1. The Central Index of Dose Information (CIDI) is the Health and Safety Executive's (HSE's) national database of occupational exposure to ionising radiation. It is operated by the National Radiological Protection Board (NRPB) under the terms of an extramural contract let by HSE.
2. The purpose of the CIDI database is to provide lifetime dose record keeping continuity for employees that, at some time in their working lives, have been designated by their employer(s) as a 'classified person' under regulation 9 of the Ionising Radiations Regulations 1985 (IRR85) or regulation 20 of the Ionising Radiations Regulations 1999 (IRR99). The former statutory instrument was revoked by the coming into force of the latter on 1st January 2000.
3. The CIDI database is kept up-to-date by annual dose summaries submitted by Approved Dosimetry Services (ADS). Employers who designate classified persons must make arrangements for their ADS to provide this information to HSE (and therefore CIDI) in order to comply with regulation 21 of IRR99 (previously regulation 13 of IRR85).
4. This document is the fourteenth published summary of CIDI annual statistics.
5. All the data provided to HSE by ADS for inclusion in the CIDI database are treated as confidential in respect of individual persons and employers.
6. The data given in this document are as held on the CIDI database on 24 July 2000.
7. This publication may be freely reproduced and distributed for noncommercial purposes provided that HSE is acknowledged as the source.
1. The HSE Central Index of Dose Information (CIDI) receives annual summaries of radiation doses recorded for employees designated as classified persons under the Ionising Radiations Regulations 1985 (IRR 85) and with effect from 1 January 2000, under the Ionising Radiations Regulations 1999[2 ](IRR 99). These annual summaries are required from Approved Dosimetry Services (ADS) which operate in the United Kingdom under IRR85/IRR99. Separate information is also sent to CIDI by an ADS whenever an employee's employment ends.
2. Approval to make assessments of doses to classified persons and/or to keep records of such assessments is granted to suitable dosimetry services by HSE. It is a condition of approval for dose record-keeping that annual dose summaries are sent to CIDI, thereby fulfilling the statutory duty on employers to make arrangements with their ADS to send such data to HSE. The most common form of dose assessment is from measurements made by an external body dosemeter of the thermoluminescent (TLD) or film type. An ADS may be approved for other kinds of measurement however, such as bio-assay, whole or partial body monitoring for internal radionuclides and personal or static air monitoring. The resulting assessments of dose are included in dose records.
3. CIDI has several functions:
4. CIDI was established on 1 January 1987. The functions and operation of CIDI are described in the Report of the Working Party on the Central Index of Dose Information (NRPB-M92) and associated Reference Manual (NRPB-M176).
5. The first year for which data were required was 1986. Annual summaries have been published for the years 1986[ ]to 1998[5-17]. This is the fourteenth annual summary. It is intended that separate reports will be published periodically on trends in annual statistics, such as that covering dose data recorded for the years 1986 to 1991 and a second report covering the period 1990 to 1996.
6. The occupational categories used in the presentation of CIDI data are given in HSE's published requirements for dosimetry service approval. Where more than one of these categories is applicable, a single category is selected that refers to the largest proportion of the dose.
7. The number of classified persons for whom records were kept in 1999 was 41,527
8. The specification of the information required in 1999 for CIDI purposes is given in HSE's[ ]published requirements for dosimetry service approval[ 20].
9. The data in the tables are as reported to CIDI by ADS; no changes, additions or deletions have been made. Table A2 is an additional table derived from Table A1 by substituting pro-rata dose estimates for notional doses.
10. The data within the various dose ranges of the tables are expressed in millisieverts (mSv). Mean and collective dose within the tables are rounded to the nearest 0.1 mSv and 1 man millisievert respectively. Values given as a percentage are> rounded to the nearest 0.1% (1% in Table B1). The data are presented in a style similar to that of previous annual summaries.
11. This section presents the main dose information in terms of occupational category and whole-body ionising radiation dose. The dosimetric quantities used are effective dose equivalent (EDE) for external exposure and committed effective dose equivalent (CEDE) for exposure arising from intakes of radionuclides. The data for the neutron component of EDE and the CEDE component arising from exposures to radon-222 and its short-lived daughters are tabulated separately.
14. Presents dose summaries for specific organs and tissues by occupational category.
15. Where no assessment of dose is available for any period of work as a classified person, an estimation of the dose for that period must be made by the employer and entered in the record in lieu of an assessed dose. No distinction is made in the data between assessed and estimated doses. If there is insufficient information upon which to make a dose estimate, the employer must authorize the ADS to enter a notional dose in the record for that period.
16. The data in this summary include doses for classified persons who were monitored for only part of the year or who changed their employment in radiation work during the year. For such persons, there will be more than one dose summary on CIDI for the year. A special check for such 'double' entries is therefore made during the preparation of the data presented in this summary. Table A8 shows the number of persons monitored and the mean of their reported doses in 1999.
17. The data submitted by ADS contain a relatively small fraction of notional doses. Notional doses are substitute dose values in the record of a person for a period when no dose assessment was available; they are based on the proportion of the relevant annual dose limit for that period. Table A1 includes notional doses. However, such values are rarely representative of the likely doses to persons. For that reason a pro-rata dose estimate for the period of each notional dose has been calculated by the CIDI statistics programme; these data are presented in Table A2. The pro-rata dose estimate is based on the doses assessed for the person during the rest of the year. This is a well established convention in the presentation of dose record data and one which gives a more realistic substitute dose value for dose analysis and epidemiological purposes. This substitution applies only to the data during their statistical analysis by CIDI and is not applied to the basic data on the CIDI database or to the source data kept by the ADS: these remain unchanged.
18. The CIDI protocol does not require submission of organ/tissue dose data if doses are less than 10% of the pro-rata dose limit. Nevertheless, some ADS have reported doses below this level and these have been included in the tables. This means that there may appear to be discrepancies between certain tables (e.g. Tables A5 and C7-C9).
19. Zero dose categories shown in the Tables, include both monitored classified persons, for whom no measurable dose was recorded in the year, and persons who were not monitored but who were reported as having received no measurable dose as classified persons.
20. In Table A3, which shows neutron doses, the zero dose category also includes zero neutron doses reported to CIDI by ADS for individuals who were not monitored for neutron dose.
Added to the HSE website 27 October 2000