Last update on October 2015
INWORKS is an international epidemiological study on workers in the nuclear sector launched in 2011 and coordinated by the International Agency for Research on Cancer (IARC) with the contribution of IRSN. It seeks to gain greater knowledge relating to the risks of cancer and non-cancerous diseases linked to chronic exposure to low doses of ionizing radiation at low dose rates.
Context and objectives
The current radiation protection system is based on the extrapolation of radiation-induced risks observed among survivors of the Hiroshima and Nagasaki (Japan) bombings in 1945. Until now, the validity of this extrapolation can not be verified due to the limited number of people included in epidemiological studies of chronic exposure to low doses of radiation and to an insufficient length of follow-up of these populations. The international INWORKS study was launched to better characterize the relationship between prolonged exposure to low doses of ionizing radiation and mortality due to cancer or non-cancerous diseases.
INWORKS is the most extensive epidemiological study ever carried out that seeks to quantify the potential health risks associated with chronic exposure to ionizing radiation in a regulated workplace environment. This study's strength lies in its protocol, which is based on combining the largest cohorts of workers in the world, standardizing inclusion criteria, verifying data uniformity and quality, applying different methods for statistical analysis and verifying the stability of results by carrying out sensitivity analyses.
INWORKS uses the same protocol as the "15-country" study launched by the IARC in the 2000s, the results of which were published from 2005 (Cardis 2005, Cardis 2007, Vrijheid 2007). It combines data from three of the most extensive cohorts of workers from the "15-country" study (French, British and American), with additional and updated information.
The INWORKS study includes 308,297 workers and has unrivalled statistical power in the epidemiology of low doses chronic exposures as it is based on accurate individual data and long-term monitoring (27 years on average).
The French cohort includes over 59,000 workers employed for at least one year between the late 1940s and 1994 by several companies.
The British cohort comprises workers employed for at least one year before 2000 by organizations that provide the National Registry for Radiation Workers (NRRW) with dosimetry monitoring data.
The American cohort includes workers employed for at least one year before 1993 by the US Department of Energy.
The INWORKS study was presented in the International Journal of Epidemiology (Hamra et al. 2015).
The annual doses absorbed by each worker in the different organs relevant for studying the risk of solid cancerous tumors, leukemia or non-cancerous diseases (i.e. the colon, lungs, bone marrow, and breasts for women) and expressed in Gray, were compiled using individual data collected during regulatory worker monitoring to which dose conversion coefficients from the International Commission on Radiological Protection (ICRP) were applied. The methodology used to compile the doses is described in an article published in Radiation Research (Thierry-Chef et al. 2015).
Confronting compiled doses and mortality rate of the cohort lead to an analysis of the death risk from leukemia, lymphoma and multiple myeloma, solid cancerous tumors and non-cancerous diseases associated with exposure to ionizing radiation:
- for each cohort, mortality was monitored using death certificates (until 2004 for France, 2001 for the UK and 2005 for the USA);
- the Excess Relative Risk (ERR) of death from chronic nonlymphocytic leukemia, lymphoma and multiple myeloma is estimated using a linear model of the total dose that takes into account the effect of the country, gender, age and time of year;
- a two-year latency period is applied for leukemia and a ten-year latency period for lymphoma and multiple myeloma;
- additional analysis was carried out on smaller dose periods;
- sensitivity analysis was also carried out for some variables (socio-professional category, latency period duration, exposure to neutrons, internal contamination).
See the news published on June 2015.
- Hamra GB, Richardson DB, Cardis E, Daniels RD, Gillies M, O'Hagan JA, Haylock R, Laurier D, Leuraud K, Moissonnier M, Schubauer-Berigan M, Thierry-Chef I, Kesminiene A. Cohort Profile: The International Nuclear Workers Study (INWORKS). Int. J. Epidemiol 2015; DOI: http://dx.doi.org/10.1093/ije/dyv122.
- Leuraud K, Richardson DB, Cardis E, Daniels RD, Gillies M, O'Hagan JA, Hamra GB, Haylock R, Laurier D, Moissonnier M, Schubauer-Berigan M, Thierry-Chef I, Kesminiene A. Ionizing Radiation and Leukaemia and Lymphoma: Findings from an international cohort study of radiation-monitored workers (INWORKS). The Lancet Haematol. 2015 July; 2: e276-e281. http://dx.doi.org/10. 1016/S2352-3026(15)00094-0.
- Thierry-Chef I, Richardson DB, Daniels RD, Gillies M, Hamra GB, Haylock R, Kesminiene A, Laurier D, Leuraud K, Moissonnier M, O'Hagan JA, Schubauer-Berigan M, Cardis E, on behalf of the INWORKS Consortium. Dose estimation for a study of nuclear workers in France, the United Kingdom and the United States of America: methods for the International Nuclear Workers Study (INWORKS). Radiat. Res. 2015; 183(6):632-642.