Environ. Sci. Technol. 2003, 37, 3537-3546
Polycyclic Aromatic Hydrocarbons and Other Semivolatile Organic Compounds Collected in New York City in Response to the Events of 9/11 ERICK SWARTZ, LEONARD STOCKBURGER,* AND DANIEL A. VALLERO National Exposure Research Laboratory, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina 27711
Concentrations of over 60 nonpolar semivolatile and nonvolatile organic compounds were measured in Lower Manhattan, NY, using a high-capacity integrated organic gas and particle sampler after the initial destruction of the World Trade Center (WTC). The results indicate that the remaining air plumes from the disaster site were comprised of many pollutants and classes and represent a complex mixture of biogenic (wood-smoke) and anthropogenic sources. This mixture includes compounds that are typically associated with fossil fuel emissions and their combustion products. The molecular markers for these emissions include the high molecular weight PAHs, the n-alkanes, a Carbon Preference Index ∼1 (odd carbon:even carbon ∼1), as well as pristane and phytane as specific markers for fuel oil degradation. These results are not unexpected considering the large number of diesel generators and outsized vehicles used in the removal phases. The resulting air plume would also include emissions of burning and remnant materials from the WTC site. Only a small number of molecular markers for these emissions have been identified such as retene and 1,4a-dimethyl-7-(methylethyl)-1,2,3,4,9,10,10a,4aoctahydrophenanthrene that are typically biogenic in origin. In addition, the compound 1,3-diphenylpropane[ 1′,1′-(1,3-propanediyl)bis-benzene] was observed, and to our knowledge, this species has not previously been reported from ambient sampling. It has been associated with polystyrene and other plastics, which are in abundance at the WTC site. These emissions lasted for at least 3 weeks (September 26-October 21, 2001) after the initial destruction of the WTC.
Introduction The September 11, 2001, attack on the World Trade Center (WTC) resulted in an intense fire (>1800 °F) and the subsequent, complete collapse of the two main structures and adjacent buildings as well as significant damage to many surrounding buildings within and around the WTC complex. This 16-acre area has become known as Ground Zero. The collapse of the buildings and the fires created a large plume comprised of both particles and gases that were injected * Corresponding author e-mail:
[email protected]; phone: (919)541-1540; fax: (919)541 0960. 10.1021/es030356l Not subject to U.S. Copyright. Publ. 2003 Am. Chem. Soc. Published on Web 07/22/2003
into the New York City air shed. The plume began at elevation (80-90 story height) with the initial combustion of the jet fuel and building materials. After the collapse of the buildings, aerosols were emitted from ground level, moving downwind and reaching many outdoor and indoor locations downwind. For the first 12-18 h after the collapse, the winds transported the plume to the east and then to the southeast toward Brooklyn, NY. The collapse of the WTC towers was an unprecedented event. Most building implosions are performed under controlled conditions in which many sources of contamination are not present. For example, in controlled demolitions, carpets, furniture, wallboard, and other flammable and aerosol-producing materials are removed prior to implosion. The primary differences between the WTC incident and that of other building fires and implosions was the simultaneous occurrence of many events: the intense fire (>1800 °F), the extremely large mass of material (>106 ton) reduced to dust and smoke, and the previously unseen degree of pulverization of the building materials (1). Characterizing the chemical composition of the plume was needed to provide data to be used to assess possible human health risk. Local citizens and emergency responders were exposed to gases and particles released directly from the site as well as from previously settled particles that became resuspended by air turbulence and mechanical disturbance. The major pathways of exposure likely were inhalation, ingestion of deposited particles, and dermal exposure. Some chemical species that have been associated with human health effects include carcinogenic compounds (e.g., benzo[a]pyrene and other polycyclic aromatic hydrocarbons (PAHs) from smoldering fires), endocrine disruptors (e.g., phthalates and styrene derivatives from plastics), and neurotoxins (such as dioxins from incomplete combustion). Chemical composition of the particles at the WTC is complex. Analyses from ICP/MS and XRF by Lioy et al. (2) found the particulate matter in settled dust contained pulverized building material, rendering it alkaline (pH > 9) and containing significant amounts of inorganic matter and metals (e.g., >35 µg g-1 Ca, >110 µg g-1 Mg, >1500 µg g-1 Ti, and >500 µg g-1 Al). The cement/carbon ratio ranged between 37 and 50%, and the glass fiber content of the dust was 40%. This chemical composition was found even in the fine fraction (200 µg g-1 total PAHs and 100 ng g-1 of dioxin total equivalents). In this paper, we will focus on PAHs and other organic compounds found in airborne particulate matter in the aftermath of the destruction of the WTC. Organic compounds are highly diverse in their physical characteristics and chemical composition. For example, volatile organic compounds (VOCs) exist almost entirely in the gas phase since their vapor pressures in the environment are usually greater than 10-2 kPa, while semivolatile organic compounds (SVOCs) have vapor pressures between 10-2 and 10-5 kPa, and nonvolatile organic compounds (NVOCs) have vapor pressures 85% of the analytes were removed after each sonication extraction. Separate quartz and XAD-4-impregnated filters were used as field blanks. Surrogate recovery was evaluated for acceptance by determining whether the measured concentration fell within the acceptance limits of 80-120%. Analysis. Analysis of the extracts was performed using a Varian Saturn IV gas chromatography-ion trap mass spectrometer (GC-MS) with a SPI injection system. The gas chromotograph used a 30-m Rtx-5Sil MS column (0.28 mm i.d., 0.25 µm film thickness) and a 10-m Integra Guard column. The carrier gas was helium at a flow rate of 1 mL min-1. The oven temperature was held at 60 °C for 5 min, heated at 10 °C min-1 to 140 °C, heated at 5 °C min-1 to 320 °C, and held at 320 °C for 15 min. The mass spectrometer was operated under the following conditions: trap temperature of 225 °C, emission current of 15 µA, scan rate of 50-350 Da in 0.5 s, and A/M amplitude of 3.0 V. The organic compounds were identified by comparison with retention times and mass spectra of authentic standards if available or referenced to VOL. 37, NO. 16, 2003 / ENVIRONMENTAL SCIENCE & TECHNOLOGY
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TABLE 1. Total Concentrations (ng m-3) of PAHs Measured at 290 Broadway (16th Floor) Lower Manhattan, NYa total
naphthalenec 2-methyl naphthalenec 1-methyl naphthalenec biphenylc 2-ethyl naphthalened 1-ethyl naphthalened 2,6-dimethyl naphthalened 1,6-dimethyl naphthalened acenaphthylene acenaphthene 2,3,5-trimethyl naphthalened fluorene 1-methyl-9H-fluorened dibenzothiophened phenanthrenee anthracenee carbazoled fluoranthenee pyrenee retene benz[a]anthracenee chrysene/triphenylenee benzo[b]fluoranthenee benzo[k]fluoranthenee benzo[a]pyrene benzo[e]pyrened,e perylened indeno[1,2,3-cd]pyrene dibenz[a,h]anthracene benzo[g,h,i]perylene
avg (range)
09/26-09/27
10/04-10/05
10/06-10/07
10/12-10/13
10/20-10/21
LAb
699 (34) 267 (6) 178 (5) 182 (4) 42 (1) 17 (1) 81 (2) 44 (2) 14 (bd) 49 (1) 29 (1) 36 (1) 3 (bd) 12 (bd) 299 (6) 23 (bd) 5 (bd) 111 (7) 59 (5) 9 ( 1) 6 ( 3) 15 (10) 11 (11) 4 ( 4) 2 ( 2) 4 ( 4) bd (bd) 2 ( 2) 1 ( 1) 3 ( 3)
824 (405) 323 (37) 212 (27) 224 (9) 42 (1) 24 (1) 77 (2) 63 (bd) 3 (bd) 55 (1) 36 (1) 52 (1) 9 (bd) 10 (bd) 411 (8) 13 (bd) 5 (bd) 179 (6) 93 (4) 10 (1) 10 (3) 30 (11) 22 (20) 8 ( 7) 3 ( 3) 8 ( 8) 1 (1) 4 ( 4) 1 ( 1) 5 ( 5)
109 54 29 11 7 4 19 bd bd 9 6 8 3 1 14 bd bd 4 2 bd bd bd bd bd bd bd bd bd bd bd
22 37 11 90 30 10 75 45 6 37 48 57 5 12 276 14 2 61 32 18 2 7 4 1 1 1 bd bd bd 1
42 165 103 190 46 26 99 75 2 46 37 47 4 10 212 8 1 52 27 13 2 8 6 2 1 2 bd 1 bd 1
6000 (0-22 600) 200 (0-1500) 100 (0-1300) nr nr nr nr nr 16 (0-80) nr nr 30 (1-88) nr 6 (0-14) 50 (4-140) 17 (1-58) nr 10 (1-28) 7 (1-26) nr 0.4 (0-2) 0.8 (0-2) nr 0.2 (0-1) 0.1 (0-1) 0.2 (0-1) 0.1 (0-1) 0.3 (0-1) nr 0.8 (0-4)
a Italicized data represent particle-only concentrations. bd, below detection. nr, not reported. b Refs 22 and 23. c Possible breakthrough of the species through the system. d Estimated concentrations based on calibrations of similar compounds. e Species used in Figure 7.
the NIST98 and Wiley mass spectra libraries. The standard deviation for repetitive GC-MS runs was 90%. As in the case for the PAHs, those species below 90% efficiency, there could be potential breakthrough: breakthrough of the denuder (in scheme 1) and/or breakthrough of the entire system (in scheme 2). Consequently, the
concentrations, below 90% efficiency, reported here represent a lower bound limit. Other SVOCs. Table 4 gives the total concentrations of the other various SVOCs found in the five periods. The compound 1,3-diphenylpropane [1′,1′-(1,3-propanediyl)bisbenzene] was observed and identified by a library search of the NIST98 mass spectral database, and to our knowledge, this species has not previously been reported from ambient sampling. In Table 4, scheme 1 sampling shows that the species is primarily found in the gas phase (with 90% of the mass found on the front denuder). Although the source of the compound in this study is not known, it may have formed during the combustion of polystyrene or other polymers. 1,3-Diphenylpropane has been found to co-occur with polystyrene plastics (37, 38), so another possibility is that the VOL. 37, NO. 16, 2003 / ENVIRONMENTAL SCIENCE & TECHNOLOGY
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TABLE 4. Total Concentrations (ng m-3) of Other Semivolatile Organic Compounds Measured at 290 Broadway (16th Floor) Lower Manhattan, NYa
etherc
diphenyl dibenzofuran bibenzylc 1,3-diphenyl propanec pristane phytane 1,4a-dimethyl-7-(methylethyl)-1,2,3,4,9,10,10a,4aoctahydrophenanthrenec no. 1 1,4a-dimethyl-7-(methylethyl)-1,2,3,4,9,10,10a,4aoctahydrophenanthrenec no. 2
total
avg (range)
09/26-09/27 10/04-10/05 10/06-10/07 10/12-10/13 10/20-10/21
LAb
7 (bd) 99 (1) 23 (1) 190 (5) 46 (4) 39 (4) 3 (bd)
bd (bd) 138 (3) 34 (1) 594 (5) 38 (4) 31 (3) 3 (bd)
bd 9 bd 5 16 13 bd
9 106 42 693 68 55 8
9 97 43 541 48 40 7
4 (bd)
4 (bd)
bd
8
7
a Italicized data represent particle-only concentrations. bd, below detection. nr, not reported. on calibrations of similar compounds.
b
nr 20 (2-57) nr nr 68 (0-392) 65 (13-188) nr nr
Refs 22 and 23. c Estimated concentrations based
FIGURE 7. Gas-particle partitioning coefficient as a function of supercooled liquid vapor pressure. The species used are listed in Tables 1 and 3. The Kp values have been corrected for denuder breakthrough. compound was already present and encapsulated in large volumes of plastics in the buildings and was off-gassed during the pulverization process. The health effects data on this compound is very limited, but it does appear to be hormonally active. In a physiologically based study on human breast tumor cells, Ohyama et al. (39) found this species to be slightly estrogenic, with a binding affinity for the human estrogen receptor to be about 0.0001 of that of estradiol at concentrations above 8.2 mg kg-1. In a similar study, by Satoh et al. (40), the compound was found not to have any binding affinity for the human androgen receptor (maximum concentration of 34.6 mg kg-1). A conservative, worst-case exposure scenario estimate would assume that a person was exposed for the entire 100-d period of the fire (September 11-December 19, fires declared out by officials) and that the ambient concentrations of 1,3diphenylpropane remain at the maximum level measured for the entire 100 d. For acute or subchronic exposure estimates, the average daily dose (mg kg-1 d-1) for inhalation of a noncarcinogenic species can be expressed as
ADD )
C (mg/m3) × IR (m3/d) BW (kg)
where C is the concentration of the species in inhaled air, IR is the inhalation rate, and BW is body weight. The default 3544
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inhalation rate for an adult (70 kg) is 20 m3 d-1 (41). Given the mean 24-h concentration of 1,3-diphenylpropane at approximately 5 × 10-4 mg m-3, the complete absorption into the body, and the density of the human body near unity, the worst case ADD of 1,3-diphenylpropane would be 1.4 × 10-4 mg kg-1 d-1. Chronic exposure for the 100 d would yield 1.4 × 10-2 mg kg-1, 2 orders of magnitude below any detectable observation by either of the Ohyama et al. (39) or the Satoh et al. (40) studies. Although these studies found that 1,3-diphenylpropane binds to estrogen receptors in tumor cells, no physiologically based, pharmacokinetic (PBPK) models have been developed to extrapolate the binding potential to human estrogenicity. In particular, the calculation of biologically effective dose and endocrine risk is not possible without a reliable absorption factor, a critical component of PBPK dose-response relationships. Along with the presence of 1,3-diphenylpropane, there is further evidence that the plume contains emissions of burning and remnant materials from the WTC site. The molecular markers for these emissions include retene and 1,4a-dimethyl-7-(methylethyl)-1,2,3,4,9,10,10a,4a-octahydrophenanthrene that are typically biogenic in origin (42). For example, retene is a known marker for wood-smoke and was seen in all samples analyzed from WTC and also observed but not shown in any of the tables or figures with various phthalates. The source of phthalates could not be determined
and has been associated with sampling artifacts in other studies (43). Gas-Particle Partitioning. A gas-particle partitioning coefficient is used to describe the distribution of semivolatile compounds between the gas and the particle phases. The measured gas-particle partitioning coefficient Kp is defined as
Kp (m3/µg) )
F (ng/m3)/TSP (µg/m3) A (ng/m3)
where F is the mass of the species found on the filters (e.g., all filters), A is the mass of the species found in the gas phase (e.g., denuders), and TSP is the mass of the total suspended particulate matter collected. Determining the mass at 2.5 µm was required since a 2.5-µm cyclone inlet was used for particle discrimination in the HiC IOGAP sampler. Measurements of PM2.5 mass by a versatile air pollutant sampler, VAPS (URG, URG-3000K), and a nephelometer were also conducted at the 290 Broadway sampling site. The correlation between for PM2.5 mass between the VAPS and the nephelometer had an R 2 ) 0.981 (31). In this study, the inferred mass from the nephelometer was used since the nephelometer made near continuous measurements and the VAPS and the HiC IOGAPS did not sample at the same time. The gas-particle partitioning coefficient has been determined to be a function of the supercooled liquid vapor pressure (p °L ) and often has a linear relationship during a sampling event and compound class (44), such that
log Kp ) mr log p °L + br Experimentally, the slope mr has been determined to be close to -1, where the intercept br is typically associated with compound class. Illustrated in Figure 7 is the linear relationship observed for selected hydrocarbons: PAHs and n-alkanes (see Tables 1 and 3). The temperature-dependent supercooled liquid vapor pressures p °L were taken from Pankow et al. (44) or calculated using the Thermophysical Properties Database (45). The Kp values have been corrected for denuder breakthrough. As stated earlier, the HiC IOGAP sampler minimizes positive artifacts, and the efficiency of a single denuder in removing the gas phase is 87-89%. Two denuders in series lead to an efficiency of 98-99%. Although the 1-2% breakthrough is small, the effect is greatest when there is a large gas-phase component and small particle phase (as in the more volatile compounds). The slope and intercept in Figure 7 are in good agreement with other values taken in rural areas (44) for hydrocarbons. However, there does not seem to be any observable temperature dependence on Kp within the temperature ranges of 16.6-25.6 °C of the data set.
Acknowledgments The authors thank the other members of the WTC Emergency Response Team, especially Marcus Kantz, Dore LaPosta, and John Fillipelli of the EPA’s New York Regional Office and Alan Vette, Thomas Ellestad, Mathew Landis, Ronald Williams, John Duncan, and Maribel Colon from the EPA’s National Exposure Research Laboratory. We appreciate the help from Lara Gundel of the Laurence Berkeley National Laboratory and Doug Lane of Environment Canada, who freely shared their expertise and materials. The United States Environmental Protection Agency through its Office of Research and Development funded and managed the researched described here. It has been subjected to Agency Review and approval for publication. Mention of trade names or commercial products does not constitute an endorsement or recommendation for use.
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Received for review February 4, 2003. Revised manuscript received May 12, 2003. Accepted May 21, 2003. ES030356L
