File Name: harmful effects of herbicides on the environment .zip
The herbicide glyphosate, N- phosphonomethyl glycine, has been used extensively in the past 40years, under the assumption that side effects were minimal.
As has been suggested above, some substantial benefits can be gained through the use of herbicides to manage unwanted vegetation.
During the last decades, the scientific community, including government and non-government organizations have increased their interest in detecting and controlling the environmental agents responsible for damages to the human health and sustainability of the ecosystems.
This interest has been intensified by the frightening increase on the reports of the anthropogenic action on the environment responsible for damages to the ozone layer, accidental release of wastes and radioactive gases, as well as contamination by pesticides used in agriculture. However, the growth of the human population and of the activities associated with agriculture, industrialization and urbanization have contributed to the depredation of the biodiversity and genetic variability, resulting in the compromise of several species, including man [ 9 ].
After the industrial revolution, a great number of chemical substances have been released into the terrestrial and aquatic environments and in the atmosphere. These substances can be transported and transformed by different processes, whose transformation by-products can cause adverse effects on man, as well as damages to the terrestrial and aquatic ecosystems.
Several studies have shown the presence of residues of several chemical substances in the air, water, soil, food and organisms in general [ 10 ]. Environmental pollution by genotoxic and mutagenic products affects the exposed organism and its future generations, this fact is observed both for animals, and in this case man is included, and for the other groups of organisms such as plants and microorganisms. In order to evaluate the consequences of the anthropogenic activities on the ecosystem it is necessary that the scientific community pays a special attention in the search for understanding the modes of action of xenobiotics present in the ecosystem in the biota exposed.
For this, extensive, detailed and ordered studies of the contaminants must be developed with the purpose of preventing the biological impairment, such as inductions of alterations in the genetic materials of the organisms [ 11 ].
Some studies have been performed in the attempt to evaluate the behaviour, transformations and effects of chemical agents, both in the environment and in the organisms. Toxicology establishes the limits of concentration or quantity of chemical substances acceptable in the environment by studies on the toxic effects of these substances in the organism and ecosystems [ 12 ]. Considering that the use of agrochemicals, such as herbicides, have caused a great environmental contamination, due to their widespread use, it has become indispensable to perform the assessment of the toxicity of these compounds.
Living beings are exposed to the action of numerous agents that are potentially toxic. These agents can be physical, chemical or biological and can provoke in the organisms physiological, biochemical, pathological effects and, in some cases, genetic effects [ 13 ]. A great variety of chemical substances with mutagenic potential, both natural and synthetic, have been investigated. Many of these substances are found in food, pharmaceutical drugs, pesticides and in complexes of domestic and industrial effluents.
It is known that these compounds can cause detrimental inheritable changes in the genetic material, without these changes being expressed immediately [ 14 ]. Thus, several compounds dispersed in the environment can represent danger to human health, since they present a potential to induce mutations [ 15 ].
The production of food can occur both by agricultural activities and by livestock. The yield of food production is directly related with the relationship established between the species of interest for production and the other plant, animal, microbial and parasitic biological systems that compete for resources available in the environment [ 16 ]. Among the species that jeopardize the agricultural production there are the weeds that, when invade crops, can cause significant loss in the yield and quality of the harvest [ 17 ].
Therefore, in order to enhance the productivity and the quality of crops, the removal of weeds from agriculture becomes important. Before the introduction of selective herbicides as an agricultural practice, the removal of weeds was accomplished manually in an extremely laborious form. Thus, the farmers sought other forms to control weeds, such as, integrating other weed control practices such as crop rotation, tillage and fallow systems [ 17 ].
The use of these chemical agents resulted in the increase of productivity, but, on the other hand, brought adverse consequences, since many are harmful substances for man and the environment. The world practice of using agrochemicals for long periods, often indiscriminate and abusive, has raised concerns among the public authorities and experts of public health and sustainability of natural resources [ 16 ].
Many agrochemicals are very toxic substances whose absorption in man are almost exclusively oral and can also occur by inhalation or dermally. As a consequence of the human exposure to pesticides, a series of disturbances can be observed, such as gastric, neurological and muscular [ 18 ]. Among the pesticides, the main agents of intoxication are the herbicides and insecticides.
According to Vasilescu and Medvedovici [ 19 ], herbicides are defined as any substance, individually or in mixtures, whose function is to control, destroy, repel or mitigate the growth of weeds in a crop. The use of herbicides, despite the fact that they are characterized as a highly effective tool in the control of weeds, has led to a change in the phytosociological composition of weeds and to a selection of biotypes resistant to herbicides, besides also causing impacts in the environment and human health.
According to He et al. The use of herbicides to control weeds has been a common practice in global agriculture, mainly with the objective to increase agricultural production. However, when these chemicals are used in an uncontrolled manner, they can cause impacts on non-target organisms, especially on those that live in aquatic environments [ 22 ]. According to Chevreuil et al. As a consequence of the lack of information about the action of herbicides in the biological environment, these chemical agents can also represent a problem to human health [ 26 , 27 ].
The impact of a pesticide in the environment depends on its dispersion mode and its concentration, as well as its own toxicity [ 28 ]. The mutagenic effects of the herbicides can result from several reactions with the organism, as a direct action of the compound on the nuclear DNA; incorporation in the DNA during cell replication; interference in the activity of the mitotic or meiotic division, resulting in incorrect division of the cell [ 29 ].
In animals, herbicides can act in several tissues or organs and, sometimes, are associated with tumorigenic processes [ 31 ]. Jurado et al. The disadvantages listed by the authors are: some herbicides are not biodegradable and, thus, can persist in the environment for a long period of time; all herbicides are, at least, mildly toxic; can cause diseases and even accidental death case of paraquat ; can be carried into rivers by rainwater or be leached to groundwater polluting these environments; some herbicides can accumulate in the food chain and are toxic for animals, including man.
Organic herbicides are classified according to their application method, chemical affinity, structural similarity, and by their mode of action [ 34 ]. In relation to the application methods, herbicides can be classified into two groups: soil application and foliar application. According to Jurado et al. Moreover, herbicides can be classified according to their mode of action.
Following, it will be presented the classes of herbicides, according to their mode of action, based in the classification of Moreland [ 33 ] :. Herbicides that inhibit the photo-chemically induced reactions are divided into the following classes:. Example: diuron, atrazine. Example: perfluidone. Example: 1,2,3-thiadiazol-phenylurea, nitrofen.
The herbicides classified in this group affect both the electron transport and the gradient of protons. Examples: acylanilides, dinitrophenols, imidazole, bromofenoxim. Examples: diquat, paraquat. The inhibition of carotenoid synthesis leads to the degradation of chlorophyll in the presence of light; degradation of 70s ribosomes; inhibition of the synthesis of proteins and loss of plastids. Examples: amitrole, dichlormate, SAN Examples: diphenylether herbicides. Generally, any compound that promotes the dissipation of the energy generated by the electron transport, except for the production of ATP, can be considered as uncoupler.
Example: isopropyl ester glyphosate. They combine with an intermediary in the coupling energy chain and, thus, block the phosphorylation sequence that leads to the ATP formation. No herbicide seems to act as an energy transfer inhibitor.
At low molar concentrations, herbicides fulfil almost all, if not all, of the requirements established for uncouplers, but at high concentrations they act as electron transport inhibitors. Herbicides that present this behaviour are the same classified as uncoupler inhibitors of the photoinduced reactions in the chloroplast.
When the herbicides disaggregates a membrane, they can influence directly the transport processes by interacting with the protein compounds, such as, ATPases and by altering the permeability by physicochemical interactions, or indirectly by modulating the supply of ATP needed to energize the membrane. Interactions with the membrane can cause:.
Examples: dinoben, chlorambem, perfluidone. Examples: paraquat, diquat, oryfluorfen, oryzalin. Several of the processes mentioned previously need energy and, therefore, interferences in the amount of energy caused by an herbicide could modulate the mitotic activity. The effects of the inhibitors of the cell division are dependent on the concentration and vary according to the species and the type of tissue. There is a relationship between cell division and cellular energy. In higher plants, cell division is prevented or suppressed in conditions in which the glycolysis or the oxidative phosphorylation is inhibited.
Another form of the herbicide to alter cell division would be interacting with the microtubules, since these cellular structures are responsible for the orientation and movement of chromosomes during cell division. Examples of herbicides that interfere in cell division: N-phenylcarbamates, ioxynil, trifluralin. Synthesis of DNA, RNA and protein: there are correlations between inhibition of RNA and protein synthesis and low concentration of ATP in tissues and these correlations suggest that interferences in the energy production, necessary to perform biosynthetic reactions, could be the mechanism by which the herbicides could express their effects.
Moreover, they can inhibit the synthesis of DNA or RNA by altering the chromatin integrity and, in these cases, the synthesis of proteins is also affected. Examples: glyphosate, trifluralin. The herbicides can still be classified according to the chemical affinity. Table 1 shows the chemical classes and examples of each class, according to Rao [ 34 ]. When a herbicide is used to control weeds, sometimes a majority of the compound ends up in the environment, whether it is in the soil, water, atmosphere or in the products harvested [ 17 ].
Due to the widespread use of these chemicals over the years, there has been an accumulation of these residues in the environment, which is causing alarming contaminations in the ecosystems [ 35 ] and negative damages to the biota. To Bolognesi and Merlo [ 3 ], the widespread use of herbicides has drawn the attention of researchers concerned with the risks that they can promote on the environment and human health, since they are chemicals considered contaminants commonly present in hydric resources and soils.
According to the same authors, herbicides represent a high toxicity to target species but it can be also toxic, at different levels, to non-target species, such as human beings. Herbicides can cause deleterious effects on organisms and human health, both by their direct and indirect action [ 2 ]. Among the biological effects of these chemicals, it can be cited genetic damages, diverse physiological alterations and even death of the organisms exposed.
Some herbicides, when at low concentrations, cannot cause immediate detectable effects in the organisms, but, in long term can reduce their lifespan longevity [ 4 ].
Herbicides can affect the organisms in different ways. As with other pesticides, the accumulation rate of these chemicals on biota depends on the type of the associated food chain, besides the physicochemical characteristics chemical stability, solubility, photo-decomposition, sorption in the soil of the herbicide [ 5 - 6 ].
Thus, despite the existence of several toxicological studies carried out with herbicides, in different organisms, to quantify the impacts of these pollutants and know their mechanisms of action [ 7 , 8 , 2 ], there is a great need to expand even more the knowledge about the effects of different herbicides in aquatic and terrestrial ecosystems. Data obtained from in situ , ex situ , in vivo and in vitro tests, derived from experiments of simulation, occupational exposure or environmental contaminations, need to enhance so that it is possible to obtain even more consistent information about the action of these compounds.
Thus, according to the same authors, the organisms can be then exposed to a great number of these xenobiotics as well as their metabolites. The fate of the compound in the soil depends on the characteristics of the compound and the soil. The hydrogenionic properties of a compound in the soil determines its sorption characteristics, such as, acid herbicides in soils with normal pH are negatively charged and consequently are movable in most of the soils [ 17 ].
Some groups of pesticides are neutral in soils with normal pH but due to electronic dislocations in the molecules, they can bind to soil colloids by several forms [ 36 ].
According to Kudsk and Streiberg [ 17 ], during the last two decades, several studies have been completed to predict the behaviour of pesticides in the soil. Despite the numerous efforts to assess the effects of herbicides in the soil, there are conflicting data in the literature on the subject, where some studies show that the residues of pesticides can be sources of carbon and energy to microorganisms, and then are degraded and assimilated by them, while other reports affirm that pesticides produce deleterious effects to the organisms and biochemical and enzymatic processes in the soil [ 37 ].
According to Hussain et al. Once in the soil, herbicides can suffer alteration in their structure and composition, due to the action of physical, chemical and biological processes. This action on the herbicides is the one that will determine their activity and persistence in the soil. Some molecules, when incorporated into the soil, are reduced by volatilization and photo-decomposition. Once in the soil, herbicides can suffer the action of microorganisms, which, added to the high humidity and high temperature, can have their decomposition favoured [ 38 ].
A variety of herbicides have been used, including paraquat in Mexico and Colombia, the chemical defoliant 2,4-D a constituent of Agent Orange in Burma and Bolivia, Tebuthurion trade name Spike in Peru and glyphosate trade name Roundup in Colombia. Typically, herbicides have been sprayed from aircraft so that larger areas of illicit cultivation could be destroyed. Planes used for aerial fumigation have come under fire, forcing them to fly higher than the optimum altitude of between 5 and 20 feet for application of herbicides and raising doubts about the accuracy and impact of the spraying. Concerns about human and environmental health have caused Peru, Bolivia, Ecuador and Thailand to ban the use of chemical agents for eradication. Each year millions of tons and litres of processing chemicals and materials are released into the environment, both as wastes from processing laboratories and from the destruction of confiscated chemicals. However, only one specific study on the environmental effects of these chemicals has been identified, that conducted in the Chapare region of Bolivia in Southwest Research Associates, , cited by Henkel,
The impact of pesticides consists of the effects of pesticides on non-target species. Pesticides are chemical preparations used to kill fungal or animal pests. Other problems emerge from poor production, transport and storage practices. Each pesticide or pesticide class comes with a specific set of environmental concerns. The arrival of humans in an area, to live or to conduct agriculture, necessarily has environmental impacts. These range from simple crowding out of wild plants in favor of more desirable cultivars to larger scale impacts such as reducing biodiversity by reducing food availability of native species, which can propagate across food chains. The use of agricultural chemicals such as fertilizer and pesticides magnify those impacts.
Pesticides are increasingly used worldwide and concurrently, evidence is mounting that they have detrimental ecological effects on the biodiversity of organisms in agricultural landscapes. However, pesticides are also perceived as a highly regulated group of chemicals in respect of their risk for the environment. The aim of this Research Topic, is to provide an overview of the state of knowledge regarding non-target effects of pesticides and to identify knowledge gaps. We collated in total 14 papers written by 61 authors, eight of which are original research papers and six are reviews. Many papers dealt with effects of herbicides and insecticides. Effects of glyphosate and neonicotinoids were addressed for various groups of organisms.
PDF | The herbicide glyphosate, N-(phosphonomethyl) glycine, has full understanding of their potential side effects on plants, animals and.
During the last decades, the scientific community, including government and non-government organizations have increased their interest in detecting and controlling the environmental agents responsible for damages to the human health and sustainability of the ecosystems. This interest has been intensified by the frightening increase on the reports of the anthropogenic action on the environment responsible for damages to the ozone layer, accidental release of wastes and radioactive gases, as well as contamination by pesticides used in agriculture. However, the growth of the human population and of the activities associated with agriculture, industrialization and urbanization have contributed to the depredation of the biodiversity and genetic variability, resulting in the compromise of several species, including man [ 9 ].
Это все равно что вычитать апельсины из яблок, - сказал Джабба. - Гамма-лучи против электромагнитной пульсации. Распадающиеся материалы и нераспадающиеся.
В это трудно было поверить, но она видела эти строки своими глазами.
Откуда вам это известно. - Это не имеет отношения к делу. Нуматака выдержал паузу.
Но… - Вы спутали нас с кем-то другим. У нас всего две рыженькие, Иммакулада и Росио, и ни та ни другая не станут ни с кем спать за деньги. Потому что это проституция, а она в Испании строжайше запрещена. Доброй ночи, сэр.
Лифт. Почему же не открывается дверца. Вглядевшись, она как в тумане увидела еще одну панель с буквами алфавита от А до Z и тут же вспомнила, что нужно ввести шифр.