Ionizing contamination

The human being has always lived and evolved in the world filled with radio-activity and ionization. Biosphere of the Earth has more than 60 natural radionuclides - primary and cosmic. Primary radionuclides are isotopes of elements with long half-life and decay product of long living isotopes of uranium and thorium; cosmic – are some which appear after interaction of space radiation with substance of atmosphere or with solid substance of the earth. Every second human's body gets tiny particle through. Ground, walls of houses, air, food, person himself are radioactive. Therefore it is possible to assert that the natural background doze which influences the mankind for thousands of years is not dangerous because mankind got accustomed to such exposure during natural selection.

Researches done in the field of atomic nucleus and using nuclear energy create artificial sources of ionizing radiation. At the first stage of using nuclear energy the problem of radiation safety concerned only to staff that worked with nuclear arrangements and radioactive substances, in modern conditions when nuclear power's got fast development it is necessary to take into account global scattering of artificial radioactive substances and increasing rate of natural radionuclides circulation what predetermines an additional exposure on any living organism. The increasing of radiation factor in global scale has set a problem on development of principles for public health services with account of direct influence of ionizing radiation on objects of a natural medium.

Radioactive contamination of environment is caused by two types of radiation – corpuscular and electromagnetic. Corpuscular radiation includes flows of α – и β – particles and neutrons, electromagnetic one is χ-rays (λ= 10 ⁹. 10 ^-12 m) and γ- radiation (λ<10 ^-12m). Corpuscular and electromagnetic radiation with indicated range of wavelength is able to split electrically neutral molecules forming charged ions during interaction with substance.

That's why the cumulative title of these types of radiation is ionizing.

Each of the mentioned above types of radiation has various properties and characteristics the most important of them are penetrating and ionizing abilities.

Source of ionizing radiation can be closed when radioactive substances can't penetrate into environment from installation, and opened, when such possibility exists.

The exposure of an organism can be external and internal. An external exposure is when the source of it can be outside of an organism, and internal - it's inside. The radioactive substances can get inside an organism with the air through respiration, as a radioactive dust, with water, food, smoke. The internal sources are more dangerous, because their influence on the organism is constant what results in accumulation of ionizing atoms and molecules.

The ionization of an organism is followed by complicated physical-chemical and biological processes, breaking of molecular bones, modification of molecules structure, killing cells, violation of normal physiological processes, exchange of substances are possible to refer to. Besides, the structure and functions of blood is infringed, the protective responses of an organism are reduced and the malignant swellings arise and develop. These and other symptoms characterize the so called radiation sickness which is fatal.

The special danger for biological world is in the fact that modifications occurring in an organism of people and animals under influence of radio-activity concerns only to them, but also the next generation which may nave inborn defects.

The radio-activity causes changes in all living things. Virus and bacterium being under exposure in future can form new mutations of morbific microbes and cause unknown epidemics.

In accordance to the standard «Нормы радиационной опасности» there are three categories of the people being under exposure set: A category is staff that constantly or temporarily works directly with sources of ionizing radiation; the category В – people who don't work directly with radiation sources, but in living conditions or working can get under the influences of radioactive substances, which are used at the appropriate technologies and expose into environment with waste; category С – rest of the country population.

Taking into account sensitivity of separate organs of the person to ionizing radiation they are divided into three groups (in order of decreasing of influence):

I - whole body, red marrow, genitals;

II - muscles, liver, kidneys, lungs, alimentary canal, eyeball;

III - skin, bones.

Using of atomic energy is not connected with the threat of an erasure of life on the Earth, but violation of norms and rules of radiation safety gets people under direct danger for health from radioactive substances. Therefore while projecting and constructing of power stations it is necessary to pay close attention to this problem. The main problem here is a problem of neutralization of nuclear industry waste.

Many countries practice radioactive waste burial at the bottom of the ocean. So into the Atlantic and Pacific oceans there were thrown hundreds of thousands of containers with high radio-active waste. The containers were rejected into deep-water areas with small circulation and low biological activity. However, as researches showed, in many areas intensity of circulation and biological activity had been increased.

The solid radioactive waste (polluted materials, workcloth etc.) are put into concrete trenches and filled up with concrete.

3.6 Nitrates in foodstuffs and their influence on the human's organism

Nitrates are saline of nitrogen acid the must widespread substance in nature. Nitrates take place in ground, water; they are the chemical component of plants, products of substances exchange in organism of humans and animals. People experience influence of nitrates during living all the time. However, in case when loading of these substances on an organism is too heavy they can have a negative effect.

Nitrates loading on the organism of the person has noticeably increased recently. This problem has arisen due to chemicalixation of the agriculture, application of mineral fertilizers containing nitrogen (potassium niter KNO3, natrium niter NaNO3, ammoniac niter NH4NO3) for increasing agricultural harvest.

The problem of nitrates has two aspects, which are interconnected but have some features. It is the aspect of nitrates in potable water and aspect of nitrates containing in foodstuffs.

Such important components as protein, fat, carbohydrate, vitamins and other, and also various chemical substances: pesticides, toxic elements, nitrates and other take place in foodstuffs. Contents of chemical substances in food can vary in wide range: from the concentration safe for people, to the level which represent actual danger for health. Nitrates serve as the obligatory part of foodstuffs, but their amount should stay in acceptable limits.

There are known over 20 factors able to increase nitrates accumulation in vegetative food. They concern to: light deficit, heat and cold in plants vegetation period, drought and constant overly moistening, large and small amount of such elements as nitrogen, potassium, phosphorum in a ground, biological activity of a ground, ground acidity, ground disease etc. But the primary factor stays non-rational applying of nitrogen fertilizers, violation of agrotechnic processing agricultural cultures.

Intoxication by nitrates is characterized by heavy passing and can cause death. Nitrates toxic action consists in hypoxia (oxygen starvation of tissues). Clinical indications of nitrates poisoning occur in l -l,5 hours after getting into an organism with potable water. At first period there's cyanosis of lips, mucous envelopes, nails, face observed. Then irritating affecting of mucous envelope is exhibited with sickness, pain in stomach area, salivary emissions, vomiting. In case when nitrates get into organism with food the latent period of disease is more prolonged - from 4 till 6 hours.

When there's suspicion of poisoning by nitrates and nitrites patient gets stomach washing out, later, on he takes activated carbon suspension (2 spoons per glass of water), and after that salt laxative mixture.

The hygienic regulation of acceptable concentration for nitrates in separate foodstuffs is carried out with account of concrete climatic and economic regions. Here it is necessary to take into account the acceptable daily doze of nitrates, daily using of food, background nitrates' level in foodstuffs. The acceptable daily doze of nitrates for the person makes 5 mg for 1 kg of body weight.

For checking out parameters of acceptable nitrates contents in separate food the counting by the following formula is carried out:

DDD > Σ_i D_k N_i Crf Cf ,/ Сь_е

where DDD - acceptable daily doze of nitrates, mg; D_k -acceptable daily doze of nitrates for foodstuffs, including potable water, mg/kg or mg/l; N_i - average daily use, kg/1; Crf- coefficient of nitrates concentration changing in ready-cooked food, Crf=0,5-1.0; Cf- coefficient of foodstuffs, Cf =0,6-0,9; Сь_е - coefficient of biological equivalence of nitrates «food : water»; for potable water I Crf=Cf= Сь_е =1,0.

Nitrates can be accumulated in increased amount not only in vegetative food, but also in food of animal origin and first of all in milk.

As the practice testifies, contents of nitrates in vegetative food quite often exceed acceptable level. That forms the basis for determination of ways for their correct use. The amount of nitrates in plants depends on their biological features. Vegetables contain the most quantity of nitrates in greens (parsley, dill, salad etc), edible roots (garden radish, beet, carrots). Nitrates contents accumulated in tomatoes and potatoes are comparatively slight. Cucumbers and cabbage take place between these two vegetable groups. The early vegetables contain nitrates more, than the latter ones. As the matter of fact nitrates, concentration in hothouse vegetables is more than in vegetables growing in open ground. Rather little nitrates quantity is accumulated in fruit and berries. The researches show, that contents of nitrates in vegetables is distributed irregularly. For example, amount of nitrates in leaves of parsley, fennel is for 50..60 % lower than in their stalks; amount of nitrates in upper part of carrot is for 80% lower than in internal. In cucumbers, radish, on the contrary, the surface layer contains for 70 % of nitrates more than internal.

Usual washing and mechanical clearing of food (potatoes, beet, carrot, cabbage etc) reduces contents of nitrates in average for 10 %. Significant reduction of nitrates is observed on steeping of the cleared food. After steeping of potatoes, carrot, beet during 1 hour the level of nitrates decreases for 25-30%, greens (parsley, fennel, green onions) - for 20 %. The reduction of nitrates contents in food can be reached by cooking. While boiling they turn into broth, what decreases nitrates contents: in potatoes - for 80 %, carrots and cabbage - for 60-70 %, beet - for 40-50 %. Preserving decreases contents of nitrates in food. It is achieved by transition of nitrates into pickle (on souring) or marinade (on pickling and preserving). Making juices and drying of vegetables, on the contrary, increases contents of nitrates.

The important element of maintenance of the guaranteed quality for foodstuffs is controlling them, including parameters of nitrates contents and others chemical polluters in foodstuffs.

Table 3.1 indicates acceptable levels of nitrates contents in some vegetables. j

The controlling of foodstuffs quality is carried out by:

-manufacturer;

- special official establishments - sanitary-epidemic stations;

- public organizations.

For detection of nitrates: there is whole arsenal a research tests:

- photometric methods are based on transformation of nitrates into nitrites with following synthesis of dyes (solution coloring) with nitrites. The intensive the coloring of a researched solution is the more concentration of nitrates is in it;

- chromographic methods: method of gas chromographing, gas-liquid and ionic chromographing. Last is the most perspective for arbitration researches which require high fidelity;

- electrochemical, volt-ampere-meter, potentiometer with application of ion-selective electrodes methods for nitrates дdetection.

Table 3.1 - Acceptable levels of nitrates contents in some vegetables

Planning foodstuffs quality tests on parameters of chemical danger the following classification of normal controlling is used:

- once for one year;

- once for one quarter;

- once for one month;

- once for ten days;

- in each foodstuffs lot.