Declining PCB Concentrations in the U.K. Atmosphere: Evidence and Possible Causes

Abstract

PCB air concentrations have been measured at a meteorological site in northwest England since 1992. Examination of this data set, comprising over 200 data points, suggests that PCB levels are decreasing with average congener specific half-lives ranging from approximately 2 to 6 yr. With the exception of congener 52, which shows the steepest decline, the slopes of other ICES congeners included in this study (i.e., 28, 101, 118, 153, and 138) were not found to be significantly different from each other. A U.K. mass balance model has been used to examine which factors are likely to be controlling present and future air concentrations. This allowed a range of fate scenarios to be examined and the controlling fate processes to be scrutinized. Estimates of fluxes using contemporary soil and air concentrations suggest that the observed long-term decrease of PCB levels in U.K. air is likely to be influenced by several factors, including existing primary emissions and recycling, volatilization from soil, advective losses from the U.K. atmosphere, reaction in the atmosphere, and soil fate processes such as microbial degradation.