Ground-based observations have insufficient coverage at the global scale to allow assessment of long-term human exposure to fine particulate matter (PM2.5). Thus, we are developing SPARTAN (Surface PARTiculate mAtter Network), a network of ground-based measurements of fine particle concentrations to evaluate and enhance satellite remote sensing estimates that can be applied in health effects research and risk assessment. The network includes a global federation of ground-level monitors of hourly PM2.5, primarily in highly populated regions in close proximity to existing ground-based sun photometers that measure aerosol optical depth. Regions in which PM2.5 levels appear to be the highest, and in which the burden of disease due to PM2.5 is estimated to be the greatest, currently have limited data on ambient levels and human exposure to health-damaging particulate PM2.5.
Satellite remote sensing offers one of the most promising means of providing estimates of population exposure to PM2.5 on a global scale, and especially for areas with limited ground-level PM2.5 measurements. However, there are outstanding questions about the accuracy and precision with which ground-level aerosol mass concentrations can be inferred from satellite remote sensing.
SPARTAN is a targeted network of ground-based measurements of fine particle concentrations and limited compositional features. Our primary focus is on PM2.5 mass, since it is a robust indicator of mortality and other adverse health impacts in epidemiologic cohort studies of long-term exposure. The SPARTAN network includes a combination of automated continuous monitoring and integrated filter samples. Priority SPARTAN locations have high population density, sparse PM2.5 monitoring, and existing sunphotometer measurements of aerosol optical depth (AOD). Together, these instruments provide an empirical measure of the AOD/PM2.5 ratio that is used to relate satellite AOD retrievals to ground-level PM2.5.