Pesticides

table_2.jpg The word “pesticide” itself to great extend outlines the problems related to it. The root “cide” which comes from Latin “kill” directly expresses the purpose of these substances – killing, destroying living creatures, war with nature. The root “pest” now in many world languages means “vermin”, and implies that man divides all creatures into useful for him and harmful denying the latter the right to existence.

“Pesticides” is a wide notion that includes many chemical compounds that have suppressing effect on animate nature. The most widely spread and known are insecticides which kill insects, herbicides which destroy herbs, fungicides directed against fungi and rodenticides which are fatal for rodents. But there exist means against other groups of living creatures: acaricides (acaridae), ichthyocides (fish), nematocides (coelelminth).

Besides, pesticides include repellents (substances to repel insects) defoliants (substances to accelerate leaves falling), desiccants (to dry plants on their roots) stimulants and inhibitors of plant growth as well as bactericides and antiseptics. About 700 (according to other data – 860) chemical substances are used as pesticides, and several thousand of medication forms are produced using them (only the Agency of Environmental Protection of the USA registered about 21,000 trade marks). But not more than 200 pesticides are widely spread.

It is usually believed that during the last century (the epoch when pesticides were used the most) there were three generations of pesticides. The first of them appeared almost simultaneously with the World War I, and according to any today’s measures it was something absolutely terrible as it consisted mostly of usual poisons toxic for humans and spine animals even more than for those “pests” against which they were used. These were compounds of arsenic and mercurial organic compounds, and what is more they were used in terrible concentrations.

Appearance and introduction of the second generation of means to fight the nature were also connected to war between people – the World War II. In the war time substance to control insects are especially needed because of overall hardships and mass movement of people bugs spread very quickly. That is why the whole world welcomed reinvented or applied for the first time to fight against insects organochlorine pesticides, including now notoriously known DDT and hexachloran which the same that 1,2,3,4,5,6-hexachlorcyclohexane (HCCH). It was then that other less known organochlorine pesticides appeared, among them aldrin, dieldrin, heptachlor, chlordane, toxaphene, mirax – later were included into “dirty dozen” of the most hazardous contaminants of the environment which today are unanimously condemned by the world community. Important fact is that nine substances from “dirty dozen”, that is two thirds are pesticides which once were gladly used as “wonderful remedy” for problems. To the class of organochlorine compounds are referred also a few herbicides including 2-4-D which is still used.

The second class of compounds which includes many pesticides of the second generation organophosphorus compounds including ethers of thiophosphorous acid. Among compounds of this class there are insecticides octamethyl, thiophos, mercaptophos. And it’s not by accident that to the same class refer substances produced as military poisonous substances for chemical wars well known as sarin and soman. The difference in the degree of poisonous characteristics of chemical weapons and pesticides is so little that there were a number of cases when militaries used pesticides storages as strategic reserve for potential military usage, and pesticides production often was the basis for producing fighting poisonous substances and vice versa. The same generation of pesticides includes carbamate herbicides and insecticides, derivatives of urea having herbicide action, various synthetic fungicides, bactericides, zoocides, nematocides. As early as in 1950s negative consequences of using pesticides of the second generation, especially DDT, became known. It gave impetus to appearance of the third generation which included mainly synthetic pyrethroids and hormonal substances. Their main characteristic difference is their ability to cause faster destruction and more intense poisonous action which allows decreasing the norms of usage. Because of this characteristic their usage implies that the content of pesticides remnants in agricultural products decreases but the probability of accidents is higher.

Among pesticides of the third generation we can mention sumicidine, ambush, cymbush and decis.

The harm caused to the living nature by pesticides cannot be measured precisely but we can say for sure that is immense. Two factors are main here: first, that all synthetic pesticides are substances alien to living nature and are not subject to metabolic decomposition and the second that all of them are capable of bioaccumulation, that is they are contained in living organisms in bigger concentration than in the environment. The most harmful pesticides are DDT, heptachlor, HCCH, that is first of all organochlorine pesticides but not only these. The process of bioaccumulation makes senseless the notion of “permissible dose” of poisonous chemicals because even if used in very little doses, they will accumulate in organisms. Sensibility to pesticides of animals of different kinds, even congenerical, may be very different; therefore, laboratory tests on one or even several species do not provide objective results. Most often an animal does not die directly because of poisoning but it gets weaker because of it and becomes a victim of predators (and as a result passes the toxin to them), diseases or severe weather conditions.

The nature of pesticides toxicity is various – it can be carcinogen or mutagen effect, impact on respiratory, endocrine, immune, nervous systems. Organisms of marine animals are especially contaminated with pesticides. As far as terrestrial mammals are concerned, the can be affected by pesticides “accidentally” in the result of agricultural usage of insecticides and herbicides as well as purposefully, for example when rodents are being killed. For both mammals and birds the most affected became the process of reproduction, as inability to produce healthy and numerous posterity is equal to death for a species. Also, for birds very disastrous effect has elimination of their food basis – insects; that is how people “paid back” to their old helpers in the matter of controlling “pests”.

It is obvious the creator of pesticides didn’t avoid their destroying effect. Pesticides poisonings of people are divided into acute and chronic, and to evaluate quantitatively others is very hard. Chronic poisonings are not yet subject to quantitative evaluation at all (though their numerousness is obvious)/ As far as acute poisonings are concerned, according to official statistics of different countries their number decreases. According to American researchers, up to 40% of people professionally related to production and usage of pesticides, judging from biochemical analysis of their blood, have characteristics of serious poisoning. But this is not the only risk group impacted by hazardous action of pesticides. Here we may also refer people living on the outskirts of the places where pesticides are applied and who get pesticides together with food products, those who drink water from springs situated close to burials of unused and prohibited pesticides and others.

Toxic influence of different classes of pesticides may cause considerable disorder of internals, in particular fatty infiltration of liver, kidneys, heart muscle, pancreas, damage of central nervous system and respiratory organs, abnormality of lipid exchange and other diseases.

Every year on December 3 International day of fighting with pesticides is marked – this is the day when in 1984 there was a catastrophe on pesticides plant in Bhopal (India) as a result of which about 200 people died.

On this day environmentalists of the whole world hold certain actions and protests reminding about accumulation in the environment of great amounts of harmful chemicals, in particular pesticides which are accumulated in the environment and build up in organisms of people and animals causing serious consequences.

In Ukraine still there is no proper registration of pesticides poisonings. Most of light poisonings are not registered, and the victims content themselves with self-assistance or a visit to first-aid post. In existing official statistic forms all poisonings including those with pesticides are placed under “other diseases”. Besides, because of the change of the ownership form and creation of small private farmers and use of seasonal workers, the owners are not eager to register cases of poisonings. Only officially employed people who suffered from group poisonings get to the Institute of Ecohygiene and Toxicology (Kyiv). The analysis of poisonings with pesticides during last 15 years shows that 13 group poisonings had place and more than 400 workers were injured.