Magnetic field exposure and prognostic factors in childhood leukemia.

We examined the association between magnetic field (MF) exposure and the presence of prognostic risk factors among 482 children diagnosed with acute lymphoblastic leukemia (ALL) between 1996 and 2001. Personal 24-h MF measurements were obtained for 412 children; 386 children were included in analyses. There were no trends seen between increasing exposure to MF and the presence of adverse clinical and tumor-specific prognostic factors. Our results suggest that exposure to MF is not associated with the presence of unfavorable cytogenetic abnormalities in leukemic blast cells or with clinical factors at the time of diagnosis that predict poor survival.

Retrospective data quality audits of the Harvard Six Cities and American Cancer Society studies.

The Harvard Six Cities (6-Cities) and American Cancer Society (ACS) studies are longitudinal cohort mortality studies of large populations that provided important information about the human health effects associated with long-term exposure to fine particulate air pollution. Possible changes to federal regulation of particulates prompted a review of data collection methods, analysis, and reported results from these two studies. This article describes the methodology used to conduct quality assurance audits of both studies and summarizes the audit findings. Statistically based, randomly selected samples of 250 health questionnaires and 250 death certificates from each study were audited against data from analysis files. In cases where study-specific data could not be located, validation was performed using information and data from other sources. Some errors were found in programming and data transformation in both studies, but none affected the results of the original investigations. Both audits confirmed that the published studies are an accurate representation of the collected data. The audits also underscored the importance of adequate attention to documentation and record-keeping practices during the conduct of all studies and proper archiving at their conclusion.

Correlation of year-to-year magnetic field exposure metrics among children in a leukemia survival study.

The Childhood Leukemia Survival Study is examining the possible association between magnetic field exposure and survival of children with newly diagnosed acute lymphocytic leukemia (ALL). We report the results of serial 24-h personal magnetic field monitoring for 412 US and Canadian children and present the correlations between annual values. The mean time-weighted average (TWA) and geometric mean (GM) were similar for first, second, and third year measurements [TWA: 0.11 microT (n = 412), 0.13 microT (n = 304), and 0.12 microT (n = 134), respectively]. There were no consistent differences in mean TWA or GM based on age or gender. Significantly lower mean TWA and GM were found for children living in rural areas. Higher exposures were noted among children living in urban areas, among apartments dwellers, and those living in rental homes. Measurements taken during summer months and among children residing in the northeast and Canada also tended to be higher. Correlations for most metrics were increased among children who had annual measurements performed during the same season. The metric with the highest year-to-year correlation was the GM. The lowest correlations were found for metrics estimating field intermittency and temporal stability. First to second year GMs were well correlated when taken in the same home (Spearman rank correlation = 0.70), but a lower correlation (0.44) was noted among residentially mobile children. Our findings suggest that summarizing exposure using a single measurement of GM can estimate exposures for residentially stable children, but is not a good predictor of personal exposures among children who change residence during the study interval.