Isolated case reports have circumstantially linked the use of the herbicide 2.4-dichlorophen-oxyacetic acid (2,4-D) to polyneuropathy. However, a critical review of the literature reveals numerous reasons for doubting...Isolated case reports have circumstantially linked the use of the herbicide 2.4-dichlorophen-oxyacetic acid (2,4-D) to polyneuropathy. However, a critical review of the literature reveals numerous reasons for doubting a relationship of 2.4-D to polyneuropathy: (1) too few cases given the wide use of the chemical: (2) no valid toxicologic or epidemiologic evidence; (3) the diversity of antecedent illness; (4) an unlikely time sequence of antecedent illness to exposure (pharmacokinetics); (5) the lack of polyneuropathy in medical patients given repetitive doses of 2.4-D; (6) the lack of polyneuropathy in heavily exposed military personnel involved in operation Ranch Hand; (7) the biological properties of 2.4-D which minimize penetration of 2.4-D into the nervous system under normal exposure conditions; and (8) the lack of polyneuropathy in a variety of experimental animal species given 2,4-D by several routes of exposure and at dose levels and durations of exposure many times greater than human applicator exposure. Thus, the weight of evidence indicates that 2.4-D is an unlikely cause of polyneuropathy. 1990 Academic Press. Inc.展开更多
Discoveries in Charles Darwin’s laboratory led to modern herbicides. Darwin discovered the internal mechanism that directed plants to grow toward sunlight and sources of water. Scientists in Europe and America later ...Discoveries in Charles Darwin’s laboratory led to modern herbicides. Darwin discovered the internal mechanism that directed plants to grow toward sunlight and sources of water. Scientists in Europe and America later called this mechanism a plant’s hormone response system. Administrators and scientists, including Dr. Ezra J. Kraus, the Head of the Botany Department at the University of Chicago and a plant physiologist, suggested on the eve of WWII that weed killers had significant military value as chemical weapons. Dr. Kraus obtained access to a synthetic chemical, 2,4-D, and found that when the chemical was absorbed through the leaves of plants, it destroyed a plant’s hormones. After exposure, the plant experienced rapid and uncontrolled growth, and then the leaves shriveled, died and fell off. Dr. Kraus obtained funding for his Department of Botany research program from Department of Defense (DOD) during World War II (WWII). Camp Detrick (Biological Weapons Laboratory) scientists later obtained samples of newly created 2,4,5-T which contained unknown amounts of the by-product dioxin TCDD. In the 1950s and 1960s, Fort Detrick military scientists formulated the herbicide Agent Orange, which was a 50 - 50 mixture of 2,4-D and 2,4,5-T. These dual purpose herbicides were used by DOD and USDA. American and European farmers in the 1940s used 2,4-D and 2,4,5-T to eliminate weeds from pastureland and cropland. After WWII, synthetic herbicides (and pesticides) development continued in tandem with production of synthetic fertilizers and breeding of high-yield plant varieties. These new agricultural products were then shipped worldwide to increase crop yields, as part of the Green Revolution. This new system of agricultural technologies was intended to eliminate global starvation and increase food security by increasing field and farm crop yields. In contrast, the goal of military use of herbicides, as chemical weapons, was to defoliate jungle forests and destroy food crops as a strategy to win battles and wars. The primary objective of this research study is to describe how agricultural herbicides became tactical chemical weapons. A current assessment will address the environmental impacts of military and environmental chemical weapons on the United States and Vietnam ecosystems and need for additional dioxin TCDD hotspot clean-up efforts.展开更多
2,4-Dichlorophenoxyacetic acid （2,4-D） was the first synthetic herbicide to be commercially developed and has commonly been used as a broadleaf herbicide for over 60 years. It is a selective herbicide that kills dic...2,4-Dichlorophenoxyacetic acid （2,4-D） was the first synthetic herbicide to be commercially developed and has commonly been used as a broadleaf herbicide for over 60 years. It is a selective herbicide that kills dicots without affecting monocots and mimics natural auxin at the molecular level. Physiological responses of dicots sensitive to auxinic herbicides include abnormal growth, senescence,and plant death. The identification of auxin receptors, auxin transport carriers, transcription factors response to auxin, and cross-talk among phytohormones have shed light on the molecular action mode of 2,4-D as a herbicide. Here, the molecular action mode of 2,4-D is highlighted according to the latest findings, emphasizing the physiological process, perception, and signal transduction under herbicide treatment.展开更多
Herbicide 2,4-D is one of the most widely used in the world.In this way,its presence on different bodies of water has been reported.In this paper the efficiency of horizontal-subsurface flow constructedwetlands for 2,...Herbicide 2,4-D is one of the most widely used in the world.In this way,its presence on different bodies of water has been reported.In this paper the efficiency of horizontal-subsurface flow constructedwetlands for 2,4-D removal in aqueous solutions was assessed.Wetlands were constructed using fiberglass,and grown with Phragmites australis.The influent consisted of synthetic wastewater under different 2,4-D and glucose initial concentrations.Results indicated that,under the evaluated experimental conditions,2,4-D extent of removal was between 71.0 and 99.0%.In general,it can be noted that an increase in the herbicide concentration reduces the removal efficiency,probably due to a toxic effect on the biological component.On the other hand,the influent dissolved organic carbon(DOC)initial concentration had a significant effect on the removal of both,the herbicide and the organic matter content in the system,demonstrating that this parameter has a significant effect on this kind of biological methods for water treatment.Finally,it can be concluded that constructed wetlands are a viable alternative for the treatment of wastewater contaminated with the herbicide 2,4-D.展开更多
文摘Isolated case reports have circumstantially linked the use of the herbicide 2.4-dichlorophen-oxyacetic acid (2,4-D) to polyneuropathy. However, a critical review of the literature reveals numerous reasons for doubting a relationship of 2.4-D to polyneuropathy: (1) too few cases given the wide use of the chemical: (2) no valid toxicologic or epidemiologic evidence; (3) the diversity of antecedent illness; (4) an unlikely time sequence of antecedent illness to exposure (pharmacokinetics); (5) the lack of polyneuropathy in medical patients given repetitive doses of 2.4-D; (6) the lack of polyneuropathy in heavily exposed military personnel involved in operation Ranch Hand; (7) the biological properties of 2.4-D which minimize penetration of 2.4-D into the nervous system under normal exposure conditions; and (8) the lack of polyneuropathy in a variety of experimental animal species given 2,4-D by several routes of exposure and at dose levels and durations of exposure many times greater than human applicator exposure. Thus, the weight of evidence indicates that 2.4-D is an unlikely cause of polyneuropathy. 1990 Academic Press. Inc.
文摘Discoveries in Charles Darwin’s laboratory led to modern herbicides. Darwin discovered the internal mechanism that directed plants to grow toward sunlight and sources of water. Scientists in Europe and America later called this mechanism a plant’s hormone response system. Administrators and scientists, including Dr. Ezra J. Kraus, the Head of the Botany Department at the University of Chicago and a plant physiologist, suggested on the eve of WWII that weed killers had significant military value as chemical weapons. Dr. Kraus obtained access to a synthetic chemical, 2,4-D, and found that when the chemical was absorbed through the leaves of plants, it destroyed a plant’s hormones. After exposure, the plant experienced rapid and uncontrolled growth, and then the leaves shriveled, died and fell off. Dr. Kraus obtained funding for his Department of Botany research program from Department of Defense (DOD) during World War II (WWII). Camp Detrick (Biological Weapons Laboratory) scientists later obtained samples of newly created 2,4,5-T which contained unknown amounts of the by-product dioxin TCDD. In the 1950s and 1960s, Fort Detrick military scientists formulated the herbicide Agent Orange, which was a 50 - 50 mixture of 2,4-D and 2,4,5-T. These dual purpose herbicides were used by DOD and USDA. American and European farmers in the 1940s used 2,4-D and 2,4,5-T to eliminate weeds from pastureland and cropland. After WWII, synthetic herbicides (and pesticides) development continued in tandem with production of synthetic fertilizers and breeding of high-yield plant varieties. These new agricultural products were then shipped worldwide to increase crop yields, as part of the Green Revolution. This new system of agricultural technologies was intended to eliminate global starvation and increase food security by increasing field and farm crop yields. In contrast, the goal of military use of herbicides, as chemical weapons, was to defoliate jungle forests and destroy food crops as a strategy to win battles and wars. The primary objective of this research study is to describe how agricultural herbicides became tactical chemical weapons. A current assessment will address the environmental impacts of military and environmental chemical weapons on the United States and Vietnam ecosystems and need for additional dioxin TCDD hotspot clean-up efforts.
文摘2,4-Dichlorophenoxyacetic acid （2,4-D） was the first synthetic herbicide to be commercially developed and has commonly been used as a broadleaf herbicide for over 60 years. It is a selective herbicide that kills dicots without affecting monocots and mimics natural auxin at the molecular level. Physiological responses of dicots sensitive to auxinic herbicides include abnormal growth, senescence,and plant death. The identification of auxin receptors, auxin transport carriers, transcription factors response to auxin, and cross-talk among phytohormones have shed light on the molecular action mode of 2,4-D as a herbicide. Here, the molecular action mode of 2,4-D is highlighted according to the latest findings, emphasizing the physiological process, perception, and signal transduction under herbicide treatment.
基金The authors want to thank the Universidad de Antioquia for itstechnical and financial support to this project.
文摘Herbicide 2,4-D is one of the most widely used in the world.In this way,its presence on different bodies of water has been reported.In this paper the efficiency of horizontal-subsurface flow constructedwetlands for 2,4-D removal in aqueous solutions was assessed.Wetlands were constructed using fiberglass,and grown with Phragmites australis.The influent consisted of synthetic wastewater under different 2,4-D and glucose initial concentrations.Results indicated that,under the evaluated experimental conditions,2,4-D extent of removal was between 71.0 and 99.0%.In general,it can be noted that an increase in the herbicide concentration reduces the removal efficiency,probably due to a toxic effect on the biological component.On the other hand,the influent dissolved organic carbon(DOC)initial concentration had a significant effect on the removal of both,the herbicide and the organic matter content in the system,demonstrating that this parameter has a significant effect on this kind of biological methods for water treatment.Finally,it can be concluded that constructed wetlands are a viable alternative for the treatment of wastewater contaminated with the herbicide 2,4-D.
