Comparison of two atmospheric-dispersion models to assess farm-site exposure to sour-gas processing-plant emissions.
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We describe two approaches for exposure assessment that we used in a large-scale retrospective cattle study conducted in Alberta, Canada. Sulfur dioxide (SO(2)) was the surrogate measure of exposure to a complex mixture of combusted sour-gas emissions. Monthly air pollution dispersion modeling (1985-1994) (based on individual industrial source processing-plant engineering specifications, emission volumes, and meteorologic information) provided exposure isopleths of sulfur dioxide concentration from each of 231 sour-gas processing-plants across the province. In contrast, a simpler measure of proximity to source(s) of varying emission rates was applied in a geographical information system based on simplified pollution decay at increasing distances from each point source. Province-wide (663,000 km(2)) surface analysis (by exposure-level classification) produced a contingency coefficient of 0.68 between the two exposure estimates. Annual exposure estimates at the 1382 dairy and 5726 beef cow-calf farms studied were highly correlated over the 10-years period (r(spearman)=0.82 and 0.83, respectively), while monthly exposure estimates were somewhat less correlated (r(spearman)=0.80 and 0.82, respectively) for the two exposure assessment methods. Crude exposure estimates from each method were similar in both direction and magnitude.
author list (cited authors)
Scott, H. M., Soskolne, C. L., Wayne Martin, S., Ellehoj, E. A., Coppock, R. W., Guidotti, T. L., & Lissemore, K. D.
complete list of authors
Scott, H Morgan||Soskolne, Colin L||Wayne Martin, S||Ellehoj, Erik A||Coppock, Robert W||Guidotti, Tee L||Lissemore, Kerry D