title: Comparison of two atmospheric-dispersion models to assess farm-site exposure to sour-gas processing-plant emissions.
abstract: 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.
authors.affiliation: Department of Public Health Sciences, University of Alberta, Edmonton, Alta., Canada T6G 2G3. hmscott@cvm.tamu.edu
authors.forename: H Morgan
authors.initials: HM
authors.lastname: Scott
authors.forename: Colin L
authors.initials: CL
authors.lastname: Soskolne
authors.forename: S
authors.initials: S
authors.lastname: Wayne Martin
authors.forename: Erik A
authors.initials: EA
authors.lastname: Ellehoj
authors.forename: Robert W
authors.initials: RW
authors.lastname: Coppock
authors.forename: Tee L
authors.initials: TL
authors.lastname: Guidotti
authors.forename: Kerry D
authors.initials: KD
authors.lastname: Lissemore
mesh_terms: D000383:Agriculture; D000393:Air Pollutants / Q000032:analysis*; D000416:Alberta; D000818:Animals; D001272:Atmosphere / Q000737:chemistry*; D002417:Cattle; D003198:Computer Simulation; D003612:Dairying; D004784:Environmental Monitoring; D005260:Female; D005740:Gases / Q000032:analysis*; D005843:Geography; D007220:Industrial Waste / Q000032:analysis; D008297:Male; D008460:Meat; D016011:Normal Distribution; D012189:Retrospective Studies; D013458:Sulfur Dioxide / Q000032:analysis*; D013997:Time Factors
chemical_list: D000393:Air Pollutants; D005740:Gases; D007220:Industrial Waste; D013458:Sulfur Dioxide