Browsing by Subject "Pesticides"
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Item Open Access Developmental exposure of zebrafish to neonicotinoid pesticides: Long-term effects on neurobehavioral function.(Neurotoxicology, 2023-05) Hawkey, Andrew B; Unal, Dilanaz; Holloway, Zade R; Levin, Edward DNeonicotinoid compounds are commonly used insecticides which have become increasingly used as replacements of older generations of insecticides, such as organophosphates. Given the established neurotoxicity of cholinergic toxicants, developmental neurotoxicity studies are needed to identify in vertebrate species the potential toxicity of these insecticides which act on nicotinic cholinergic receptors. Previously, developmental exposure to a neonicotinoid insecticide imidacloprid was shown to cause persisting neurobehavioral toxicity in zebrafish. The current study evaluated neurobehavioral effects of embryonic exposure to two other neonicotinoid insecticides, clothianidin (1-100 µM) and dinotefuran (1-100 µM) in zebrafish (5-120 h post-fertilization), concentrations below the threshold for increased lethality and overt dysmorphogenesis. Neurobehavioral tests were conducted at larval (6 days), adolescent (10 weeks) and adult (8 months) ages. Both compounds caused short-term behavioral effects on larval motility, although these effects were distinct from one another. At a lower concentration (1 µM) clothianidin increased dark-induced locomotor stimulation the second time the lights turned off, while a higher concentration (100 µM) reduced activity in the dark at its second presentation. By contrast, dinotefuran (10-100 µM) caused a general decrease in locomotion. Specific longer-term neurobehavioral toxicity after early developmental exposure was also seen. clothianidin (100 µM) reduced locomotor activity in the novel tank in adolescence and adulthood, as well as reduced baseline activity in the tap startle test (1-100 µM) and reduced activity early (1-10 µM) or throughout the predator avoidance test session (100 µM). In addition to locomotor effects, clothianidin altered the diving response in a dose-, age- and time-block-dependent manner (1 µM, 100 µM), causing fish to remain further away from a fast predator cue (100 µM) relative to controls. Dinotefuran produced comparatively fewer effects, increasing the diving response in adulthood (10 µM), but not adolescence, and suppressing initial locomotor activity in the predator avoidance test (1-10 µM). These data indicate that neonicotinoid insecticides may carry some of the same risks for vertebrates posed by other classes of insecticides, and that these adverse behavioral consequences of early developmental exposure are evident well into adulthood.Item Open Access Developmental exposure to pesticides that disrupt retinoic acid signaling causes persistent retinoid and behavioral dysfunction in zebrafish.(Toxicological sciences : an official journal of the Society of Toxicology, 2024-03) Hawkey, Andrew B; Shekey, Nathan; Dean, Cassandra; Asrat, Helina; Koburov, Reese; Holloway, Zade R; Kullman, Seth W; Levin, Edward DEarly developmental exposure to environmental toxicants may play a role in the risk for developing autism. A variety of pesticides have direct effects on retinoic acid (RA) signaling and as RA signaling has important roles in neurodevelopment, such compounds may cause developmental neurotoxicity through an overlapping adverse outcome pathway. It is hypothesized that a pesticide's embryonic effects on retinoid function may correspond with neurobehavioral disruption later in development. In the current studies, we determined the effects of RA-acting pesticides on neurobehavioral development in zebrafish. Buprofezin and imazalil caused generalized hypoactivity in the larval motility test, whereas chlorothalonil and endosulfan I led to selective hypoactivity and hyperactivity, respectively. With buprofezin, chlorothalonil, and imazalil, hypoactivity and/or novel anxiety-like behaviors persisted in adulthood and buprofezin additionally decreased social attraction responses in adulthood. Endosulfan I did not produce significant adult behavioral effects. Using qPCR analyses of adult brain tissue, we observed treatment-induced alterations in RA synthesis or catabolic genes, indicating persistent changes in RA homeostasis. These changes were compound-specific, with respect to expression directionality, and potential patterns of homeostatic disruption. Results suggest the likely persistence of disruptions in RA signaling well into adulthood and may represent compensatory mechanisms following early life stage exposures. This study demonstrates that early developmental exposure to environmental toxicants that interfere with RA signaling causes short as well as long-term behavioral disruption in a well-established zebrafish behavioral model and expand upon the meaning of the RA adverse outcome pathway, indicating that observed effects likely correspond with the nature of underlying homeostatic effects.Item Open Access Evaluating Variation in Terrestrial Plant Toxicity Tests(2008-04-25T14:28:35Z) Kurnath, LindseyThe Office of Pesticide Programs of the U.S. EPA conducts the national pesticide review process, under authority granted by FIFRA. Ecological risk assessments are performed on many different organisms to identify ecosystem-level impacts. Among these organisms are non-target terrestrial plants, which are specifically used to understand the risk to plants exposed to spray drift or runoff. Guidelines were developed from field-based methods rather than a traditional interlaboratory precision analysis, thus the natural variation in measurement endpoints for terrestrial plant toxicity tests has not been established. Recognizing the inherent sensitivity of the assessments currently conducted helps the U.S. EPA better understand the implications of the pesticide review process. The following report aims to determine the natural variability of the response endpoints (i.e. emergence, plant length, plant weight) for these studies. This project involved the development and design of two databases in MS Access, the selection of control data from existing studies, an analysis of the among and within laboratory variability in response measures, and a trend analysis for environmental conditions. The findings supported the currently accepted coefficient of variation (CV) of 20% used by the U.S. EPA. All seedling emergence studies in all laboratories had average CV values of less than 40% and laboratories who were responsible for conducting a majority of the studies exhibited CV values less than 20%. Similar patterns were observed in the length data from the vegetative vigor studies. The weight data presented variation that was often greater than the expected 20% even for the most frequently tested species. The most data was available for corn and soybean plants and these species were also the least variable. The historical value of a 20% coefficient of valuation seems to be, on average, an acceptable value for the terrestrial plant toxicity tests used for pesticide registration. The data of this report indicates particular species, specifically corn and soybean, tend to have CV values closer to 10%. The addition of more data and a more sophisticated analysis into the underlying causes of variation could reveal a lower CV across all species.Item Open Access Organophosphorus Pesticide Exposure Effects on Neurobehavioral Development of Zebrafish and Characterization of Developmental Switch Between Two Cation-chloride Cotransporters (zfnkcc1 and zfkcc2)(2012) Yen, JerryOrganophosphorus pesticides (OPs) are neuroactive compounds that can affect the development of the nervous system and behavior. Using zebrafish, we compared the effectiveness of three different OPs, chlorpyrifos (CPF), diazinon (DZN) and parathion (PA) on survival, AChE inhibition and larval motility. We conclude that at equimolar concentrations CPF is the most effective OP of the three tested. 300nM CPF inhibited AChE when measured at 5 days post fertilization (dpf) by 80%, which correlated to a 35% decrease in larval motility when measured at 6 dpf.
We isolated the cDNA of zfkcc2, which encodes for an important cation-chloride cotransporter responsible for establishing a chloride gradient that allows for the neurotransmitter GABA to become inhibitory for a subset of neurons. By isolating the cDNA of zfkcc2, we were able to characterize its expression pattern up to 4 dpf. Using qRT-PCR, we showed that the expression of zfkcc2 rises from 2 to 96 hours post fertilization (hpf). The expression of zfkcc2 is found at 1 dpf in the forebrain, midbrain and hindbrain in a distinct pattern. By 3 dpf, zfkcc2 expression is found throughout most of the developing zebrafish brain. We were then able to characterize the expression pattern of zfnkcc1, which encodes for a cation-chloride cotransporter that works opposite to zfkcc2 and establishes a chloride gradient allowing GABA to be excitatory during development. Expression of zfnkcc1 is found at 1 dpf throughout most of the developing zebrafish head including in some non-neural tissue, but appears concentrated to the otic vesicle at 3 dpf. Using double in situ hybridization, we investigated the nature of the developmental switch from zfnkcc1 to zfkcc2 by looking at regions where there was an interaction between both genes' expression patterns in the developing zebrafish nervous system.
We preliminarily examined how affecting nicotinic signaling with exposures to nicotinic agonists/antagonists can affect the expression of zfnkcc2 and zfkcc2. While there were no apparent changes in the expression pattern from any of the exposures at 2 dpf, we found that by 3 dpf nicotine and CPF exposures resulted in an incomplete expression pattern for zfkcc2 that seemed to be delayed. However, the expression of zfnkcc1 at the otic vesicle was unaffected by exposure.
Our results suggest that disrupting nicotinic signaling during development can affect the expression of an important cation-chloride cotransporter, zfkcc2, that plays a major role in establishing the necessary chloride gradient for the proper functioning of GABA during development. Future studies should focus on investigating the nature of the developmental switch between zfnkcc1 and zfkcc2 to see if the possibility of their regulation being coupled is a target for exposures.
Item Open Access The toxicology of climate change: environmental contaminants in a warming world.(Environ Int, 2009-08) Noyes, Pamela D; McElwee, Matthew K; Miller, Hilary D; Clark, Bryan W; Van Tiem, Lindsey A; Walcott, Kia C; Erwin, Kyle N; Levin, Edward DClimate change induced by anthropogenic warming of the earth's atmosphere is a daunting problem. This review examines one of the consequences of climate change that has only recently attracted attention: namely, the effects of climate change on the environmental distribution and toxicity of chemical pollutants. A review was undertaken of the scientific literature (original research articles, reviews, government and intergovernmental reports) focusing on the interactions of toxicants with the environmental parameters, temperature, precipitation, and salinity, as altered by climate change. Three broad classes of chemical toxicants of global significance were the focus: air pollutants, persistent organic pollutants (POPs), including some organochlorine pesticides, and other classes of pesticides. Generally, increases in temperature will enhance the toxicity of contaminants and increase concentrations of tropospheric ozone regionally, but will also likely increase rates of chemical degradation. While further research is needed, climate change coupled with air pollutant exposures may have potentially serious adverse consequences for human health in urban and polluted regions. Climate change producing alterations in: food webs, lipid dynamics, ice and snow melt, and organic carbon cycling could result in increased POP levels in water, soil, and biota. There is also compelling evidence that increasing temperatures could be deleterious to pollutant-exposed wildlife. For example, elevated water temperatures may alter the biotransformation of contaminants to more bioactive metabolites and impair homeostasis. The complex interactions between climate change and pollutants may be particularly problematic for species living at the edge of their physiological tolerance range where acclimation capacity may be limited. In addition to temperature increases, regional precipitation patterns are projected to be altered with climate change. Regions subject to decreases in precipitation may experience enhanced volatilization of POPs and pesticides to the atmosphere. Reduced precipitation will also increase air pollution in urbanized regions resulting in negative health effects, which may be exacerbated by temperature increases. Regions subject to increased precipitation will have lower levels of air pollution, but will likely experience enhanced surface deposition of airborne POPs and increased run-off of pesticides. Moreover, increases in the intensity and frequency of storm events linked to climate change could lead to more severe episodes of chemical contamination of water bodies and surrounding watersheds. Changes in salinity may affect aquatic organisms as an independent stressor as well as by altering the bioavailability and in some instances increasing the toxicity of chemicals. A paramount issue will be to identify species and populations especially vulnerable to climate-pollutant interactions, in the context of the many other physical, chemical, and biological stressors that will be altered with climate change. Moreover, it will be important to predict tipping points that might trigger or accelerate synergistic interactions between climate change and contaminant exposures.Item Open Access Understanding Pathways to Contaminant Exposure in North Carolina’s Community Gardens(2017-04-28) Henson, Reilly; Tenorio Fenton, Sofia; Tikalsky, ElissaUrban agriculture and community gardens can be a means to increase the wellbeing of vulnerable communities, including reductions in food insecurity, opportunities for outdoor exercise and social interaction and even increases property values (Folstad et al., 2015). Unfortunately, community gardeners may potentially be exposed to contaminants through contact with soil at garden sites or through pesticide usage. There are three major factors that can increase the potential for the presence of contaminants and for subsequent exposure: i) the site's history and surrounding land uses; ii) land management practices in the garden; and iii) community gardeners' behaviors and perceptions (US EPA, 2011a). Additionally, based on previous research in North Carolina by the Duke Superfund Research Center, community gardens at risk of having contaminated soils often overlap with areas with a higher-than-average percentage of low-income and minority populations. There are, however, a number of land use practices that may reduce the potential for exposure to contaminants. In addition, individual behaviors surrounding personal hygiene, food safety, use of protective equipment, and additional precautions may also reduce the potential for exposure (Folstad et al., 2015). Our study applied a mixed methods approach to understand the extent to which community gardeners currently employ the land use management practices and individual behaviors that reduce exposure, as well as the barriers to adoption of these behaviors. Our findings will inform future efforts on the part of the Duke University Superfund Research Center to collaborate with community gardeners to reduce the potential for contaminant exposure.