From Big Medical Encyclopedia

MARGINAL DOSE OF THE RADIATION (TRAFFIC REGULATIONS) — the hygienic standard regulating the greatest value of an individual equivalent dose in a year a cut at uniform influence will not cause in the state of health of personnel (persons, constantly or temporarily working with sources of ionizing radiation — category A) the adverse changes found by modern methods of a research. For a limited part of the population (persons who do not work directly with sources of ionizing radiation, but under the terms of accommodation or placement of jobs are affected by radioactive materials or other sources of radiation — category B) the limit of a dose (LD) — a limit equivalent dose in a year is set, the edge is 10 times less than traffic regulations. The limit of a dose is set for the purpose of prevention of unreasonable radiation of this contingent of people which joins children, women of reproductive age and pregnant women.

As the main dose limits depending on group critical bodies (see) for category A the marginal dose for a year (traffic regulations), and for category B — a limit for a year (PD) is established.

Recommendations of the International commission on to radiation protection (see) about tolerance levels of radiation were under construction earlier on idea of threshold action of ionizing radiation since it was considered to be that its harmful effects can be shown only after exceeding of certain threshold doses. Since 1977. The international commission on radiation protection (MKRZ) accepted the new principle of rationing of traffic regulations, to-rogo idea of nonthreshold action is the cornerstone ionizing radiation (see) concerning hereditary and nek-ry somatic reactions. The post-radiation effect which is shown directly at the irradiated person, and hereditary — shown at its posterity is called somatic. Distinguish stochastic nonthreshold (hereditary, Oncogenous) and threshold (not stochastic) effects which arise after exceeding of certain doses. For stochastic effects of MKRZ accepts linear nonthreshold relation between a dose and probability of emergence post-radiation effect (see).

The purpose of radiation protection is in preventing harmful not stochastic effects and to limit probability of stochastic effects to the level which is considered accepted (see. Antiactinic protection , Radiation safety ). According to the recommendation of MKRZ the method of definition of the acceptability of risk level in the work connected with radiation consists in comparison of assessment of this risk with risk from other professions which admit the safest i.e. where, but to the existing representations, average annual mortality from the prof. of the reasons does not exceed 10 - 4 .

MKRZ recommends a limit of an equivalent dose for personnel (category A) of 5 rem (50 mzv) in a year. At the same time it is emphasized that distribution of an annual equivalent dose in big professional groups corresponds logarifmi - cheski - normally to distribution with an arithmetic average value apprx. 0,5 rem (5 mzv).

See also Doses of ionizing radiation .

Bibliography: Moskalyov Yu. I. Some results of the International commission but radiological protection (MKRZ) in 45 years (from 1928 to 1973), in book: From radiobiol. an experiment to the person, under the editorship of Yu. I. Moskalyov, page 253, M., 1976; Standards of radiation safety (NRB-76), M., 1978; Radiation protection, Recommendations of MKRZ, the Publication-26, the lane with English, M., 1978.

Yu. I. Moskalyov.