New Study Strengthens Link Between Pesticides and Lymphoma

(Beyond Pesticides, May 10, 2007)

The risk of non-Hodgkin’s lymphoma is significantly increased with substantial exposure to pesticides, regardless of asthma or atopy history, according to findings from a study published in the May issue of the International Journal of Cancer. This study further strengthens the link between exposure to pesticides and cancer and specifically to lymphoma.

“Occupational exposure to pesticides and a personal history of atopy have been widely examined as risk factors for non-Hodgkin’s lymphoma (NHL), a neoplasm arising from cells of the immune system,” writes Claire M. Vajdic, Ph.D., of the University of New South Wales, Australia, and colleagues. “These studies have typically found that exposure to pesticides increases risk of NHL, while asthma, or atopy more generally, has been inconsistently protective.”

In an Australian population-based, case-control study, the researchers examined the interaction between occupational pesticide exposure and atopy on the risk of NHL. Included in the study were 694 incident cases and 694 randomly selected controls that were matched to cases by age, sex, and state of residence.

Participants completed telephone-administered job-specific questionnaires. Experts used the information collected to determine occupational pesticide exposure. History of atopy (including asthma, hay fever, eczema, and food allergy) was self-reported.

The odds ratio (OR) for NHL with substantial exposure to pesticides and any history of asthma was 3.07. With substantial pesticide exposure and no history of asthma, the OR was 4.23. The risk of NHL was less for subjects with non-substantial pesticide exposure and a history of asthma (OR = 0.30), and was close to null with non-substantial pesticide exposure and no history of asthma (OR = 0.99).

“This finding was consistent for several measures of pesticide exposure and asthma, including lifetime pesticide dose, subtype-specific pesticide dose and history of asthma as an adult, teenager, or child,” Dr. Vajdic and colleagues report.

Furthermore, “The pattern of risk for a history of hay fever, eczema, food allergy or any type of atopy was similar; risk was increased with substantial pesticide exposure and no history of atopy, but less so when atopy was reported.”

Non-Hodgkin’s lymphoma is a cancer of the immune system. There are several different types of NHL, which are differentiated by the type of immune cell that is cancerous, the characteristics of the cancerous cell, and different genetic mutations of the cancerous cells. Treatment for NHL varies depending on NHL type, patient age, and other existing medical conditions.

A number have studies have established a link between NHL and pesticide exposure. According to a 2000 study, parents who used pesticides in the home once or twice a week were nearly 2.5 times as likely to have children with non-Hodgkin’s lymphoma. Parents who used pesticides on a daily basis were 7 times more likely to have children with the disease. In 2002, The Lymphoma Foundation of America released a report that found that the majority of 117 scientific studies and articles reviewed showed a significant increase in lymphoma in populations with higher exposures to pesticides, especially herbicides. A May 2006 study published in the journal Blood found that agricultural exposure to insecticides, herbicides, and fumigants are associated with increased risk of developing non-Hodgkin’s lymphoma (NHL).

Source: Reuters