All but xenobiotics. The influence of xenobiotics on the human body. See what “Xenobiotics” are in other dictionaries
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Isn't that what we
call it the progress of civilization,
really madness?
Sturmer
The number of xenobiotics polluting the natural environment is increasing on an alarming scale. The pursuit of economic profit is far ahead of the problem of preserving the purity of the natural environment. There is another danger, namely the potentiation of the action of xenobiotics, when the adverse effect of one of them enhances the effect of the other. Global pollution of the biosphere with xenobiotics, which exceeds the capabilities of its natural self-purification, urgently requires a change in the strategy of its development and the way of life of people on Earth.
According to foreign researchers, the share of damage to health care (increased morbidity of the population in total damage National economy caused by environmental pollution) ranges from 60 to 80%.
All these enterprises, in the absence of clean technology, violations of safety rules and technological discipline, lack of production standards and treatment facilities, are the main sources of all ills for nature and people. Thus, the causes of environmental pollution are diverse. However, what they have in common is that all this happens due to the fault of people. Environmental illiteracy, professional negligence, criminal negligence, selfish attitude towards the environment often leads to tragedies and disasters.
Toxicants can also be natural toxic substances, for example gases from volcanic eruptions. However, more often these are products of human economic activity, which he imprudently included in the cycle of nature.
Biologically active substances contained in minerals, poisonous plants, and medicines are not environmental toxicants until they are “brought back”, for example as pesticides, or end up as persistent residues in wastewater and cause disaster .
Lisovsky V.A., Evseev S.P., Golofeevsky V.Yu., Mironenko A.N.
TABLE OF CONTENTS.
INTRODUCTION 3
XENOBIOTIC ENVIRONMENTAL PROFILE 4
SECRET AND UNforeseen DANGER. 5
DIOXIN'S MARCH ACROSS THE PLANET 9
"OPERATION RANCH HAND" - CRIME OF THE CENTURY 9
WHAT IS KNOWN ABOUT THE PROPERTIES OF DIOXIN. eleven
DIOXIN TOXICITY DURING SINGLE ADMINISTRATION. 12
DIOXIN AND ITS TRACES IN VIETNAM. 13
DO NOT ALLOW DIOXIN TO ACCUMULATE IN THE BIOSPHERE! 15
BIBLIOGRAPHY. 17
INTRODUCTION
The development of industry is inextricably linked with the expansion of the range of chemicals used. Increasing the volume of pesticides, fertilizers and other chemicals used - characteristic modern Agriculture and forestry. This is the objective reason for the steady increase in chemical danger to the environment, hidden in the very nature of human activity.
Just a few decades ago, chemical waste from production was simply dumped into environment, and pesticides and fertilizers were sprayed almost uncontrollably, based on utilitarian considerations, over vast areas. At the same time, it was believed that gaseous substances should quickly dissipate in the atmosphere, liquids should partially dissolve in water and be carried away from the emission sites. Although particulate matter accumulated significantly in the regions, the potential hazard from industrial emissions was considered low. The use of pesticides and fertilizers gave economic effect, many times greater than the damage caused by toxicants to nature.
However, already in 1962, Rachel Carson's book Silent Spring appeared, in which the author describes cases of mass death of birds and fish from the uncontrolled use of pesticides. Carson concluded that the observed effects of pollutants on wildlife foreshadow impending disaster for humans as well. This book attracted everyone's attention. Environmental protection societies and government legislation regulating xenobiotic emissions have appeared. With this book, in fact, the development of a new branch of science began - animal toxicology.
Ecotoxicology was identified as an independent science by Rene Traut, who for the first time, in 1969, linked together two completely different subjects: ecology (according to Krebs, the science of relationships that determine the distribution and habitat of living beings) and toxicology. In fact, this area of knowledge includes, in addition to those indicated, elements of other natural sciences such as chemistry, biochemistry, physiology, population genetics, etc.
There has been a tendency to use the term ecotoxicology only to refer to the body of knowledge concerning the effects of chemicals on ecosystems other than humans. Thus, according to Walker et al. (1996), ecotoxicology is the study of the harmful effects of chemicals on ecosystems. By eliminating human objects from the range of objects considered by ecotoxicology, this definition determines the difference between ecotoxicology and environmental toxicology and determines the subject of study of the latter. The term environmental toxicology is proposed to be used only for studies of the direct effects of environmental pollutants on humans.
In the process of studying the effects of chemicals present in the environment on humans and human communities, environmental toxicology operates with already established categories and concepts of classical toxicology and, as a rule, applies its traditional experimental, clinical, and epidemiological methodology. The object of research is the mechanisms, dynamics of development, manifestations of the adverse effects of toxicants and the products of their transformation in the environment on humans.
While sharing this approach in general and positively assessing its practical significance, it should be noted, however, that the methodological differences between ecotoxicology and environmental toxicology are completely erased when the researcher is tasked with assessing the indirect effects of pollutants on human populations (for example, caused by toxic modification of biota), or, on the contrary, to find out the mechanisms of action of chemicals in the environment on representatives of a particular species of living beings.
XENOBIOTIC ENVIRONMENTAL PROFILE
From the position of a toxicologist, the abiotic and biotic elements of what we call the environment are all complex, sometimes organized agglomerates, mixtures of countless molecules.
For ecotoxicology, only molecules that are bioavailable are of interest, i.e. capable of interacting non-mechanically with living organisms. As a rule, these are compounds that are in a gaseous or liquid state, in the form of aqueous solutions, adsorbed on soil particles and various surfaces, solid substances, but in the form of fine dust (particle size less than 50 microns), and finally substances entering the body with food.
Some of the bioavailable compounds are utilized by organisms, participating in the processes of their plastic and energy exchange with the environment, i.e. act as habitat resources. Others, entering the body of animals and plants, are not used as sources of energy or plastic material, but, acting in sufficient doses and concentrations, are capable of significantly modifying the course of normal physiological processes. Such compounds are called foreign or xenobiotics (alien to life).
The totality of alien substances contained in the environment (water, soil, air and living organisms) in a form (aggregate state) that allows them to enter into chemical and physicochemical interactions with biological objects of the ecosystem constitute the xenobiotic profile of biogeocenosis. The xenobiotic profile should be considered as one of the most important environmental factors (along with temperature, light, humidity, trophic conditions, etc.), which can be described by qualitative and quantitative characteristics.
An important element of the xenobiotic profile are foreign substances contained in the organs and tissues of living beings, since all of them are sooner or later consumed by other organisms (i.e., they have bioavailability). Against, chemical substances, fixed in solid, non-air-dispersible and water-insoluble objects (rock, solid industrial products, glass, plastic, etc.) do not have bioavailability. They can be considered as sources of the formation of a xenobiotic profile.
Xenobiotic profiles of the environment, formed during evolutionary processes that have taken place on the planet for millions of years, can be called natural xenobiotic profiles. They are different in different regions of the Earth. The biocenoses existing in these regions (biotopes) are, to one degree or another, adapted to the corresponding natural xenobiotic profiles.
Various natural collisions, and in recent years, human economic activity, sometimes significantly change the natural xenobiotic profile of many regions (especially urbanized ones). Chemical substances that accumulate in the environment in quantities unusual for it and cause changes in the natural xenobiotic profile act as ecopollutants (pollutants). A change in the xenobiotic profile may result from excessive accumulation of one or many ecopollutants in the environment (Table 1).
Table 1. List of main environmental pollutants
Air pollutants | Water and soil pollutants |
Gases: Dust particles: | Metals (lead, arsenic, cadmium, mercury) |
This does not always lead to harmful consequences for wildlife and the population. Only an ecopollutant that has accumulated in the environment in an amount sufficient to initiate a toxic process in the biocenosis (at any level of organization of living matter) can be designated as an ecotoxicant.
One of the most difficult practical problems ecotoxicology - determination of quantitative parameters at which an ecopollutant is transformed into an ecotoxicant. When solving this problem, it is necessary to take into account that in real conditions the entire xenobiotic profile of the environment affects the biocenosis, thereby modifying the biological activity of an individual pollutant. Therefore, in different regions (different xenobiotic profiles, different biocenoses), the quantitative parameters of the transformation of a pollutant into an ecotoxicant are strictly speaking different.
Ecotoxicokinetics is a branch of ecotoxicology that examines the fate of xenobiotics (ecopollutants) in the environment: the sources of their appearance; distribution in abiotic and biotic elements of the environment; transformation of xenobiotic in the environment; elimination from the environment.
SECRET AND UNforeseen DANGER.
Dioxins and dioxin-like compounds were found in the waters of Baikal, in fish, zoo- and phytoplankton, as well as in the eggs of birds inhabiting the shores and islands of the “sacred sea”. They are also called “degradation hormones” or “premature aging hormones.” Dioxins are classified as particularly dangerous persistent organic pollutants, as they are highly resistant to photolytic, chemical and biological degradation. As a result, they can persist in the environment for a long time. At the same time, there is no “threshold of action” for dioxins, that is, even one molecule is capable of initiating abnormal cellular activity and causing a chain of reactions that disrupt the functions of the body. It is known, for example, that during the hostilities in Vietnam, the US armed forces actively used, among other types chemical weapons, the herbicide "Orange Agent", which contains dioxin. This drug caused artificial leaf fall in the jungle, depriving the Vietnamese guerrillas of their natural and main refuge
The effect of dioxins on humans is due to their influence on receptors for endocrine and hormonal disorders, the content of sex hormones, thyroid and pancreatic hormones changes, which increases the risk of developing diabetes mellitus, and the processes of puberty and fetal development are disrupted. Children are lagging behind in development, their education is hampered, and young people develop diseases characteristic of old age. In general, the likelihood of infertility, spontaneous abortion, congenital defects and other anomalies increases. The immune response also changes, which means the body’s susceptibility to infection increases, and the frequency of allergic reactions and cancer increases.
In toxicology, the term “dioxin” refers to a derivative of this compound, namely 2,3,7,8-tetrachlorodibenzo-p-dioxin, which is a representative of a large group of extremely dangerous xenobiotics from among polychlorinated polycyclic compounds. Particularly hazardous substances include polychlorinated aromatic compounds with condensed rings. Once in the body, they activate (induce) the synthesis of iron-containing enzymes - cytochromes P-450, which usually leads to metabolic disorders and damage to individual organs and tissues. Possessing high symmetry, such compounds can exist in the body for a long time. Dioxin is one of the most insidious poisons, known to mankind. In contrast, the history of mankind knows many cases of the appearance in the biosphere of large quantities of potentially dangerous substances. The impact of these foreign compounds (xenobiotics) on living organisms has sometimes caused tragic consequences, as exemplified by the story of the insecticide DDT. Dioxin became even more notorious, appearing in the environment of a number of Western countries in the 50-60s, as well as in South Vietnam during the chemical war waged by the United States from 1961 to 1972. Dioxin in organic chemistry called a six-membered heterocycle in which two oxygen atoms are linked by two carbon-carbon double bonds. In toxicology, the term “dioxin” refers to a derivative of this compound, namely 2,3,7,8-tetrachlorodibenzo-p-dioxin, which is a representative of a large group of extremely dangerous xenobiotics from among polychlorinated polycyclic compounds. Particularly hazardous substances include polychlorinated aromatic compounds with condensed rings. Once in the body, they activate (induce) the synthesis of iron-containing enzymes - cytochromes P-450, which usually leads to metabolic disorders and damage to individual organs and tissues. Possessing high symmetry, such compounds can exist in the body for a long time.
Dioxin is one of the most insidious poisons known to mankind. Unlike conventional poisons, the toxicity of which is associated with the suppression of certain functions of the body, dioxin and similar xenobiotics affect the body due to the ability to greatly increase (induce) the activity of a number of oxidative iron-containing enzymes (monooxygenases), which leads to disruption of the metabolism of many vital substances and suppression functions of a number of body systems. Dioxin is dangerous for two reasons. Firstly, it persists in the environment, is effectively transported through food chains and thus affects living organisms for a long time. Secondly, even. in quantities that are relatively harmless to the body, dioxin greatly increases the activity of highly specific liver monooxygenases, which convert many substances of synthetic and natural origin into poisons dangerous to the body. Therefore, even small amounts of dioxin create a danger of damage to living organisms by usually harmless xenobiotics available in nature. Even from the above cursory description it is obvious how important and complex the problem of protection against this dangerous xenobiotic is. Therefore, in the USA, where a significant amount of dioxin has been introduced into the environment, studying this problem is only federal government$5 million is allocated annually.
Since 1971 the problem of dioxin and related compounds is regularly discussed in the USA at special conferences, which have recently been held annually as international forums of scientists from interested countries. Attention to this problem is reflected in the abundant scientific literature on dioxin, partially summarized in the collections: Dioxin: toxicological and chemical aspects. N.Y.-Ln, 1978, v.1; Dioxins. Sources, exposure, transport and control. Ohio, 1980, v.1,2. Over the past 10-12 years, the scientific aspects of this problem have been widely reviewed. Everything that has been learned about dioxin indicates the extreme danger of this substance for humans, especially in conditions of chronic poisoning, and allows us to formulate the main tasks facing humanity in connection with the appearance of this xenobiotic in nature. At the same time, the dioxin problem also has social, political and military aspects. That is why in some Western countries, and especially in the United States, they are deliberately trying to obscure certain aspects of the problem, not making public information that reveals the danger of this poison for humanity, using the results of incorrect experiments to make judgments about dioxin, etc.
The history of dioxin is closely connected with the problems of profitable assimilation of polychlorinated benzenes, which are waste from a number of large-scale chemical industries. In the early 30s, Dow Chemical (USA) developed a method for producing polychlorophenols from polychlorobenzenes by alkaline hydrolysis at high temperature under pressure and showed that these preparations, called daucides, are effective means for preserving wood. Already in 1936, there were reports of mass illnesses among workers. Mississippi engaged in timber conservation with these agents. Most of them suffered from a severe skin disease - chloracne, which had previously been observed among workers in chlorine production. In 1937, cases of similar diseases were described among workers at a plant in Midland (Michigan, USA) involved in the production of daucides. An investigation into the causes of damage in these and many similar cases led to the conclusion that the chloracnogenic factor is present only in technical daucides, and pure polychlorophenols do not have a similar effect. The expansion of the scale of damage caused by polychlorophenols was subsequently due to their use for military purposes. During the Second World War, the first herbicides with hormone-like action based on 2,4-dichloro- and 2,4,5-trichlorophenoxyacetic acids (2,4-D and 2,4,5-T) were obtained in the USA. These drugs were developed to kill Japanese vegetation and were adopted by the US Army shortly after the war. At the same time, these acids, their salts and esters began to be used for chemical weeding in cereal crops, and mixtures of 2,4-D and 2,4,5-T esters - for the destruction of unwanted tree and shrub vegetation. This allowed the US military-industrial circles to create large-scale production of 2,4-dichloro-, 2,4,5-trichlorophenols, and on their basis the acids 2,4-D and 2,4,5-T. Fortunately, the production and use of 2,4-D have had no negative consequences for humanity. On the contrary, the study of the properties of 2,4-D and its derivatives was a powerful impetus for the development of modern herbicide chemistry.
Events related to the expansion of the scale of production and use of 2,4,5-T developed in a completely different way. Already in 1949 An explosion occurred at the Nitro plant (West Virginia, USA), which produces 2,4,5-trichlorophenol. 250 people were seriously injured. True, this fact became known only in the late 70s, and as for the consequences of the explosion for the local population and the environment, they are still shrouded in mystery. In the 50s, reports appeared about frequent injuries from technical 2,4,5-T and trichlorophenol at chemical plants in Germany and France, with the consequences of explosions in Ludwigshafen (1953, BASF plant) and Grenoble (1956, BASF plant) "Ron Poulenc") were discussed widely and in detail. Numerous cases of workers being injured by trichlorophenol in the 50s also occurred in the United States (at the plants of Dow Chemical, Monsanto, Hooker, Diamond, etc.). However, these incidents were not made public until the late 70s. The period from 1961 to 1970, when 2,4,5-T plants were operating at maximum capacity due to massive military procurement by the US Army, was particularly rich in dioxin-related events. Mass casualties caused by explosions at factories occurred in the USA, Italy, Great Britain, Holland and France. All of these incidents (with the exception of those that occurred in France) were not covered in the press until the late 70s. Particularly terrible were the consequences of the explosion at the Philips Duffard plant in Amsterdam (1963), after which the plant administration was forced to dismantle equipment and production facilities and flood them into the ocean. The last decade has also not been without numerous incidents at production and processing plants 2,4,5-trichlorophenol. The most terrible disaster was in Seveso (1976, Italy), as a result of which not only workers suffered, but also local population. To eliminate the consequences of this incident, the surface layer of soil had to be removed from a large area.
The way to avoid contaminating the country with dioxins is to do everything according to the rules. Scheme of dioxin formation during alkaline hydrolysis of tetrachlorobenzene. This reaction is usually carried out in a solution of methanol (CH 3 OH) under pressure at a temperature above 165 o C. The sodium trichlorophenolate atom formed is always partially converted into predioxin, and then into dioxin. With an increase in temperature to 210 o C, the rate of this side reaction increases sharply, and under more severe conditions, dioxin becomes the main product of the reaction. In this case, the process is uncontrollable and ends in an explosion under production conditions. The causes of injury to workers involved in the production and processing of 2,4,5-trichlorophenol were established in 1957. almost simultaneously by three groups of scientists. G. Hoffmann (Germany) isolated the chloracnogenic factor of technical trichlorophenol in its pure form, studied its properties, physiological activity and attributed to it the structure of tetrachlorodibenzofuran. The synthesized sample of this compound actually had the same effect on animals as technical trichlorophenol. At the same time, K. Schulz (Germany), a specialist in the field of skin diseases, drew attention to the fact that the symptoms of damage to his client, working with chlorinated dibenzo-para-dioxins, were identical to the symptoms of damage caused by technical trichlorophenol. His studies showed that the chloracnogenic factor of technical trichlorophenol is indeed 2,3,7,8-tetrachlorodibenzo-para-dioxin (dioxin) - an inevitable by-product of the alkaline processing of symmetric tetrachlorobenzene. Later, K. Schultz’s information was confirmed in the works of other scientists. The high toxicity of dioxin was established in 1957. and in the USA. This happened after an accident with the American chemist J. Dietrich, who, while synthesizing dioxin and its analogues, received a severe injury reminiscent of technical trichlorophenol and was hospitalized for a long time. This fact, like many other incidents at trichlorophenol production in the United States, was hidden from the public, and the halogenated dibenzo-p-dioxins synthesized by an American chemist were seized for study by the military department. Thus, at the end of the 50s, the cause of frequent injuries from technical trichlorophenol was identified and the toxicity of dioxin and tetrachlorodibenzofuran was established. Moreover, in 1961, K. Schultz published detailed information about the extremely high toxicity of dioxin for animals and showed the special danger of chronic damage by this poison. Thus, 25 years after its appearance in nature, dioxin ceased to be an unknown “chloroacnogenic factor.” By this time, despite its high toxicity, 2,4,5-trichlorophenol had penetrated into many areas of production. Its sodium and zinc salts, as well as the processed product - hexachlorophene, have become widely used as biocides in technology, agriculture, the textile and paper industries, medicine, etc. On the basis of this phenol, insecticides, preparations for veterinary needs, and technical liquids for various purposes were prepared. However, 2,4,5-trichlorophenol has found its most widespread use in the production of 2,4,5-T and other herbicides intended not only for peaceful but also for military purposes. As a result, by 1960 Trichlorophenol production reached an impressive level - many thousands of tons per year.
THE MARCH OF DIOXIN AROUND THE PLANET
After the publication of K. Schultz’s work, one could expect that factories for the production of trichlorophenol would be closed or new technological schemes for producing this product would be developed that would not allow the accumulation of such a strong poison in it. However, not only did this not happen, but, contrary to common sense, further publications on the physiological activity and pathways of formation of dioxin and tetrachlorodibenzofuran simply ceased. At the same time, reports of cases of human injury from trichlorophenol and its derivatives almost ceased, although it was during this period, as it became known later, that they were most frequent.
At the same time, the production of trichlorophenol and its processed products according to the old technological scheme of the 50s in Western countries, and especially in the USA, has expanded significantly and has been preserved high level consumption of these dangerous products and their exports continuously increased. Biocidal, insecticidal and herbicidal preparations based on 2,4,5-trichlorophenol have arrived in many countries of the American continent, in some countries in Africa and Southeast Asia, in Australia and Oceania. Together with them, dioxin was continuously introduced into the soils and water areas, cities and towns of vast areas of the world. Especially large quantities of it entered the environment with wastewater in areas where factories producing trichlorophenol were located. The results of this activity were immediate: in the late 60s and early 70s, numerous cases of mass destruction of poultry and even the offspring of wild animals were registered in the United States.
It was later shown that herbicides of the 2,4,5-T type, supplied to the US domestic and foreign markets in the 60s, contained dioxin in concentrations from 1 to 100 parts per million (ppm), i.e. in quantities , which exceed the permissible values by tens, hundreds and even thousands of times. If we assume that trichlorophenol processing products used for peaceful purposes contained only 10 ppm of dioxin, then in this case, in the decade that has passed since the causes of the toxicity of these products were established, hundreds of kilograms of this poison have been introduced into the US environment, along with many thousands of tons of pesticides. A similar amount of dioxin appeared in countries that imported these products from the United States.
OPERATION RANCH HAND - THE CRIME OF THE CENTURY
The US military program for the use of trichlorophenol processing products turned out to be especially extensive. By the 1960s, the US military had completed a broad plan to study herbicides as a potential weapon of environmental warfare, which was to be carried out in Indochina under the code name Operation Ranch Hand. Moreover, by this time herbicide formulations had already been selected, methods and means of their use had been developed, and extensive tests had been carried out under conditions simulating the tropical zones of Indochina. During the testing period, the main attention of military specialists was paid to herbicide formulations containing 2,4,5-T esters.
When you look at materials from the 60s, you are especially struck by the scale of propaganda carried out in the United States for this type of weapon of mass destruction. The innocuous name “defoliants” was chosen for it, in other words, agents that cause plant leaves to fall off. In reality, however, the US Army only had herbicide formulations in service, designed to completely destroy plants. In the open instructions of the US Army, “defoliants” were assigned the role of unmasking the partisans and suppressing their food supply. The press extolled the “humanity” of this new type of weapon. Statements by high-ranking representatives of the army and even the US administration guaranteed the complete safety of its use for the environment, humans and animals.
What really happened? In the summer of 1961, in the presence of a representative of the White House, the US Air Force began implementing Operation Ranch Hand in South Vietnam, and three years later completed its first stage. About 2 thousand tons of herbicides were needed to solve the main problems of the first stage related to the selection of the most effective formulations, methods, tactics and strategies for their use. In the fall of 1964 The US Air Force began a systematic massive destruction of the Vietnamese environment, after which it became clear to the scientific community that the US Army in Vietnam was conducting large-scale tests of new types of weapons of mass destruction - weapons of ecocide and genocide. To the credit of progressive American scientists, they were the first to raise their voices of protest against chemical warfare in Vietnam. However, neither their statements in the press nor their collective petitions to the US administration were taken into account.
After 1965, the scale of chemical campaigns began to increase; tens of thousands of tons of herbicides were thrown into the forests and fields of Vietnam every year. According to incomplete official data, in the chemical war of 1961-1972. The USA used about 96 thousand tons of herbicides, of which 57 thousand tons were formulations containing dioxin. Information about the volume of herbicide use in 1970-1972 remained classified. in Vietnam and the scale of herbicide treatments in Laos and Kampuchea. However, from the balance of production and consumption of herbicides it follows that, due to US military purchases, the increase in the production of 2,4,5-T in the 60s reached 50 thousand tons, from this amount more than 100 thousand tons of only herbicide formulations containing dioxin.
When assessing the amount of dioxin introduced into the Vietnamese environment, it is necessary to take into account that its concentration in technical 2,4,5-T esters is determined by production technology, which in the 50s and 60s was unchanged and led to a high content of poison. From the overwhelming number of primary sources it follows that the concentration of dioxin in the herbicide formulations of the US Army reached several tens of ppm. This is consistent with information about the contamination of 2,4,5-T ethers produced in the 60s, given in the work of K. Rappe (up to 100 ppm) and in the report of the US National Academy of Sciences (up to 50 ppm). This is confirmed by official data from the US Air Force on the dioxin content of the US Army purple, pink and green formulations (33-66 ppm). American scientists studying the properties of the Orange Agent formulation used typical samples containing 15-30 ppm of dioxin. Only the official US Air Force data obtained by A. Young for Orange Agent contrasts sharply with the information given above: they state that the average dioxin content in this formulation, the most widely used in Vietnam, is close to 2 ppm. However, as follows from the official data of the US Department of Agriculture, 2,4,5-T ethers of this degree of purity were not always obtained in the USA even in the early 70s, when technological scheme a trichlorophenol purification step was included.
Only after the implementation of a scheme with double purification of trichlorophenol was it possible to obtain products with a dioxin content below 1 ppm. A. Young and other representatives of US official circles claim that the purification of trichlorophenol from dioxin in the US has been included in the technological scheme since the mid-60s. However, from the technical and patent literature it follows that improvements in the production of trichlorophenol began after 1970. Calculations made by A. Young are based on the quality of 2,4,5-T esters produced in 1971-1973. All this allows us to consider more plausible the data on the high content of dioxin in herbicides such as 2,4,5-T, produced in the 60s. Thus, 57 thousand tons of formulations based on 2,4,5-T, the use of which in Vietnam is officially recognized in the United States, brought more than 500 kg of dioxin to the relatively small territory of Indochina. There is a great danger that this number must at least be doubled to obtain a real picture.
When assessing the degree of environmental pollution with dioxin, it is also necessary to take into account the possibility of its secondary formation after the use of trichlorophenol derivatives. The thermal conversion of predioxin, usually present in technical preparations based on trichlorophenol, into dioxin has now been demonstrated unambiguously. The yield of dioxin during thermolysis of other non-volatile trichlorophenol derivatives, including 2,4,5-T, is high.
The negative results reported in the literature were associated either with the use of volatile dioxin precursors or with the presence of conditions for their effective removal from the reaction sphere. Since trichlorophenol and 2,4,5-T esters quickly turn into non-volatile derivatives in various environmental objects, various materials preserved with biocides, as well as the remains of plants affected by 2,4,5-T herbicides, when burned, are obviously sources of additional amount of dioxin. The probability of secondary formation of dioxin in the conditions of chemical warfare, which was carried out in Vietnam, should be considered especially high. Here, during the period of hostilities, more than 500 thousand tons of napalm were burned (including in vast areas of affected forests), more than 13 million tons of air bombs, shells and mines were exploded. Therefore, dioxin entered the Vietnamese environment in much larger quantities than was contained in the many tens of thousands of tons of herbicides used by the US Army. To imagine the consequences of the accumulation of dioxin in the environment, we will introduce the reader in more detail to the properties of this dangerous poison.
WHAT IS KNOWN ABOUT THE PROPERTIES OF DIOXIN.
Structure, physical and Chemical properties. The dioxin molecule is flat and has high symmetry. The distribution of electron density in it is such that the maximum is in the zone of oxygen and chlorine atoms, and the minimum is in the centers of benzene rings. These structural features and electronic state determine the observed extreme properties of the dioxin molecule.
Dioxin is a crystalline substance with a high melting point (305 o C) and very low volatility, poorly soluble in water (2x10-8% at 25 o C) and better in organic solvents. It is characterized by high thermal stability: its decomposition is observed only when heated above 750 o C, and is effectively carried out at 1000 o C.
Dioxin is a chemically inert substance. It does not decompose by acids and alkalis even when boiled. It enters into the chlorination and sulfonation reactions characteristic of aromatic compounds only under very harsh conditions and in the presence of catalysts. The replacement of chlorine atoms of the dioxin molecule with other atoms or groups of atoms is carried out only under the conditions of free radical reactions. Some of these transformations, such as reaction with sodium naphthalene and reductive dechlorination under ultraviolet irradiation, are used to destroy small quantities of dioxin. When oxidized under anhydrous conditions, dioxin easily gives up one electron and turns into a stable radical cation, which, however, is easily reduced by water into dioxin due to its ability to form strong complexes with many natural and synthetic polycyclic compounds.
Toxic properties. Dioxin is a total poison, since even in relatively small doses (concentrations) it affects almost all forms of living matter - from bacteria to warm-blooded animals. The toxicity of dioxin in the case of simple organisms is apparently due to disruption of the functions of metalloenzymes with which it forms strong complexes. The damage caused by dioxin to higher organisms, especially warm-blooded ones, is much more difficult. In the body of warm-blooded animals, dioxin initially enters the adipose tissue, and then is redistributed, accumulating mainly in the liver, then in the thymus and other organs. Its destruction in the body is insignificant: it is excreted mainly unchanged, in the form of complexes of an as yet unknown nature.
The half-life ranges from several tens of days (mouse) to a year or more (primates) and usually increases with slow intake. With increased retention in the body and selective accumulation in the liver, the sensitivity of individuals to dioxin increases.
In case of acute poisoning of animals, signs of the general toxic effect of dioxin are observed: loss of appetite, physical and sexual
Subject of xenobiology, problems and tasks, connections with other sciences
Xenobiotics are foreign organic and inorganic compounds that have not previously been found in the body. Such substances include, for example, drugs, pesticides, industrial poisons, industrial wastes, food additives, cosmetics, etc. Since tissues usually contain many inorganic elements in trace quantities, the biological function of which is unknown, therefore inorganic substances can be classified as xenobiotics only if they are not necessary for metabolic processes.
A living organism is an open system. Among the substances entering the body from the environment, a distinction is made between the natural flow (nutrients) and the flow of substances of natural and synthetic origin that are not part of the body. These flows interact at all levels of the body (molecular, cellular, organ). An excess of toxic foreign compounds (xenobiotics) causes a slowdown or cessation of the processes of growth, development, and reproduction. To maintain homeostasis in the body, there are regulatory mechanisms.
Xenobiology studies the patterns and pathways of entry, excretion, distribution, transformation of foreign chemical compounds in a living organism and the mechanisms of biological reactions caused by them.
Xenobiology is divided into narrower areas - xenobiophysics, xenobiochemistry, xenophysiology, etc. The objectives of xenobiophysics are to study the processes of interaction of exogenous xenobiotics with the transport systems of the body, with various cellular structures, primarily with the plasmalemma, and the mechanisms of entry of xenobiotics.
The subject of xenobiochemistry is the metabolism of xenobiotics in the body. This area of xenobiology includes a number of sections of biological, organic and analytical chemistry, pharmacology, toxicology and other sciences. The task of static xenobiochemistry includes establishing the structure of molecules of xenobiotic metabolites formed in the body, studying their distribution, localization in organisms and tissues. Dynamic xenobiochemistry studies the mechanisms of transformation of xenobiotics in the body, the structure and catalytic properties of enzymes involved in these transformations.
Xenophysiology studies the life processes and functions of living organisms throughout their development under the influence of xenobiotics. Xenophytophysiology studies the characteristics of intake and excretion, the specifics of the processes of biotransformation and accumulation of xenobiotics in a plant organism.
Xenobiology is associated with biotechnology, which uses the principles of xenobiotic metabolism, in particular enzyme catalysis, in the synthesis of organic substances. The connection between xenobiology and medicine ensures the safety of treatment as a result of studying the mechanism of action and metabolism of new drugs.
The increasing relevance of problems considered in xenobiology is due to the rapid increase in the number of synthetic compounds involved in the cycle of substances in nature. Among xenobiotics, there are a number of useful substances necessary for medicine, crop production, animal husbandry, etc. Therefore, one of the tasks of xenobiology is the development of techniques and approaches for creating a system for determining the biological activity of xenobiotics.
Types of xenobiotics, their classification according to the degree of danger and toxicity
The following types of substances that cause global chemical pollution of the biosphere are distinguished:
Gaseous substances;
Heavy metals;
Fertilizers and nutrients;
Organic compounds;
Radioactive substances (radionuclides) are the subject of radiobiology.
Many xenobiotics and pollutants are highly toxic substances.
In the broadest sense, poisons are chemical substances of exogenous origin (synthetic and natural), which, after penetration into the body, cause structural and functional changes, accompanied by the development of characteristic pathological conditions.
Depending on the source of origin and practical application Toxic substances (poisons) are divided into the following groups:
Industrial poisons: organic solvents (dichloroethane, carbon tetrachloride, acetone, etc.), substances used as fuel (methane, propane, butane), dyes (aniline and its derivatives), freons, chemical reagents, organic synthesis intermediates, etc.;
Chemical fertilizers and plant protection products, including pesticides;
Medicines and intermediate products of the pharmaceutical industry;
Household chemicals used as insecticides, dyes, varnishes, perfumes and cosmetics, food additives, antioxidants;
Plant and animal poisons;
Chemical warfare agents.
Depending on the predominant damage to the corresponding organs and tissues of a person, poisons are divided into the following categories: cardiac poisons, nerve poisons, liver poisons, kidney poisons, blood (hemic) poisons, gastrointestinal poisons, pulmonary poisons, poisons that affect the immune system, poisons that affect skin.
Toxicity- a measure of the incompatibility of a substance with life, the reciprocal of the absolute value of the average lethal dose or concentration.
The LC50 or LD 5 o values are, respectively, the concentration or dose of a substance that causes half the suppression of the recorded reaction (for example, the death of 50% of organisms).
Foreign substance danger- the likelihood of harmful health effects occurring under actual conditions of their production and use.
Harmful substances, with which a person comes into contact, are divided into four classes according to the degree of danger (toxicity):
I. extremely dangerous (extremely toxic);
II.highly hazardous (highly toxic);
III.moderately hazardous (moderately toxic);
IV. low-hazard (low toxic).
Criteria for classifying xenobiotics according to their degree of toxicity:
Value of LD 5 o or LC50;
Routes of entry (inhalation, through the skin);
Exposure time;
The property of being destroyed in the environment or undergoing transformations in living organisms (biotransformation).
In addition to toxicity and danger, any effect of a xenobiotic on an object can be characterized by some features of its biological action:
By type of biological effect on the target
According to LD 5 o or LC50;
By type of toxicity and danger
By the selectivity of the action of xenobiotics (substances can be toxic to some organisms and non-toxic to others);
According to concentration limits (threshold values) of toxic and/or hazardous effects;
According to the nature of the pharmacological action (hypnotics, antipsychotics, hormonal, etc.).
Related information.
Man is a heterotroph, i.e. receives nutrients and energy from outside in the form organic compounds(see Table 1).
Table 1 Main components
|
Carbohydrates |
Vitamins, elements |
|||
|
Energy value |
1g = 4.1 kcal |
1 g oil = 9.3 kcal (39.0 kJ) |
1g = 4.1 kcal 1 g alcohol = 7.1 kcal |
|
|
Biological value |
50% animal proteins, because |
25% vegetable oils, because they contain polyunsaturated fatty acids |
fiber |
Vitamins, elements |
There are two ways for the products of food digestion, including xenobiotics, to enter the internal environment of the body: water-soluble components enter the hepatic portal system and the liver; Fat-soluble substances enter the lymphatic vessels and then into the blood through the thoracic lymphatic duct.
For xenobiology, the idea of anti-alimentary nutritional factors is important. This term applies to substances of natural origin that are part of food. These include:
1) digestive enzyme inhibitors (Kunitz soybean trypsin inhibitor, Bauman-Birk family of soybean inhibitors, potato chemotrypsin and trypsin inhibitors I and II families, trypsin/α-amylase inhibitor family);
2) cyanogenic glycosides are glycosides of some cyanogenic aldehydes and ketones, which, upon enzymatic or acid hydrolysis, release hydrocyanic acid (white bean limarin, stone fruit amygdalin);
3) biogenic amines (serotonin in fruits and vegetables, tyramine and histamine in fermented foods);
4) alkaloids (lysergic acid diethylamide - a hallucinogen from ergot, morphine from poppy juice, caffeine, theobromine, theophylline from coffee beans and tea leaves, solanines and chaconines from potatoes);
5) antivitamins (leucine disrupts the metabolism of tryptophan and vitamin PP, indolylacetic acid is an antivitamin of niacin, ascorbate oxidase from vegetables is an antivitamin of ascorbic acid, fish thiaminase is an antivitamin of thiamine, linatin from flax seeds is an antagonist of pyridoxine, avidin from egg white is an antivitamin of biotin, etc. );
6) factors that reduce the absorption of minerals (oxalic acid, phytin - inositol hexaphosphoric acid from legumes and cereals, tannins);
7) poisons of peptide nature (ten toxic cyclopeptides from toadstool, the most toxic is α-amanitin);
8) lectins – glycoproteins that change membrane permeability (toxic are ricin (lectin from castor bean seeds), cholera toxin);
9) ethanol – disruption of the normal biochemical processes of formation and use of energy with a transition to psychological and biological dependence on exogenous alcohol.
Human food contains many chemicals, some of which are xenobiotics. Xenobiotics can be a normal component of food, can enrich food during its preparation (for example, food additives), and can also be contaminants in cooked food for some reason. Some food additives are purposefully added to food to optimize its preparation. Chemicals (indirect additives in food) are used in technologies for its preparation, storage, preservation, etc. Contaminants (mercury, arsenic, selenium and cadmium) come from the environment and are a result of the urbanization of society. It is possible to obtain the main components of food (proteins, fats, carbohydrates) from natural sources; substances that can change the functioning of organs and tissues (allergies, goiter development, proteolysis inhibitors, etc.); substances that are poisonous to the food consumer.
Food additives are natural or synthetic, physiologically active and inert chemical substances purposefully or accidentally added to food. Direct food additives include substances that are added to food during its preparation to impart certain characteristics to it. Such food additives include antioxidants, preservatives, vitamins, minerals, flavors, dyes, emulsifiers, stabilizers, acidifiers, etc.
By decision of the countries of the European Union, the presence of a food additive must be indicated on the label. In this case, it can be designated as an individual substance or as a representative of a specific functional class in combination with code E. According to the proposed system of digital codification of food additives, their classification is as follows: E100–E182 – dyes; E200 and further – preservatives; E300 and further – antioxidants (antioxidants); E400 and beyond – consistency stabilizers; E500 and further – acidity regulators, leavening agents; E600 and beyond – flavor and aroma enhancers; E700–800 – spare indexes; E900 and further – glazing agents, bread improvers; E1000 – emulsifiers. The use of food additives requires knowledge of the maximum permissible concentration of foreign substances - MPC (mg/kg), permissible daily dose - ADI (mg/kg body weight) and permissible daily intake - ADI (mg/day), calculated as the product of ADI by the average weight body – 60 kg.
Indirect food additives include substances that are included in food unintentionally (for example, when food comes into contact with technological equipment or packaging material). Three groups of food pollutants are most often considered: 1) aflatoxins; 2) pesticides; 3) dioxins and lead.
Of particular interest is the use of chemical food components (vitamins, minerals) for the treatment of specific diseases in doses exceeding the daily requirement. The clinical use of iron, fluorine, and iodine has been studied in sufficient detail. The safety of using vitamins and minerals as food additives or drug components depends on: 1) the cytotoxicity of the chemical; 2) its chemical form; 3) total daily consumption; 4) duration and regularity of consumption; 5) morphofunctional state of target tissues and human organs. Fat-soluble vitamins are more toxic than water-soluble vitamins due to their increased accumulation in the lipid phase of cell membranes and low rates of elimination.
Niacin in high doses (grams) is used to reduce cholesterol levels in the blood. In almost all cases of using nicotinic acid, side effects occur (redness of the skin, flushing of the head).
Copper is the most toxic, but most important trace element. Copper is found in trace amounts in almost all food products, which does not cause intoxication, with the exception of Wilson-Konovalov disease (combined damage to the liver and hypothalamic nuclei). Humans are less sensitive to copper compared to mammals (sheep). The toxicity of copper should be related to its interaction with iron, zinc and proteins.
Iron in the form of oxides it gives color to food. In the United States, phosphates, pyrophosphates, gluconates, lactates, ferrous sulfates, and reduced iron are approved as dietary supplements. Absorption of non-heme iron is strictly controlled in the intestinal mucosa. Excessive intake of iron from food and the action of substances that accelerate its absorption can lead to the accumulation of iron in the body. The retention and accumulation of iron in the human body is very individual and is not supported by general laws.
Zinc in the form of several compounds it is used in food supplements. Feeding poultry and livestock feed fortified with zinc can lead to the accumulation of this metal in meat foods. It is known that individual intolerance to zinc in humans is very variable. However, the use of medium concentrations of zinc salts in food as food additives, as a rule, is not accompanied by the development of intoxication.
Selenium is one of the most toxic elements. To date, the need for selenium has not been scientifically substantiated, and the widespread use of selenium in food supplements is based on intuitive assumptions. Geographical provinces with different levels of selenium in the environment should be taken into account when using dietary supplements fortified with selenium in order to prevent complications. Selenium deficiency in the body is perhaps one of the leading reasons why ordinary air becomes our terrible enemy. In conditions of selenium deficiency, air oxygen, through its active forms, destroys most vitamins in the body, disrupts the activity of the immune system and the system for neutralizing internal toxins of the body. In conditions of selenium deficiency, the immune system loses its aggressiveness towards pathogenic microorganisms and cancer cells, and the thyroid gland, which is dependent on it, regulates most metabolic processes, reduces its functional activity, which negatively affects the growth and development of the body.
The overall result of selenium deficiency in the human body is the emergence and development of dozens of severe diseases, ranging from increased capillary fragility and sperm immobility, premature hair loss and infertility to anemia, diabetes, endemic goiter, hepatitis, myocardial infarction and stroke, and a number of oncological diseases.
Selenium is widely distributed in environmental objects. There is a deficiency of selenium in the environment in New Zealand and some regions of China, and an excess in some regions of China and in the state of North Dakota (USA). Plants can accumulate selenium. In them it becomes part of organic compounds. When a plant dies, selenium returns to the soil and is used by other plants. Cereals can accumulate large amounts of selenium from selenium-enriched soils. In such regions, grazing animals can lead to intoxication of animals, and with chronic poisoning, visual damage and “alkali disease” may develop. With an excessive intake of selenium, disorders of the digestive tract and hepatobiliary system occur. Chronic intoxication of residents with selenium has been described in China. Main symptoms: brittle hair, lack of pigmentation of new hair, brittle nails with spots, longitudinal stretch marks of the skin. Neurological symptoms were found in half of affected people. Similar symptoms have also been described in Venezuelans living in regions enriched with selenium.
Let's look at some xenobiotics used to improve the organoleptic and physicochemical properties of food.
1. Saccharin 300–500 times sweeter than sucrose. Does not accumulate
in tissues, is not metabolized and is excreted unchanged from the body. Does not have a mutagenic effect. In some cases, it contributes to the development of experimental tumors (bladder cancer). However, the threat of the risk of tumor development has not yet been confirmed in epidemiological studies.
2. Cyclamate used as a sweetener. Its metabolism depends on the intestinal microflora. After the first dose, cyclamate is excreted in large quantities without changes. With repeated doses, metabolites appear in the intestines, which may be associated with the negative effects of the drug: the development of bladder cancer in an experiment on rats. Although this effect has not been replicated in dogs, mice, hamsters or primates, the use of cyclamate was banned in the United States in 1969.
3. Aspartame as a sugar substitute it is less toxic, since its hydrolysis produces phenylalanine and aspartic acid. The accumulation of phenylalanine can worsen the condition of patients with felylpyruvic mental retardation (phenylketonuria).
The most commonly used sweeteners: sorbitol, acesulfame potassium (Sunet), aspartame (Sanecta, Nutrasvit, Sladex), cyclamic acid and its salts (spolarin, cyclomates), isomalt (isomalt), saccharin and its salts, sucralose (trichlorgalactosucrose), thaumatin, glycyrrhizin , neohesperidin dihydrochalcone (neohesperidin DS), maltitol and maltitol syrup, lactitol, xylitol.
4. Food colorings include natural and synthetic substances. Natural ones include carmine, paprika, saffron and turmeric. Some nutrients give color to foods (carotenes, riboflavin, chlorophylls) and are found in juices, oils and extracts of vegetables and fruits. Synthetic compounds are introduced into food at the stages of its preparation and are certified by the state. Some of the potential dyes may be involved in cell malignancy (most often they are not carcinogens, but promoters). Synthetic food colors and some flavorings (methyl salicylate) can cause hyperactivity in children. Cases of hyperactivity can result in local brain damage (stroke). However, the problem of coloring food, both for the purpose of its attractiveness and biomedical use, remains relevant today. The unauthorized introduction of additives that improve the appearance and marketing value of food products has become very widespread and requires mandatory regulation by state supervisory authorities.
5. Preservatives include antioxidants and antimicrobial agents. Antioxidants suppress the development of changes in color, nutritional value and shape of foods by suppressing lipid peroxidation of food membranes, as well as free fatty acids. Antimicrobial agents inhibit the growth of microorganisms, yeasts, whose waste products cause intoxication or the development of an infectious process, and also change the physicochemical properties of food products. Chemical preservatives are counteracted by methods of preserving food at low temperatures or by using the method of irradiating food. However, technical means are still inferior to chemical ones due to the high cost and radiophobia of people.
5.1. Antioxidant dietary supplements include ascorbic acid, ascorbic acid palmitic ester, tocopherols, butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT), ethoxyquin, gallic acid propyl ester and t-butylhydroquinone (TBHQ). Widely used antimicrobial agents (nitrites, sulfites) also have antioxidant properties. For many years, BHA and BHT have been considered potentially hazardous substances. Both are fat-soluble antioxidants and are capable of increasing the activity of certain liver enzymes in the blood plasma. Antioxidants provide protection against certain electrophilic molecules that can bind to DNA and be mutagenic and induce tumor growth. Administration of BHA in large doses (2% of the diet) causes cell hyperplasia, papillomas, and cell malignancy in the stomach of some animals. At the same time, BHA and BHT provide protection to liver cells from the action of the carcinogen – diethylnitrosourea.
5.2. Antimicrobial agents (nitrites and sulfites). Nitrites inhibit the growth of Clostridium botulinum and thereby reduce the risk of botulism. Nitrites react with primary amines and amides to form the corresponding N-nitroso derivatives. Many, but not all N-nitroso compounds are carcinogens. Ascorbic acid and other reducing agents inhibit these nitrite reactions, especially in the acidic environment of the stomach. Some nitrosamines are produced during cooking, but the majority of nitrosamines are formed in the stomach. The non-carcinogenic toxic effects of nitrites occur at high concentrations. People who consume relatively large amounts of nitrites for a long time develop methemoglobinemia.
Sulfur dioxide and its salts are used to prevent browning of foods, for bleaching, as a broad-spectrum antimicrobial agent, and as antioxidants. Sulfites are very reactive, and therefore only low levels of them are allowed in food products. Sulfites can cause asthma in sensitive individuals. About 20 deaths are associated with human idiosyncrasy to nitrites (particular sensitivity to drinks containing sulfites). Approximately 1–2% of patients bronchial asthma exhibit increased sensitivity to sulfites. The pathogenesis of sulfite-induced asthma is not yet clear. A pathogenetic role of IgE-mediated reactions is possible.
Toxic food substances were first summarized in the list of “Substances Generally Recognized as Safe” - GRAS substances in the 60s of the last century. It is constantly replenished and plays an important role in ensuring food safety for people and animals.
It has long been noted that a low-calorie diet prolongs the life of many organisms - from single-celled organisms to primates; Thus, rats that consume 30–50% less calories than usual live not three years, but four. The mechanism of the phenomenon is not yet entirely clear, although it is known that there is some general change in metabolism, which reduces the formation of free radicals (many scientists blame them for aging). In addition, the concentration of glucose and insulin in the blood decreases, which indicates the participation of the neuroendocrine system in these processes. It is possible that moderate fasting also acts as a mild stress that mobilizes the body’s hidden reserves.
American microbiologists worked with yeast, whose lifespan is determined by the number of their possible divisions. It turned out that in an environment with a low nutrient content, the number of generations increases by 30%. At the same time, microorganisms significantly increase the rate of respiration, which is a key point, since yeast with a defective protein gene involved in the respiratory chain do not become long-lived.
It should be taken into account that yeast obtains energy in two ways - respiration and fermentation. When there is enough glucose in the environment, the genes that control respiration are silent and the fermentation of glucose into ethanol occurs anaerobically, that is, without the participation of oxygen. If glucose is in short supply, respiration turns on - a much more efficient process of producing energy.
With the development of industrial society, changes occurred in the formation of the biosphere. Many foreign substances, the product of human activity, have entered the environment. As a result, they affect the life activity of all living organisms, including ours.
What are xenobiotics?
Xenobiotics are synthetic substances that have a negative effect on any organism. This group includes industrial waste, household products (powders, dishwashing detergents), construction materials, etc.
A large number of xenobiotics are substances that accelerate the appearance of crops. It is very important for agriculture to increase the crop’s resistance to various pests, as well as to give it a good appearance. To achieve this effect, pesticides are used, which are substances foreign to the body.
Construction materials, glue, varnishes, household goods, food additives - all these are xenobiotics. Oddly enough, some biological organisms, for example, viruses, bacteria, helminths, also belong to this group.
How do xenobiotics act on the body?
Substances that are foreign to all living things have a detrimental effect on many metabolic processes. For example, they can stop the functioning of membrane channels, destroy functionally important proteins, destabilize the plasmalemma and cell wall, and cause allergic reactions.
Any organism is adapted to one degree or another to eliminate toxic poisons. However, large concentrations of the substance cannot be completely removed. Metal ions, toxic organic and inorganic substances eventually accumulate in the body and after a certain period of time (often several years) lead to pathologies, diseases, and allergies.
Xenobiotics are poisons. They can penetrate the digestive system, respiratory tract, and even through intact skin. Routes of entry depend on the state of aggregation, structure of the substance, as well as environmental conditions.
Through the nasal cavity with air or dust, gaseous hydrocarbons, ethyl and methyl alcohols, acetaldehyde, hydrogen chloride, ethers, and acetone enter the body. Phenols, cyanides, and heavy metals (lead, chromium, iron, cobalt, copper, mercury, thallium, antimony) penetrate the digestive system. It is worth noting that microelements such as iron or cobalt are necessary for the body, but their content should not exceed a thousandth of a percent. In higher doses they also lead to negative effects.
Classification of xenobiotics
Xenobiotics are not only chemical substances of organic and inorganic origin. This group also includes biological factors, including viruses, bacteria, pathogenic protists and fungi, and helminths. Oddly enough, but such as noise, vibration, radiation, radiation also belong to xenobiotics.
According to their chemical composition, all poisons are divided into:
- Organic (phenols, alcohols, hydrocarbons, halogen derivatives, ethers, etc.).
- Organoelement (organophosphorus, organomercury and others).
- Inorganics (metals and their oxides, acids, bases).
Based on their origin, chemical xenobiotics are divided into the following groups:
Why do xenobiotics affect health?
The appearance of foreign substances in the body can seriously affect its performance. An increased concentration of xenobiotics leads to the appearance of pathologies and changes at the DNA level.
Immunity is one of the main protective barriers. The influence of xenobiotics can extend to the immune system, interfering with the normal functioning of lymphocytes. As a result, these cells do not function properly, which leads to a weakening of the body's defenses and the appearance of allergies.
The cell genome is sensitive to the effects of any mutagen. Xenobiotics, penetrating into a cell, can disrupt the normal structure of DNA and RNA, which leads to the appearance of mutations. If the number of such events is large, there is a risk of developing cancer.
Some poisons act selectively on the target organ. Thus, there are neurotropic xenobiotics (mercury, lead, manganese, carbon disulfide), hematotropic (benzene, arsenic, phenylhydrazine), hepatotropic (chlorinated hydrocarbons), nephrotropic (cadmium and fluorine compounds, ethylene glycol).
Xenobiotics and humans
Economic and industrial activities have a detrimental effect on human health due to the large amount of waste, chemicals, and pharmaceuticals. Xenobiotics are found almost everywhere today, which means that the likelihood of them entering the body is always high.
However, the most powerful xenobiotics that people encounter everywhere are drugs. Pharmacology as a science studies the effect of drugs on a living organism. According to experts, xenobiotics of this origin are the cause of 40% of hepatitis, and this is no coincidence: the main function of the liver is to neutralize poisons. Therefore, this organ suffers the most from large doses of drugs.
Prevention of poisoning
Xenobiotics are substances foreign to the body. The human body has developed many alternative pathways to eliminate these toxins. For example, poisons can be neutralized in the liver and released into the environment through the respiratory, excretory systems, sebaceous, sweat and even mammary glands.
Despite this, the person himself must take measures to minimize the harmful effects of poisons. First, you need to choose your food carefully. Group “E” supplements are strong xenobiotics, so the purchase of such products should be avoided. You shouldn’t choose fruits and vegetables just by appearance. Always pay attention to the expiration date, because after it expires, poisons form in the product.
It is always worth knowing when to stop taking medications. Of course, for effective treatment this is often a necessary necessity, but make sure that this does not develop into systematic unnecessary consumption of pharmaceuticals.
Avoid working with hazardous reagents, allergens, and various synthetic substances. Minimize the impact of household chemicals on your health.
Conclusion
It is not always possible to observe the harmful effects of xenobiotics. Sometimes they accumulate in large quantities, turning into a time bomb. Substances foreign to the body are harmful to health, which leads to the development of diseases.
Therefore, remember the minimum preventive measures. You may not notice any negative effects right away, but after a few years, xenobiotics can lead to serious consequences. Don't forget about this.
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