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Lymphoma and Pets
What Causes Lymphoma?
What causes lymphoma is not well known. DNA mutations may be what causes lymphoma to develop but what triggers these mutations is largely unknown. Family history does not provide much of a clue; except in the case of some rare forms, lymphoma does not appear to be linked to genetic inheritance.
However, as lymphoma incidence rises and research accelerates, several risk factors for lymphoma have been established. We outline some of them below. Please keep in mind that there are volumes of published research on the twenty to thirty known forms of lymphoma, and much remains to be learned. This page identifies some of the better-known risk factors for lymphoma and should serve as a launching point for further investigation.
Environmental Risk Factors for Lymphoma
It will probably not to surprise you to learn that exposure to certain chemicals and radiation has been linked to lymphoma.
Chemical solvents such as acetone, alcohol (various alcohols, not just ethyl alcohol), toluene, xylene, turpentine, and benzene, are highly toxic and linked to lymphoma. Benzene exposure in particular, already a known cause of leukemia, is now linked to lymphoma and is the subject of much research and many lawsuits.
A meta-analysis of 22 benzene exposure studies by the UC Berkeley School of Public Health concluded that, "The finding of elevated relative risks in studies of both benzene exposure and refinery work provides further evidence that benzene exposure causes NHL." Benzene, a solvent manufactured from petroleum, is found in gasoline, cigarette smoke, and in many solvents such as . Benzene exposure is also an occupational risk for oil industry jobs, particularly refining jobs, and plastics manufacturing.
Herbicides and Pesticides
Chemicals used for defoliation and pest control have been linked to lymphoma and are a significant risk factor. These chemicals are an occupational hazard for farmers and agricultural workers in particular. Populations in agricultural areas are also at significant risk from airborne exposure via crop dusting, and from groundwater exposure via contaminated water supplies. Herbicides and pesticides are also a potential threat to the general population who may ingest them through the food supply.
"Agent Orange," named after the orange-striped drums used for shipping, refers to any of the phenoxy herbicides used for defoliation during the Vietnam War. Herbicides can enter the body not only from direct contact, but also through food and soil contamination and inhalation. Both soldiers and the Vietnamese population endured significant herbicide exposure. One herbicide in particular, 2,4,5-trichlorophenoxyacetic acid [2,4,5-T], was particularly toxic because it contained dioxins. Dioxins remain in the environment–particularly the soil–for years and are linked to many cancers.
While it has not been irrefutably proven that exposure to Agent Orange causes cancer, the evidence is strong enough to put both Hodgkin's and non-Hodgkin's lymphoma on the U.S. Department of Veterans Affairs list of "Current Conditions Considered by VA Presumptive to AO Exposure."
There has been a lot of press over the years linking hair dye to lymphoma and other cancers. Although there has been some inaccurate reporting on this issue, it is true that some link has been established, particularly in the case of hair dyes manufactured before 1980. A 2008 study of over 10,000 people published in the American Journal of Epidemiology (4,461 NHL patients and 5,799 controls) concluded the following:
"In summary, the results from this large InterLymph-based pooled analysis indicate that personal use of hair dye may play a role in the risk of NHL, particularly for follicular lymphoma and CLL/SLL. Our study also indicates that although the risk associated with personal hair-dye use was observed mainly among women who started using hair dyes before 1980, the risk was not limited to those women. Future studies are needed to examine the risk of NHL by time period of hair-dye use and by genetic susceptibility."
Genetic Risk Factors for Lymphoma
The genetic links to lymphoma are complicated and uncertain. Direct inheritance does not seem to be a factor. Even in the rare cases in which lymphoma occurs in family clusters it is not clear whether genetics or environmental exposure–or a combination of the two–is the determining factor.
Inherited Immune Deficiencies
Lymphoma and genetics are most closely associated with inherited immune disorders. Lupus, rheumatoid arthritis, celiac disease and Sjögren's syndrome all appear to increase a person's chances of developing lymphoma.
Immune System Disorders
Lymphoma is essentially an immune system disease and positive correlations exist between many immune deficiencies and various lymphomas.
HIV / AIDS
The incidence of lymphoma in HIV/AIDS patients is substantially higher than that of the general population, so much so that the condition, usually a type of B-Cell lymphoma, has its own description: "AIDS-related lymphoma." It is still the same cancer suffered by HIV-negative patients, but demands special attention because it is so closely linked to the virus. HIV patients are determined to have AIDS when they develop significant conditions and/or diseases in conjunction with the virus; lymphoma is frequently a determining factor.
Epstein Barr virus [EBV], a member of the herpes virus family, is extremely common and can result in infectious mononucleosis in young adults. In most cases EBV infection and "mono" are not serious conditions. However, in patients with compromised immune systems in which T-cells do not destroy infected B-cells, EBV-infected cells may become cancerous. The strongest correlation between lymphoma and EBV pertains to Burkitt's lymphoma.
H. Pylori is a bacteria found in populations worldwide. It can result in minor stomach inflammation, ulcers, and can lead to stomach cancer. H. Pylori is also linked to MALT lymphoma, a rare type of B-cell tumor.
- Study: "Non-Hodgkin lymphoma and benzene exposure: A systematic literature review"
- "Solvents and Lymphoma," from LymphomaHelp (pdf)
- Search Occupational and Environmental Medicine for "benzene"
- "Benzene exposure and risk of non-Hodgkin lymphoma," Berkeley School of Public Health
- JAMA search: "herbicides and lymphoma"
- JAMA search: "pesticides and lymphoma"
- "Agent Orange and Cancer" from the ACS
- "Agent Orange and NHL" - NHL CyberFamily
- Agent Orange Widows Awareness Coalition
- "Agent Orange and Your VA Claim" - VietNow
- Chang, E.T. et. al: Family History of Hematopoietic Malignancy and Risk of Lymphoma, JNCI, Vol 97, No. 19, 1466-1474, October 5, 2005
- Risks and causes of Hodgkin's lymphoma - CancerHelp (UK)
- Do We Know What Causes Non-Hodgkin's Lymphoma? - American Cancer Society
- What Causes Hodgkin's Disease? Can It Be Prevented? - American Cancer Society