What is MPC? The maximum permissible concentration of harmful substances in the air

The MPC of harmful substances is the permissible value of a polluting chemical compound contained in soil, water or air that does not affect - directly or indirectly - the living organisms. Values in the appropriate units are determined by toxicological studies.

Characterization of MPC as a measuring instrument

What is MPC in environmental regulation? This is the main indicator of industrial ecology, to which all production enterprises are oriented. The values of MPC of substances are deduced and distributed according to the type of chemical structure and toxicological effect on living organisms. GOSTs are created, compliance with which is mandatory.

Depending on the environment in which harmful substances are located, the MPC is measured in:

• Mg / dm ³ - for measurement in the hydrosphere;
• Mg / m ³ - for measurements in the atmosphere and air in the working space;
• Mg / kg - to determine the index in the soil.

When deducing the value of MPC, a harmful effect not only on the person, but also on all living organisms as a whole is taken into account. Compliance with established norms allows to preserve the entire ecosystem, and not individual species of flora and fauna.

Classification

MPC of harmful substances, depending on the degree of exposure to living organisms, are divided into 4 groups of hazards:

1. I class is extremely dangerous.
2. II class is very dangerous.
3. III class - it's dangerous.
4. IV class - moderately dangerous.

Depending on the belonging of the pollutant to the groups of danger, its MAC and the residence time in the environment of living organisms in the presence of chemical compounds are changed.

Varieties of MPC

Depending on the criteria for assessing the environment, several values of MPC are derived.

For industrial zones, there are:

• MPC.r. - used to assess the health of the atmosphere in the work area. Work area - this is the space in which the employees are in the performance of the task, which includes 2 meters above the level of the site. The coefficient expresses the amount of pollutant in the air, which does not cause any deviations in human health for several decades.
• MPKp.p. - is allocated at industrial enterprises or on a separate site. Usually, the value is taken to be 0.3 MPC.

For the urban zone, there are other standards of the ecological state of the atmosphere, which is determined by the following factors:

• MAC. - the total permissible value of the pollutant in the atmosphere of the settlement. Separately, the coefficients of daily average and maximum one-time environmental pollution.
• MPCm.r. - the amount of pollutant in the atmosphere of the urban zone in the maximum expression, which is acceptable for a single inhalation. The coefficient is calculated in such a way that the substance does not cause a reaction to chemical stimuli during a short-term exposure (not more than 20 minutes).
• MPCs.s. - regulates the amount of harmful substances in a concentration that does not have a detrimental effect on human health, provided it is inhaled 24 hours a day.

It is necessary to understand what is the MAC of the working and urban space. MPC.r. Are calculated from the following initial data:

• In a polluted environment are adults with good health;
• The length of stay is limited by the job description and usually does not exceed 8 hours.

Harmful substances in the atmosphere of the settlement affect every resident: an adult or a child, sick or healthy, and it is round the clock and continuously throughout life. As a consequence, for the same pollutants, the values of the maximum permissible concentrations that can differ significantly from each other can be determined. Usually the MAC coefficient of substances in the air of the working area is much higher than the MAC.

Definitions of MPC values in water and soil

What is the maximum permissible concentration of water bodies? This is the established standard for the concentration of pollutant per 1 liter of water. Values of the coefficient are determined separately for each type of water body. Distinguish the waters of fish-economic, drinking and domestic purposes.

The definition of MPC of contaminants in the soil is the most difficult task. The calculation is based on soil properties and the chemical nature of the harmful substances. The indicators are always different, and the tabulated values for each contaminating compound are not deduced.

Distribution of MPC by the nature of the impact

What is the MAC of chemical compounds, if each substance can act differently?

For the systematized classification of harmful chemicals, several groups are distinguished according to the characteristic signs of the effect on the living organism, in particular, man:

• Total toxic;
• Annoying;
• Sensitizers;
• Carcinogens;
• Mutagens;
• Affecting reproductive health.

Each of the groups has specific signs of poisoning, terms of action and deduced MPC.

Pollutants with general toxicity

Common toxins cause a strong poisoning of the body as a whole. The most obvious violations are visible from the nervous system of the person: there are convulsions, disorders of consciousness, paralysis. The group of substances of common toxins include aromatic hydrocarbons and their nitro and amido derivatives, organic compounds with phosphorus, chlorine, and also some inorganic substances.

The most common ones are:

• Arsenic and its compounds;
• Benzene, toluene, aniline, xylene;
• Dichloroethane;
• Hg;
• Pb;
• Carbon monoxide (IV).

Infection with many of the substances occurs not only in production, but also in everyday life.

MPC in the air of general toxic substances

Consider the indicators of daily average and single MPC in the air of the urban and working area. For convenience and visibility, we submit the information in the form of a table.

The average daily concentration of harmful substances implies interaction with the human body for several years without the development of any consequences.

Effects of irritating chemicals

Chemical compounds affect the skin, mucous membranes and respiratory tract. Most often in the role of irritants are halogens and oxides of nitrogen and sulfur.

Prolonged inhalation of harmful fumes leads to serious violations of breathing, intoxication and death.

Sensitizers and their MPC in the atmosphere

Substances of sensitizing action cause an allergic reaction in humans. Common compounds of this group include aldehydes and hexachlorane.

Sensitizers enter the atmosphere during fuel combustion and production activities. A small amount of formaldehyde is released at home: it is found in many building and finishing materials, furniture.

Carcinogens and mutagens

The most dangerous group of chemical pollutants, whose influence on the human body has been underestimated for a long time. Carcinogens and mutagens are potent substances with a long latent period of action. Carcinogens include asbestos, beryllium, benzpyrene, aromatic amines. They provoke the formation of various malignant tumors.

Mutagens provoke changes in the human genotype that are transmitted to the offspring. These include radioactive substances, manganese, lead, organic peroxides, formaldehyde.

Many mutagenic substances further affect reproductive health, including benzene and any of its derivatives, lead, antimony, manganese, pesticides, chloroprene and others.