Rules of Sanitary Estimation of the Environment at Combined Pollution

1. In case of antagonism at combined effect the estimation of environment (water, air, etc.) is carried out by comparison of concentration of each revealed substance with its MPC separately. Estimation of the object is given by formula:

 

C / MPC < 1,

 

where

C — concentration of revealed substance,

MPC — its maximal permissible concentration in the given object of the environment.

2. At summarizing the combined effect the estimation of the environment is carried out according to the formula of summational toxicity (Аveryanov’s formula):

 

 

where

C — concentration of the revealed substances,

MPC1 MPC2 MPC3 — their standards

3. In case of potentiation in the above-stated formula 1/К is taken instead of 1 (K — factor of potentiation, i.e. how many times is toxic effect amplified at combined effect in comparison with separate effect of each poison).

 

 

where К — an increasing coefficient (factor of potentiation)

Hygienic Normalization of Biological Factors in the Environment

To such factors in the environment the following refers:

· Pathogenic organisms of infectious or invasive nature — bacteria, viruses, helminthes, protozoa or their toxins

· Allergens of biological nature

Main Principles of Normalization of Microbe Pollution of the Environment

· Absence of causative agents of infectious diseases in certain volumes or amounts of the environmental object.

· Substantiation of allowable content of microorganisms in objects of the environment at which they are considered safe in the epidemiological respect.

· Use at normalization of indicative (sanitary-indicative) microorganisms.

The indicative principle of normalization of microbes in the environment, offered more than 100 years ago by R. Koch, up to now remains a leading principle of normalization of microbe environmental pollution.

On choice of sanitary-indicative microorganisms as indicators of pathogenic microbes the following is taken into account:

· Commonplace of dwelling in a human organism

· Identical ways of entering the environment and a human organism (ways of transfer)

· Higher survival rate in the environment in comparison with pathogenic microbes, higher resistance to disinfection

· Harmlessness for a human being (inability to cause infectious diseases)

Now as an indicator of virus pollution of the environment bacteriophages of colibacillus (E.coli) are used. By structure, survival rate, resistance they are similar to enteroviruses, causing intestinal infections.

Various sanitary-indicative microorganisms for estimation of various objects of the environment were offered, for example, for reservoir water — bacteria of Escherichia coli group (BECG), coli-phages.

The quantitative evaluation is made by coli-index — quantity of BECG in a certain volume of sample and by coli titer — volume of sample in which one BECG is found out.

For example, for drinking water coli-index is up to 3, coli titer is more than 300 ml, in sewage coli-index — up to 1,000, coli-phages — up to 1,000, absence of pathogenic microbes in 1 L of water (Table 6).

Table 6

Bacterial Standards in Objects of the Environment for Water Estimation

Kind of water	Coli-index	Coli-phage	Absence of pathogenic viruses in volume of water
Drinking	< 3	-	10 L
For bathing	< 1000	< 1000 in 1 L	1 L
Sewage after cleaning	< 1000	< 1000 in 1 L	1 L

Sanitary Estimation of Microbe Air Pollution

The indicative parameter of microbe air pollution of premises is a common microbe number (CMN) — quantity of microorganisms per m3 of air, a parameter of direct epidemiological danger — quantity of haemolytic streptococci per m3 of air. The criteria of estimation of bacterial pollution of premise air is given in Table 7.

Special requirements to microbe air pollution are established for operating-rooms, maternity wards for prevention of intra-hospital infections, postoperative complications (see Table 8).

 

 

Table 7

Bacterial Standards in Objects of the Environment for Estimation of Premise Air

Quality of air	Common microbe number per m3	Amount of haemolytic streptococci per m3
Clear	< 2000	< 10
Satisfactory clear	2000 — 4000	11 — 40
Low polluted	4000 — 7000	40 — 120
Polluted	> 7000	> 120

 

Table 8

Bacterial Standards in Objects of the Environment for Estimation of Operating-Room Air

Time of definition	Total microbe number per m3	Amount of golden staphylococci per m3
Before operation	< 500	0
During operation	< 1000	< 4

 

For estimation of bacterial pollution of ground coli-titer, Cl. Perfringens titer, amount of helminth eggs per kg are used.

 

 

Effect of the Environment Quality on the Population Health

Now it is conventional that the integrated criteria of quality of environment (degree of contamination) is the health of the population. It is used at social-hygienic monitoring environment of the country.

The Concept of "Health of Population"

Paradoxical though it may seem, but there is no universal definition of concept "health"up to now.

In medicine and hygiene most frequently the concept of health is used as an average statistical valuecharacterizing a health state of a certain population, being in identical socio-economic and ecological conditions.

The border between health and illness is the so-called a 95 % confidence interval — in a healthy person all the investigated parameters should range within the limits, characteristic of 95 % of people of the given population.