Principles of Hygienic Normalization of Harmful Factors in the Environment

v Priority of medical indications at establishing a standard. At determining the value of a standard only the levels of its safe effect on organism are taken into account, instead of technical and economic reasons for observance of this specification.

v Differentiation of degree of biological response of organism to action of a harmful factor. Depending on level of a harmful factor, which influences organism, and resistibility of organism to harmful influence we can distinguish the following levels of biological responses:

Ø destruction of organism,

Ø llness,

Ø prepathology (disturbances of organism’s functions without clinical signs of disease),

Ø tension of adaptive-compensatory processes (functional disturbances of unknown aetiology),

Ø accumulation of substance in organs and tissues without functional and clinical changes.

Regulationsmust be established not higher than the 4th level.

v Division of objects of the environment for sanitary protection. As each object of the environment (air, water, ground, foodstuffs) has the physical and chemical features and different conditions of contact with a human organism, regulationsare established separately for each object of the environment.

v Principle of registering all probable adverse effects of the normalized factor on a certain object of the environment. There are the most important parameters reflecting the harmful action of the investigated factors on quality of a certainobject of the environment. Such parameters are called signs or criteria of a harmful action. They include: organoleptic, common sanitary, phytoaccumulative, water-migratory, air-migratory, reflectory, toxicological, etc. (see table below).

 

 

Table5

Signs of Harmful Action at Regulation of Harmful Factors in Objects
of the Environment

Sign of harmful effect	Type of unfavorable effect
Organoleptic	change of odour, taste, colouring, etc.
Common sanitary	influence on a saprophytic microflora, processes of self-cleaning
Phytoaccumulative	accumulation of pollutant in vegetative products
Water-migratory	accumulation of pollutant in ground waters
Air-migratory	evaporation of pollutant in the air not higher than MPC
Reflective	irritating activity on mucous membranes of organism
Toxicological	toxical effects on organism of animal
Specific	allergenic, gonadotropic, embryotropic effects
The remote effects	oncogenic, mutagenic effects

 

At studying each sign of harmful effect in laboratory a threshold concentration (TC) of pollutant for each sign of harm is determined; the parameter of harmful effect with the least TC is called a limiting sign of harmful action and according to it MPC is proved.

· Principle of presence of threshold (limiting) harmful effect is the central principle of normalization. For each harmful factor there is a threshold of harmful action — a level at which the harmful effect is registered (LOAEL) and a low level (NOAEL) — when such effect is absent.

· Principle of dependence of harmful effect on concentration (dose) of the investigated factor and time of its effect. It is based on mathematical dependences "concentration (dose) — effect" or "time — effect". The latter dependence is observed at chronic effect in the presence of cumulation (chronoconcentration poisons).

· Principle of laboratory experiment. The investigations of effect of the normalized factor on organism and sanitary living conditions are carried out in laboratory conditions at unification and standardization of techniques for comparison of results received by different researchers.

· Principle of aggravation. In laboratory researches the most adverse conditions are modelled promoting the maximal manifestation of harmful effects of the investigated factor. To the same principle the transfer of toxicological data received on laboratory animals to the human organism refers.

· Principle of relativity of standards. The established standards are not constant and final. At occurrence of new experimental data or results of negative effect of the normalized factor on health of population at levels lower than maximal permissible concentration, standards are reconsidered towards decreasing.