Features of Hygiene of Work in Agriculture

As a whole the work in agriculture has a number of features as compared to work in other spheres of industry which can negatively affect the health of working people. They include the following:

· Seasonal irregularity and urgency of work - nonuniform load during a year; in some periods there is very hard work with no fixed hours (for example, sowing, harvesting seasons,). It can cause early fatiguability, overstrain and possible disorders of health.

· Work in the open air in different seasons at influence of adverse meteorological factors - overheating, overcooling, excess UVR + chemicals – melanomas on the skin are more often encountered in agricultural workers in South regions.

· Hard physical work may cause early overfatigue.

· Contact with traumatically dangerous mechanisms. The level of traumatism in agriculture is higher than in industry.

· Remoteness of work places from residence. Absence of transport causes big energy losses, hence early fatiguability.

· A wide chemization of agriculture - contact with a big amount of different toxicants at combined and complex action on organism. It is the most unfavourable feature of agricultural work and we’ll stop on it in detail.

Hygiene of Application and Toxicology of Agrochemicals

Agrochemicalsare a big group of chemical substances of natural and anthropogenic origin applied in agriculture. There are more than 5,000 chemical substances used as agrochemicals. The basic groups of agrochemicals are pesticides, fertilizers, growth stimulators, etc.

Hygiene and Toxicology of Pesticides

Pesticides (in translation “eliminating harm”) are chemical and biological means of protecting plants from pests, weeds and illnesses. It is the most dangerous group of agrochemicals due to a high level of toxicity for person.

Despite the great toxicological and ecological damage from application of pesticides, it is impossible to refuse their usage, as it leads to destruction of about 50 % of crop that in conditions of world deficiency of foodstuffs, especially proteins, is inadmissible.

To decrease danger of pesticides for the man and environment their assortment is constantly changed and updated by prohibition of especially stable and toxic preparations, a constant toxicological and hygienic selection of newly synthesized preparations with high selective toxicity for vermins and low toxicity for man and biota. The leading world chemical concerns (“Bayer”, etc.) constantly synthesize new pesticides, though only 1 of one million suggested preparations is allowed for application.

The Development of Hygiene and Toxicology of Pesticides

The USSR was a leading country in studying this problem. The researches began in the 30s of the XX century. The founder of the doctrine about hygiene of work with pesticides academician L. I. Medved worked in Kiev scientific research institute of hygiene of work and occupational diseases. In 1965 he organized an All-Union research institute of hygiene and toxicology of pesticides; academician J. I. Kundiev developed the doctrine of percutaneous effect of pesticides. Academician J. S. Kagan is a leading scientist in toxicology of pesticides, academician E. I. Goncharuk created the theory of regulation of pesticides in soil.

Classifications of Pesticides

v Hygienic classification of pesticides (Table 42)

Ø by general toxicity for animals

Table 43

Degree of toxicity	LD 50 mg/kg per os
Extremely poisonous substances	< 50
Highly toxic	50-200
Moderately toxic	200-1000
Low toxic	> 1000

 

Ø by percutaneous toxicity for animals

 

Degree of toxicity	LD 50 on the skin, mg/kg
Sharply expressed toxicity	< 300
Expressed toxicity	300-1000
Poorly expressed toxicity	> 1000

 

Ø by ability to cumulation

Ability to cumulation	Factor of cumulation
Supercumulation	< 1
Expressed cumulation	1-3
Moderate cumulation	3-5
Slight cumulation	> 5

 

 

Ø by degree of volatility

Danger of inhalation poisoning	Parameters
Very dangerous substances	The saturating concentration at 20ºС is higher or equal to toxic one
Dangerous substances	The saturating concentration is higher than the threshold concentration
Low-dangerous substances	The saturating concentration is lower than the threshold concentration

 

Ø by stability in the environment

 

Degree of stability	Time of decomposition up to non-toxic components
Very stable	> 2 years
Stable	0.5-2 years
Moderately stable	1-6 month
Not stable	< 1 month

 

Classification by application:

Ø Insecticides - for struggle against insects

Ø Acaricides - for destruction of ticks

Ø Algicides – for destruction of seaweeds

Ø Arboricides - for destruction of trees and bushes

Ø Bactericides – for struggle against bacterial illnesses of plants

Ø Larvicides - for destruction of larvae and caterpillars of insects

Ø Ovicides - for destruction of insect eggs

Ø Zoocides - for struggle against rodents

Ø Limacides - for destruction of molluscs

Ø Fungicides – for destruction of fungi

Ø Herbicides - for struggle against weeds:

Ø Defoliants - for removal of plant foliage.

v Classification by way of entry into organism of insects:

Ø Contact - at contact with any part of an insect body;

Ø Intestinal – getting into insect organism per os;

Ø Fumigants - through the respiratory organs of insect;

Ø Systemic – getting to all parts of plants.

v Classification of pesticides according to chemical structure:

Ø Chlorine-organic pesticides (CHOP) - DDT, aldrin, dildrin, hexachloran, etc.

Ø Organophosphorus pesticides (OPHP) – carbophos, chlorophos, phosphamide, etc.

Ø Carbamates - derivatives of aminoformic acids – sevin, zineb, maneb, ziram, etc.

Ø Mercury and arsenic-containing pesticides – mercuran, granozan, arsenit calcium, etc.

Ø Copper preparations – compounds of copper - copper sulfate, Bordo liquid.

Ø Derivatives of symmetric triazines – atrazin, propazin, simazin.

Ø Synthetic pyretroids – ambush, zimbush, decis, etc.

Toxicological Characteristics of the Main Groups of Pesticides

· CHOP (Chlorine organic pesticides). The mechanism of insecticide and toxic action consists in blockade of respiratory enzymes in tissues, especially cytochrome oxidase (an indicator enzyme for diagnostics of poisoning). The symptoms of poisoning are: affection of the CNS, liver, kidneys, endocrine system, a mutagenic, gonadotropic, cancerogenic action.

· The ecological danger consists in the fact that they are very stable in biosphere, therefore practically all of them are forbidden for application. According to data of Washington Academy of Sciences the half-life period of DDT in biosphere is some centuries.

· PHOP (Phosphorus organic pesticides). The mechanism of their action consists in blockade of enzyme cholinesterase in blood. Cholinesterase is necessary for destruction of acetylcholine, when it is inactivated, the accumulation of acetylcholine in synapses takes place. Two stages of poisoning are distinguished - excitation, then suppression and destruction of vital centers of CNS. The symptoms are overexcitation of choline-reactive systems. Poisonings due to small stability of PHOP in the environment (1-3 months) are more often acute. Last years the remote neurotoxicity is found out for PHOP, i.e. damage of the peripheral nervous system and CNS in years after poisoning (functional cumulation). Prospects for further application are insignificant because of high toxicity and adaptation of pests (the oldest group of pesticides).

· Carbamates(salts of carbaminic acids). Now this group is frequently suggested by chemical firms. The mechanism of their action is similar to that of OPHP, but blockade of cholinesterase is reversible and in some time its activity is restored, therefore poisonings are less severe than at action of OPHP. They are rather stable in biosphere (about a year and more); for some preparations the remote effects are established (in experiment).

· Mercury and arsenic-containing pesticides. The mechanism of their action is blockade of carbothiolic enzymes (containing SH-group). They are extremely toxic and are applied as fungicides for grain.

· Preparations of copper. It is an old group of preparations applied on vineyards, including in Crimea. They are low-toxic - in intestines copper albuminates are formed – there is no absorption in blood, they have an irritating action in intestines. Poisonings are usually of mild or moderate degree. The treatment is gastric lavage, application of antidotes against heavy metals - pectins, unitiol.

· Symmetric triazines. They are widely applied as herbicides in rice fields in the Crimea and with waste waters they pollute the coastal sea water areas. Basically they are low-toxic. They have high stability in biosphere. They produce a cytotoxic action, i.e. affect the structure of nucleic acids.

· Synthetic pyretroids – a rather new group with high selectivity for insects. They are synthesized on the basis of natural pyrethrins (flowers of Dalmatia camomile at the beginning of 20th century were applied as insecticides). They are low-toxic for man and are also unstable in the environment, the mechanism of their action is poorly investigated; there is certain evidence about the remote effects. This is a promising group of preparations but they are rather expensive.

Hygiene of Work with Pesticides

As it is a very toxic group of agrochemicals, the demands to conditions of work and contact with these substances are very strict.

Hygiene of Work at Pesticide Storage

The territory of pesticide warehouse should be protected from access of other people, it must be removed from dwelling houses and other objects at a distance of 200-1000 m depending on toxicity of stored preparations; if there is an extremely toxic group of pesticides the distance should be 1 km. On the territory, apart from warehouse building, there should be platforms for washing off motor transport and mechanisms from remnants of pesticides, facilities for prevention of sewage into the surroundings. The internal covering of warehouse should be made of non-adsorbing materials, preparations should be stored in a hermetic container, there should be good ventilation, premises for staying the personnel, storage of clothes, and shower. There should be constant current sanitary control over levels of pesticide pollution of air, hands, overalls of personnel, containment of preparation packing, rules of work with toxic substances.

Hygiene of Work at Pesticide Transportation

The common rules of transportation of chemically dangerous cargoes include the following: special transport, routes specially chosen by sanitary service – far off towns, hospitals, sanatoria, etc. In the car there should be means of individual defence and disintoxication of pesticides in case of accident.

Hygiene of Work at Pesticide Application

As many pesticides are highly toxic substances, strict security measures are required at work with them, including:

· Restriction of working time - 4 hours (pesticides of 2-3 class of danger) or 2 hours (1 class of danger);

· Observance of terms of work resumption (after processing plants), in greenhouses it is very small - 1-3 days;

· Observance of expectation term - the period between processing and harvesting (it depends on toxicity, stability of preparation, culture of plants), for example, for OPHP on apple trees - 20 days;

· Preliminary and current physical examinations, early revealing and treatment of pesticide poisonings (in special clinics);

· Preventive and current sanitary control at application of pesticides;

· Use of individual means of protection of respiratory organs and skin;

· Observance of rules of personal hygiene – taking shower after work, meals in special places.

Ecologic and Hygienic Estimation of Ways of Pesticide Application

Pesticides in agriculture are applied by 3 ways: aircraft sprayers, tractor sprayers and individual sprayers. Each way has its advantages and disadvantages concerning health of working people and protection of biosphere.