Concentrations of tetra- through octa-chlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) were determined in exterior window films from Manhattan and Brooklyn in New York City (NYC), USA, 6 weeks after the World Trade Center (WTC) attacks of I I September 2001. High concentrations of the 2,3,7,8-substituted congeners (P2378CDD/Fs) were observed, at levels up to 6600 pg-TEQg(-1) nearest the WTC site. An equilibrium partitioning model was developed to reconstruct total gas + particle-phase atmospheric concentrations Of P2378CDD/Fs at each site. The reconstructed atmospheric and window film concentrations were subsequently used in a preliminary human health risk assessment to estimate the potential cancer and non-cancer risks posed to residents of lower Manhattan from these contaminants over the 6 week exposure period between the WTC attacks and sampling dates. Residents of lower Manhattan appear to have a slightly elevated cancer risk (up to 1.6% increase over background) and increased P2379CDD/F body burden (up to 8.0% increase over background) because of above-background exposure to high concentrations Of P2378CDD/Fs produced from the WTC attacks during the short period between I I September 200 1, and window film sampling 6 weeks later. (c) 2004 Elsevier B.V. All rights reserved.