AMBIENT AIR PCDD PCDF CONCENTRATIONS IN MONTGOMERY COUNTY, OHIO/

In September 1995, ambient air concentrations of polychlorinated diben zo-p-dioxins and polychlorinated dibenzofurans (PCDD/PCDF) were measur ed at five locations in Montgomery County, Ohio. Montgomery County is an industrialized urban area with two known and many other potential s ources of PCDD/PCDF, The known sources are the north and south municip al waste incinerators operated by the county government. Stack emissio ns tests in 1988, 1994, and 1995 showed that PCDD/PCDF emissions incre ase dramatically with electrostatic precipitator (ESP) temperature, pa rticularly above 230 degrees C, After the 1994 tests, incinerator impr ovements to maintain ESP temperatures below 230 degrees C were complet ed. Ambient air 24-h total mass PCDD/PCDF concentrations measured in 1 995 ranged from 1.2 pg/m(3) (rural location) to 29.7 pg/m(3) (Edgemont neighborhood in the city of Dayton), Meteorological conditions, opera tional data, and chemical mass balance modeling suggest that a polyvin ylchloride (PVC) pyrolyzer, and not the municipal waste incinerators, may be the principal source of ambient air PCDD/PCDF concentrations in Montgomery County.