Chloroacetanilide herbicides are used worldwide to control weeds that affect crops such as corn, soybeans, and cotton. These herbicides are frequently paired with a "safener", which prevents herbicidal damage to the crop without... more
Chloroacetanilide herbicides are used worldwide to control weeds that affect crops such as corn, soybeans, and cotton. These herbicides are frequently paired with a "safener", which prevents herbicidal damage to the crop without diminishing weed control. Formulated herbicide products that include safeners and other ingredients are infrequently assessed for toxicity. The goal here was to understand the potential toxicity of safeners and herbicide + safener formulations relative to the toxicity of associated active ingredients. We quantified the concentration of safeners in commercially available formulations and tested effects on non-target algae, Raphidocelis subcapitata, when exposed to individual herbicide active ingredients, safeners, and commercial formulations. The EC50s (effective concentration causing 50% reduction in population growth) for the herbicide active ingredients S-metolachlor and acetochlor were 0.046 ppm and 0.003 ppm, respectively. Safeners benoxacor, AD-67, furilazole, and dichlormid were all substantially less toxic than the herbicides and were not toxic at environmentally relevant concentrations. Commercial formulations Dual II Magnum®, Me-Too-Lachlor II®, Harness®, and Surpass EC® all resulted in EC50 values that fell within the 95% confidence interval of the associated active ingredient herbicide. Interestingly, a significant increase on cell size was observed when algae were exposed to all the formulations, herbicides (acetochlor and S-metolachlor), and safener (dichlormid). The safener furilazole caused a significant decrease in cell size, while benoxacor and AD-67 had no observed effect on algae cell size. Significant algae cell size effects all occurred at or above the EC50 concentrations for each chemical, suggesting other morphological effects may be occurring. Importantly, safeners in commercial formulations appeared not to impact toxicity to R. subcapitata compared to the active ingredient alone. This article is protected by copyright. All rights reserved. © 2022 SETAC.
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Per‐ and polyfluoroalkyl substances (PFAS) are globally distributed and present in nearly every environmental compartment. Characterizing the chronic toxicity of individual PFAS compounds and mixtures is necessary because many have been... more
Per‐ and polyfluoroalkyl substances (PFAS) are globally distributed and present in nearly every environmental compartment. Characterizing the chronic toxicity of individual PFAS compounds and mixtures is necessary because many have been reported to cause adverse health effects. To derive toxicity reference values (TRVs) and conduct ecotoxicological risk assessments (ERAs) of PFAS‐contaminated ecosystems for wildlife, species‐specific PFAS chronic toxicity values (CTVs) are needed. The present study quantified PFAS residues from liver and eggs of birds chronically exposed to perfluorohexanoic acid (PFHxA) or a mixture of perfluorooctane sulfonate (PFOS) and PFHxA that produced a no‐observable‐adverse‐effect level (NOAEL) and/or a lowest‐observable‐adverse‐effectlevel (LOAEL). The CTVs we present are lower than those previously reported for birds and should be considered in future regulatory evaluations. From the estimated species‐ and tissue‐specific PFAS CTVs, we found that PFOS and perfluorohexane sulfonate (PFHxS) were more bioaccumulative than PFHxA in avian tissues, but PFHxA was more toxic to reproducing birds than either PFOS or a PFOS:PFHxS mixture. We further determined that avian toxicity was not necessarily additive with respect to PFAS mixtures, which could have implications for PFAS ERAs. The PFAS LOAEL CTVs can be used to predict reproductive and possible population‐level adverse health effects in wild avian receptors. Environ Toxicol Chem 2022;41:219–229. © 2021 SETAC
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To further characterize avian toxicity to environmental levels of select per‐ and poly‐fluoroalkyl substances (PFAS), we established species‐ and tissue‐specific PFAS chronic toxicity values (CTVs) associated with a... more
To further characterize avian toxicity to environmental levels of select per‐ and poly‐fluoroalkyl substances (PFAS), we established species‐ and tissue‐specific PFAS chronic toxicity values (CTVs) associated with a lowest‐observable–adverse effect level (LOAEL) threshold previously established for northern bobwhite quail (Colinus virginianus) chronically orally exposed via drinking water to either perfluorooctane sulfonate (PFOS) or a simple PFAS mixture. Aided by advances in analytical techniques, the novel avian oral PFAS CTVs reported in the present study are lower than the previously reported toxicity reference values (TRVs) estimated for birds chronically exposed via feed. Thus, current avian PFOS TRVs may not be fully protective of wild avian populations at PFAS‐impacted sites. Also, likely due to differences in bioavailability, bioaccessibility, and toxicokinetics among individual PFAS between oral exposure types, we found higher bioaccumulation factors in all assessed tissues from birds exposed via water versus feed. Thus, we propose that future characterization of chemical toxicity due to ingestion exposure initially include a full examination of all probable sources of oral exposure for the most accurate derivation of TRVs and a more complete picture of ecological risk. The avian PFAS LOAEL CTVs established in the present study can be modified with the use of uncertainty factors to derive site‐specific avian TRVs for ecological risk assessment at PFAS‐impacted sites. From differences observed in the behavior of PFOS when administered as either a single chemical or part of a binary mixture with perfluorohexane sulfonate (PFHxS), we verified that PFOS was absorbed and distributed differently when coadministered with PFHxS and that PFOS likely interacted with PFHxS differently among tissues, helping to explain the differences observed in avian toxicity between exposures. Environ Toxicol Chem 2021;40:899–909. © 2020 SETAC
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Per- and poly-fluoroalkyl substances (PFAS) are a broad class of environmentally persistent chemicals that include thousands of potentially toxic synthetic organic molecules. Some PFAS have been shown to cause adverse health effects... more
Per- and poly-fluoroalkyl substances (PFAS) are a broad class of environmentally persistent chemicals that include thousands of potentially toxic synthetic organic molecules. Some PFAS have been shown to cause adverse health effects including decreased total cholesterol, birth weight, and reproductive success in laboratory animals; however, a lack of chronic toxicity data exists for PFAS in avian ecological receptors. The present study reports the chronic toxicity of perfluorooctane sulfonic acid (PFOS) and a mixture of PFOS and perfluorohexane sulfonic acid (PFHxS) to Northern Bobwhite quail (Colinus virginianus) via oral exposure from drinking water. Female weight gain was significantly adversely affected at an average daily intake (ADI) of 3.10x10-3 ± 0.15x10-3 mg PFOS:PFHxS (1.2:1) mixture x kg-1 body weight x day-1 . Successful liberation from shell once pipped was significantly adversely affected at an ADI of 2.45x10-3 ± 0.01x10-3 mg PFOS x kg-1 body weight x day-1 . These values are comparatively much lower than the current dietary avian toxicity reference value (TRV) where birds were exposed via the feed suggesting the need for updated avian TRVs. Relationships between test chemical (PFOS) and test substance (PFOS:PFHxS) showed that PFOS and PFHxS have possible interacting effects in avian receptors and likely differing mechanisms of toxicity depending on chemical co-occurrence and dose. Both the single chemical and mixture exposures produced similar and possibly additive toxicity values. This article is protected by copyright. All rights reserved.
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ABSTRACTMosquito surveillance and pesticide treatment data can be combined in statistical models to provide insight into drivers of mosquito population dynamics. In cooperation with the county-based public health authority, multiple... more
ABSTRACTMosquito surveillance and pesticide treatment data can be combined in statistical models to provide insight into drivers of mosquito population dynamics. In cooperation with the county-based public health authority, multiple municipalities in Tarrant County, Texas, supplied surveillance and pesticide treatment data available from the 2014 mosquito season for analysis. With these data, general linear mixed modeling was used to model population dynamics of Culex quinquefasciatus, the primary vector for West Nile virus. Temporally lagged pesticide treatment information, weather data, and habitat variables were used as predictors of log + 1 transformed mosquito count data, and Akaike information criteria corrected for small sample sizes (AICc)-based model selection and multimodel averaging was used to produce a final model of mosquito abundance. The model revealed that mosquito counts were driven mainly by seasonally fluctuating temperature, precipitation, human population densi...
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Organismal energetics provide important insights into the effects of environmental toxicants. We aimed to determine the effects of pyraclostrobin on Lymnaea stagnalis by examining energy allocation patterns and life history traits.... more
Organismal energetics provide important insights into the effects of environmental toxicants. We aimed to determine the effects of pyraclostrobin on Lymnaea stagnalis by examining energy allocation patterns and life history traits. Juvenile snails exposed to pyraclostrobin decreased feeding rate and increased apparent avoidance behaviors at environmentally relevant concentrations. In adults, we found that sublethal concentrations of pyraclostrobin did not affect reproductive output, however, there were significant effects on developmental endpoints with longer time to hatch and decreased hatching success in pyraclostrobin-exposed egg masses. Further, there were apparent differences in developmental effects depending on whether mothers were also exposed to pyraclostrobin suggesting this chemical can exert intergenerational effects. Pyraclostrobin also affected protein and carbohydrate content of eggs in mothers that were exposed to pyraclostrobin. Significant effects on macronutrient content of eggs occurred at lower concentrations than effects on gross endpoints such as hatching success and time to hatch suggesting potential value for these endpoints as early indicators of ecologically relevant stress. These results provide important insight into the effects of a common fungicide on important endpoints for organismal energetics and life history.
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Intent. The intent of Learned Discourses is to provide a forum for open discussion. These articles reflect the professional opinions of the authors regarding scientific issues. They do not represent SETAC positions or policies. And,... more
Intent. The intent of Learned Discourses is to provide a forum for open discussion. These articles reflect the professional opinions of the authors regarding scientific issues. They do not represent SETAC positions or policies. And, although they are subject to editorial review for clarity, consistency, and brevity, these articles are not peer reviewed. The Learned Discourses date from 1996 in the North America SETAC News and, when that publication was replaced by the SETAC Globe, continued there through 2005. The continued success of Learned Discourses depends on our contributors. We encourage timely submissions that will inform and stimulate discussion. We expect that many of the articles will address controversial topics, and promise to give dissenting opinions a chance to be heard. Rules. All submissions must be succinct: no longer than 1000 words, no more than 6 references, and at most one table or figure. Reference format must follow the journal requirement found on the Internet at http://www.setacjournals.org. Topics must fall within IEAM’s sphere of interest. Submissions. All manuscripts should be sent via email as Word attachments to Peter M Chapman (peter_chapman@golder.com).
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Per‐ and polyfluoroalkyl substances (PFAS) are a large class of persistent chemicals used for decades in industrial and commercial applications. A key challenge with regard to estimating potential risk to ecological (and human) receptors... more
Per‐ and polyfluoroalkyl substances (PFAS) are a large class of persistent chemicals used for decades in industrial and commercial applications. A key challenge with regard to estimating potential risk to ecological (and human) receptors associated with PFAS exposure lies in the fact that there are many different PFAS compounds and several to many can co‐occur in any given environmental sample. We applied a data science approach to characterize and prioritize PFAS and PFAS mixtures from a large dataset of PFAS measurements in surface waters associated with US Air Force Installations with a history of the use of aqueous film‐forming foams (AFFFs). Several iterations of stakeholder feedback culminated in a few main points that advanced our understanding of a complex dataset and the larger ecotoxicological problem. First, perfluorooctane sulfonate (PFOS) was often a dominant PFAS in a given surface water sample, frequently followed by perfluorohexane sulfonate (PFHxS). Second, a 4‐chemical mixture generally accounted for >80% of the sum of all routinely reported PFAS in a sample, and the most representative 4‐chemical mixture was composed of PFOS, PFHxS, perfluorohexanoic acid (PFHxA), and perfluorooctanoic acid (PFOA). We suggest that these results demonstrate the utility of formalized data science analysis and assessment frameworks to address complex ecotoxicological problems. Specifically, our example dataset results can be used to provide perspective on toxicity testing, ecological risk assessments, and field studies of PFAS in and around AFFF‐impacted sites. Environ Toxicol Chem 2021;40:871–882. © 2020 SETAC
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Per- and polyfluoroalkyl substances (PFASs) continue to receive significant attention, with particular concern for PFASs such as perfluorooctane sulfonate (PFOS), which was a constituent of aqueous film-forming foam used widely as a fire... more
Per- and polyfluoroalkyl substances (PFASs) continue to receive significant attention, with particular concern for PFASs such as perfluorooctane sulfonate (PFOS), which was a constituent of aqueous film-forming foam used widely as a fire suppressant for aircraft since the 1970s. We were interested in the potential for risk to ecological receptors inhabiting Cooper Bayou, which is adjacent to 2 former fire-training areas at Barksdale Air Force Base (LA, USA). Previous research showed higher PFOS concentrations in surface water and biota from Cooper Bayou compared to reference sites. To estimate risk, we compared surface water concentrations from multiple sites within Cooper Bayou with several PFOS chronic toxicity benchmarks for freshwater aquatic organisms (∼0.4-5.1 μg PFOS/L) and showed probability of exceedances from 0.04 to 0.5, suggesting a potential for adverse effects in the most contaminated habitats. A tissue-residue assessment similarly showed some exceedance of benchmarks ...
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Perfluoroalkyl substances (PFAS) have recently received increased research attention, particularly concerning aquatic organisms and in regions of exposure to aqueous film forming foams (AFFFs). Air Force bases historically applied AFFFs... more
Perfluoroalkyl substances (PFAS) have recently received increased research attention, particularly concerning aquatic organisms and in regions of exposure to aqueous film forming foams (AFFFs). Air Force bases historically applied AFFFs in the interest of fire training exercises and have since expressed concern for PFAS contamination in biota from water bodies surrounding former fire training areas. Six PFAS were monitored, including perfluorooctane sulfonate (PFOS), in aquatic species from 8 bayou locations at Barksdale Air Force Base in Bossier City, Louisiana (USA) over the course of 1 yr. The focus was to evaluate temporal and spatial variability in PFAS concentrations from historic use of AFFF. The PFOS concentrations in fish peaked in early summer, and also increased significantly downstream of former fire training areas. Benthic organisms had lower PFOS concentrations than pelagic species, contrary to previous literature observations. Bioconcentration factors varied with time...
Research Interests: Environmental Science, Environmental Monitoring, Environmental Chemistry, Medicine, Biological Sciences, and 12 moreAquatic Ecosystem, Environmental Sciences, Humans, Animals, Fishes, Louisiana, Contamination, CHEMICAL SCIENCES, Seasons, Biota, Environmental Toxicology and Chemistry, and pelagic zone
Historically, ecological risk assessments have rarely included amphibian species, focusing preferentially on other aquatic (fish, invertebrates, algae) and terrestrial wildlife (birds and mammal) species. Often this lack of consideration... more
Historically, ecological risk assessments have rarely included amphibian species, focusing preferentially on other aquatic (fish, invertebrates, algae) and terrestrial wildlife (birds and mammal) species. Often this lack of consideration is due to a paucity of toxicity data, significant variation in study design, uncertainty with regard to exposure or a combination of all three. Productive risk assessments for amphibians are particularly challenging given variations in complex life history strategies. Further consideration is needed for the development of useful laboratory animal models and appropriate experimental test procedures which can be effectively applied to the examination of biological response patterns. Using these standardized techniques, risk estimates can be more accurately defined to ensure adequate protection of amphibians from a variety of stress agents. Patterns in toxicity may help to ascertain whether test results from one amphibian group (e.g., Urodela) could be...
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There is growing interest in improving ecological risk assessment exposure estimation, specifically by incorporating dermal exposure. At the same time, there is a growing interest in amphibians and reptiles as receptors in ecological risk... more
There is growing interest in improving ecological risk assessment exposure estimation, specifically by incorporating dermal exposure. At the same time, there is a growing interest in amphibians and reptiles as receptors in ecological risk assessment, despite generally receiving less research than more traditional receptors. Previous research has suggested that dermal exposure may be more important than previously considered for reptiles. We measured reptile skin permeability to four pesticides (thiamethoxam, malathion, tebuthiuron, trifluralin) using ventral skin samples. All four pesticides penetrated the skin but generally had low permeability. There was no apparent relationship between physicochemical properties and permeability coefficients. Malathion had a significantly greater permeability rate at all time points compared to the other pesticides. Tebuthiuron had a greater permeability than thiamethoxam. Reptiles and mammals appear to have similar skin permeability suggesting t...
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Questions: Do behavioural, morphological, and life-history responses to predators differ among offspring of laboratory and newly captured snails from the same field site? The risk allocation hypothesis states that prey should balance... more
Questions: Do behavioural, morphological, and life-history responses to predators differ among offspring of laboratory and newly captured snails from the same field site? The risk allocation hypothesis states that prey should balance predator avoidance and feeding time according to the degree of predation risk. Are there patterns in behavioural, morphological, and fitness traits that provide insight into predictions of this hypothesis? Organism: We used offspring from two parentage lines of the freshwater gastropod, Physapomilia, obtained from the exact same stream location but either (1) maintained in the laboratory for 3-4 generations or (2) newly field captured. Methods: We employed a caged-snail design in which offspring obtained from the laboratory culture and the newly field-captured snails were both exposed to a crayfish predator cue plus alarm cue for 40 days. We assessed behavioural, morphological, and fitness-related traits and conducted a short-term predator avoidance ass...
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Aedes aegypti is a globally important mosquito species because it is a principle vector of dengue, yellow fever, and chikungunya. In order to better control A. aegypti populations it’s necessary to thoroughly understand its ecology, life... more
Aedes aegypti is a globally important mosquito species because it is a principle vector of dengue, yellow fever, and chikungunya. In order to better control A. aegypti populations it’s necessary to thoroughly understand its ecology, life history traits and response to control methods (primarily insecticides). Larval density is important because it has strong effects on survival and future fitness. Density effects can result from resource competition or crowding, the latter of which has received less research attention despite its ecological importance. Both physical and chemical components cause crowding interactions in larval mosquitoes, which result in increased mortality, prolonged development, and reduced size. The objectives of this research were to determine how different crowding conditions affect insecticide sensitivity. I hypothesized that stress due to crowding would increase insecticide sensitivity and that a specific density can be determined where the combined effect be...
... DOUGLAS E. RUBY,13 LINDA C. ZIMMERMAN,14 SUSAN J. BULOVA,2 CHRISTOPHER J. SALICE,1 MICHAEL P. O'CONNOR,1 AND JAMES R. SPOTILA' 'Department of Bioscience and Biotechnology, Drexel University, Philadelphia, PA... more
... DOUGLAS E. RUBY,13 LINDA C. ZIMMERMAN,14 SUSAN J. BULOVA,2 CHRISTOPHER J. SALICE,1 MICHAEL P. O'CONNOR,1 AND JAMES R. SPOTILA' 'Department of Bioscience and Biotechnology, Drexel University, Philadelphia, PA 19104, USA 2Department ... 8 zen, 1980 ...
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Research Interests: Ecotoxicology, Biology, Genomic Imprinting, Medicine, Biological Sciences, and 13 moreEnvironmental Sciences, Animals, Predator, CHEMICAL SCIENCES, Genetic Fitness, Environmental Pollutants, Offspring, Predatory Behavior, Paternal Care, Drug Tolerance, Biomphalaria, Stress Physiological, and stressor
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Perfluoroalkyl acids (PFAAs) are environmentally persistent components of surfactants that consist of fully fluorinated carbon chains and a terminal sulfonate or carboxylate polar head moiety. Due to their unique amphiphilic properties,... more
Perfluoroalkyl acids (PFAAs) are environmentally persistent components of surfactants that consist of fully fluorinated carbon chains and a terminal sulfonate or carboxylate polar head moiety. Due to their unique amphiphilic properties, PFAAs are used in the manufacturing of products such as aqueous film forming foams (AFFF). There is cause for concern for PFAA contamination resulting from runoff and groundwater infiltration of AFFF that were used during fire training. This study analyzed water and sediment samples that were collected over a 13-month sampling period from bayous upstream and downstream of two former fire training areas located near Barksdale Air Force Base (BAFB); the occurrence and magnitude of PFAAs supported an aquatic ecological risk assessment of potential impacts of PFAAs at the site. Liquid chromatography coupled with mass spectrometry was used for determination of 6 PFAAs listed under the third Unregulated Contaminant Monitoring Rule (UCMR 3). Total PFAA conc...
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The effectiveness of many stream restorations in improving water quality is unmeasured. In the Mid-Atlantic region of the United States, activity by European settlers resulted in upland erosion and deposition of sediments 1–3 m in... more
The effectiveness of many stream restorations in improving water quality is unmeasured. In the Mid-Atlantic region of the United States, activity by European settlers resulted in upland erosion and deposition of sediments 1–3 m in thickness in stream valleys. Subsequently, streams incised those legacy sediments creating steep, exposed banks, infrequent floodplain inundation, and water tables disconnected from floodplains. Legacy sediment removal (LSR) and floodplain reconnection (FR) proposes water quality improvement by restoration to a hydrological state closer to pre-European. We investigated water quality at nine sites, six restored with LSR/FR and three comparison sites. Nitrogen baseflow concentrations and fluxes were elevated in urban and agricultural watersheds with little apparent effect due to restoration. Denitrification appeared to be constrained by carbon availability. Ion concentrations were elevated in all watersheds compared to a forested reference and represent a su...
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The Texas Horned Lizard (Phrynosoma cornutum) is found in a variety of habitats. Although several studies have been conducted on habitat use by this species, none have been performed in central Texas, a more mesic habitat than most of... more
The Texas Horned Lizard (Phrynosoma cornutum) is found in a variety of habitats. Although several studies have been conducted on habitat use by this species, none have been performed in central Texas, a more mesic habitat than most of those previously studied. This area is of special interest because horned lizard populations have been experiencing sharp declines in central Texas over the last approximately 50 years. We collected habitat data at two sites in central Texas, Camp Bowie and Blue Mountain Peak Ranch. Microhabitat data included canopy cover and ground cover from digitized photographs of Daubenmire quadrats; macrohabitat variables included vegetation height and length, cactus height, soil penetrability, woody plant species richness, tree density, tree diameter at breast height (DBH), and density of ant mounds collected along 100-m by 2-m transects. Similar patterns of habitat use were observed between the two sites. At Blue Mountain Peak Ranch, lizards appeared to be loca...
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In ecotoxicology, analytical compartmentalization analysis can be used to better understand metal sequestration and detoxification. Metals are typically found in two main compartments, biologically detoxified metal (BDM) and metal... more
In ecotoxicology, analytical compartmentalization analysis can be used to better understand metal sequestration and detoxification. Metals are typically found in two main compartments, biologically detoxified metal (BDM) and metal sensitive fractions (MSF). The purpose of this study was to analyze the subcellular distribution of cadmium (Cd) in Lymnaea stagnalis. Adult snails were exposed to three concentrations of Cd for 56 days as part of a global ring test for L. stagnalis. At the end of the 56-day exposure, organisms were separated in two sections (viscera and foot). Each section was subsequently divided by differential centrifugation into five total fractions including (metal rich granules, debris, Organelles, heat denatured proteins, and heat stable proteins) followed by Cd analysis. The concentration in each compartment, BDM, MSF, and bioconcentration factors were estimated as well. There was significantly higher bioconcentration of Cd in the viscera section compared with the...
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Ecotoxicology provides data to inform environmental management. Many testing protocols do not consider offspring fitness and toxicant sensitivity. Cadmium (Cd) is a well-studied and ubiquitous toxicant but little is known about the... more
Ecotoxicology provides data to inform environmental management. Many testing protocols do not consider offspring fitness and toxicant sensitivity. Cadmium (Cd) is a well-studied and ubiquitous toxicant but little is known about the effects on offspring of exposed parents (transgenerational effects). This study had three objectives: to identify endpoints related to offspring performance; to determine whether parental effects would manifest as a change in Cd tolerance in offspring and how parental exposure duration influenced the manifestation of parental effects. Adult snails were exposed to Cd 0, 25, 50, 100, 200 and 400 μg Cd/L for eight weeks. There were effects on adult endpoints (e.g., growth, reproduction) but only at the highest concentrations (>100 μg/L). Alternatively, we observed significant transgenerational effects at all Cd concentrations. Surprisingly, we found increased Cd tolerance in hatchlings from all parental Cd exposure concentrations even though eggs and hatc...
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The environmental effects of safeners, agrochemicals that protect crops from herbicide toxicity, are largely unknown, perhaps because they are classified as inert ingredients. We assessed the toxicity of 1) the dichloroacetamide safener... more
The environmental effects of safeners, agrochemicals that protect crops from herbicide toxicity, are largely unknown, perhaps because they are classified as inert ingredients. We assessed the toxicity of 1) the dichloroacetamide safener benoxacor, 2) its degradation product, monochloro-benoxacor, 3) the herbicide with which benoxacor is paired, S-metolachlor and 4) a mixture of S-metolachlor + benoxacor, to larvae of Chironomus riparius. Under iron-reducing conditions, benoxacor can undergo reductive dechlorination producing monochloro-benoxacor. To simulate iron-reducing conditions, we prepared benthic microcosms containing iron-rich silt-clay sediment amended with cellulose. Larval C. riparius were exposed to single chemicals via spiked sediment at nominal concentrations ranging from 0.01mg/kg to 100 mg/kg . Concentrations of a 1:1 mixture of safener and herbicide ranged from 0.02 mg/kg to 200 mg/kg . Kinetic modeling of microcosm aqueous-phase concentrations indicated that benoxa...
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The dunes sagebrush lizard (Sceloporus arenicolus) is a habitat specialist of conservation concern limited to shin oak sand dune systems of New Mexico and Texas. Because much of the dunes sagebrush lizard's habitat occurs in areas of... more
The dunes sagebrush lizard (Sceloporus arenicolus) is a habitat specialist of conservation concern limited to shin oak sand dune systems of New Mexico and Texas. Because much of the dunes sagebrush lizard's habitat occurs in areas of high oil and gas production, there may be direct and indirect effects of these activities. We used the congeneric Western fence lizard (Sceloporus occidentalis) as a surrogate species to determine direct effects of 2 contaminants associated with oil and gas drilling activities in the Permian Basin: herbicide formulations (Krovar and Quest) and hydrogen sulfide gas (H2 S). We exposed lizards to 2 concentrations of H2 S (30 or 90 ppm) and herbicide formulations (1x or 2x label application rate) representing high-end exposure scenarios. We evaluated sublethal behavioral endpoints including sprint speed and time to prey detection and capture. Neither H2 S nor herbicide formulations caused significant behavioral effects compared to controls. In order to ...
Research Interests: Petroleum, Biology, Ecology, Medicine, Biological Sciences, and 15 moreEnvironmental Sciences, Predation, Lizards, Animals, Artemisia, New Mexico, Herbicides, Lizard, CHEMICAL SCIENCES, Texas, Ecosystem, Hydrogen Sulfide, Environmental Pollutants, Environmental Toxicology and Chemistry, and Oil and Gas Industry
Background/Question/Methods Considered one of the world’s 100 most invasive species, the cane toad (Bufo marinus) has proven to be highly adaptable and difficult to extirpate. In Australia, invasive cane toads are particularly problematic... more
Background/Question/Methods Considered one of the world’s 100 most invasive species, the cane toad (Bufo marinus) has proven to be highly adaptable and difficult to extirpate. In Australia, invasive cane toads are particularly problematic with quantified negative effects on many native species. Deterministic population models have been used to examine potential impacts of different control strategies and have generally shown that removal of adults is likely most effective. However, these models have neglected to incorporate variability in vital rates despite available cane toad life history data from both native and invasive ranges. The effect that this variability may have on cane toad population models, on the life stage(s) that should be targeted for control, and on what management strategies should be pursued to control existing populations, is unknown. A stochastic stage-based population model with density dependence at the tadpole stage was constructed using life history data ...
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Perchlorate-induced inhibition of thyroidal iodide uptake was measured in normal and iodine-deficient female Sprague-Dawley rats. Rats that were made iodine-deficient by long-term restriction of iodine in the diet absorbed a gavage dose... more
Perchlorate-induced inhibition of thyroidal iodide uptake was measured in normal and iodine-deficient female Sprague-Dawley rats. Rats that were made iodine-deficient by long-term restriction of iodine in the diet absorbed a gavage dose of 131I to the thyroid in proportionally greater amounts than rats fed a normal diet. Furthermore, the iodine-deficient rats maintained their high rates of absorption even when challenged by levels of perchlorate in their drinking water sufficient to produce pronounced inhibition of 131I uptake in rats fed a normal diet. Every dose of perchlorate used in this study (1.1, 5.6, and 28 mg/L) produced significant inhibition of iodide uptake in normally fed rats, but only the highest level of perchlorate (28 mg/L) significantly inhibited thyroidal uptake of 131I in the iodine-deficient rats. Taken together, these results demonstrate that iodide-deficient animals exhibit increased resistance to the inhibition of iodine absorption resulting from perchlorate exposure.
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Considerable concentrations of the explosive, 2,4,6-trinitrotoluene (TNT) have been found in the soil at many installations where explosives have been used, manufactured, assembled, or destroyed. To evaluate risk to avian receptors,... more
Considerable concentrations of the explosive, 2,4,6-trinitrotoluene (TNT) have been found in the soil at many installations where explosives have been used, manufactured, assembled, or destroyed. To evaluate risk to avian receptors, measures of exposure are compared with a threshold level of sublethal toxicity. To date, a single feeding study has evaluated the responses of oral TNT exposure to birds with equivocal results regarding sublethal effects. The present study followed a controlled dosing regime comprising four dose groups and a control (200, 120, 70, 20, and 0 mg TNT/kg body weight [bw]-day) in the common pigeon ( Columba livia) for 60 days. Overt signs of toxicity occurred with both sexes between 2 and 3 weeks of exposure. Signs included weight loss, neuromuscular effects (e.g., ataxia, tremors, etc.), and scant red feces (chromaturia). Emetic events following dosing were common and proportional to dose; however, attempts to quantify vomitus compound concentration suggests...