministry of the Environment and from the database developed in this study Data from the sediment quality database were also used to determine the frequency with which sediment quality criteria were exceeded in recently (<20 years) collected sediment samples Excesses beyond the proposed equilibrium partitioning-derived sediment quality criteria were observed in less than 10% of the samples in the database for which chemical concentrations of dieldrin, endrin, acenaphthene, fluoranthene, and phenanthrene were available. Based on the results of this study, sediment quality criteria based on equilibrium partitioning theory and final chronic water-quality criteria are consistent with sediment quality criteria based on screening-level concentrations determined from field samples.

Environmental Toxicology and Chemistry, Jul 24, 2012

A next-generation mobile automobile airconditioning (MAC) refrigerant, HFO-1234yf (CF 3 CF ¼ CH 2... more A next-generation mobile automobile airconditioning (MAC) refrigerant, HFO-1234yf (CF 3 CF ¼ CH 2), is being developed with improved environmental characteristics. In the atmosphere, it ultimately forms trifluoroacetic acid (TFA(A); CF 3 COOH), which is subsequently scavenged by precipitation and deposited on land and water as trifluoroacetate (TFA; CF 3 COO-). Trifluoroacetate is environmentally stable and has the potential to accumulate in terminal water bodies, that is, aquatic systems receiving inflow but with little or no outflow and with high rates of evaporation. Previous studies have estimated the emission rates of HFO-1234yf and have modeled the deposition concentrations and rates of TFA across North America. The present study uses multimedia modeling and geographic information system (GIS)-based modeling to assess the potential concentrations of TFA in terminal water bodies over extended periods. After 10 years of emissions, predicted concentrations of TFA in terminal water bodies across North America are estimated to range between current background levels (i.e., 0.01-0.22 mg/L) and 1 to 6 mg/L. After 50 years of continuous emissions, aquatic concentrations of 1 to 15 mg/L are predicted, with extreme concentrations of up to 50 to 200 mg/L in settings such as the Sonoran Desert along the California/Arizona (USA) border. Based on the relative insensitivity of aquatic organisms to TFA, predicted concentrations of TFA in terminal water bodies are not expected to impair aquatic systems, even considering potential emissions over extended periods. Environ. Toxicol. Chem.

Chemosphere, 1989

The Microtox R bioassay was used to evaluate the toxicity of sediment and dredge spoil elutriates... more The Microtox R bioassay was used to evaluate the toxicity of sediment and dredge spoil elutriates from several potentially-contaminated sites in Mobile and Pascagoula Bays. Elutriatcs were prepared using either local seawater or distilled deionized water (osmotically adjusted with NaCI prior to testing), and Microtox" assays were performed with the elutriates and three reference toxicants. There were marked differences in the toxicity of several elutriates and reference toxicants in the two different waters, with the seawater generally resulting in the same or lesser toxicity than the osmotically-adjusted distilled deionized water.

Toxicology Letters, Jul 10, 2007

The development of a risk management system for nanoscale or ultrafine particle-types requires a ... more The development of a risk management system for nanoscale or ultrafine particle-types requires a base set of hazard data. Assessing risk is a function of hazard and exposure data. Previously, we have suggested "parallel tracks" as a strategy for conducting nanoparticle research. On the one hand, mechanistic studies on "representative" nanoparticles could be supported by governmental agencies. Alternatively, with regard to commercial nanoparticles, the environmental, health and safety (EHS) framework would include a minimum base set of toxicity studies which should be supported by the companies that are developing nano-based products. The minimum base set could include the following criteria: substantial particle characterization, pulmonary toxicity studies, acute dermal toxicity and sensitization studies, acute oral and ocular toxicity studies, along with screening type genotoxicity, and aquatic toxicity studies. We report here the toxicity results of a base set of hazard tests on a set of newly developed, well-characterized, ultrafine TiO 2 (uf-TiO 2) particle-types. In vivo pulmonary toxicity studies in rats demonstrated low inflammatory potential and lung tissue toxicity. Acute dermal irritation studies in rabbits and local lymph node assay results in mice indicated that uf-TiO 2 was not a skin irritant or dermal sensitizer. Acute oral toxicity studies demonstrated very low toxicity and uf-TiO 2 produced short-term and reversible ocular conjunctival redness in rabbits. Genotoxicity tests demonstrated that uf-TiO 2 was negative in both the bacterial reverse mutation test and in an in vitro mammalian chromosome aberration test with Chinese hamster ovary cells. The results of aquatic toxicity screening studies demonstrated that uf-TiO 2 exhibited low concern for aquatic hazard in unaerated, 48 h, static acute tests using the water flea, Daphnia magna; exhibited low concern for aquatic hazard in unaerated, 96 h, static acute tests using the rainbow trout, Oncorhynchus mykiss; and exhibited medium concern in a 72 h acute test using the green algae Pseudokirchneriella subcapitata. To summarize the findings, the results of most of the studies demonstrated low hazard potential in mammals or aquatic species following acute exposures to the ultrafine TiO 2 particle-types tested in this program.