This article is a commentary on the following study: Mulder YM, Drijver M, Kreis IA. Case-control study on the association between a cluster of childhood hematopoietic malignancies and local environmental factors in Aalsmeer, The Netherlands. J Epidemiol Community Health. 1994 Apr;48(2):161-5. In the 1980s, the parents of a boy with leukemia reported to their pediatrician that, in their opinion, 12 people suffering from a "similar" condition lived within a 1-kilometer radius. They wondered whether regular swimming in a pond (which they suspected was polluted by pesticides and petroleum products) or the proximity of Schiphol Airport might be the cause of this spatial cluster. The cancer cluster was subsequently confirmed using the national disease registry. Over the 1980–1985 period, the incidence of leukemia was found to be at least four times higher among people aged 0 to 40 living in Aalsmeer. Furthermore, analysis of soil and surface water from a natural swimming area revealed concentrations exceeding "acceptable" limits for pesticides, polycyclic aromatic hydrocarbons, and benzene. While this case-control study appears legitimate following the discovery of a spatial cluster, it contributes little to our understanding of the health risks associated with exposure to atmospheric chemical pollution in airport areas, primarily due to the poor metrological quality of the exposure indicators used. (Excerpt from the article)