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Central Index of Dose Information

Summary of Statistics for 1998

CONTENTS


FOREWORD

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 under contract by the National Radiological Protection Board (NRPB). CIDI receives annually from Approved Dosimetry Services (ADS) summaries of radiation doses recorded for employees designated as classified persons in the United Kingdom. This document is the thirteenth CIDI Summary of Annual Statistics to be published.

All the data provided to HSE by ADS for the purposes of CIDI are treated as confidential in respect of individual persons and employers. The computer files are protected by various safeguards (Registration No CO607047). The style of data presentation used here maintains this confidentiality. The data given are as held on the database on 22 July 1999.

This publication may be freely reproduced, except for advertising, en dorsement or commercial purposes. The information is current at 9/99. Please acknowledge the source as HSE.

Enquiries on this document should be addressed in the first instance to:

Mr M K Williams
Health and Safety Executive
Health Directorate Protection Policy, HD B7
Rose Court
2 Southwark Bridge
London SE1 9HS

This publication may be freely reproduced, except for advertising, en dorsement or commercial purposes. The information is current at 9/99. Please acknowledge the source as HSE.

The Central Index of Dose Information is operated by the National Radiological Protection Board under contract to the Health and Safety Executive.

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INTRODUCTION

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[1] (IRR 85). These annual summaries are required from Approved Dosimetry Services (ADS) which operate in the United Kingdom under IRR 85. Separate information is also sent to CIDI by an ADS whenever an employee terminates employment.

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 should be sent to CIDI, thus fulfilling the statutory duty on employers under IRR 85 to make arrangements with their ADS to send such data to HSE. The most common form of dose assessment is from measurements by an external body dosemeter of the thermoluminescent (TLD) or film type but ADS may be approved for other kinds of measurement, 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.

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PURPOSE

3 CIDI has several functions:

(a) to receive annual dose summaries from which to generate statistical information;

(b) to provide an index to show which ADS is, or has been, responsible for the dose record keeping of a classified person and to act as a back-up for dosimetric information on a person;

(c) to verify annually that the number of classified persons is known and is consistent with the number of registrations and terminations of classified persons since the previous year;

(d) to act as the link between the old and new ADS when a person changes employers. This may, in exceptional cases, include relaying subsequently revised data to the current ADS.

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BACKGROUND

4 CIDI was established on 1 January 1987. The functions and operations of CIDI are described in the Report of the Working Party on the Central Index of Dose Information (NRPB-M92)[2] and associated Reference Manual (NRPB-M176)[3]. The first year for which data were required was 1986. Annual summaries have been published for the years 1986[ ]to 1997[4-15]. This is the thirteenth 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[16] and the second report covering the period 1990 to 1996[17].

5 The occupational categories used in the presentation of CIDI data are given in part 3 of the HSE Requirements for Approval.[18] Where more than one of these categories is applicable, a single category is selected that refers to the largest proportion of the dose.

6 The number of classified persons for whom records were kept in 1998 was 41 295.

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Dose data

7 The specification of the information required in 1998 for CIDI purposes was given in part 3 of the HSE Requirements for Approval.[18]

8. 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. (See paragraph 13).

9 The data within the various dose ranges of the tables are expressed in millisieverts (mSv). However, the mean doses and collective doses within the tables are rounded to the nearest 0.1 mSv and 1 man mSv respectively and values given as a percentage have been rounded to the nearest 0.1% (1% in Table B1). The data are presented in a style corresponding to that of the previous annual summaries.

10 Section A presents the main dose information in terms of occupational category and whole body dose, which comprises effective dose equivalent (EDE) from external exposure to ionising radiation and/or committed effective dose equivalent (CEDE) from internal exposure. Separate data are given for the neutron component of EDE and for the CEDE component due to radon-222 and its short-lived daughters. Table A5 only contains data from those ADS that report CEDE separately. Section B is devoted to distribution of whole body dose (EDE + CEDE) by age and sex according to occupational category, and Section C is concerned with dose equivalent (DE) and/or committed dose equivalent (CDE) to specified organs or tissues in terms of occupational category.

11 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 has been made in the data between assessed and estimated doses. If no adequate information exists to make an estimation, the employer must authorise the ADS to enter a notional dose in the record for that period (but see paragraph 13).

12. 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. Table A8 shows the number of persons monitored and the mean of their reported doses in 1998; the proportion of records extending over the full year was 82%. A special check is made to minimise the possibility of double counting doses for individuals reported by more than one ADS.

13 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; these notional doses 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 and entered in Table A2 by the CIDI statistics programme. A 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, which remain unchanged.

14 CIDI protocol does not require the submission of organ/tissue dose data (Part C) 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 there may appear to be discrepancies between certain tables (e.g. Tables A5 and C7-C9).

15 Where a zero dose category is shown in the Tables, this includes both the classified persons who were monitored but 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. 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.

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Section A - Whole body dose (EDE/CEDE)

16 Most classified persons were monitored for whole body radiation, ie EDE and/or CEDE. In Table A2, where notional doses have been substituted by a pro-rata dose estimate, the mean dose averaged over all occupational categories was 0.6 mSv. The highest mean dose (12.5 mSv) was for the occupational category comprising underground miners in non-coal mines, for whom the principal source of exposure is radon-222 and its short-lived daughters (see also Table A4). Table A2 also shows that 36.1% of classified persons were reported as receiving no dose at all, 85.6% as receiving 1 mSv or less, and 97.4% as receiving 5 mSv or less.

17 The data in Table A2, indicate that after corrections for notional doses an annual dose in excess of 15 mSv was reported for 48 persons, <1 % of the number of classified persons for whom doses were reported (Table A1 shows 100 persons with reported doses above this level before corrections). Table A2 shows that one classified person had a reported whole body dose that exceeded the annual dose limit of 50 mSv.

18 The collective dose (Table A2) for the 41 295 classified persons for whom doses were reported for 1998 was 27 man Sv.

19 Table A3 shows that a non-zero neutron dose was reported for 411 classified persons. No neutron doses in excess of 15 mSv was reported.

20 Table A4 shows doses from radon-222 and its short-lived daughters. The mean of the doses reported for 68 classified persons was 12.3 mSv. The figures are dominated by the contribution of doses reported for underground miners in non-coal mines.

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Section B - Variation with age and sex

21 Table B1 provides a summary of mean doses by sex. Tables B2 and B3 show a breakdown of the number of classified persons by age and sex for the calendar year. Tables B4 and B5 give the corresponding breakdown of mean doses.

Section C - Doses to specific organs and tissues

22 Table C1 shows that 15 656 classified persons had a reported dose to the skin greater than zero. No classified persons were reported as having received a skin dose in excess of 500 mSv.

24. The remaining tables in this section includes reported dose to the hands, feet and eyes, together with reported doses to internal organs.

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REFERENCES

  1. Statutory Instrument SI No 1333, 1985. The Ionising Radiations Regulations 1985 HMSO.
  2. Kendall, G M; Greenslade, E; and Young, T 0. Report of the Working Party on the Central Index of Dose Information, Chilton, NRPB-M92 (1983).
  3. Greenslade, E; Kendall, G M; Iles, W J; Gardner, P H; and Young, T 0. Reference Manual for Data Transfer to the Central Index of Dose Information. Chilton, NRPB-M176 (1989).
  4. Central Index for Dose Information. Summary of Statistics for 1986. NRPB, HMSO, ISBN 0 85951 347 5.
  5. Central Index of Dose Information. Summary of Statistics for 1987. NRPB, HMSO, ISBN 0 85951 355 6.
  6. Central Index of Dose Information, Summary of Statistics for 1988. NRPB, HMSO, ISBN 0 85951 357 2.
  7. Central Index of Dose Information, Summary of Statistics for 1989. HSE Books, ISBN 0 7176 0654 6.
  8. Central Index of Dose Information. Summary of Statistics for 1990. HSE Books, ISBN 0 7176 0655 4.
  9. Central Index of Dose Information. Summary of Statistics for 1991. HSE Books, ISBN 0 7176 0656 2.
  10. Central index of Dose Information. Summary of Statistics for 1992. HSE Books, ISBN 0 7176 0757 7.
  11. Central index of Dose Information. Summary of Statistics for 1993. HSE Books, HSE London 1995.
  12. Central index of Dose Information. Summary of Statistics for 1994. HSE Books, HSE London 1995.
  13. Central index of Dose Information. Summary of Statistics for 1995. HSE Books, HSE London 1996
  14. Central index of Dose Information. Summary of Statistics for 1996. HSE Books, HSE London 1997
  15. Central index of Dose Information. Summary of Statistics for 1997. HSE Books, HSE London 1998
  16. Occupational exposure to ionising radiation 1986-1991. Analysis of doses reported to HSE's Central Index of Dose Information. HSE Books, ISBN 0 7176 9657 0.
  17. Occupational exposure to ionising radiation 1990-1996 Analysis of doses reported to HSE's Central Index of Dose Information. HSE Books, HSE London 1998
  18. Requirements for the Approval of Dosimetry Services under the Ionising Radiations Regulations 1985. Part 3 Co-ordination and Record Keeping. HSE London 1996.
Updated 2011-09-14