University of Kerbala
Assit Prof Dr. Ban Mousa Hassan
College of Education pure science
Pesticides are defined as any substance or mixture of substances that works to prevent, destroy, expel, reduce or eliminate any pest, whether it is insects, rodents, nematodes, fungi, weeds, wild or aquatic plants, viruses, bacteria or any microorganisms .And because pesticides are basically toxic substances, they are divided into several sections, but the division may differ according to its purpose, for example, the division may be according to the type of target pest (insecticides, fungicides —- etc.) or according to the chemical composition of the pesticide, it is divided It is divided into organic and inorganic pesticides, and there are various sub-groups within each section. The division may be according to the degree of their toxicity to mammals (severe harm, moderate harm, and little harm based on the values of the lethal half doses), and the division may also be according to the mechanism of action (mechanism of action events or according to the method entry of the pesticide into the target pest).
Despite the great benefits of pesticides that have accrued to humans, they are very dangerous in the event of their excessive use, because of their negative effects on life and the environment in general. The use of any compound that has biological activity is expected to result in poisoning problems in one way or another. For example, we find that the people most affected by pesticides are those who deal with them directly, such as workers in the field of manufacturing and processing or spray workers.
In addition, if the use of the pesticide is within the domestic scope, whether inside or outside, then the individuals within this scope will also be affected, and the use of the pesticide at any stage of food production will have residues (the original compound or its derivatives or metabolites or degradation products) in a manner It is fixed on food and then fed on it. Therefore, any of the living organisms, including humans, is exposed to the residues of that pesticide and thus may be affected in some way depending on the type of pesticide, method of use, concentration, degree of stability, and the amount of its toxicity. Its effects may reach (paralysis, liver failure, kidney failure, Hormonal imbalance, nervous tension, insomnia —etc.).There may also be a conflict between what the pesticide causes and its side effects, which cannot be avoided. Hence, specialists in the field of toxicology found their interest in evaluating the problems arising from the use of pesticides and finding methods that would prevent harm and reach the development of special methods for treating disease conditions after they appear.The types of toxicity (poisoning) can be divided according to the nature of the damage and the time period it takes for the pesticide to cause that damage after the completion of the process of exposure to a dose of the pesticide. Sensitivity or in the form of a decrease or increase in the activity of a particular enzyme system .Also, the time period of exposure has a major role in the amount of damage. Research in this field has found that there are three independent factors that control the nature of whether the pesticide has a toxic effect or not, namely:
1- The exterminator 2- The dose 3- The time period for the dose.
There are pesticides by nature that have chronic effects (as a result of repeated exposure to them for long periods of time), while others have a non-reversible (non-curable) effect. On the other hand, the effect may be reverse, meaning it diminishes until it cures, and this depends on the nature and how the pesticide causes its toxic action and whether the pesticide has a mechanical effect. one or more to bring about his poisonous deed. The distribution of the pesticide through the blood to the tissues of the body is usually fast at first, depending on the nature of the blood circulation, and the concentration of the pesticide in the blood, whether the exposure is acute or chronic, is affected by many factors such as the degree of solubility of the pesticide in the blood serum and the association of the pesticide with blood proteins and red blood cells, and there is another factor More important is whether the pesticide is of the type that accumulates in tissues or not (especially fatty ones). On the other hand, the toxicity of the pesticide to humans and mammals is strongly affected by the distribution processes between organs, and even its transfer from the blood to the organs is extremely dangerous and sensitive, such as the brain. Where it was found that the pesticide, in order to reach the brain, must pass through the blood-brain barrier, and this of course is very difficult to pass through, especially in the case of polar pesticides, while non-polar pesticides reach the brain more easily. The greatest danger is in the penetration of toxins into the placental barrier ( the placenta) which keeps the embryos inside during their growth. It was found that the placental barrier is less specialized and less efficient than the blood-brain barrier, as some polar pesticides pass through the placenta to reach the fetus. As for non-polar pesticides, they do not find any difficulty in penetrating from the placenta to reach the fetus. Many researchers have proven that pesticides (after marking them radioactively) reach embryos through the placenta, causing many toxic effects (death, deformities, biochemical changes) on embryos at the beginning of their formation, embryotoxicity, or in the final stages of formation, fetotoxicity, due to incomplete removal and excretion mechanisms. In fetuses, as many studies have shown that some pesticides may be transmitted through breast-feeding milk from the mother to the newborn. Pesticides penetrate the human body in various ways, depending on the method of exposure, it may be through the skin, mouth, or inhalation. In other words, the non-polar pesticide may be absorbed and stored in the subcutaneous fatty layer. In the case of oral exposure to the pesticide (pesticide residues found in food, drinking water, suicide cases), the absorption of the pesticide is controlled by several factors such as the degree of its solubility in the oral and pharynx fluids, and then the degree of its polarity and its influence on digestive fluids in the stomach and mucous fluids in the intestine until it reaches Blood, either if the exposure was through inhalation (volatile fumes from the pesticide, dry powders of the pesticide, or inhalation of its mist). The effect and penetration here depends on the diameter of the pesticide granules and whether they reach the lungs or are removed by the oropharyngeal septum. The granules, whose diameter is less than 3 micrometers, reach the alveoli and are deposited in them. Inhalation poisoning is the most dangerous of the other types, due to the connection of the alveoli. directly into the blood vessels. Pesticides are stored and accumulate in tissues, especially persistent and lipophilic pesticides, such as organochlorine pesticides. Storage of pesticides depends on several factors such as sex, strain, age, nutritional status, distribution rates, permeability of various barriers, chemical transformation reactions and removal. Among the most important organs in which chlorine pesticides accumulate are the liver, kidneys, nervous system, and adipose tissue. In the event that the pesticide reaches the cells and tissues of the organism, it is exposed to oxidation and reduction reactions, hydrolysis, or coupling with vital molecules present in the tissues of the organism, such as glutathione. At the end of these reactions, the pesticide may turn into a more toxic compound or turn into less toxic metabolites, and then they. The result in most cases is a change in the physical and chemical characteristics of the pesticide particles. Toxic effects caused by the pesticide on the liver and kidneys through functional, physiological or histological effects, which may lead to the death of some tissues by necrosis or apoptosis, which leads to failure in the function of any of these two organs as a result of the effect on hepatocytes in the liver or on The nephritic units and renal tubules of the kidney. It is worth noting that there is no completely safe pesticide, but it has been found that species are less harmful to human health if they are used in the right way. At the global level, poisoning cases that could be attributed to pesticides could be attributed to 3 million cases of acute poisoning annually, in addition to unregistered cases, in addition to deaths, which amounted to 220,000 cases, according to WHO statistical reports for the year 1990.
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