A Case-Control Study of Pesticides and Childhood Leukemia

Childhood leukemia is the most common type of childhood cancer and its etiology is largely unknown. Most case-control studies of childhood leukemia have reported elevated risks among children whose parents were occupationally exposed to pesticides or who used pesticides in the home or garden. Investigators at the University of California at Berkeley (UCB) conducted a case-control study of childhood leukemia in 35 counties in the San Francisco Bay area and the agricultural Central Valley of California. A major focus of the UCB study is to evaluate whether household or occupational exposure to pesticides increases the risk of childhood leukemia. Our collaboration provided additional funding to collect carpet dust samples for the measurement of pesticides and other chemicals. For 470 participants, we attempted to collect carpet dust using a special high volume small surface sampler (HVS3) vacuum and by taking dust from participants vacuum cleaner. As of July 2006, dust samples will be collected only from participant's vacuum cleaner. Samples were collected at a home visit approximately 3-6 months after the first in-person interview. We will also provide support for mapping of the crops (i.e., determining crop field boundaries and crop species) within 1200 meters (3/4 mile) of residences so that the residential proximity to agricultural fields treated with pesticides can be determined. We will conduct the epidemiologic analysis of pesticide and other chemical levels in carpet dust and risk of childhood leukemia. We will also evaluate whether residential proximity to agricultural pesticide use is associated with risk of leukemia. Further, we will conduct an Exposure Pilot Study that will include a subset of the study population. Two components of the Pilot Study will evaluate how well a used vacuum bag and a window sill wipe predict pesticide and other chemical concentrations in carpet dust samples collected with the more complicated HVS3 vacuum method. The third component will compare pesticides detected in carpet dust with pesticides predicted by geographic proximity to agriculture.