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Jun 3, 2004 - Semivolatile Organic Compounds in Window Films from Lower Manhattan after the September 11th World Trade Center Attacks. Craig M. Butt ...
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Environ. Sci. Technol. 2004, 38, 3514-3524

Semivolatile Organic Compounds in Window Films from Lower Manhattan after the September 11th World Trade Center Attacks CRAIG M. BUTT, MIRIAM L. DIAMOND,* AND JENNIFER TRUONG Department of Geography, University of Toronto, Toronto, Ontario M5S 3G3, Canada MICHAEL G. IKONOMOU Contaminants Science Section, Institute of Ocean Sciences, Department of Fisheries and Oceans Canada, Sidney, British Columbia V8L 4B2, Canada PAUL A. HELM AND GARY A. STERN Freshwater Institute, Department of Fisheries and Oceans Canada, Winnipeg, Manitoba R3T 2N6, Canada

The September 11th World Trade Center (WTC) terrorist attacks resulted in the large-scale release of contaminants that were deposited on the environment of New York City (NYC). Six weeks after the attacks, samples of an organic film on window surfaces were collected and analyzed for polybrominated diphenyl ethers (PBDE), polychlorinated biphenyls (PCB), polychlorinated naphthalenes (PCN), polycyclic aromatic hydrocarbons (PAH), and organochlorine pesticides (OCPs). Concentrations dropped by an order of magnitude within 1 km of the WTC and reached background concentrations by 3.5 km. Concentrations within 1 km of the WTC averaged 3280 ng/m2 for ΣPBDE, 900 ng/m2 for ΣPCB, 33 ng/m2 for ΣPCN, and 77100 ng/m2 for ΣPAH. Congener profiles of the sites nearest the WTC suggested a combination of combustion and evaporative sources of all compounds, whereas the background sites exhibited profiles consistent with evaporative sources. PBDE profiles showed enrichment in lower molecular weight congeners near the WTC, suggesting that these congeners were formed as a result of the combustion conditions. Homologue fractions of PCN combustion markers were ∼2-9 times greater at near WTC sites compared to background NYC. Gasphase air concentrations were back-calculated from measured film concentrations using the film-air partition coefficient (KFA), and calculated air concentrations followed spatial trends observed in films.

Introduction On September 11, 2001, two airplanes collided into the north and south towers of the World Trade Center (WTC), initiating a succession of events that would result in New York City’s worst human and environmental disaster. The initial explosions and fires, which were fed by an estimated 90 000 L of fuel in each airplane (1), immediately spread a large plume * Corresponding author phone: 416-978-1586; fax: 416-946-5992; e-mail: [email protected]. 3514

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of contaminants throughout lower Manhattan and the adjacent boroughs of New York City (NYC). The fires reached maximum temperatures of 750-800 °C, sufficiently weakening the steel of the floor joists and eventually causing the collapse of the Twin Towers (1). As more than 1.2 million tons of building materials fell to the ground (2), a dense cover of pulverized cement, asbestos, and glass blanketed the lower Manhattan landscape (3). The fires continued to burn in the wreckage pile until December 14th but at lower temperatures than the initial explosions, further releasing contaminants into the atmosphere. Therefore, contaminants were released into the environment through four primary routes: (1) during the initial explosions and higher temperature fires within the Twin Towers, (2) during the collapse of the buildings, releasing a cloud of building dust, (3) from the resuspension of the settled dust during cleanup efforts, and (4) during the smoldering, lower temperatures fires within the WTC rubble. Combustion processes are known to generate concentrations of polycyclic aromatic hydrocarbons (PAH), polychlorinated biphenyls (PCB), and polychlorinated naphthalenes (PCN) (4-6). PAH are produced during the incomplete combustion of hydrocarbons, and large quantities were emitted on September 11th during the initial WTC explosions, as evidenced by the massive clouds of black smoke. Further quantities of PAH were generated during the fires in the wreckage piles. PCBs have recently been shown to form during pyrolysis in the presence of chlorinated organics and metal catalysts (4). The miles of polyvinyl chloride (PVC) coated copper wires within the WTC likely provided the precursors sufficient for PCB formation (4, 7, 8). PCNs and PCBs were also released to the atmosphere through evaporation from past usages, such as within capacitors, transformers, wires, paints, and lubricants, many of which were likely within the WTC as these buildings were constructed before PCB restrictions. The destruction of two electrical substations, located underneath “7 World Trade Center” and containing ∼130 000 gal (492 000 L) of PCB-contaminated transformer oil, was a likely source of PCBs and PCNs to the environment (2, 9). The WTC fires consumed tons of miscellaneous office equipment, furnishings, and building materials including an estimated 50 000 personal and 300 mainframe computers (2). These materials likely contained amounts of PBDEs, flame retardants that are added to materials such as plastics, textiles, and polyurethane foams (10). However, the fate of PBDEs during pyrolysis has not been well characterized. This paper presents evidence of the contamination of the lower Manhattan environment as a result of the September 11th terrorist attacks with respect to five classes of persistent, bioaccumulative, toxic compounds: PBDEs, PCBs, PCNs, PAH, and organochlorine pesticides (OCPs). Contaminant deposition was measured through the collection of a surface film on window surfaces, a novel environmental medium that has been used to investigate the time-integrated deposition of atmospheric contaminants (11-13). In addition to film concentrations, principal component analysis (PCA) and known PCB and PCN combustion markers were used to distinguish between sites located within 1-2 km of the WTC and background New York City. While the events of the WTC disaster were extraordinarily large in scale, smaller building and house fires frequently occur within urban cities. For example, New York City experienced 27 800-29 500 structural fires per year from 1999 to 2001 (www.nyc.gov). Furthermore, this paper explores the use of the window film as a convenient passive sampler of ambient atmospheric 10.1021/es0498282 CCC: $27.50

 2004 American Chemical Society Published on Web 06/03/2004

FIGURE 1. Surface window film sampling sites in lower Manhattan and Brooklyn. conditions. In the case of the September 11th disaster, window films provided a rapid means of obtaining data on relative concentrations, likely sources and spatial patterns of atmospherically derived constituents, while requiring minimal logistical support and prior activities as is necessary for traditional air sampling and even passive sampling networks.

Experimental Section Sample Collection. Surface film samples were collected from the exterior of window surfaces in New York City using methods described by Diamond et al. (11). Films were sampled for analysis of semivolatile organic compounds (SOCs) by scrubbing windows with precleaned laboratory Kimwipes, soaked in HPLC-grade 2-propanol. Between 1 and 5 m2 of window area were cleaned, dependent upon the apparent “dirtiness” of the window. Field blanks were prepared at three sites by soaking 10 precleaned Kimwipes with 2-propanol and waving in the air until dry. Samples were kept frozen until extraction. Field sampling was conducted between October 27 and 29, 2001, during which time the air temperature ranged between 5 and 14.5 °C

(www.erh.noaa.gov). Eight samples were collected from seven sites in lower Manhattan in addition to a control site in Brooklyn (Figure 1). The last time the windows were cleaned was before September 11, 2001 for four of the five sites for which this information was available. Samples were obtained from windows located either on the ground level or second story. Split samples of approximately the same window area were collected at each site due to requirements of the chemical analyses. One of the split samples was processed and analyzed for PBDEs and the second for PCBs/OCpesticides/PCNs/PAHs. Sample Analysis. Kimwipe samples were spiked with a suite of PBDE surrogate internal standards (13C-BDE28, 13CBDE47, 13C-BDE99, 13C-BDE154, 13C-BDE183, 13C-BDE209) and Soxhlet extracted overnight with an 80:20 toluene:acetone mixture. Extracts were acid-base washed with H2SO4 and KOH and returned to neutral pH by rinsing with HPLCgrade water, reduced to dryness, and reconstituted in 1:1 DCM:hexane. Sample cleanup took place sequentially using three columns. First, the sample was passed through a multilayered acidic/basic silica column, eluted with 1:1 DCM:hexane, blown down to dryness, and reconstituted in VOL. 38, NO. 13, 2004 / ENVIRONMENTAL SCIENCE & TECHNOLOGY

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hexane. The sample was then passed through a copper column and eluted with hexane for the removal of sulfur impurities, reduced in volume, and applied directly to an alumina column for fractionation. The fraction containing the PBDEs was eluted with 1:1 DCM:hexane, blown down to dryness, reconstituted in toluene, spiked with a known amount of 13C-BDE77, and analyzed by gas chromatography high-resolution mass spectrometry (GC-HRMS). The GCHRMS was operated in the positive-ion mode, and data were acquired under selected-ion monitoring (SIM) conditions. Complete details of the sample extraction and cleanup conditions, the instrumental analysis conditions used, the criteria used for identification, the QA/QC conditions used, and the quantification procedures are presented in detail elsewhere (14). A total of 41 PBDE congeners were quantified along with several unidentified congeners. Total PBDE concentrations presented below refers to the sum of identified and unidentified congeners. Unidentified congeners comprised 1.6-5.8% of the total sample concentration. Recoveries of the internal standards ranged from 25% to 117%, within the allowable limits, and all analyte concentrations presented below were corrected for recovery of the internal standards. Kimwipe samples selected for PAH, PCB, coplanar PCB (nonortho-substituted PCB), and PCN analysis were spiked with representative surrogate internal standards and Soxhlet extracted with DCM. Details describing the cleanup and instrumental analysis are presented elsewhere for PAH/PCB/ OC pesticides (11) and coplanar PCB/PCN (15). Following extraction, samples were reduced in volume under a nitrogen stream, dehydrated by passage through a column of anhydrous sodium sulfate, and separated into two portions: one portion was used for PAH analysis and the other for PCB/OC pesticide/PCN analysis. The PAH portion was separated into two fractions on a silica/alumina column; each fraction was analyzed separately using GC-MS with mass-selective detection in order to quantify a total of 43 PAH compounds. The PCB/OC pesticide/PCN portion was separated into three fractions using a Florisil column. PCB and OC pesticide fractions were analyzed by GC with 63Ni electron capture detection (ECD). A total of 103 PCB congeners were quantified using external standard mixtures. The three Florisil fractions were recombined and added to mini-carbon columns to isolate the PCNs and coplanar PCBs. PCNs and coplanar PCBs were analyzed by GC-MS with the MS operated in the negative-ion mode. Forty-seven PCN and four coplanar PCB congeners (CB-81,-77,-126, -169) were quantified. Recovery surrogates for PCNs were not added; however, spikes of Halowax 1014 (n ) 3) which were carried through the extraction process were greater than 86% for individual PCN congeners. PCB values were blank corrected but not corrected for recoveries. Organic Carbon/Matter. Samples for organic carbon analysis were collected using methods similar to that for chemical analysis but using precleaned glass fiber filters (PallGelman, type A/B, diameter 47 mm). Split samples were taken at each site, each with an identical surface area of 100-930 cm2. Both samples were analyzed for total carbon but with one sample analyzed after ashing overnight in a muffle furnace (475 °C), thus yielding a measurement for inorganic carbon. Total carbon was measured by an elemental carbon analyzer (Exeter CE440) with a combustion temperature of 985 °C and a reduction temperature of 700 °C. Total “carbonaceous” carbon (elemental and organic carbon) was calculated by subtracting inorganic carbon from total carbon. Organic mass (OM) was converted from carbon mass by multiplying total carbonaceous carbon by 1.5 (16). Data Analysis and Treatment. Principal component analysis (PCA) was performed using SPSS version 11.0 (Chicago, IL). Congeners were removed from the data set, only for the PCA, if greater than 30% of the values were below 3516

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the method detection limit. Sample concentrations were expressed as fraction of the total concentration, and individual congeners were normalized to unit variance. Measured film concentrations were used, in conjunction with the film-air partition coefficient (KFA), to calculate average gas-phase air concentrations. The KFA is a function of the octanol-air partition coefficient (KOA), where foc is the film organic carbon fraction, for compounds whose log KOA 3.5 km from the WTC, film concentrations near the WTC were ∼3, ∼10, ∼8, and ∼8 times greater for ΣPBDE, ΣPCB, ΣPCN, and ΣPAH, respectively. At all sites, ΣPBDE concentrations were higher than ΣPCB, by as much as 14 times in the case of the Church/Warren location. This result was not expected as PCB concentrations

are generally greater than PBDE concentrations in ambient urban air (23); however, this trend has also been observed in ambient window films from Toronto, Canada (17). These results may be explained by the greater quantities of PBDEs relative to PCBs in the WTC buildings. The electrical substations located under 7 World Trade Center contained 130 000 gal (492 000 L) of transformer oil (2) that was estimated to contain between 1 and 10 ppm of PCBs (24), resulting in ∼0.75-7.5 kg of ΣPCB (assuming a specific gravity of 1.5, that of Aroclor 1254 (25)). This calculation does not consider PCBs that may have been contained in other building materials, which is unknown but probable considering the time period in which the buildings were constructed. In contrast, it is estimated that office chairs contributed ∼125 kg of ΣPBDE, primarly the penta-BDE product, while personal computers contributed a further ∼125 kg of ΣPBDE, mostly the deca-PBDE product. PBDE calculations assume one office chair and personal computer per WTC employee (∼50 000 employees in the Twin Towers (2)), 0.20 kg of PBDE-treated foam per chair, and 0.20 kg of plastics per computer; foam and plastics contain 5% PBDE by mass, 50% of chairs and computers contain PBDE-treated materials, and 50% of PBDEs contained in parent materials volatilized. In addition to wash-off, chemical concentrations would have been affected by changing air concentrations. This is particularly true in the case of the September 11th disaster since air concentrations, both particle and gas phases, decreased rapidly after the initial fires (www.epa.gov/wtc). Since the film accumulates particles, particle-bound chemicals, and gas-phase condensates over time, we can expect a wide range of concentrations within the film with high concentrations just after September 11th followed by decreasing concentrations thereafter. While desorption from particles can be rapid (26), diffusion through the film likely controls its response time. If we assume that the film resembles a mixture of particles and liquid/crystallized organic material (model 4 of ref 27), then we can use estimated diffusion coefficients obtained from experiments of gas-phase desorption from atmospheric particles (27, 28). On the basis of this model, diffusion is retarded by tortuosity through the complex material. Estimated diffusion times using the diffusion coefficients of Strommen and Kammens (27) and a mean path length of 50 nm (one-half the film thickness), VOL. 38, NO. 13, 2004 / ENVIRONMENTAL SCIENCE & TECHNOLOGY

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FIGURE 2. Principle components analysis score plot for polychlorinated biphenyls. Fifty-nine congeners were used in the analysis. A 1254, A 1260 and A 1263 represent commercial Aroclor mixtures reported by Frame et al. (46). “Toronto Hotspot” represents a sample from a site in Toronto, Ontario, located adjacent to a suspected PCB source. “Background Toronto” represents a sample collected from downtown Toronto and is characteristic of ambient Toronto window film samples. the time necessary for mass transfer ranges from 2.5 s to 1.4 days for fluorene and 350 s to 4.8 days for benz[a]anthracene. The estimates should be regarded as preliminary since they rely on a series of assumptions related to a different medium than the film. However, the results suggest that the film responds rapidly to changes in air concentrations with diffusion acting as the rate-limiting step for volatilization. The control site, Brooklyn, exhibited generally similar contaminant concentrations to that of Union Square, the site furthest (4 km) from the WTC. The only exception was the Brooklyn ΣPBDE concentration, which appears to be anomalously high. The similarities in film concentrations of the other constituents between these two sites suggests that they are either indicative of background NYC levels or were equally impacted by the WTC disaster. Brooklyn ΣPCB and ΣPAH concentrations were similar to those measured from background Toronto, Ontario (∼95 ng/m2 for ΣPCB and ∼6100 ng/m2 for ΣPAH) (12) and Baltimore, MD (∼100 ng/ m2 and ∼4270 ng/m2) (13), confirming that the Brooklyn and Union Square sites were indicative of a background signal (figure 1 in Supporting Information). These results suggest that all three cities have somewhat equal background ΣPCB and ΣPAH concentrations. Conversely, “background” NYC ΣPBDE concentrations were about 2 orders of magnitude greater than background Toronto films (∼9 ng/m2, (17)), presumably due to an increased number of PBDE sources in NYC. Comparisons for PCNs could not be made as this study represents the first measurements of PCNs in surface window films. These results indicate that a large quantity of contaminants was released by the events during and following the September 11th attacks and that the main geographic area of contaminant deposition was relatively contained to within a 1 km radius of the WTC. However, another source of PAH leading to the observed elevated concentrations near the WTC may have been the large number of diesel-powered construction equipment operating at the Ground Zero site (2). While the zone of impact is small, the lower Manhattan region is one of the most densely populated regions in the world and its complex building topography represents a significant surface area for chemical deposition and accum3518

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ulation. Once deposited on the building surfaces, contaminants may volatilize back into the atmosphere or be transported to aquatic systems during wash-off (29). This latter transport process may explain the elevated contaminant levels observed in the rivers near the WTC shortly after September 11th (2). Although PCB and PAH concentrations in films collected near the former WTC site were elevated compared to background sites in New York, these concentrations were significantly lower (3-7-fold for ΣPCB and 55-520-fold for ΣPAHs) than those measured on surfaces of an apartment subject to an experimental fire (2600-6400 ng/m2 for PCB and 4 200 000-40 000 000 ng/m2 for PAHs) (5) (figure 1 in Supporting Information). This suggests that the exponential decrease in concentration of these compounds with distance from Ground Zero was a result of atmospheric dispersion and mixing. The lower concentrations observed may have also been due to wash-off, as suggested earlier, and diffusion back to “cleaner” air. Wash-off is expected to occur episodically with precipitation events, while diffusion is expected to occur somewhat continuously with the decline in ambient air concentrations. Quantifying the contributions of these processes requires additional data that are not available. Mass Concentrations. Aerial film concentrations (ng/m2) were converted to mass-based concentrations (ng/g) using an assumed film mass of 500 mg/m2 for sites nearby the WTC. While it is recognized the there would be variation in film mass between sites, this variation is not considered significant for these illustrative purposes. The assumed value was slightly greater than the range typically measured in Toronto window films (100-400 mg/m2), consistent with the appearance of a thicker NYC film compared to Toronto film. Mass concentrations of PBDEs and PCBs in window films were ∼2.3 and ∼2.7 times higher than surface dust samples taken 5-6 days after September 11th (3, 30) (film mass concentrations presented in Table S2 of Supporting Information). We attribute the higher concentrations reported here, taken after 6 weeks compared to 5-6 days, to the settling and removal of large quantities of course building debris that may have diluted concentrations of these compounds. Further, the coarse building debris is expected to have had a lower organic carbon content that provides less of a sorptive medium. Conversely, PAH film concentrations were about 3 times less than those measured in bulk WTC dust (30), which may be due to the photoreactivity of many PAH compounds relative to PBDEs and PCBs and the operation of heavy diesel equipment at the site during cleanup operations. Total PBDE concentrations in films near the WTC were about 10-fold greater than Chicago air particulate that were calculated from total air concentrations (23), yearly mean total suspended particulate (TSP) concentrations, and values of KOA (18). Films near the WTC ranged from 4815 to 11 800 ng/g (mean ) 6570 ng/g), whereas Chicago air particulate ranged from 260 to 700 ng/g. Further, PBDE mass concentrations were about an order of magnitude greater than the geometric mean for house dust samples (570 ng/g) collected in Germany (31). Organic carbon concentrations were not available for organic carbon normalized comparisons. PCN concentrations in films near the WTC ranged from 29 to 130 ng/g (mean ) 67 ng/g), approximately 6 times greater than the geometric mean concentration of 11 ng/g in TSP from Chicago (32). The Chicago values likely overestimate the particulate concentration as these samples were collected during the months of February and March, during which time the cold air temperatures favored gas-phase condensation. Film concentrations near the WTC were within the range reported in municipal waste incinerator ashes, 1.8-269 ng/g (33-35), but were much lower than those from a medical waste incinerator ash, 5400 ng/g (33).

FIGURE 3. Geometric mean PBDE profile of surface window films collected from lower Manhattan and Brooklyn. Bars show one standard deviation.

FIGURE 4. Enrichment/depletion profiles for Church/Warren site. Figure constructed by dividing congener mass fraction (percent of total PBDE mass) of near WTC sample by the background New York City sample (Union Square). Values greater than 1 (above line) indicate enrichment of congener relative to background, whereas values less than 1 indicate depletion. Film concentrations of ΣPAH from sites nearby WTC were about 4 and 1.4 times greater, respectively, than those of air particles (mean ) 36 000 ng/g, n)10) collected in Toronto, Canada, between March 1, 2000, and July 20, 2001 (Diamond, unpublished data), and in New Jersey (30). It should be noted that the atmospheric particulate samples were analyzed for only 27 PAH compounds and in a different lab from the films; however, the most abundant PAH were analyzed in both samples. Contaminant Profiles. Contaminant profiles in films near the WTC were unique from background NYC and showed evidence of combustion sources. Differences between sample profiles were examined using the statistical technique of principal component analysis (PCA). Samples collected within 1-2 km of the WTC site clustered together on the PCA score plots (Figure 2 for PCB, figures for PBDE, PCN, and PAH in Supporting Information) and differed from sites at 3-4 km distance. Films from the sites near the WTC exhibited enrichment in PCN and PCB compounds that are indicative of combustion (33, 36), suggesting that pyrolysis was a source of some of the chemicals to these films. Background New York films were deficient in combustion-related congeners, and on the PCA score plots these samples were located close to the technical mixtures of Aroclor (PCB), Halowax (PCN), and Bromkal/Great Lakes Chemical (PBDE), suggesting that evaporation from past or current usage was the main source of contaminants to these films. Therefore, the clustering of nearby WTC films, together with elevated concentrations in

these films, indicates the events resulting from the September 11th attacks released contaminants that were deposited within the lower Manhattan environment. PBDEs. PBDE congener profiles were similar among all sites and dominated by the congeners that comprise the commercial penta-, octa- and deca-BDE mixtures (37) (Figure 3). The main five congeners comprised between 86% and 95% of the total PBDE mass: BDE-209 (geometric mean, 60.3%), -99 (10.9%), -47 (9.0%), -100 (2.0%), and -207 (2.0%). Film profiles of the dominant PBDE congeners were similar to those in bulk dust collected 6 days after September 11th, although fewer congeners were analyzed in the dust (3) and similar to surface films from interior and exterior window surfaces in Toronto, Canada (17). Profiles dominated by BDE209 are characteristic of condensed phases such as house dust and bulk and particulate atmospheric deposition (31, 38, 39). Congener-specific combustion markers of PBDEs do not exist; however, PBDEs may be formed during fires by either the degradation of technical mixtures or by de novo synthesis (40, 41). Further, a similar class of compounds, polychlorinated diphenyl ethers (PCDEs), is known to form during pyrolysis, and PCDEs have been measured in fly ash (42, 43). On a normalized mass percent basis (percent of total ΣPBDE), films near the WTC were enriched in several of the lower brominated congeners relative to sites located 3-4 km from the WTC (Figure 4). We postulate that combustion influences (44) were responsible for the occurrence of congeners not VOL. 38, NO. 13, 2004 / ENVIRONMENTAL SCIENCE & TECHNOLOGY

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FIGURE 5. PCB congener profiles (percent of total PCB) for Church/Warren, Museum-North and Brooklyn sites. associated with the technical mixture in the near WTC films, since other factors such as photolytic degradation (45) were similar at all sites. This is consistent with findings from Sakai et al. (40), who showed the production of tetra- through nonasubstituted BDE congeners from the combustion of TV casting materials (originally containing nona- and decaBDEs). Their study also noted the near complete destruction of the original PBDE source mass (40), which is consistent with our findings of the lower brominated congeners being detected in trace amounts as compared to the congeners that comprise the commercial mixtures. PCBs. PCB congener profiles were, in most cases, dominated by congeners predominant in commercial Aroclor mixtures (46), CB-138, -180, -153, and -110 (Figure 5), and 3520

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which characterized films and air particles from downtown Toronto, Canada (12, Diamond, unpublished data). Three general patterns were evident in the WTC films. First, the profile of Church/Warren, the site closest to Ground Zero, was unique with CB-180 comprising the greatest proportion of total PCB concentration. The Church/Warren profile was similar to those from the Toronto PCB “hotspot”, which is adjacent to a suspected PCB source, and from bulk dust samples collected 6 days after September 11th (30). Second, the other sites within 1-3 km of the WTC had similar congener profiles with equal proportions of CB-138 and CB180. Third, the sites furthest from the WTC (Brooklyn, NYU, and Union Square) had similar and distinct congener profiles that were low in CB-180. Thus, PCB congener profiles became

FIGURE 6. PCN congener profiles for Church/Warren and Brooklyn. Percentages calculated in terms of ΣPCN. progressively “lighter” in their congener profiles with distance from the WTC, similar to the fractionation observed during atmospheric transport (12). Coplanar PCBs, and particularly CB-126, have been suggested to be preferentially formed during combustion processes (36). Ratios of CB-126 (“combustion” PCB) to congeners predominant in Aroclor mixtures (“Aroclor” PCBs: CB-110, -138, -153, -180) were generally higher in films sampled near the WTC, which is consistent with combustion as a source of some of the PCBs (Table S3 in Supporting Information). Three mechanisms likely contributed PCBs to the Manhattan films: evaporation of PCBs at low to intermediate temperatures, combustion of non-PCB-containing materials that are capable of producing PCBs, and burning of PCBs at high temperatures. Sources for these mechanisms included the ∼130 000 gal of PCB-contaminated transformer oil beneath 7 World Trade Center, PCBs within the WTC building materials, and, to a lesser extent, the de novo production from the kilometers of PVC-coated copper wire within the WTC (8). We deduced the minor importance of de novo production from the observation that the ratios of “combustion” to “Aroclor” PCBs were much less than 1 in all films. However, this conclusion is highly uncertain as data regarding the latter two mechanisms are limited. PCNs. PCN profiles were dominated by the higher chlorinated congeners with the P5CNs and P6CNs homologues contributing a mean of 41% and 31% to the total PCN mass, respectively. At the sites nearby the WTC (Church/Warren, Park Row/Spruce, and Worth/Broadway), CN-66/67 was the dominant congener (12%) followed by CN-59 (7%) and CN35 (5%) (Figure 6). The remaining sites were dominated by CN-59 (11%). Within the latter subset, the sites closer to the WTC (Museum-North and -South, Canal/Broadway) had moderate (5-8%) proportions of CN-66/67 whereas those sites furthest from the WTC had low (2-3%) proportions of this congener (NYU, Union Square, Brooklyn). Similar to the PCBs, films nearby the WTC were enriched in PCN combustion markers as compared to background sites. For example, the Church/Warren profile, which was representative of other sites within 1-2 km of the WTC, was very similar to the MSWI profiles with respect to enrichment in combustion marker congeners (Figure 7). Conversely, the Brooklyn profile was most similar to Halowax 1014 as indicated by a depletion of combustion markers. Homologue fractions of the combustion markers were ∼2-9 times greater at the Church/Warren site than for Brooklyn. These results indicate that PCN profiles at sites within 1-2 km of the WTC were strongly influenced by the WTC fires, with evidence of de novo production, while profiles from sites 3-4 km away were primarily from evaporative emissions of past usages.

PAHs. PAH profiles from nearby WTC samples were enriched in lower molecular weight compounds as compared to background samples (Figure S5 in Supporting Information). For example, the Church/Warren sample was dominated by fluoranthene (12.5%), followed by pyrene (10%), phenanthrene (9.5%), chrysene + triphenylene (7.5%), and benzo[b]fluoranthene (6.5%), whereas the Brooklyn sample was dominated by benzo[b]fluoranthene (8.5%) followed by C1-chrysene (8.5%), pyrene (7%), fluoranthene (7%), and C2chrysene (6.5%). Profiles from bulk dust collected near the WTC were similar to window film samples near the WTC (30). PAH profiles from ambient air over Jersey City, NJ, were dominated by benzo[b+k]fluoranthene (30), similar to the Brooklyn sample. Film profiles are complicated by the contribution of vehicle traffic, which represents a major source of PAH in most urban environments and is ubiquitous throughout New York City. Similar to PBDEs, no unique markers for different combustion types exist (e.g., building material vs jet fuel vs gasoline). However, the clustering of near WTC sites on the PCA score plot and elevated film concentrations suggest events from the September 11th tragedy impacted PAH deposition. Organochlorine Pesticides (OCPs). OCPs are not expected to originate from NYC or the WTC fires but accumulated in the window films. The most abundant OCPs were p,p′-DDT, p,p′-DDE, trans- and cis-chlordane, trans-nonachlor, and β-HCH (Table S1 in Supporting Information). The pattern of abundance is similar to that reported for Toronto films (12) and is attributed to long-range atmospheric transport followed by partitioning between this surface layer and ambient air as well as enhanced particle accumulation. As noted above, these concentrations are relatively low and are unlikely to pose a health risk, but they do provide insight into the pattern of chemical accumulation. Concentrations of OCP (on an aerial basis) are higher in thicker films near the WTC, which we attribute to gas-phase partitioning and higher particle accumulation rates in thicker films (11) as well as more atmospheric scavenging by higher particle concentrations nearby the WTC. The broader environmental significance of this process is that the films are an efficient intermediary between the air and urban surface waters, even for those chemicals not originating in the urban environment. Relative Toxicity. Toxic equivalents (TEQs) were calculated from measured film concentrations and literature toxic equivalency factors (TEFs), determined for PCNs (47) and non-/mono-ortho PCBs (48) using H4IIE enzyme induction assays. The geometric mean total PCN and PCB TEQ was 56.6 pg/m2 for near WTC sites and 3.6 pg/m2 for background NYC sites (Table 2). Spatial trends in TEQ values followed that of PCN and coplanar PCB window film concentrations. VOL. 38, NO. 13, 2004 / ENVIRONMENTAL SCIENCE & TECHNOLOGY

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FIGURE 7. Tetra-, penta-, and hexa-CN homologue profiles from surface window films and other sources. PCN combustion markers CN-44, -29, -35, -54, and -66/67, as identified by Helm and Bidleman (33), are represented by the solid bars. Percentages calculated on a homolog basis. Mean TEQ contributions of PCNs, mono-ortho, and nonortho PCBs were 27%, 0.3%, and 73% for near WTC sites, respectively, whereas the background NYC TEQ contributions were 41%, 0.6%, and 52%. The results indicate an enhanced non-ortho PCB TEQ contribution as a result of the WTC fires. A similar trend of enhanced non-ortho PCB TEQ contribution was observed in air samples from a combustion-influenced location in Toronto, Ontario (33). Total PCN and PCB TEQ accounted for 0.5-5% of total TEQ when PCDD/Fs are incorporated (49). These percentages are within the range but at the lower end of values presented by Helm and Bidleman for Toronto air samples (33). The PCB TEQ was dominated by CB-126, contributing ∼97% of the total TEQ among all sites. This result can be explained by the relatively high CB-126 TEF, despite the fact that CB-105 and CB-118 had much higher film concentra3522

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TABLE 2. Toxic Equivalents (TEQs) for ΣPCN and ΣCoplanar PCB (pg/m2) in Surface Window Films from Manhattan and Brooklyn % ΣPCN + mono% ΣPCN ΣCpPCB ΣCpPCB % ortho nonortho TEQ TEQ TEQ PCN PCB PCB Church/Warren Museum-North Museum-South Park Row/Spruce Worth/Broadway Canal/Broadway NYU Union Square Brooklyn

7.6 28.0 17.4 3.2 13.3 4.7 0.2 2.3 0.9

26.0 63.5 41.4 8.0 40.6 10.2 0.3 1.4 2.6

33.7 91.5 58.8 11.2 53.8 14.9 0.5 3.7 3.5

22.7 30.6 29.6 28.3 24.7 31.8 41.8 62.2 26.4

0.1 0.4 0.7 0.2 0.2 0.1 0.6 0.5 0.6

77.2 69.0 69.7 71.5 75.1 68.1 57.6 37.3 72.9

TABLE 3. Back-Calculated Gas-Phase Air Concentrations (pg/m3) Church/Warren Museum-North Museum-South Park Row/Spruce Worth/Broadway Canal/Broadway NYU Union Square Brooklyn

ΣPBDE

ΣPCB

ΣPCN

2020 860 496 103 256 104 10.5 165 41

1320 7050 6520 509 2480 567 80.1 363 475

969 3150 1880 384 684 424 29.9 311 229

tions. CB-126 has also been found to contribute most of the PCB TEQ in air samples from Toronto, Ontario, and the Arctic (33, 50), although at somewhat lower percentages than the present study. PCN TEQs were dominated by CN-66/67 (29%) followed by CN-69 (25%) and CN-63 (19%). PCN TEQ contributions were influenced by the combustion events of the WTC as sites near the WTC had a greater TEQ contribution from CN-66/67 of 38% as compared to 15% from background NYC. Thus, the results of the September 11th attacks increased proportions of more toxic PCN congeners within 1 km of the WTC, although this contribution is very low relative to PCDD/F. Calculated Gas-Phase Air Concentrations. As mentioned earlier, measured film concentrations were used, with the film-air partition coefficient (KFA), to calculate average gasphase air concentrations. Spatial trends in back-calculated gas-phase air concentrations followed those of organic film concentrations with near WTC air concentrations being 7-12 times greater than background NYC (Table 3). ΣPBDE air concentrations at near WTC sites ranged from 500 to 2000 pg/m3 (geometric mean ) 950 pg/m3), which were ∼20 times greater than that measured in Chicago using high-volume air samplers (high-vols) (23) and ∼200 times greater than that in Toronto (51). Near WTC, ΣPCB air concentrations ranged from 1320 to 7050 pg/m3 (geometric mean ) 3920 pg/m3), within the range measured by the EPA using highvols (www.epa.gov/wtc) and also within the range measured in other urban centers (23). Calculated ΣPCN air concentrations at near WTC sites were 25-65 times greater than those from Chicago and Toronto (32, 33), ranging from 970 to 3150 pg/m3 (geometric mean ) 1790 pg/m3) at near WTC sites. These back-calculated gas-phase air concentrations were 1 order of magnitude higher than reported total air concentrations reported for other cities and represent approximate concentrations 6 weeks after the WTC attacks.

Acknowledgments We are grateful to the building managers and owners of New York City for sampling permission. We thank J. Archbold, H. Jones-Otazo, and K. Tsoi of the University of Toronto; D. Armstrong, A. MacHutchon, and B. Rosenberg of the Freshwater Institute; and analysts of the Regional Dioxin Laboratory at the Institute of Ocean Sciences and the Department of Fisheries and Oceans. Funding was provided by the Meteorological Service of Canada (Environment Canada) and the Canadian Foundation for Climate and Atmospheric Sciences. The U.S. EPA is thanked for their support. Ronald Hites’ laboratory at Indiana University kindly provided TSP measurements for PBDE air samples.

Supporting Information Available Five figures and three tables. This material is available free of charge via the Internet at http://pubs.acs.org.

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Received for review February 2, 2004. Revised manuscript received March 29, 2004. Accepted April 13, 2004. ES0498282