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Pregnant women exposed to household pesticides may increase the risk of their children developing leukemia, according to a recent study conducted in France. These findings add more weight to the idea that pesticides play a role in childhood blood cancers and may shed light on the actual causes of the diseases.

In the study, parents of leukemia patients were more likely to have used pesticides and insecticides either at home or at work. Exposure to these chemicals is a risk factor for blood cancers, particularly if children are exposed in the womb, the authors’ conclude.

Study participants were selected randomly from the French population using a quota sampling method of phone numbers equally distributed within 22 geographic regions in France.

Of 60,000 phone numbers dialed, 1,682 mothers were interviewed for the study. Mothers classified their exposure to pesticides during pregnancy as “ever used,” “never used” or “do not know.” They also reported the type of pesticide exposure (insecticide, herbicide, fungicide), if it was household or occupational exposure and whether the father was exposed during the pregnancy.

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The use of household pesticides by mothers during their pregnancies was higher in the leukemia group than the randomly chosen controls. More than half of the mothers whose children had acute leukemia or non Hodgkins lymphoma used pesticides at lease once during their pregnancy compared with a little more than a third of the control group mothers.

There were significant associations between maternal pesticide use and acute leukemia (AL) and non-Hodgkin’s lymphoma (NHL), but not with Hodgkin’s lymphoma (HL). Paternal use of household pesticides was significantly associated with AL and NHL, but the associations were slightly weaker.

The strongest link was found was between insecticide use, with weaker associations with herbicides and no association with fungicides.

Children exposed to household pesticides before birth may have an increased risk of developing certain types of leukemia. The results reinforce findings from other studies that also identified associations between pesticide exposure before birth and the risk of developing a blood cancer. The authors’ conclude that “the consistency of the findings with those of previous studies on AL raises the question of the advisability of preventing pesticide use by pregnant women.”

The underlying causes and risk factors associated with leukemia initiation and recurrence are poorly understood. Nevertheless, a growing body of evidence suggests that exposure to a variety of environmental factors may interact with and modify genetic factors, thus increasing the risk for new and recurrent cases (Birnbaum and Fenton 2003, Freedman et al. 2001, Meinert et al. 2000, Schuz et al. 2000, Shu et al. 1999, Stjernfeldt et al. 1986).

Leukemia and lymphoma are two of the most common childhood cancers worldwide. Rates of these blood cancers have increased during the last three decades, but more children survive due to better diagnosis and treatment.

Leukemia and lymphoma are classified by the kind of blood cell that is causing the cancer. Leukemia describes a family of diseases with at least four different types of bone marrow cell invaders: acute myelogenous leukemia, acute lymphocytic leukemia, chronic myelogenous leukemia (cml) and chronic lymphocytic leukemia.

In the United States, approximately 27% of all childhood cancers are leukemias. It is estimated that in 2007, 3,800 children under the age of 20 will be diagnosed with leukemia in the United States.

Treatment of new and recurrent cases of leukemia cost $2.6 billion dollars a year (Brown et al. 2002). This number does not include costs associated with job and/or productivity losses for patients and their families. While considerable gains have been made in leukemia survivability over the last 40 years, 22,000 people died from the disease in 2006 (SEER and NCI 2006).

Treatments and cure rates for childhood leukemia are improving, but there is a need to understand the origins of the diseases. Exposure to household pesticides has been suggested to be one potential risk factor for childhood leukemia, particularly if mothers were exposed during their pregnancy.

Source: “Household exposure to pesticides and risk of childhood haematopoietic malignancies: the ESCALE study (SFCE).” Rudant, J, F Menegaux, G Leverger, A Baruchel, B Nelken, Y Bertrand, C Patte, H Pacquement, C Vérité, A Robert, G Michel, G Margueritte, V Gandemer, D Hémon and J Clavel. 2007. Environmental Health Perspectives 115:1787–1793. 

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