What it is
First, let’s understand what pesticides are. The root “cid” , which comes from the Latin word “kill”, says that the direct purpose of these substances is to kill the living. The root “pestle” , which still means “pest” in many languages of the world, makes it clear that a person divides all creatures into useful and harmful ones, denying the latter the right to exist.
Pesticides, at least on a small scale, have been used since ancient times. The ancient Greeks and Romans used arsenic as a pesticide. There is evidence that the Chinese used arsenic derivatives as pesticides as early as the sixteenth century. In the late nineteenth century, arsenic compounds began to be widely used as an insecticide in Europe and North America. This led to the first pesticide legislation in 1900.
But the use of synthetic chemical pesticides only began in the 1930s . And then, after the Second World War, large-scale production and use of synthetic chemical pesticides and fertilizers began. Initially, this led to a dramatic increase in yields as a result of the use of pesticides and other agrochemicals. Agricultural production expanded rapidly in developing countries to sell products to industrialized countries. Another consequence of the new agrochemical technology was the expansion of the practice of monoculture : the same crop was grown year after year on the same site, without crop rotation and without leaving the land fallow.
With increasing use of pesticides, many target pests have begun to develop resistance to them. This often forced farmers to increase the doses of pesticides to combat them. The pesticides not only killed the target insects, but also the beneficial species. This led to a new phenomenon called secondary pest outbreaks : insects or mites, previously kept in check by beneficial species, began to appear in epidemic numbers. New pesticides were introduced to control secondary pests, and the total amount of pesticides in soil and water in use continued to rise.
The pesticides used killed soil microorganisms , which play a key role in providing plants with the nutrients they need to grow and develop.
Pesticides were often carried by air currents, contaminating nearby areas, and harming populations of birds, mammals, fish, and other species. Pesticide infiltration into surface water bodies and groundwater has begun to threaten drinking water sources. By the mid-1950s, numerous studies had been performed showing these and other problems associated with pesticides.
“Pesticides”- a broad concept that covers many chemicals that have a depressing effect on wildlife. The most common and known insecticides that kill insects; herbicides that destroy herbaceous plants; fungicides against fungi; rodenticides harmful to rodents, etc. Most pesticides are poisons, poisoning target mechanisms, but they also include sterilizers (substances that cause infertility) and growth inhibitors. Initially, according to the provisions of the Stockholm Convention, nine types of organochlorine pesticides were classified as persistent organic compounds (POPs). This list is currently expanded. All these compounds are highly toxic, can accumulate in the environment and the human body, and are able to travel long distances. Their decay period lasts for decades.
Sometimes repellents are also referred to as pesticides. Harmful can be considered any animal, plant or other organism that is undesirable at a given time or in some situation, mainly for medical, economic or aesthetic reasons.
Over the centuries, people have invented various ways to control pests and weeds. Methods such as crop rotation, swamp drainage, weeding, pest traps and insect nets can be considered classic and are still used today. However, today they are trying to solve this problem with the help of pesticides. Every day the issue of their placement and disposal becomes more and more urgent. The harm caused by pesticides to wildlife cannot be accurately assessed. But with absolute certainty we can say that it is huge.
Pesticides are divided into groups depending on which organisms they affect. Herbicides are used against weeds; bactericides – against bacteria; fungicides – against parasitic fungi; algicides – against algae. To control animal pests, insecticides (against insects), acaricides (against ticks), rodenticides (against rodents), avicides (against birds), etc. are used.
Generally, pesticides are poisons, but not always; they also include desiccant (withering the body) and growth regulators. Most pesticides are chemical compounds, but not always; viruses and other pathogens are also used to control weeds and pests.
The use of pesticides allowed not only to obtain stable crops, but also to limit the spread of infections transmitted by animal vectors, such as malaria and typhus. However, the ill-conceived use of pesticides has negative consequences. It leads to the emergence of resistant species of organisms, especially among insects; destroys predators (natural enemies of pests) and other useful animals. Polluting the environment, pesticides also threaten humans: now they are found even in groundwater.
Growing concerns about the misuse of pesticides have led to the development of regulations for their use adopted in industrialized countries. They cover all aspects of the handling of these products: their transportation, storage, disposal of empty containers, maximum allowable residual quantities and much, much more. Because of the danger they pose, organochlorine insecticides (chlorinated hydrocarbons), such as chlordane, DDT, and others, are being phased out, although they have undoubtedly brought some benefit to both public health and agriculture. Some fumigants that were previously used for gas disinfection of soil and stored grain are also prohibited.
Although the number of different insecticidal preparations is the most commercialized in terms of the number of titles, herbicides lead in terms of the amount applied, and insecticides are in second place. The use of pesticides continues to grow, and this trend is likely to continue in the future.
According to their function, herbicides can be divided into several groups. One of them includes substances used to sterilize the soil; they completely prevent the development of plants on it. This group includes sodium chloride and borax. Herbicides of the second group destroy plants selectively, without affecting the desired species. For example, 2,4-dichlorophenoxyacetic acid (2,4-D) kills dicotyledonous weeds and unwanted trees and shrubs, but does not harm grasses. The third group includes substances that destroy all plants, but do not sterilize the soil, so that plants on this soil can then grow. This is how, for example, kerosene acts, apparently the first substance used as a herbicide. The fourth group combines systemic herbicides; applied to the shoots, they move down the vascular system of plants and destroy their roots.
Many fungicides are inorganic substances containing sulfur, copper or mercury. Sulfur was probably the first effective fungicide and is still widely used today, especially to control powdery mildew. Of the organic compounds, formaldehyde was the first to be used against fungi. Synthetic organic fungicides, such as dithiocarbamates, are now the most common. Streptomycin-type antibiotics are also used to fight fungi, but more often to protect plants from bacteria. A systemic fungicide travels throughout the plant and acts like an antibiotic, curing or preventing disease caused by fungi. Fungicides are widely used to control mold. For example, sodium propionate is added to bread for this purpose.
Insecticides are usually classified according to their mode of action. Intestinal poisons, such as arsenic, poison pests that eat the plants they have treated. Contact insecticides, such as rotenone, kill insects when they land on the surface of their body. Fumigants, such as methyl bromide, work by entering the body through the respiratory tract.
DDT (C14H9Cl5) is a classic example of an insecticide. In form, DDT is a white crystalline substance, tasteless and almost odorless. First synthesized in 1873 by the Austrian chemist Othmar Zeidler (en: Othmar Zeidler), it was not used for a long time until the Swiss chemist Paul Müller discovered its insecticidal properties in 1939, for which he received the Nobel Prize in Medicine in 1948 year, as “For the discovery of the high effectiveness of DDT as a contact poison.”
DDT is highly resistant to decomposition: neither critical temperatures, nor enzymes involved in the neutralization of foreign substances, nor light can have any noticeable effect on the process of DDT decomposition. As a result, getting into the environment, DDT one way or another gets into the food chain. Circulating in it, DDT accumulates in significant quantities, first in plants, then in animals and, finally, in the human body.
High fat solubility and low water solubility cause DDT to be retained in adipose tissue. The rate of accumulation of DDT in the body varies depending on the type of organism, duration of exposure and concentration, as well as environmental conditions. The high retention rate of DDT means that toxic effects in organisms can occur with a time delay, as well as at a significant geographic distance from the site of exposure. In general, organisms of high nutritional levels tend to accumulate large amounts of DDT compared to organisms of lower nutritional levels. DDT is able to be transported around the world in migratory animals, as well as ocean and air currents.
Thus, DDT, accumulating in living organisms, has a toxic effect on them, varying in strength depending on the concentration of DDT in a living organism. It should be noted that many sources contain statements about the carcinogenic, mutagenic, embryotoxic, neurotoxic, immunotoxic effects of DDT on the human body. DDT has also been claimed to cause or contribute to a variety of human diseases not previously thought to be associated with any chemical. These include cardiovascular disease, cancer, SARS, retrorental fibroplasia, polio, hepatitis, and “neuropsychiatric manifestations.”
Available data on the consequences of the toxic effects of DDT on other living organisms can be summarized as follows. Aquatic microorganisms are more sensitive to the action of DDT than terrestrial ones. At an environmental concentration of 0.1 µg/l, DDT is able to inhibit the growth and photosynthesis of green algae.
Indicators of both acute and chronic toxicity for different types of aquatic invertebrates of DDT are not the same. In general, DDT exhibits high acute toxicity to aquatic invertebrates at concentrations as low as 0.3 µg/L, with toxic effects including reproductive and developmental disorders, cardiovascular changes, and neurological changes.
DDT is highly toxic to fish: LC50 values (96 h) obtained in static tests range from 1.5 µg/l (largemouth bass) to 56 µg/l (guppies). Residual levels of DDT above 2.4 mg/kg in winter flounder roe caused abnormal development of embryos; with similar residual concentrations, as was found, the death of fry of lake trout in natural conditions is associated. The main target of the toxic action of DDT may be cellular respiration.
Another classification method comes from the chemical nature of insecticides: they are divided into inorganic or organic (natural and synthetic). Inorganic, in particular fluorine compounds, are not very effective and accumulate in the soil. Natural organic insecticides, such as the alkaloid nicotine, have largely fallen out of use; however, feverfew is still widely used both in the house and in the garden, since it is not dangerous for warm-blooded animals. Most often, synthetic organic compounds are now used, especially organophosphorus, organosulfur, carbamates and pyrethroids. Almost all organochlorine insecticides are banned in most countries because they poison the environment.
Pesticides are inhibitors (poisoners) of enzymes (biological catalysts). Under the influence of pesticides, part of the biological reactions ceases to occur and this allows you to: fight diseases (antibiotics), keep food longer (preservatives), destroy insects (insecticides), destroy weeds (herbicides). Pesticides are used primarily in agriculture, although they are also used to protect food supplies, timber and other natural products. In many countries, pesticides are used to chemically control forest pests, as well as vectors of human and domestic animal diseases (for example, malarial mosquitoes).
Pesticides vary in their specificity and effectiveness, that is, in the range of organisms they affect. DDT, for example, has a wide spectrum of activity, killing many animal species. Pirimicarb has a much narrower spectrum of action – it acts on aphids and dipterans, but does not affect beetles and many other insects. Similarly, dalapon kills monocots but spares dicots, and herbicides based on phenoxyacetic acid have exactly the opposite effect.
The use of broad-spectrum pesticides is fraught with the “revival” of pests, that is, their appearance after treatment in a greater quantity than before. This is due to the fact that the drug kills not only pests, but also predators that destroy them.