Table 13.2 Risk factors for leukaemia, by direction of association and strength of evidence
| Increases risk | Decreases risk |
Convincing or probable | Ionizing radiation1,2,3 | |
| Anti-neoplastic drugs4 | |
| Myelodysplastic syndromes5,6 | |
| Human T-cell lymphotrophic virus, type-1 (HTLV-1)7 | |
| Smoking8 | |
| Occupational exposure to formaldehyde, benzene or styrene9,10,11 | |
| Employment in the rubber manufacturing industry9 | |
| Family history of leukaemia12 | |
Possible | Employment in pesticide manufacturing13 | |
| Overweight and obesity14,15 | |
|
1 exposure to alpha-particle or beta-particle emitters, x-rays or gamma rays; 2 El Ghissassi et al., 2009; 3 Daniels and Schubauer-Berigan, 2011; 4 International Agency for Research on Cancer, 2011a; 5 conditions of the blood or bone marrow, where individuals have too few of one or more types of healthy blood cells; 6 Garcia-Manero, 2011; 7 International Agency for Research on Cancer, 2011b; 8 Secretan et al., 2009; 9 Baan et al., 2009; 10 Schwilk et al., 2010; 11 National Toxicology Program, 2011; 12 Brown, 2008; 13 Van Maele-Fabry et al., 2008; 14 Larsson and Wolk, 2008; 15 Lichtman, 2010 |
The chronic leukaemias (CLL, CML) almost never affect children; AML may affect adults and children; while ALL is the most common type of leukaemia in children, but may affect adults also. The description of risk factors below refers to leukaemia in adults.
Ionizing radiation exposure has long been established as a risk factor for leukaemia. Risk of all types of leukaemia other than CLL is increased in individuals who receive particular types of radiation therapy or undergo multiple x-rays, or have protracted exposure to low-dose gamma radiation. A variety of anti-neoplastic drugs (alkylating agents), given as part of the treatment for other types of cancer, can cause leukaemia, most usually AML. Risk is increased in individuals with myelodysplastic syndrome, a diverse collection of conditions related to the blood and bone marrow which, if left untreated, may progress to AML. Infection with the human T-cell lymphotrophic virus, type 1 (HTLV-1) causes a rare type of leukaemia known as adult T-cell leukaemia. Approximately 10% of individuals with CLL report a family history of the condition or a related lymphoproliferative disorder, but the genes which account for increased susceptibility have not been identified.
Occupational exposure to benzene (an industrial solvent and precursor to basic industrial chemicals including drugs, plastics, synthetic rubber, and dyes); formaldehyde (used in the production of industrial resins that are then used in the manufacture of products such as adhesives and binders for wood products, plastic and synthetic fibres); and styrene (used in the production of polymers, which are incorporated into products such as rubber, plastic, insulation, fibreglass, and car parts) are all linked with leukaemia. Formaldehyde is particularly associated with AML. Workers in the rubber manufacturing industry have increased risk, but due to the complexity of exposures in this industry, the causative agents have not yet been firmly identified. Risk of myeloid leukaemias may also be raised in individuals employed in plants manufacturing pesticides.
In terms of lifestyle-related risk factors, tobacco smoking is a causal agent for myeloid leukaemia. Overweight and obesity may modestly increase risk of all four main subtypes, but the evidence-base is sparse.
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