Polychlorinated Naphthalenes in the Atmosphere of the United Kingdom TOM HARNER,* ,† ROBERT G. M. LEE, ‡ AND KEVIN C. JONES ‡ Meteorological Service of Canada, Environment Canada, 4905 Dufferin Street, Downsview, Ontario, M3H 5T4 Canada, and Environmental Science, Lancaster University, Lancaster, LA1 4YQ U.K. Archived extracts from two air sampling campaigns were used to investigate PCNs in the U.K. atmosphere. In the first study, daily air samples were collected at a semi-rural location (Hazelrigg) in northwest England in 1994. Air parcel back-trajectories were used to distinguish air masses that stemmed from distinct sectors, and 18 samples representing four regions (Arctic/Scandinavia; Atlantic; mainland Europe; U.K.) were selected for PCN analysis. The mean for all samples was ∑PCN ) 59 pg m -3 and ∑PCN/ ∑PCB ) 0.31 with a profile that was dominated by the 3-Cl and 4-Cl PCN homologue groups. Atmospheric concentrations of PCN and the ratio ∑PCN/ ∑PCB were lowest for samples that had trajectories that stemmed from the Arctic/Scandinavia sector s20 pg m -3 and 0.24, respectively. Highest values were observed for air that lingered over the U.K. before arriving at the sampling sites 108 pg m -3 and 0.41, respectively. These results are consistent with elevated PCN burdens in the eastern Arctic Ocean for air samples that stemmed from the U.K. region and suggest that the U.K. is a significant emission source of PCNs. On the basis of this study, we also conclude that a ∑PCN/ ∑PCB ratio of 0.2-0.25is characteristic of background air resulting from diffuse emission sources and that a ratio much greater than 0.25 indicates an increasing contribution from “ nondiffuse” or “ point sources” of PCNs. In the second study, extracts were obtained for 1998-1999from four stations operated under the TOMPS monitoring programsManchester (urban), Hazelrigg (semi- rural), Stoke Ferry (rural), and High Muffles (rural). PCN air burdens were highest at Manchester (138-160 pg m -3 ) and decreased to ∼22-35 pg m -3 at the rural sites. Introduction The ubiquitous nature of polychlorinated naphthalenes (PCNs) is of concern because of their dioxin-like toxicity. Exposure to PCNs has been blamed for the death of two Britons in the 1940s (1, 2). Early studies reported high concentrations of ∑PCN in British birds of prey (3) and freshwater and marine biota in Sweden (4). More recently, they have been reported in human tissue (5) and a wide range ofbiologicalsamples(6, 7)on a congener-specific basis. Several congeners exhibit high dioxin-like toxicity, and 2,3,7,8,-tetrachlorodibenzo- p -dioxin (TCDD) toxic equiva- lents (TEFs) have been reported (8, 9) and are of similar magnitude to some of the coplanar PCBs (10). The use-historyofPCNs has paralleled and preceded that ofthe PCBs.Produced bychlorination ofmolten naphthalene, PCNs exist as 75 possible congeners that contain one to eight chlorine atoms (Figure 1). They are structurally similar to the polychlorinated biphenyls (PCBs) and exhibit similar chemical and thermal stability. They were first used com- mercially in the early 1900s for wood, paper, and textile impregnation but were shortly thereafter replaced by PCBs after incidents of worker-related toxicity (11). Koppers Company (Pennsylvania) was one of the largest producers of technical PCN formulations (Halowaxes) until they voluntarily ceased production in 1977 (12). PCNs were produced in Europe under various names including Seekay Waxes (ICI, United Kingdom) and Nibren Waxes (Bayer, Germany) (12). Little is known of the production volumes and production historyin the United Kingdom,and no studies ofPCNs in the atmosphere have been made.However,some insight to the historical inputs of PCNs to the U.K. environ- ment has been gained through analysis ofa rural freshwater sediment core (13), which shows peak inputs of PCNs ca. 1960 at ∼20%ofthe value ofthe peak for PCBs that occurred ca. 1978. Beland and Greer (14) estimate that the global cumulative PCN production represents ∼10% of the PCB value. Although the use ofPCNs has declined in the past few decades, they are not prohibited in most countries and still occur in manyPCB-like applications such as capacitor fluids, engine oil additives, and electrical insulators (12) and as contaminantsin commercialPCBfluids(15). PCNs have also been found in incinerator emissions (16) and are believed to be formed bycombustion ofPAHsbya “de novo”synthesis pathway (17). Recent atmospheric concentrations of PCNs have been reported in Germany (18), urban Chicago (19), Sweden (20), and the eastern Arctic Ocean and land-based Arctic moni- toring stations (21). Back-trajectory analysis for the eastern Arctic Ocean samples has related episodes of elevated PCN and PCB concentrations to air trajectories that stem from the United Kingdom and other European regions in the 5-day period prior to their collection, implicating these regions as potential sources. Here we investigate the assertion that the U.K. is a significant “source” of PCNs. PCNs are analyzed in archived samples from two intensive studies.In the first study, air samples were collected at a semi-rural location in northwest England in 1994over the course ofseveralmonths *Correspondingauthor phone: (416)739-4837;fax: (416)739-5708; e-mail: Tom.harner@ec.gc.ca. † Environment Canada. ‡ Lancaster University. FIGURE 1. Structure of polychlorinated naphthalenes show ing the numbering of the chlorine substitution positions. Substitution in the r or peri positions leads to greater distortion of the molecule. Environ. Sci. Technol. 2000, 34, 3137-3142 10.1021/es000883u CCC: $19.00  2000 American Chemical Society VOL. 34, NO. 15, 2000 / ENVIRONMENTAL SCIENCE & TECHNOLOGY 9 3137 Published on Web 06/21/2000