Non-Hodgkin's Lymphoma - Risk Factors

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Note on Allergies: There appears to be no association between NHL and allergy, which is an overactive response of the immune system and is the most common immune disorder.

Industrial Chemicals and Other Environmental Risk Factors

Overexposure to a number of industrial and agricultural chemicals has been frequently linked to an increased risk for lymphomas. The data, however, are not consistent.

• Organochlorines are chemicals produced when solid waste is burned. These by-product chemicals include dioxin, polychlorinated biphenyls (PCBs), and furans. Many studies have indicated that exposure to these chemicals increases the risk of developing NHL.
• A number of studies have found an association between NHL and certain pesticides and herbicides, although more research is needed to confirm any definitive risk.
• White spirits, thinners, phenoxy herbicides, wood preservative, aviation gasoline, plastic, and rubber chemicals have been associated with a higher risk for lymphomas. Specifically, in one study, painters and lumberjacks had a higher risk for NHL, while office and house workers had a lower risk.
• Some studies have found an association with long duration and early use of permanent dark hair dyes. There is no consistent evidence, however, that hair dye increases the risk for lymphomas.

Other Conditions Associated with Non-Hodgkin's Lymphomas

Autoimmune Diseases. Patients with autoimmune diseases may have increased risks for developing NHL. A 2005 review found that patients with Sjögren syndrome had 18.8 times more risk for NHL than healthy patients. Systemic lupus erythematosus increased risk by 7.4 times, and rheumatoid arthritis increased risk by 3.9 times. For patients with rheumatoid arthritis, the lymphoma risk appears highest for those with very severe and chronic forms of this autoimmune disease.

Tumor necrosis factor (TNF) blockers used to treat autoimmune conditions -- such as infliximab (Remicade), etanercept (Enbrel), and adalimumab (Humira) -- may also increase the risk for developing NHL. According to one study, lymphoma rates for patients who took infliximab for Crohn's disease or RA were six times higher than those found in the general public. However, several 2006 studies suggested that the inflammatory process of rheumatoid arthritis, rather than its drug treatments, is the main factor in increasing lymphoma risk.

Pregnancy and Childbirth. One study observed a higher risk for lymphomas in children with a low weight at birth or with mothers who were heavy smokers during pregnancy. (Breastfeeding for more than 6 months, on the other hand, may offer some protection.)

Review Date: 01/17/2007
Reviewed By: Harvey Simon, MD, Editor-in-Chief, Associate Professor of Medicine, Harvard Medical School; Physician, Massachusetts General Hospital.