|
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. Household exposure to pesticides and risk of childhood haematopoietic malignancies: the ESCALE study (SFCE). Environmental Health Perspectives 115:1787–1793. |
|
|
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.
|
|
|
Context: 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).
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).
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. |
|
What did they do? This study looked at mothers' exposure to household pesticides during pregnancy and the child's risk of developing leukemia or lymphoma. Using the French National Registry of Childhood Blood Malignancies, the authors identified 1,316 cases of childhood leukemia. Of these, only French speaking parents whose children survived and are currently healthy were contacted for the study. This left a study population of 764 volunteers who were surveyed by telephone about pesticide exposure and use for both mother and father during the pregnancy.
Controls 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.
Identical surveys were given by the same trained staff to both control and study subjects. 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.
Other personal and family history, such as socioeconomic status, degree of urbanization, housing type (flat or house) and a child’s contact with pets, were also determined by the survey and controlled for during analysis.
Using these data, the authors' performed a statistical analysis to determine if there was a higher exposure to pesticides during pregnancy among the mothers whose children had cancer. They also asked if the exposures could implicate pesticides as a contributing environmental risk factor for developing leukemia.
What did they find? 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 authors further broke down their analysis based on the type of pesticides used (insecticide, herbicide, or fungicide). When breaking down the analysis by pesticide type, the strongest association found was between insecticide use and AL and NHL, with weaker associations with herbicides and no association with fungicides.
What does it mean? 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." |
Human epidemiology studies try to pinpoint factors that may be associated with a particular disease. Epidemiological studies, however, cannot prove causation. While the current study demonstrates a strong association between the use of pesticides and several types of childhood leukemia, it cannot determine whether pesticide exposure in the womb actually caused these particular children to develop the disease.
Due to their complex nature, assumptions made during independent epidemiology studies may overestimate - or underestimate - the relative risk of a particular event and the disease in question. In this study, one of the assumptions made could underestimate the pesticide-leukemia association, while another assumption could over estimate it.
The first assumption, about pesticide exposure, was based on women reporting if they ever used or never used pesticides during pregnancy. More specific information about the frequency of pesticide exposure and/or the amounts of prenatal pesticide exposure could have strengthened the associations with leukemia.
The second assumption, about recall bias, was that mothers whose children were healthy would as clearly recall their activities during pregnancy (particularly as it pertains to pesticide use) as the mothers whose children had leukemia would. Recall bias is the strong probability that some groups of people remember past details better than others do. In this case, parents of children with serious diseases worry and think about why their children are sick and suffering. The authors did not fully account for potential recall bias of the control mothers, which could influence the findings.
Despite the potential limitations of this study, several important conclusions can be made, particularly if the study is taken in the context of other related studies in the field. First, the associations between pesticide use during pregnancy and childhood leukemia are strong enough that limiting or eliminating their use during pregnancy is advisable, according to the authors.
Second, the findings add to a growing body of literature that has identified associations between childhood leukemias and exposure during pregnancy to a growing number of household chemicals. This list includes, but is not limited to, paints, glues and solvents, cigarette smoke and pesticides. The broad class of compounds that may increase risk of developing leukemia indicates that there may be common features associated with these compounds. Alternatively, and perhaps more importantly, it confirms that children and babies in particular, with their growing and developing organs and tissues, are especially sensitive to chemicals in the environment.
Resources:
Anderson, LM, BA Diwan, NT Fear and E Roman 2000. Critical windows of exposure for children's health: cancer in human epidemiological studies and neoplasms in experimental animal models. Environmental Health Perspectives. 108 Suppl 3:573-94.
Birnbaum, LS and SE Fenton. 2003. Cancer and developmental exposure to endocrine disruptors. Environmental Health Perspectives 111(4):389-94.
Brown, ML, GF Riley, N Schussler and R Etzioni 2002. Estimating health care costs related to cancer treatment from SEER-Medicare data. Med Care, 2002. 40(8 Suppl): p. IV-104-17.
Center for Disease Control and Prevention. Hematologic (blood) cancers statistics.
Freedman, DM, P Stewart, RA Kleinerman, S Wacholder, EE Hatch, RE Tarone, LL Robison and MS Linet. 2001. Household solvent exposures and childhood acute lymphoblastic leukemia. American Journal of Public Health 91(4):564-7.
Leukemia and Lymphoma Society. Childhood leukemia and lymphoma.
Meinert, R, J Schüz, U Kaletsch, P Kaatsch and J Michaelis. 2000. Leukemia and non-Hodgkin's lymphoma in childhood and exposure to pesticides: results of a register-based case-control study in Germany. American Journal of Epidemiology 151(7):639-46 and 647-50. |
|
More news about
|
National Resources Defense Fund. Children, cancer and the environment.
Schuz, J, U Kaletsch, R Meinert, P Kaatsch and J Michaelis. 2000. Risk of childhood leukemia and parental self-reported occupational exposure to chemicals, dusts, and fumes: results from pooled analyses of German population-based case-control studies. Cancer Epidemiology Biomarkers and Prevention. 9(8):835-8.
SEER and NCI. 2006. Surveillance epidemiology and end results.
Shu, XO, P Stewart, W-Q Wen, D Han, JD Potter, JD Buckley, E Heineman and LL Robison. 1999. Parental occupational exposure to hydrocarbons and risk of acute lymphocytic leukemia in offspring. Cancer Epidemiology Biomarkers Prev 8(9):783-91.
Stjernfeldt, M, et al. 1986. Maternal smoking during pregnancy and the risk of childhood cancer. Lancet 2(8508):687-8.
© Environmental Health Sciences. Articles may be used for educational and other not-for-profit purposes with credit to Environmental Health Sciences.
|
