Epidemiological literature review on the risk of cancer among firefighters

Nota : aucunes données n'étant disponibles en ce qui concerne plus précisément la période de latence des cancers chez les pompiers, une période de latence présumée de plus de 10 ans pour la plupart des cancers, de plus de 20 ans pour le cancer du poumon, et de plus de 30 ans pour le mésothéliome correspond aux valeurs convenues à l'échelle internationale, bien qu'un mésothéliome se soit occasionnellement déclaré après une plus courte période. Sauf en ce qui concerne le mésothéliome, les données issues de la présente analyse documentaire se sont avérées insuffisantes pour confirmer ou infirmer de façon concluante quelque association que ce soit entre le cancer et la profession. Il existe néanmoins certaines preuves d'association entre la profession de pompier et les cancers de la vessie, du cerveau, du côlon/rectum, de la tête et du cou, des reins, de l'œsophage, de la peau et de l'intestin grêle, de même qu'avec la leucémie et le myélome multiple. Une méta-analyse effectuée en 2007 indiquait que certains de ces cancers (cerveau, côlon/rectum et peau) pouvaient être reliés à la profession de pompier, mais pas l'analyse documentaire du CIRC. Les liens entre la profession et d'autres types de cancer relevés dans la présente revue de la littérature ne sont pas étayés par les revues antérieures, de sorte qu'on ne peut en tirer aucune autre conclusion.

Abstract

A review of the literature on cancer in firefighters, published since the IARC review of 2007, was undertaken to establish any new evidence for associations of occupation of firefighter with cancer, or pointers to possible associations. The review gave attention to 21 cancer sites indicated inconclusively by previous reviews.

In total, more than 600 publications on exposure and epidemiology were screened for data related to cancer in firefighters. From these papers 11 key studies were identified to provide primary epidemiological data and a further 14 supportive case-control studies were selected. Every study screened and rejected is detailed in an annex to the report, with a brief reason for exclusion, as part of the comprehensive reporting of the review.

The studies of firefighters reported in this review cover long periods of employment (up to 40 years) with some large cohorts and therefore provide useful additions to the data previously available.

The studies identified were summarised and scored for quality, and conclusions were reached for each of the 21 cancer sites, taking account of the results of the study and the plausibility of an association, based upon the known chemical exposures of firefighters. The combined evidence for each specific site was classified in two dimensions: one which focused on the presence of statistically significant associations of cancer with the occupation of firefighter (None, Limited, Mixed, Consistent) and the second which was based on the qualities of the study, the existence of a plausible mechanism and a demonstration of a trend with categories: Very weak, Weak, Moderate, Strong.

The classifications for those cancers where a statistical association was seen are summarised in the table below. The outcome is compared with the conclusions of the previous review by IARC.

Because this study spanned a limited publication time-frame with a limited number of sometimes small studies, addressing a particular cancer, it was unlikely to be able to provide strong statistical evidence and thus to definitively link cancers with occupation. The evidence is limited in part by the number and the quality of the available studies but also by the lack of availability of comprehensive data on specific exposures for each firefighter. A more limited objective of assessing existence of new pointers or suggestive evidence was possible.

The conclusions of this report are based only on the evidence published since 2007 plus a few published slightly earlier which did not get included in the IARC review. In particular, no attempt has been made to review and integrate all published evidence to date. A full assessment of the evidence for association and risk for a specific cancer type would require a full review of all available data for that cancer type, with a meta-analysis of data from all studies, to increase the statistical power of the investigation. The evidence of association for each cancer type reported here is based on the limited publication date- range covered by this review and conclusions are necessarily limited by this.

Based upon the current review there is the strongest evidence for an excess of mesothelioma for those who were employed as a firefighter more than 30 years ago, probably as a result of asbestos exposure. Lung cancer is not as strongly associated but is known to be linked to the same exposures, so cannot be ruled out as occupationally related. There is no conclusive evidence for association of any other cancer type with the occupation of firefighter, however, NHL and prostate cancers have been found more frequently in firefighters in both the current review and in that made previously by IARC (2010a).

Summary of the conclusions on cancer and firefighters Site Degree of statistical association Quality of evidence for associationPrevious IARC Conclusion (IARC, 2010a) Bladder Limited Weak Brain Mixed Weak Not confirmed* Colon/rectum (large intestine) Mixed Very weakNot confirmed* Head & Neck (including larynx and pharynx) Limited Weak Kidney Mixed Weak-moderate Leukaemia – all types Limited Weak Lung Mixed Weak-moderate Mesothelioma Consistent Strong Multiple myeloma Limited Very weak Not confirmed Non-Hodgkin lymphoma (NHL) Mixed Moderate Possible (approximately 20% excess) Oesophagus Mixed Weak Prostate Mixed Moderate Possible (approximately 30% excess) Skin – melanoma Mixed Weak-moderate Not confirmed* Skin – non-melanoma Limited Very weak Small intestine Limited Very weak * Site indicated by meta-analysis (LeMasters et al., 2006), but not confirmed by IARC.