Assessment of levels, distribution, and risks of polychlorinated dibenzo-p-dioxins and dibenzofurans in the vicinity of a vinyl chloride monomer production plant

Levels of polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs), and biphenyls (PCBs) were analyzed from environmental and human samples to assess contaminant distribution and risks associated with vinyl chloride m onomer (VCM) production. Extremely high concentration of PCDD/Fs, 26 mu g/g dry weight, was detected in the waste sludge. As a result of improper wast ewater treatment practices in the 1970s, PCDD/Fs (11.4 kg, 32.0 g of I-TEQ) leached into the Gulf of Finland in the Baltic Sea. Despite high concentra tions near the plant,the polluted area was restricted (about 26 km(2)), and VCM production could not be a significant contributor to the PCDD/F load o f the sea. Frequent consumption of local fish was considered to be the most probable source of human exposure. However, serum samples taken from local residents and former workers did not indicate exposure to elevated levels of total PCDD/Fs. Octachlorinated furan was the main congener (73% of PCDD/ F sum) in the waste sludge, and it also dominated in marine sediments. Cont aminated sediments also had a characteristic PCB composition, containing ex ceptionally high proportions of IUPAC 206 and 209 congeners.