This highly spatially resolved concentration metric is available for the entire state of NC, which allows us to include women that would typically be excluded from analyses that use only monitoring networks as exposure surrogates.
No similar monitoring network exists to assess exposure from indoor sources, which may need to rely on questionnaire information and substudies across regions.
Most research groups (11 of 14; 79%) used routinely collected monitoring network data to estimate exposures (Table 2), although its use differs among studies [e.g., averages over geographic areas; nearest monitor measurement, or inverse distance-weighted (IDW) averages from multiple monitors, from residence].
Strengths include the large population-based sample size and the availability of data on health and potential confounders, the 10-year address histories used to estimate long-term NO2 and traffic exposure markers, and the dense NO2 and traffic monitoring network data used to estimate exposures at each participant's residences.
Establishing an air pollution monitoring network for intra-urban population exposure assessment: a location-allocation approach.
For the purposes of this investigation we assume that it is the association of ambient pollution with mortality at the small-area level that is important (because of the link to regulation, [ 11]) rather than exposure at the level of the individual and leave consideration of disparities between background monitoring networks and personal exposure to others [ 4, 11, 12].
Because the existing environmental data with aggregated yearly exposure from air monitoring network are only indexed to calendar years, both approaches offer the advantages of avoiding misalignment between estimated exposures at large time scales and the occurrence of study outcomes.
Several studies assessed PM2.5 exposure based on monitoring network data and remote sensing data; we preferentially chose estimates based on monitoring network data because this assessment method was more common across all studies, which could potentially reduce the heterogeneity between studies in this meta-analysis.
The monitoring network adopts two networking protocols.
Details about the various UV monitoring networks can be found via the web at: http://www.arl.noaa.gov/research/programs/uv.html Between 1996 and 2004, EPA, in conjunction with the National Park Service, operated a 21-site monitoring network with a goal of characterizing UV exposures and trends in a range of ecoregions across the United States.
