病棟勤務の看護師が、自身が診療を補助しない状況で、診療放射線技師が操作する移動型X線装置の使用により受ける放射線への曝露は、職業被ばくであるが、公衆の線量限度を適用するとされています。

IAEA: SSG-46

2.GENERAL RECOMMENDATIONS FOR RADIATION PROTECTION AND SAFETY IN MEDICAL USES OF RADIATION

TYPES OF EXPOSURE SITUATION AND CATEGORIES OF EXPOSURE

2.5項

職業被ばく：職業に関連した被ばく
公衆被ばく
バックグラウンドの被ばく

EU BSS

Article 9

Dose limits for occupational exposure

1. Member States shall ensure that dose limits for occupational exposure apply to the sum of annual occupational exposures of a worker from all authorised practices, occupational exposure to radon in workplaces requiring notification in accordance with Article 54(3), and other occupational exposure from existing exposure situations in accordance with Article 100(3). For emergency occupational exposure Article 53 shall apply.

2. The limit on the effective dose for occupational exposure shall be 20 mSv in any single year. However, in special circumstances or for certain exposure situations specified in national legislation, a higher effective dose of up to 50 mSv may be authorised by the competent authority in a single year, provided that the average annual dose over any five consecutive years, including the years for which the limit has been exceeded, does not exceed 20 mSv.

3. In addition to the limits on effective dose laid down in paragraph 2, the following limits on equivalent dose shall apply:

(a) the limit on the equivalent dose for the lens of the eye shall be 20 mSv in a single year or 100 mSv in any five consecutive years subject to a maximum dose of 50 mSv in a single year, as specified in national legislation.

(b) the limit on the equivalent dose for the skin shall be 500 mSv in a year, this limit shall apply to the dose averaged over any area of 1 cm2, regardless of the area exposed;

(c) the limit on the equivalent dose for the extremities shall be 500 mSv in a year.

法令への取り入れの多様性の例

Table 2 gives the new individual dose limits in the countries that have already implemented the BSS, and the most recent drafted values in the other European countries that have yet to implement them.
All countries have, or will have, a dose limit for the public that is 1 mSv per year, Denmark and Finland specifying that such a limit corresponds to the contributions of all sources together. However, some countries have been or will be more restrictive with regards to each source. The Lithuania, UK, Germany and the Netherlands have introduced some constraints and specified that each source may not contribute to more than 0.2, 0.3, 0.3, and 0.1 mSv per year.
The situation is somehow different in the case of occupational exposure limits. The interpretation of the BSS has led the countries to select either 100 mSv for five years with a maximum of 50 mSv per single year (Finland, Spain, Sweden, Czech Republic, Switzerland), or to be more stringent in selecting 20 mSv per calendar year (Denmark, Germany, Italy, the Netherlands, UK, Norway) or per 12 consecutive months (Austria, Belgium, France).
One country has introduced an annual averaged dose limit of 10 mSv: 400 mSv over the work life in Germany

CEPN ISOE Information Sheet No. 29 – April 2002

Regulation should be flexible, but the European Commission should define minimal requirements for the content of the passport, allowing countries to ask for more data from workers of their nationality if they wish to. For example, the EC should elaborate guidance on what type of exposure data should be provided for workers travelling in different countries with, sometimes, different dose limits (20 mSv as annual calendar dose limit, 20 mSv for a 12 month rolling period, 100 mSv for a five year period…). It was reminded during the Seminar that about half of the EU countries have an annual dose limit of 20 mSv (only within old Member States), while the others have a dose limit of 100 mSv for 5 years. Additionally to regulatory requirements, some companies may request from their workers to respect dose constraints below 20 mSv. However, the passports are used only as a tool to enable travelling of workers between the sites (not to wait for official dose reports). Member Countries suggest a flexible way of regulation of personal dose data information exchange.

EUROPEAN COMMISSION: RADIATION PROTECTION NO 166

NEA/CRPPH/R(2011)1Committee on Radiation Protection and Public HealthExpert Group on Occupational ExposureDose constraints – Dose constraints in optimisation of Occupational Radiation Protection andimplementation of the Dose constraint concept into Radiation Protection regulations and its use inoperators’ practices
Japan: Views of all utilities Under Japanese law, individual dose limits are set at 50 mSv/y and 100 mSv/5 years (for each five year period from April 1, 2001). As might be expected and in the spirit of the ALARA, utilities take measures to keep individual doses at or below the legal limits, as well as measures to reduce radiation exposure to achieve lower individual doses.

線量拘束値の利用

IAEAのORPASでの指摘例

S2: Suggestion: The SLAERC(SRI LANKA ATOMIC ENERGY REGULATORY COUNCIL) is encouraged to provide guidance for the establishment of dose constraints by the license holders and their use as tool for optimization and the basis for design and shielding calculations.
S19: Suggestion: The dose constrains should be established, with the guidance of SLAERC.

OCCUPATIONAL RADIATION PROTECTION
APPRAISAL SERVICE (ORPAS) MISSION TO SRI LANKA 24 November – 2 December 2019