The cumulative effect of adverse factors on the human body. OBZhD

BASICS OF SAFE LIFE
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The cumulative effect of adverse factors on the human body. Basics of safe life

Fundamentals of Safe Life Activities (OBZhD)

When assessing the impact adverse factors on the human body the degree of their influence on human health, the level and nature of changes in the functional state of the body, as well as the possibility of developing individual disorders are taken into account.

Assessing the admissibility of the impact of harmful factors on the body, they proceed from the biological law of the subjective quantitative assessment of the stimulus (Weber-Fechner law), which expresses the relationship between the change in the intensity of the stimulus and the strength of the evoked sensation.

On the basis of the Weber-Fechner law, the rationing of harmful factors is built, excluding irreversible maximum permissible levels or maximum permissible concentrations.

The maximum permissible level (MPL), or maximum permissible concentration (MPC), is the maximum value of a factor at which this factor, acting on a person (in isolation or in combination with other factors), does not cause biological changes in him and his offspring (even hidden or temporarily compensated), including diseases, changes in reactivity, adaptive-compensatory processes, immunological reactions, disorders of physiological cycles, as well as psychological disorders (decrease in intellectual and emotional abilities, mental performance). MPC and MPC are set for the production and environment. At the same time, they are guided the following principles:

priority of medical and biological indications for the establishment of sanitary regulations over other indications (technical, economic, etc.);
threshold action of adverse factors (including chemical compounds with a mutagenic or carcinogenic effect of action, ionizing radiation);
advancing the development and implementation of preventive measures in relation to the appearance of harmful factors.

Under environmental conditions, especially in industrial conditions, a person is usually exposed to multifactorial effects, the effect of which may be more significant than with their isolated action.

It has been established that the toxicity of poisons in a certain temperature range is the lowest, increasing both with an increase and a decrease in air temperature. The main reason for this is a change in the functional state of the body: violation of thermoregulation, loss of water during increased sweating, changes in metabolism and acceleration of biochemical processes. In particular, increased breathing and increased blood circulation lead to an increase in the penetration of poisons into the tissues of the body. The expansion of the vessels of the skin and mucous membranes increases the rate of absorption of toxic substances through the skin and respiratory tract. Thus, an increase in the toxicity of action at elevated air temperatures was noted in relation to many volatile poisons: gasoline vapors, mercury vapors, nitrogen oxide, etc. Low temperatures increase the toxicity of benzene, carbon disulfide, etc.

An increase in air humidity also increases the risk of poisoning, especially from poisonous gases. The reason for this is the intensification of hydrolysis processes, an increase in the retention of poisons on the surface of the mucous membranes, and a change in the aggregate state of poisons. The dissolution of poisons with the formation of weak solutions of acids and alkalis enhances their irritating effect.

Changes in atmospheric pressure also affect the toxic effect. At elevated pressure, the increase in the toxic effect occurs due to two reasons. It matters, firstly, the greatest intake of poisons due to an increase in the partial pressure of gases and vapors in the atmospheric air and their accelerated transition into the blood, and secondly, a change in the functions of respiration, blood circulation and the central nervous system. Reduced atmospheric pressure enhances the effect of poisons such as benzene, alcohol, nitrogen oxides.

Of the many combinations of adverse factors, dust and gas combinations are the most common. Gases are adsorbed on the surface of particles, as a result of which the local concentration of adsorbed gases can exceed their concentration directly in the gas phase. The toxicity of aerosols largely depends on the gases adsorbed in them. The toxicity of gas-aerosol compositions is subject to the following rule: if the aerosol penetrates the respiratory tract deeper than the other component of the mixture, then there is an increase in toxicity.

Considering the combined effect of unfavorable factors of physical and chemical nature, it should be noted that at high levels of exposure, potentiation, antagonism and an independent effect are observed. At low levels, as a rule, there are additive dependencies (obtained by addition, from Latin additio - addition). It is known to increase the effect of the toxic effect of lead and mercury, benzene and vibration, karbofos and ultraviolet radiation, noise and manganese-containing aerosols.

Noise and vibration always increase the toxic effect of industrial poisons. The reason for this is changes in the functional state of the central nervous system and the cardiovascular system. Noise enhances the toxic effect of carbon monoxide, styrene, etc. Vibration, changing the reactivity of the body, increases its sensitivity to other factors, such as cobalt, silicon dust, dichloroethane; carbon monoxide is also more toxic when combined with vibration.

Ultraviolet radiation, influencing the interaction of gases in the atmospheric air, contributes to the formation of smog. At the same time, ultraviolet irradiation can reduce the body's sensitivity to certain harmful substances due to increased oxidative processes in the body. Thus, the toxicity of carbon monoxide under ultraviolet irradiation is reduced due to the accelerated dissociation of carboxyhemoglobin and faster removal of the poison from the body.

Heavy physical labor is accompanied by increased ventilation of the lungs and increased blood flow, which leads to an increase in the amount of poison entering the tissues. In addition, intense physical activity can lead to the depletion of adaptation mechanisms with the subsequent development of occupational diseases.

Assessing the combined effect of unfavorable factors on the body, it should be noted that, as a rule, early changes in the body are not specific to the action of any of them and reflect only the breakdown of adaptive reactions.

With continued exposure to overdose levels, the frequency of occupationally caused general diseases increases or various forms of such diseases form.

Occupational diseases caused by external physical factors include: vegetative-vascular dystonia (due to exposure to ionizing radiation), vibration disease (due to vibration), cochlear neuritis (with systematic exposure to industrial noise), visual impairment from exposure to electromagnetic radiation, etc. .

Authors: Aizman R.I., Krivoshchekov S.G.

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