Maximum Permissible Concentration MPC

the maximum quantity of an injurious-substance per unit volume (air, water or other liquid) or weight (for example, food products) to which daily exposure for an indefinite period of time does not cause any pathological deviations or unfavorable hereditary changes in offspring.

MPC’s are established on the basis of theoretical calculations, the results of biological experiments, and data on dynamic observations of healthy people exposed to injurious substances. The MPC of a given substance varies in different circumstances. In the USSR, for example, the MPC of lead and its inorganic compounds in water used for drinking and household purposes is 0.1 mg/l. Whereas the lead content in the atmosphere may reach only 0.007 mg/m³, in industrial plants it may be as high as 0.01 mg/m³. In the USSR, MPC’s are established by taking into account the effects of a substance on healthy and sick persons of all ages over a lifetime. Other factors are also taken into consideration, for example, the possibility of water pollution or the emission of noxious odors into the environment. Regulations for protecting surface waters are used in establishing separate MPC’s for lakes and streams whose water is intended for household use and drinking, or for fishing. It was found that the MPC’s adopted for substances in the air and calculated to protect human health sometimes provide inadequate protection for trees, flowers, and grass. Hygienists have worked out standards for MPC’s that take into account the harmful effects of certain substances on vegetation.

MPC’s are specified in the All-Union State Standards, health standards, and similar regulations, which are valid throughout the USSR. They are taken into account in the design of waste treatment facilities and technological processes and equipment. The sanitary-epidemiological service, as part of its inspection work, regularly checks on compliance with standards for MPC’s in lakes, streams, and reservoirs whose water is used for drinking and household purposes. The air and industrial plants are also inspected. Appropriate agencies inspect bodies of water used for commercial fishing.

In the foreign socialist countries, the list of substances for which standards are set and their MPC are similar to those in the USSR. MPC’s have also been established in some capitalist countries for certain injurious substances in water used for household and drinking purposes, in the atmosphere and at industrial work areas. However, in the opinion of Soviet hygienists, the number of substances for which standards are set is insufficient, and the MPC’s in most cases are too high.

A. M. STOCHIK