Research links pesticides, non-Hodgkin's lymphoma.

Nov 11, 2011

Bräuner, EV, M Sørensen, E Gaudreau, A LeBlanc, KT Eriksen, A Tjønneland, K Overvad and O Raaschou-Nielsen. 2011. A prospective study of organochlorines in adipose tissue and risk of non-Hodgkin’s Lymphoma. Environmental Health Perspectives http://dx.doi.org/10.1289/ehp.1103573.

Synopsis by Brandon Moore

Higher pesticide levels measured in people well before they were diagnosed with cancer are associated with an elevated risk of lymphoma later in life.

Elevated levels of organochlorine pesticides years before the cancer develops increases the risk of non-Hodgkin’s lymphoma – a form of lymph cancer – later in life, report cancer researchers in Denmark. Their results are published in the journal Environmental Health Perspectives.

The study is the first to show the association based on pesticide levels in fat tissues prior to the diagnosis of cancer. The study specifically tied the increased risk to three chemicals no longer used in the United States but still found in people and the environment – DDT, cis-nonachlor and oxychlordane.

Because the samples were collected years before cancer diagnosis, the results are more informative than other types of studies in forecasting an increased probability of disease. This type of study, which epidemiologists call a 'prospective' study, is especially useful in linking exposure to disease risk. The results strengthen an argument for an environmental link to increased risk for human non-Hodgkin’s lymphoma that is linked to higher levels of organochlorine pollutants.

Lymphoma is cancer that affects the lymphatic cells of the immune system. The frequency of non-Hodgkin’s lymphoma has increased in Western countries since the 1970s but has stabilized since the 1990s. While genetics and previous cancers play a role in the disease, environmental exposures also may contribute.

According to the International Agency for Research on Cancer (IARC) – part of the World Health Organization – animal studies show DDT and other organochlorine pesticides are carcinogens and can affect the immune system. Previous human studies also suggest a link between pesticide exposures and increased risks of lymphoma. These retrospective studies measured pesticide level only after cancer diagnosis or death. The results could not make strong predictions about if contamination results in disease.

In this study, fat tissues were collected between 1993 and 1997 from Danish men and women in the general population when they were in their 50s and 60s. The samples were analyzed for 10 PCBs and eight organochlorine pesticide or metabolites. Contaminants tend to accumulate in fat tissues. Therefore, the tissues serve as long-term markers of exposures. Participants were tracked through the Danish Cancer Registry, which collects comprehensive data on all cancer patients nationwide.

Pesticide levels of the 239 participants who developed non-Hodgkin’s lymphoma – some up to 15 years after samples were collected – were compared to a matched, cancer-free group. When analyzing the results, the researchers controlled for the effects of differences in the participants' age, gender and body mass index.

Measured levels of the pesticides DDT, cis-nonachlor and oxychlordane showed positive relationships with non-Hodgkin’s lymphoma risk. This risk was stronger in men, but was not associated with body-mass index – a measure of body fat. No associations to lymphoma were found with the PCBs analyzed.

 

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