Combining data from multiple monitors in air pollution mortality time series studies

In community time series studies on the effect of particulate air pollution on mortality, particulate air pollution data are often available from multiple monitors. Published studies have combined the data from the multiple monitors using a simple or trimmed average. In this paper, I describe an alternative method for combining the particulate air pollution data available from multiple monitors. Using time series data from Cook County, Illinois the proposed method yields more meaningful biologically plausible particulate air pollution mortality effect estimates without loss of statistical accuracy and reduces the full set of monitors to a smaller set without loss of information. The proposed monitor combination may be more highly correlated with the average population exposure to particulate air pollution than a simple or trimmed average of the monitors. (C) 2003 Elsevier Ltd. All rights reserved.