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Objectives: To investigate a cluster of leukaemia among young people and assess the plausibility of a disease-exposure relationship., Design: Descriptive analysis of population-based leukaemia incidence data, review of evidence related to the causation of leukaemia, assessment of environmental exposures to known leukaemogens, and resulting risks of leukaemia., Setting: Illawarra region of New South Wales, Australia, focusing on suburbs between the Port Kembla industrial complex and Lake Illawarra (the Warrawong area)., Main Outcome Measures: Standardised incidence ratios (SIRs) for leukaemia; current measured and past estimated ambient air benzene concentrations; and expected leukaemia cases attributable to estimates of ambient air benzene concentrations., Results: In 1989-1996, 12 leukaemia cases among Warrawong residents aged less than 50 years were observed, more than the 3.49 cases expected from the rate in the rest of the Illawarra region (SIR, 343.8; 99% CI, 141.6-691.7). These people lived in suburbs immediately to the south-southwest of a coke byproducts plant (a major industrial source of benzene, one of the few known leukaemogens). The greatest excess was among 15-24-year-olds (SIR, 1085.6; 99% CI, 234.1-3072.4). In 1996, ambient air concentrations of benzene averaged less than 1 part per billion (ppb). Since 1970, ambient air concentrations of benzene were estimated to have averaged up to 3 ppb, about one-thousandth of the level at which leukaemia risk has been identified in occupational epidemiological studies. Using the risk assessment model developed by the US Environmental Protection Agency, we estimate that past benzene levels in the Warrawong area could have resulted in 0.4 additional cases of leukaemia in 1989-1996., Conclusions: The excess occurrence of leukaemia in the Warrawong area in 1989-1996 is highly unusual. Current environmental benzene exposure and the reconstructed past environmental benzene exposure level are too low to explain the large excess of leukaemia. The cause of the cluster is uncertain.

Study Objective and Design: In Aalsmeer, a horticultural community near the main international airport in The Netherlands, a more than fourfold increase in the incidence of haematopoietic malignancies in young people was observed between 1980 and 1985. In a population based case-control study, the association with local environmental factors was investigated., Participants: For each patient younger than 40 years of age (n = 14) diagnosed between 1975 and 1989, four age and sex matched controls were selected via local general practitioners., Methods: All parents of patients and controls completed a questionnaire on their lifestyle, living conditions, and health, for several years preceding each individual diagnosis. Odds ratios (ORs) with 95% confidence intervals (CI) were calculated, matched, and, if necessary, stratified for neighbourhood., Main Results: Increased ORs were recorded for intensive use of petroleum products and pesticides by the patients themselves and their fathers: OR petroleum products: 8.0 (95% CI 2.2, 129.9) and 9.0 (1.0, 66.1) respectively; OR pesticides: 6.0 (0.6, 49.3) and 3.2 (1.0, 10.1) respectively. Swimming in a local pond was also significantly associated with the disease: OR = 5.3 (1.3, 17.4). In the 1970s this pond had been polluted by petroleum products and pesticides., Conclusions: The increased incidence of childhood haematopoietic malignancies in Aalsmeer may have been associated with several specific local environmental factors. Interpretation of the results, however, should take into account the fact that confidence intervals were wide because of the limited number of cases.

In Aalsmeer, a horticultural community near the main international airport in the Netherlands, an incidence of haematopoietic malignancies in young people over four times the national mean was observed in the period 1980-1985. A population based case-control study investigated the association with local environmental factors. For each case younger than 40 years of age (n = 14), diagnosed between 1975 and 1989, four controls, matched for age and gender, were selected via local general practitioners. All parents of patients and controls completed a questionnaire on their life style, living conditions and health for several years preceding each individual diagnosis. Odds ratios (ORs) were calculated, matched and--if necessary--stratified for neighbourhood. Increased ORs were recorded for intensive use of petroleum products and pesticides, by the patients themselves and their fathers (OR petroleum products: 8.0, resp. 9.0; OR pesticides: 6.0, resp. 3.2). Most of these increases were statistically significant. Swimming in a local pond was also significantly associated with the disease (OR = 5.3); in the seventies this pond had been polluted by accidents with petroleum products and pesticides. contributed to the increase of the disease: ORs for several indirect exposure parameters were all above 2. It can be concluded that the increased incidence of childhood haematopoietic malignancies in Aalsmeer may have been associated with several specific local environmental factors. However, interpretation of the results should take into account that confidence intervals were wide, due to the necessarily limited number of cases.