scispace - formally typeset
Search or ask a question
Author

Stephen J. Klaine

Bio: Stephen J. Klaine is an academic researcher from Clemson University. The author has contributed to research in topics: Daphnia magna & Acute toxicity. The author has an hindex of 45, co-authored 129 publications receiving 10112 citations. Previous affiliations of Stephen J. Klaine include University of Memphis & North-West University.


Papers
More filters
Journal ArticleDOI
TL;DR: This review critiques existing nanomaterial research in freshwater, marine, and soil environments and illustrates the paucity of existing research and demonstrates the need for additional research.
Abstract: The recent advances in nanotechnology and the corresponding increase in the use of nanomaterials in products in every sector of society have resulted in uncertainties regarding environmental impacts. The objectives of this review are to introduce the key aspects pertaining to nanomaterials in the environment and to discuss what is known concerning their fate, behavior, disposition, and toxicity, with a particular focus on those that make up manufactured nanomaterials. This review critiques existing nanomaterial research in freshwater, marine, and soil environments. It illustrates the paucity of existing research and demonstrates the need for additional research. Environmental scientists are encouraged to base this research on existing studies on colloidal behavior and toxicology. The need for standard reference and testing materials as well as methodology for suspension preparation and testing is also discussed.

2,566 citations

Journal ArticleDOI
TL;DR: In this paper, an expert panel was convened to conduct a comprehensive aquatic ecological risk assessment based on several newly suggested procedures and included exposure and hazard subcomponents as well as the overall risk assessment.
Abstract: The triazine herbicide atrazine (2-chloro-4-ethylamino-6-isopropyl-amino-s-triazine) is one of the most used pesticides in North America. Atrazine is principally used for control of certain annual broadleaf and grass weeds, primarily in corn but also in sorghum, sugarcane, and, to a lesser extent, other crops and landscaping. Atrazine is found in many surface and ground waters in North America, and aquatic ecological effects are a possible concern for the regulatory and regulated communities. To address these concerns an expert panel (the Panel) was convened to conduct a comprehensive aquatic ecological risk assessment. This assessment was based on several newly suggested procedures and included exposure and hazard subcomponents as well as the overall risk assessment. The Panel determined that use of probabilistic risk assessment techniques was appropriate. Here, the results of this assessment are presented as a case study for these techniques. The environmental exposure assessment concentrated on monitoring data from Midwestern watersheds, the area of greatest atrazine use in North America. This analysis revealed that atrazine concentrations rarely exceed 20 μg/L in rivers and streams that were the main focus of the aquatic ecological risk assessment. Following storm runoff, biota in lower-order streams may be exposed to pulses of atrazine greater than 20 μg/L, but these exposures are short-lived. The assessment also considered exposures in lakes and reservoirs. The principal data set was developed by the U.S. Geological Survey, which monitored residues in 76 Midwestern reservoirs in 11 states in 1992-1993. Residue concentrations in some reservoirs were similar to those in streams but persisted longer. Atrazine residues were widespread in reservoirs (92% occurrence), and the 90th percentile of this exposure distribution for early June to July was about 5 μg/L. Mathematical simulation models of chemical fate were used to generalize the exposure analysis to other sites and to assess the potential effects of reduction in the application rates. Models were evaluated, modified, and calibrated against available monitoring data to validate that these models could predict atrazine runoff. PRZM-2 overpredicted atrazine concentrations by about an order of magnitude, whereas GLEAMS underpredicted by a factor of 2 to 5. Thus, exposure models were not used to extrapolate to other regions of atrazine use in this assessment. The effects assessment considered both freshwater and saltwater toxicity test results. Phytoplankton were the most sensitive organisms, followed, in decreasing order of sensitivity, by macrophytes, benthic invertebrates, zooplankton, and fish. Atrazine inhibits photophosphorylation but typically does not result in lethality or permanent cell damage in the short term. This characteristic of atrazine required a different model than typically used for understanding the potential impact in aquatic systems, where lethality or nonreversible effects are usually assumed. In addition, recovery of phytoplankton from exposure to 5 to 20 μg/L atrazine was demonstrated. In some mesocosm field experiments, phytoplankton and macrophytes were reduced after atrazine exposures greater than 20 μg/L. However, populations were quickly reestablished, even while atrazine residues persisted in the water. Effects in field studies were judged to be ecologically important only at exposures of 50 μg/L or greater. Mesocosm experiments did not reveal disruption of either ecosystem structure or function at atrazine concentrations typically encountered in the environment (generally 5 μg/L or less). Based on an integration of laboratory bioassay data, field effects studies, and environmental monitoring data from watersheds in high-use areas in the Midwestern United States, the Panel concluded that atrazine does not pose a significant risk to the aquatic environment. Although some inhibitory effects on algae, phytoplankton, or macrophyte production may occur in small streams vulnerable to agricultural runoff, these effects are likely to be transient, and quick recovery of the ecological system is expected. A subset of surface waters, principally small reservoirs in areas with intensive use of atrazine, may be at greater risk of exposure to atrazine. Therefore, it is recommended that site-specific risk assessments be conducted at these sites to assess possible ecological effects in the context of the uses to which these ecosystems are put and the effectiveness and cost-benefit aspect of any risk mitigation measures that may be applied.

951 citations

Journal ArticleDOI
TL;DR: It is not possible to assess the risks associated with the use of ENM by investigating only the pristine form of the ENM, without considering alterations and transformation processes, and a more definitive classification scheme for ENM should be adopted.
Abstract: The risks associated with exposure to engineered nanomaterials (ENM) will be determined in part by the processes that control their environmental fate and transformation. These processes act not only on ENM that might be released directly into the environment, but more importantly also on ENM in consumer products and those that have been released from the product. The environmental fate and transformation are likely to differ significantly for each of these cases. The ENM released from actual direct use or from nanomaterial-containing products are much more relevant for ecotoxicological studies and risk assessment than pristine ENM. Released ENM may have a greater or lesser environmental impact than the starting materials, depending on the transformation reactions and the material. Almost nothing is known about the environmental behavior and the effects of released and transformed ENM, although these are the materials that are actually present in the environment. Further research is needed to determine whether the release and transformation processes result in a similar or more diverse set of ENM and ultimately how this affects environmental behavior. This article addresses these questions, using four hypothetical case studies that cover a wide range of ENM, their direct use or product applications, and their likely fate in the environment. Furthermore, a more definitive classification scheme for ENM should be adopted that reflects their surface condition, which is a result of both industrial and environmental processes acting on the ENM. The authors conclude that it is not possible to assess the risks associated with the use of ENM by investigating only the pristine form of the ENM, without considering alterations and transformation processes. Environ. Toxicol. Chem. 2012;31:5059. (C) 2011 SETAC

552 citations

Journal ArticleDOI
TL;DR: Development of techniques for extraction, cleanup, separation, and sample storage that introduce minimal artifacts to increase the speed, sensitivity, and specificity of analytical techniques, as well as the development of techniques that can differentiate between abundant, naturally occurring particles, and manufactured nanoparticles are needed.
Abstract: Advances in the study of the environmental fate, transport, and ecotoxicological effects of engineered nanomaterials (ENMs) have been hampered by a lack of adequate techniques for the detection and quantification of ENMs at environmentally relevant concentrations in complex media. Analysis of ENMs differs from traditional chemical analysis because both chemical and physical forms must be considered. Because ENMs are present as colloidal systems, their physicochemical properties are dependent on their surroundings. Therefore, the simple act of trying to isolate, observe, and quantify ENMs may change their physicochemical properties, making analysis extremely susceptible to artifacts. Many analytical techniques applied in materials science and other chemical/biological/physical disciplines may be applied to ENM analysis as well; however, environmental and biological studies may require that methods be adapted to work at low concentrations in complex matrices. The most pressing research needs are the development of techniques for extraction, cleanup, separation, and sample storage that introduce minimal artifacts to increase the speed, sensitivity, and specificity of analytical techniques, as well as the development of techniques that can differentiate between abundant, naturally occurring particles, and manufactured nanoparticles.

446 citations

Journal ArticleDOI
TL;DR: The effects of microplastic ingestion on the freshwater amphipod, Hyalella azteca, were evaluated to evaluate the toxicological implications of the exposure of aquatic organisms to plastic particles and to quantify effects on reproduction, growth, and egestion.
Abstract: Limited information is available on the presence of microplastics in freshwater systems, and even less is known about the toxicological implications of the exposure of aquatic organisms to plastic particles. The present study was conducted to evaluate the effects of microplastic ingestion on the freshwater amphipod, Hyalella azteca. Hyalella azteca was exposed to fluorescent polyethylene microplastic particles and polypropylene microplastic fibers in individual 250-mL chambers to determine 10-d mortality. In acute bioassays, polypropylene microplastic fibers were significantly more toxic than polyethylene microplastic particles; 10-d lethal concentration 50% values for polyethylene microplastic particles and polypropylene microplastic fibers were 4.64 × 104 microplastics/mL and 71.43 microplastics/mL, respectively. A 42-d chronic bioassay using polyethylene microplastic particles was conducted to quantify effects on reproduction, growth, and egestion. Chronic exposure to polyethylene microplastic particles significantly decreased growth and reproduction at the low and intermediate exposure concentrations. During acute exposures to polyethylene microplastic particles, the egestion times did not significantly differ from the egestion of normal food materials in the control; egestion times for polypropylene microplastic fibers were significantly slower than the egestion of food materials in the control. Amphipods exposed to polypropylene microplastic fibers also had significantly less growth. The greater toxicity of microplastic fibers than microplastic particles corresponded with longer residence times for the fibers in the gut. The difference in residence time might have affected the ability to process food, resulting in an energetic effect reflected in sublethal endpoints. Environ Toxicol Chem 2015;34:2564–2572. © 2015 SETAC

432 citations


Cited by
More filters
Journal ArticleDOI
TL;DR: The mechanisms of generation and potential impacts of microplastics in the ocean environment are discussed, and the increasing levels of plastic pollution of the oceans are understood, it is important to better understand the impact of microPlastic in the Ocean food web.

4,706 citations

Journal ArticleDOI
TL;DR: This review critiques existing nanomaterial research in freshwater, marine, and soil environments and illustrates the paucity of existing research and demonstrates the need for additional research.
Abstract: The recent advances in nanotechnology and the corresponding increase in the use of nanomaterials in products in every sector of society have resulted in uncertainties regarding environmental impacts. The objectives of this review are to introduce the key aspects pertaining to nanomaterials in the environment and to discuss what is known concerning their fate, behavior, disposition, and toxicity, with a particular focus on those that make up manufactured nanomaterials. This review critiques existing nanomaterial research in freshwater, marine, and soil environments. It illustrates the paucity of existing research and demonstrates the need for additional research. Environmental scientists are encouraged to base this research on existing studies on colloidal behavior and toxicology. The need for standard reference and testing materials as well as methodology for suspension preparation and testing is also discussed.

2,566 citations

Journal ArticleDOI
TL;DR: An overview of the key aspects of graphene and related materials, ranging from fundamental research challenges to a variety of applications in a large number of sectors, highlighting the steps necessary to take GRMs from a state of raw potential to a point where they might revolutionize multiple industries are provided.
Abstract: We present the science and technology roadmap for graphene, related two-dimensional crystals, and hybrid systems, targeting an evolution in technology, that might lead to impacts and benefits reaching into most areas of society. This roadmap was developed within the framework of the European Graphene Flagship and outlines the main targets and research areas as best understood at the start of this ambitious project. We provide an overview of the key aspects of graphene and related materials (GRMs), ranging from fundamental research challenges to a variety of applications in a large number of sectors, highlighting the steps necessary to take GRMs from a state of raw potential to a point where they might revolutionize multiple industries. We also define an extensive list of acronyms in an effort to standardize the nomenclature in this emerging field.

2,560 citations

Journal ArticleDOI
TL;DR: It is concluded that when nonmonotonic dose-response curves occur, the effects of low doses cannot be predicted by the effects observed at high doses, and fundamental changes in chemical testing and safety determination are needed to protect human health.
Abstract: For decades, studies of endocrine-disrupting chemicals (EDCs) have challenged traditional concepts in toxicology, in particular the dogma of “the dose makes the poison,” because EDCs can have effects at low doses that are not predicted by effects at higher doses. Here, we review two major concepts in EDC studies: low dose and nonmonotonicity. Low-dose effects were defined by the National Toxicology Program as those that occur in the range of human exposures or effects observed at doses below those used for traditional toxicological studies. We review the mechanistic data for low-dose effects and use a weight-of-evidence approach to analyze five examples from the EDC literature. Additionally, we explore nonmonotonic dose-response curves, defined as a nonlinear relationship between dose and effect where the slope of the curve changes sign somewhere within the range of doses examined. We provide a detailed discussion of the mechanisms responsible for generating these phenomena, plus hundreds of examples from...

2,475 citations