Pronounced decrease of PCDD/PCDF burden in ambient air

Concentrations (annual means) of PCDD/PCDF in the ambient air of four cities in North-Rhine-Westfalia (NRW, Germany) were measured at the same locations in 1987/88 [1] and again in 1993/94. During this time period, the annual averages of the PCDD/PCDF concentrations decreased from 130 to 40 fg I-TE/m 3 in Köln (69%), from 332 to 124 fg I-TE/m 3 in Duisburg (63%), from 204 to 76 fg I-TE/m 3 in Essen (63%) and from 224 to 120 fg I-TE/m 3 in Dortmund (46%). This decrease can be related to abatement actions taken since 1989. In the measurement campaign of 1993/94, polychlorinated biphenyls (PCB) were measured simultaneously with the PCDD/PCDF. At urban locations the annual averages of PCB (total of trichloro- to decachlorobiphenyl) in urban air ranged between one and two ng/m 3 and in rural areas between 0.1 and 0.3 ng/m 3.