Characterization of Background Concentrations in Upper Manhattan

The terrorist attack upon the World Trade Center (WTC) in New York on ..... The TEQs were calculated using International Toxicity Equivalence Factors ...
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Environ. Sci. Technol. 2004, 38, 6482-6490

Characterization of Background Concentrations in Upper Manhattan, New York Apartments for Select Contaminants Identified in World Trade Center Dust KAI M. TANG,† CHARLES G. NACE, JR.,‡ CAROL L. LYNES,† MARK A. MADDALONI,‡ D O R E L A P O S T A , * ,‡ A N D KATHLEEN C. CALLAHAN‡ U.S. Environmental Protection Agency, Edison, New Jersey 08837, and U.S. Environmental Protection Agency, 290 Broadway, New York, New York 10007-1866

Residential indoor concentration of asbestos, lead, synthetic vitreous fiber (SVF), crystalline silica, calcite, gypsum, dioxin, and polycyclic aromatic hydrocarbons (PAHs) were measured in 25 residences and 9 building-interior common areas in upper Manhattan, NY. This was done to characterize the background levels of contaminants, identified in dust related to the collapse of the World Trade Center towers, at locations that were minimally impacted by the dust fallout. The study was initiated due to the paucity of background concentrations on building-related materials and combustion byproducts in urban residential dwellings. Asbestos, lead, SVF, crystalline silica, and dioxin were detected at very low concentration at some locations, and many samples tested below their respective analysis detection limits. Almost all of the environmental samples for PAHs, calcite, gypsum, and certain other building materials tested below their respective analysis detection limits. A comparative analysis to the limited literature data showed general agreement with the values found in this study. This study provides insight into the levels of these contaminants in lower Manhattan residential buildings prior to the attack, and these data will serve to enhance the available database for characterizing indoor environments for these contaminants.

Introduction The terrorist attack upon the World Trade Center (WTC) in New York on September 11, 2001, resulted in the destruction of both 110-story towers and several other buildings within the WTC complex. The collapse of the towers sent a large dust cloud across lower Manhattan, and fires, initially fueled by jet fuel, burned for several months. The dust cloud consisted of pulverized building materials, and the smoke consisted of combustion byproducts that originated from incomplete combustion of jet fuel, building materials, furniture, and office equipment. Substances identified in the dust associated with the WTC collapse included asbestos, * Corresponding author phone: (212)637-4000; fax: (212)637-4035; e-mail: [email protected]. † U.S. Environmental Protection Agency, NJ. ‡ U.S. Environmental Protection Agency, New York. 6482 9 ENVIRONMENTAL SCIENCE & TECHNOLOGY / VOL. 38, NO. 24, 2004

lead, synthetic vitreous fiber (SVF) or fibrous glass, crystalline silica (as alpha-quartz), calcite, and gypsum. The dust also included combustion byproducts such as dioxin and polycyclic aromatic hydrocarbons (PAHs) (1-3). Due to the force associated with the dispersal of the dust cloud, the length of time the fires burned, and the amount of dust disturbance during the removal of WTC-related debris from the site, the residential indoor environments of buildings in lower Manhattan were potentially impacted to a varying degree by WTC-related dust and fire-related particulate matter. Evaluating the degree of significance to the indoor environments required knowledge regarding typical preattack indoor dust/air concentrations of the specific analytes identified in the WTC-related dust. Although the analytes identified have been used extensively in building construction or studied as environmental contaminants, there was limited information available that reported background concentrations of these compounds in urban residential indoor environments. This study was undertaken to ascertain the background concentrations of the contaminants associated with the WTCrelated dust in an area, upper Manhattan, that was minimally impacted by the WTC collapse. The objective was to determine the indoor residential background concentrations of selected building-related materials and materials found in fire-related combustion byproducts. The study results were compared to other concentrations of these analytes that were reported in the literature and were evaluated to estimate the range of concentrations in a typical urban environment for these specific analytes.

Methods Participant Selection. We recruited volunteer participants residing in upper Manhattan locations. The outer boundary of the affected area was determined from a preliminary dispersal and dilution model using meteorologic data on September 11, 2001, and shortly thereafter. Computer modeling results showed that upper Manhattan locations north of 78th Street, approximately 8 kilometers (5 miles) from the WTC site, would be minimally affected by WTC fallout dust. The concentration of fallout particulate matter for areas north of 78th Street would be from 1000-10 000 times less than that at the WTC site (4-6). Considerable effort was made to obtain access to building types that were similar to the downtown residential stock; however, difficulty in enlisting participants necessitated a change in focus to accept volunteers from any building type. In the end, we collected indoor environmental samples from 25 residential units and 9 building-interior common areas within 14 buildings. The buildings sampled were approximately 8-19 kilometers (512 miles) from the WTC site and were constructed between 1892 and 1981. Figure 1 shows the relative locations of the sampled buildings with respect to the WTC site. Environmental sample collection activities began on August 20, 2002, and concluded on September 25, 2002. Contaminants of Interest Selection. The contaminants included in this background study were selected by a committee with representation from the following government agencies: U.S. Environmental Protection Agency (EPA), Agency for Toxic Substances and Disease Registry (ATSDR), Occupational Safety and Health Administration, New York State Department of Health (NYSDOH), and New York City Department of Health and Mental Hygiene. This interagency committee identified the contaminants of potential concern for monitoring purposes and established health-based benchmarks and cleanup goals for indoor air and settled 10.1021/es035468r Not subject to U.S. copyright. Publ. 2004 Am. Chem.Soc. Published on Web 11/06/2004

FIGURE 1. Generalized locations of buildings sampled in the background study. dust (7-9). The selection process entailed a review of sampling data of ambient air, indoor air, and settled dust collected around the WTC site after the attack. Then, based on the frequency of detection, concentration, and inherent toxicity, contaminants that exceeded health-based screening levels for the ambient air or existing regulatory standards were identified as contaminants of potential concern. Combustion byproducts such as dioxin and PAHs were identified through this process. Building materials with carcinogenic (asbestos) or irritant effects (SVF, alpha-quartz) that were found in bulk and indoor dust samples around the WTC site were also included. Lead was included after a

comparison of sampling data with existing Clean Air Act regulatory standards and U.S. Department of Housing and Urban Development (HUD) clearance standards. Data from this background study provided insight into preexisting conditions in residential dwellings, and these data will serve to enhance the available database for characterizing indoor environments for these specific analytes. Environmental Sampling Methodology. Standard methods, when available, were used in the collection and analysis of the environmental samples (10-23). Specific methods and protocols are tabulated in Table 1. The study results were viewed as a point in time sample of the indoor environment VOL. 38, NO. 24, 2004 / ENVIRONMENTAL SCIENCE & TECHNOLOGY

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TABLE 1. Environmental Sample Collection and Analysis Methods sampling type air

wipe

microvacuum

contaminant

sample collection method

literature cited

sample analysis method

literature cited

asbestosa PCM TEM-AHERA PCMe SVF lead alpha-quartz asbestos SVF lead alpha-quartz dioxin PAHs asbestos lead

NIOSH 7400 NIOSH 7400 NIOSH 7400 NIOSH 7400 NIOSH 7300 NIOSH 7500 ASTM D 6480-99 ASTM D 6480-99 HUD Appendix 13.1 HUD Appendix 13.1 ASTM D 6661-01 ASTM D 6661-01 ASTM D 5755-95 ASTM E 1973-99

(11) (11) (11) (11) (13) (15) (17) (17) (18) (18) (19) (19) (22) (23)

NIOSH 7400 TEM-AHERA TEM-AHERA MSD 0310 SW-846 6010B MSD 0700 ASTM D 6480-99 MSD 0310 SW-846 6010B MSD 0700 ASTM D 6661-01/SW-846 8290 ASTM D 6661-01/SW-846 8270C ASTM D 5755-95 SW-846 6010B

(11) (10) (10) (12) (14) (16) (17) (12) (14) (16) (19, 20) (19, 21) (22) (14)

a Airborne asbestos results as determined by three analysis protocols were separately reported. Microscopy analyses included phase contract microscopy (PCM), phase contrast microscopy-equivalent (PCMe), and transmission electron microscopy (TEM) as specified in the Asbestos Hazard Emergency Response Act (AHERA).

at the sampled sites. Due to a need to ascertain the background information in a timely manner (to inform the other response and assistance programs), no attempts were made to account for seasonal- or time-dependent variability. Furthermore, no attempts were made to distinguish variations due to occupant life styles; dwelling cleaning, repairs, or maintenance practices; or other similar individual factors. Sampling locations within each site were identified, on a case-by-case basis, to best represent each apartment or common area. The sample collection regimen consisted of collecting indoor air samples of airborne fibers and particulate matter; microvacuum samples of settled dust on carpeting or area rugs, and upholstered fabric furniture or drapery; wipe samples of settled dust from ceilings, walls, bare floors, and counter tops or tabletops; and bulk dust samples from filters of window-mounted air conditioners. The samples were collected from areas typically occupied and used by residents: living rooms or bedrooms within an apartment and entrance hallways or basement laundry rooms within a building common area. Indoor Air Sampling. Asbestos and SVF. Mixed cellulose ester filter (MCEF) cassettes, with electrically conductive cowl extensions, were used to sample the indoor air for airborne asbestos and SVF. The filters used were 25 mm in diameter with a pore size of 0.8 µm for each analyte. Typical air volume for each sample was 4800 L at 10 L per minute for 480 min. Alpha-Quartz and Other Minerals. Poly(vinyl chloride) filter cassettes fitted with an aluminum cyclone were used to sample the indoor air for airborne alpha-quartz, calcite, gypsum, and portlandite. Each sample was used in the analysis for these four minerals. The filters used were 37 mm in diameter with a pore size of 5 µm. Typical air volume for each sample was 1200 L at 2.5 L per minute for 480 min. Lead. MCEF cassettes, with electrically conductive cowl extensions, were used to sample the indoor air for airborne lead particles. The filters used were 37 mm in diameter with a pore size of 0.8 µm. Typical air volume for each sample was 4800 L at 10 L per minute for 480 min. Porous Surface Microvacuum Sampling. Asbestos. MCEF cassettes, with electrically conductive cowl extensions, were used to microvacuum porous surfaces for settled asbestos fibers. The filters used were 25 mm in diameter with a pore size of 0.45 µm. Typical air volume for each sample was 4 L at 2 L per minute for 2 min. Lead. MCEF cassettes, with electrically conductive cowl extensions, were used to microvacuum porous surfaces for settled lead particles. The filters used were 37 mm in diameter 6484

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TABLE 2. Asbestos Fiber Dimensional Definitions Utilized by Microscopy Analysis Methods analysis methodology

fiber length-to-width ratio

fiber length (µm)

PCMa TEM-AHERAb PCMec

g3:1 g5:1 g5:1

g5 g0.5 g5

a PCM: Phase Contrast Microscopy. b TEM-AHERA: Transmission Electron Microscopy per Asbestos Hazard Emergency Response Act. c PCMe: Phase Contrast Microscopy-equivalent.

with a pore size of 0.8 µm. Typical air volume for each sample was 5 L at 2.5 L per minute for 2 min. Surface Wipe Sampling. Wipe samples were collected with the aid of dedicated, disposable 10 × 10 cm templates. This ensured consistency in the surface area wiped and facilitated locating adjacent samples for the various analyses. Wipe samples for asbestos and SVF analyses were collected using 9 × 9 in. Class 10 clean room wipes wetted with 10 to 20 mL of a 1:1 mixture of 2-propanol and deionized water. Wipe samples for lead analysis were collected using certified lead-free wipes wetted with distilled water. Wipe samples for alpha-quartz, calcite, gypsum, portlandite, and total dust were collected using the same wipe material as for the lead samples and were wetted with distilled water. Wipe samples for dioxin and PAHs analyses were collected using 3 × 3 in. cotton gauze wetted with 2 mL of acetone. Sample Analysis Methods. Sample analyses were conducted at EMSL Laboratories, NY, and Paradigm Analytical Laboratories, NC. The analytical methods are listed in Table 1. Airborne Asbestos. Three separate asbestos fiber counts were maintained for each airborne asbestos sample: phase contrast microscopy (PCM), transmission electron microscopy (TEM), and phase contrast microscopy-equivalent (PCMe). A summary of the dimensional definitions of asbestos fibers used in these microscopy methods can be found in Table 2. Traditional PCM analysis and counting procedures were used to provide results that would be compatible with historical asbestos studies. The sample filters were then analyzed using TEM in accordance with protocols in the Asbestos-Containing Materials in Schools regulations (10) promulgated under the Asbestos Hazard Emergency Response Act (AHERA) of 1986. Both total TEM-AHERA fiber counts (i.e., fiber length 0.5 µm or greater) and PCMe counts (i.e., fiber length 5 µm or greater) were recorded. The TEMAHERA results would be compatible with other similar

TABLE 3. Summary of the Analytical Results from the Residential Areas of the Background Study range residential area samples analyte

matrix

n

freq of detection

air - PCM 50 21/50 (42%) air - TEM AHERA 48 2/48 (4%) air - TEM PCMe 48 2/48 (4%) microvacuum 143 15/143 (10%) wipe 104 14/104 (13%) SVF air 48 1/48 (2%) wipe 99 11/99 (11%) lead bulk dust 9 9/9 (100%) air 32 1/32 (3%) microvacuum 144 12/144 (8%) wipe 80 39/80 (49%) a dioxin wipe 80 19/80 (24%) PAHs wipe 80 0/80 (0%) alpha-quartz bulk dust 9 8/9 (89%) air 32 8/32 (25%) wipe 81 31/81 (38%) asbestos

detection limit (DL)

minimum detected

maximum detected

0.001 f/cm3 0.0004-0.0005 s/cm3 0.0004-0.0005 s/cm3 633-3957 s/cm2 1183-11 832 s/cm2 0.064-0.068 s/L 57.23 s/cm2 1 mg/kg 0.051-0.061 µg/m3 2.32 µg/ft2 0.5 µg/ft2 congener specific 290 µg/m2 5 µgb 4 µg/m3 25-50 µg/ft2

0.001 f/cm3 0.0004 s/cm3 0.0004 s/cm3 3957 s/cm2 1188 s/cm2 0.072 s/L 57.2 s/cm2 44.5 mg/kg 0.051 µg/m3 2.46 µg/ft2 0.53 µg/ft2 0.48 ng/m2

0.005 f/cm3 0.0004 s/cm3 0.0004 s/cm3 474 864 s/cm2 83 893 s/cm2 0.216 s/L 286 s/cm2 242 mg/kg 0.058 µg/m3 9.73 µg/ft2 10.5 µg/ft2 0.83 ng/m2

1.01% 4 µg/m3 30 µg/ft2

6.89% 259 µg/m3 370 µg/ft2

arithmetic mean ND ) 0

ND ) DL

0.001 f/cm3 0.002 f/cm3 0.00002 s/cm3 0.0004 s/cm3 0.00002 s/cm3 0.0004 s/cm3 4500 s/cm2 6500 s/cm2 1500 s/cm2 3100 s/cm2 0.02 s/L 0.08 s/L 13 s/cm2 64 s/cm2 130 mg/kg 130 mg/kg 0.002 µg/m3 0.05 µg/m3 0.5 µg/ft2 3 µg/ft2 0.9 µg/ft2 1 µg/ft2 0.63 ng/m2 c 0 µg/m2 290 µg/m2 2% 2% 10 µg/m3 13 µg/m3 36 µg/ft2 66 µg/ft2

a Dioxin values are reported in TEQ with congeners that were below the detection limit being set to one-half of the detection limit. The TEQs were calculated using International Toxicity Equivalence Factors (24). Detection limits ranged from 0.2 ng to 1 ng depending on the specific congener. b Detection limit of the XRD instrument was 5 µg; the reporting limit for the units of % were dependent on the mass of the sample. c Non-detects for each sample were set to one-half of the detection limit.

asbestos studies. The PCMe results were generated to be compatible with the health-based benchmark for airborne asbestos. Asbestos structures that were 5 µm or greater in length with a length-to-width aspect ratio of 5 or greater qualified as PCMe structures. These PCMe structures have been closely associated with adverse health effects (i.e., cancer). Note that the terms “structures” and “fibers” are used interchangeably in this paper. As per AHERA counting rules, structures may be classified as fibers, bundles, clusters, or matrices. Structures also include asbestiform cleavage fragments meeting the minimum length and aspect ratio described above. SVF. There is no standard method for airborne or wiped SVF analyses; therefore, we utilized a procedure, developed by EMSL Laboratories, that was based on an asbestos analytical method (12). Dioxin. The health-based benchmark for dioxin is based on 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD) equivalents and the toxicity equivalence method (TEQ) that account for the varying toxicity of the several congener groups (20). Each dioxin test result, reported as TEQ values in 2,3,7,8TCDD equivalents, also represents the estimated maximum potential concentration (EMPC) for that sample. The TEQ EMPC value included analysis results that indicated the presence of a congener above zero but may not have met all of the quality assurance and quality control reporting level criteria. PAHs. The health-based benchmark for PAHs is based on benzo[a]pyrene equivalencies that account for the varying toxicity of the seven compounds ranked as probable human carcinogens (B2) in EPA’s Integrated Risk Information System (8). Analysis results for PAHs are reported as toxicity equivalency factors (TEF) values. These values are the sums of the seven B2 PAHs, modified to reflect benzo[a]pyrene equivalents. The PAHs analysis could potentially identify an additional 16 PAHs (23 total); however, these additional compounds are less toxic and, in general, are not carcinogenic. Therefore, they are not included in the TEF calculations. Quality Control. Quality control (QC) samples including duplicate samples, lot blanks, field blanks, and spiked samples, were collected to assess and to ensure that the sampling and analytical processes were conducted properly. These QC samples were identified as if they were actual samples and were shipped with actual field samples for

analysis. Results of the QC blank samples indicated that there was not any contamination above the reporting limit. Results for the field spike wipe samples for lead met the percent recovery QC limit except for two samples that were marginally below the QC limit.

Results Summary data for asbestos, SVF, lead, dioxin, PAHs, and alpha-quartz are shown in Tables 3 and 4, for residential spaces and common spaces, respectively. Table 5 contains summary data for additional building-related compounds that were included in the analysis. The results in Tables 3-5 show the analyte and matrix sampled, the number of samples, the percent of samples with detectable concentrations, the method detection limit (or range of detection limits), the range of concentrations detected, and the arithmetic means calculated using both left- and right-censored data. The values reported in the summary tables for the method detection limit and the minimum and maximum detected concentrations were reported as received from the laboratory without rounding. The arithmetic means were rounded at least to a maximum of two significant figures. Most of the data sets contained a relatively large percentage of values that were below the detection limit; therefore, means are provided for left- and right-censored data to provide a range of mean concentrations. The ranges reported in the tables are within an order of magnitude. A comparison of residential space results to common space results showed that with the exception of alpha-quartz in air, which was higher in the residential spaces, the mean values for the common spaces were similar or greater than the mean values for the residential spaces. Additionally, the frequency of detection was generally higher for the common spaces when compared to the residential spaces. Based on frequency of detection, the most frequently detected compounds in bulk dust samples and wipe samples were lead and alpha-quartz. Additionally, total fibers in the air, based on PCM, were frequently detected. This is in contrast to a much lower frequency of detection of asbestos for air samples using TEM, which can distinguish between asbestos and nonasbestos fibers, and for air samples analyzed for SVF. This indicates that although fibers were detected in the air samples, the majority of the fibers were neither asbestos fibers nor SVF. VOL. 38, NO. 24, 2004 / ENVIRONMENTAL SCIENCE & TECHNOLOGY

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TABLE 4. Summary of the Analytical Results from the Common Areas of the Background Study range common area samples compound

matrix

air - PCM air - TEM AHERA air - TEM PCMe microvacuum wipea SVF air wipe lead bulk dust air microvacuum wipe dioxinb wipe PAHs wipe alpha-quartz bulk dust air wipe asbestos

freq of detection

n 14 14 14 18 42 14 42 0 14 18 34 34 33 0 14 33

detection limit (DL)

minimum detected

f/cm3

arithmetic mean

maximum detected

f/cm3

ND ) 0

f/cm3

f/cm3

ND ) DL 0.003 f/cm3 0.0004 s/cm3 0.0004 s/cm3 8000 s/cm2 150 000 s/cm2 0.08 s/L 65 s/cm2

10/14 (71%) 2/14 (14%) 1/14 (7%) 6/18 (33%) 11/42 (26%) 4/14 (29%) 3/42 (7%)

0.001 0.0004-0.0005 s/cm3 0.0004-0.0005 s/cm3 1582-3957 s/cm2 1183-2 366 410 s/cm2 0.064-0.068 s/L 57.23 s/cm2

0.001 0.0004 s/cm3 0.0004 s/cm3 4352 s/cm2 1187 s/cm2 0.196 s/L 57.2 s/cm2

0.007 0.0004 s/cm3 0.0004 s/cm3 61 732 s/cm2 3 798 910 s/cm2 0.196 s/L 286 s/cm2

0.003 0.00006 s/cm3 0.00003 s/cm3 6400 s/cm2 95 000 s/cm2 0.01 s/L 12 s/cm2

0/14 (0%) 1/18 (6%) 18/34 (53%) 7/34 (21%) 0/33 (0%)

0.051-0.053 µg/m3 2.32 µg/ft2 0.5 µg/ft2 congener specific 290 µg/m2

3.6 µg/ft2 0.6 µg/ft2 0.518 ng/m2

3.6 µg/ft2 49.2 µg/ft2 1.66 ng/m2

0 µg/m3 0.05 µg/m3 0.2 µg/ft2 2 µg/ft2 3 µg/ft2 4 µg/ft2 0.68 ng/m2 c 0 µg/m2 290 µg/m2

4 µg/m3 35 µg/ft2

9 µg/m3 1880 µg/ft2

2 µg/m3 140 µg/ft2

4/14 (29%) 4 µg/m3 20/33 (61%) 25-50 µg/ft2

5 µg/m3 160 µg/ft2

a High detection limits for asbestos wipe samples may be due to high concentration of asbestos and/or high levels of matrix interference (nonasbestos). b Dioxin values are reported in TEQ with congeners that were below the detection limit being set to one-half of the detection limit. The TEQs were calculated using International Toxicity Equivalence Factors (24). Detection limits ranged from 0.2 ng to 1 ng depending on the specific congener. c Non-detects for each sample were set to one-half of the detection limit.

TABLE 5. Summary of the Analytical Results for the Mineral Compounds from the Background Study residential areas

common areas range

analyte calcite

cristobalite

gypsum

portlandite

tridymite

matrix

n

freq of detection

detection limit (DL)

bulk dust air wipe bulk dust air wipe bulk dust air wipe bulk dust air wipe bulk dust air wipe

9 32 80 9 32 80 9 32 80 9 32 80 9 32 80

1/9 (11%) 0/32 (0%) 2/80 (3%) 0/9 (0%) 0/32 (0%) 0/80 (0%) 1/9 (11%) 0/32 (0%) 0/80 (0%) 0/9 (0%) 0/32 (0%) 0/80 (0%) 0/9 (0%) 0/32 (0%) 0/80 (0%)

20 µg 16-20 µg/m3 100-200 µg/ft2 20 µg 16-20 µg/m3 100-200 µg/ft2 10 µg 8-11 µg/m3 50-100 µg/ft2 20 µg 16-20 µg/m3 100-200 µg/ft2 20 µg 16-20 µg/m3 100-200 µg/ft2

minimum detected 5%

5%

350 µg/ft2

785 µg/ft2

2%

Other Minerals. There were 121 samples collected, consisting of a combination of bulk dust, air, and wipe samples, that were analyzed for cristobalite, tridymite, calcite, gypsum, and portlandite (1415 results). The majority of the results (99.6%) were below the detection limits with only six results being above the detection limits. Calcite was detected four times, and cristobalite and gypsum were each detected once. The summary details from these samples are reported in Table 5.

Discussion The objective of this study was to determine the indoor background concentrations of analytes associated with the dust and fires from the WTC collapse and to compare these concentrations to the limited values reported in the literature. A literature search was conducted for published data on residential indoor measurements of asbestos, SVF, lead, dioxin, PAHs, and alpha-quartz. The focus was for relevant data, collected in the past 10 to 15 years, that could be used for comparison with the measurements from this study. For many of the analytes, the literature provided points of comparisons for the concentrations detected in our study, 6486

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2%

range n 0 14 34 0 14 34 0 14 34 0 14 34 0 14 34

freq of detection

detection limit (DL)

minimum detected

maximum detected

0/14 (0%) 1/34 (3%)

16-20 µg/m3 100-200 µg/ft2

260 µg/ft2

260 µg/ft2

0/14 (0%) 1/34 (3%)

16-20 µg/m3 100-200 µg/ft2

260 µg/ft2

260 µg/ft2

0/14 (0%) 0/34 (0%)

8-10 µg/m3 50-100 µg/ft2

0/14 (0%) 0/34 (0%)

16-20 µg/m3 100-200 µg/ft2

0/14 (0%) 0/34 (0%)

16-20 µg/m3 100-200 µg/ft2

and in general the literature showed similar concentrations being reported. Several analytes did not have comparison studies available. Included in this section is a discussion of each analyte that consists of comparison to studies identified in the literature, a discussion of analytes without comparison studies, and observations made regarding differences between residential and common spaces. A summary comparing the midpoint of the range of background concentrations from our study to literature values is presented in Table 6. Comparison to Literature. Asbestos in Air via PCMe. The literature review focused on PCMe measurements. This metric employs an analytical technique (TEM) that distinguishes asbestos from other fibrous material and counts only long fibers - those most closely associated with adverse health effects (i.e., cancer). We reported PCMe results for 62 air samples collected from residences and common spaces (n ) 48 and 14, respectively) with an overall range of mean asbestos (PCMe) concentration of 0.00002-0.0004 s/cm3 (from Tables 3 and 4). The Consumer Product Safety Commission (CPSC) reported on airborne asbestos concentration in houses that contained asbestos containing material (ACM) (25). Thirty samples were collected from 15 homes in

TABLE 6. Comparison of Midpoint of Mean Concentrations of Background Values from This Study to Background or Historical Values Reported in the Scientific Literature compound

midpoint of mean concns from WTC background studya

historical/literature value

asbestos - air (PCMe) asbestos - settled dust SVF - air SVF - settled dust lead - air lead - settled dust dioxin - settled dust PAHs - settled dust alpha-quartz - air alpha-quartz - settled dust

0.00022 s/cm3 21 000 s/cm2 0.04 s/L 38 s/cm2 0.03 µg/m3 1.6 µg/ft2 0.64 ng/m2 145 µg/m2 9.2 µg/m3 80 µg/m2

0.00022 s/cm3 1000 s/cm2 e0.1 s/L N/Ab 0.02 µg/m3 2.8 µg/ft2 0.67-1.2 ng/m2 5-270 µg/m2 N/Ab N/Ab

literature cited (25) (27) (28) (30) (29) (37, 38) (40, 38)

a Midpoint calculated using combined residential and common space data as well as combined microvacuum and wipe sample data for settled dust. The midpoint value would be equal to the arithmetic mean using 1/2 of the detection limit for samples that were reported below the detection limit. b N/A - could not find a comparison value in the literature.

Cleveland, OH. Similarly, 29 samples were collected from 15 homes in Philadelphia, PA. The Health Effects Institute (HEI) summation (26) of the CPSC study assigned a zero concentration to nondetects (ND) in the averaging process. The mean PCMe asbestos concentration was 0.00023 f/cm3 and 0.00007 f/cm3 for the Cleveland and Philadelphia samples, respectively. The means from both the Cleveland and Philadelphia studies fall within the range determined from our background study. The midpoint of the range reported in our study (0.00022 s/cm3) is similar to the mean reported for Cleveland. The primary strength of the above comparison is the common metric (PCMe) employed to measure airborne asbestos concentration. The comparison also focused on urban settings similar to New York. However, there are a number of limitations. The CPSC reported on houses with ACM. The known existence of ACM in the CPSC study homes would likely serve as a positive bias. Also, the particular housing stock differed. The CPSC looked at individual houses, whereas our study focused on apartments. Asbestos in Settled Dust via TEM. Our study collected measurements of asbestos surface loading (fibers per unit area) in settled dust by two methods: microvacuum (22) and wipe sampling (17). Microvacuum sampling was performed on porous surfaces (carpets and couches) and resulted in the collection of 162 samples, while 146 wipe samples were collected on hard surfaces (ceilings, counters, walls, and floors). The range of arithmetic means for TEM asbestos loading was 4500-8000 s/cm2 for the microvacuum samples and 1500-152300 s/cm2 for the wipe samples. Ewing (27) reported a TEM geometric mean of 1000 s/cm2 for settled dust microvacuum samples collected in six buildings without friable asbestos-containing surfacing materials. A meaningful comparison with the Ewing study was limited because of three significant shortcomings. First, unlike our study, the Ewing study reported a geometric, rather than arithmetic, mean. Second, the microvacuum samples in the Ewing study were obtained from hard surfaces, whereas our study used microvacuum sampling only on porous surfaces. Finally, the building type was not identified in the Ewing study. However, even given these inconsistencies the geometric mean reported in the Ewing study is below the range for both the wipe samples and microvacuum samples as well as the midpoint value for both data sets combined (Table 6). SVF in Air. This study reported a range of mean concentrations of 0.01-0.08 s/L. The ATSDR reported that airborne concentrations of SVFs in outdoor and indoor air samples usually are less than or equal to 0.1 s/L (28). This ATSDR report is very general and does not provide a specific concentration or range of values, only a concentration that

is less than or equal to a typical value. Since the value from our study is below the value reported in the literature, we concluded that our reported value falls within that presented in the literature. In addition, our value may provide a more detailed range for SVFs in indoor environments. Lead in Air. Our study reported a range of mean concentrations of 0-0.05 µg/m3. These values are well below the National Ambient Air Quality Standard of 1.5 µg/m3 (three-month average basis). Although no studies on background concentration of lead in air within residential dwellings were identified in the literature search, estimated values may be calculated using ambient concentrations reported in the literature. The ATSDR reported that lead concentrations in the ambient air vary widely but usually decrease with increasing distance (both vertical and horizontal) from emission sources (29). Historical measurements reported in the literature included the following values. The EPA reported a composite urban air measurement of lead for 1991 of 0.08 µg/m3 (30). ATSDR (29) estimated urban airborne concentrations of lead for the years 1994-1995 to be 0.04 µg/m3. In addition, indoor air lead concentrations are reported as being generally 0.3-0.8 times lower than the corresponding outdoor concentrations, with an average ratio of 0.5 (29). Based on this information, an estimate of indoor airborne lead concentration in urban areas can be made by multiplying the composite ambient air concentration (0.04 µg/m3) by 0.5 (average value of indoor/outdoor concentrations) to give a product of 0.02 µg/m3. This value falls near the midpoint of the range (0.03 µg/m3) reported in our study. Lead in Settled Dust. This study recorded lead measurements in settled dust by concentration (mass per unit mass) and load (mass per unit area). In addition, the load measurements were obtained by wipes for hard surfaces and microvacuum for porous surfaces. Unlike the other contaminants included in this study, settled dust lead concentrations in residential dwellings have been extensively studied. Several key studies were identified from the literature (31-36). Lanphear et al. (31) focused on the relationship between lead-contaminated house dust and children’s blood lead concentrations. They evaluated pooled epidemiologic data from many different communities, some of them with significant sources of lead contamination from activities such as mining and smelting. Consequently, their reported lead concentrations (median lead loading of 13.5 µg/ft2) are likely to be biased high. Gallicchio et al. (32) focused on a comparison of methods (wipe, questionnaire, and visual inspection) to assess household lead concentrations. An advantage is that its targeted community (i.e., “old and urban”) is much like New York City. However, their study selected low socioeconomic status VOL. 38, NO. 24, 2004 / ENVIRONMENTAL SCIENCE & TECHNOLOGY

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(SES) households (i.e., Medicaid recipients). Similar to the Lanphear et al. study, the selection of SES household could provide lead concentrations that are biased high due to fewer available resources for building maintenance. Also, like the Lanphear et al. study, lead loadings (12 µg/ft2 and 5 µg/ft2 for noncarpeted floors and carpeted floors, respectively) were reported as median rather than mean values. Rich et al. (33) studied lead dust reduction techniques in urban New Jersey homes. They reported precleaning geometric mean lead loading on hard floors of 26.7-65.2 µg/ft2 from their three cleaning trials. Yiin et al. (34) described the carpet and upholstery results from the same lead dust reduction techniques study. They reported precleaning geometric mean lead loading of 47.9 µg/ft2 and 5.11 µg/ft2 on carpets and upholstery, respectively, from vacuum samples. Adgate et al. (35) reported a geometric mean lead loading of 19.5 µg/ft2 on floors from another lead exposure study conducted in Jersey City, New Jersey. These values also are likely biased high as a result of the selection of study homes with children having elevated blood lead level or with indication of lead on surfaces in residences or in house dust. The most appropriate comparison for our study can be made with the HUD survey on lead in housing (36). HUD’s data were categorized by census region and building age. In the Northeast, there was a greater than 4-fold increase in lead load in pre-1939 versus post-1939 housing. Excluding the pre-1939 housing (mean 15.4 µg/ft2), the weighted mean lead load for 1940-1998 housing stock is 2.8 µg/ft2. The results from the HUD evaluation are consistent with the results of the range of lead loads obtained in our study (range of 0.9-4 µg/ft2, midpoint 2.45 µg/ft2). This comparison benefits from both studies reporting results in the same metric (i.e., arithmetic means) and for the same surfaces (hard and porous surfaces). A limited disadvantage of the comparison is the gross characterization of housing by geographic location (e.g., Northeast) in the HUD survey, the exclusion of pre-1939 housing stock, and the inclusion of other surfaces in addition to floors (i.e., counter tops, tables, upholstered furniture). Dioxin in Settled Dust. This study reported a range of mean dioxin concentrations of 0.63-0.68 ng/m2. Results were reported for dioxin toxicity equivalents (TEQs) using onehalf of the detection limits for congeners that tested below the detection limits. The literature search identified no studies that reported surface loading (mass per unit area) of dioxin in settled dust in residential dwellings; however, several studies were identified that permit a limited comparison. Christmann et al. (37) reported concentrations (mass per mass or µg/kg) of various dioxin congeners. Converting these results into dioxin TEQs yields a value of 1.34 ng/g. Using this value in conjunction with a range of average dust load of 0.5-0.9 g/m2 from Rodes et al. (38) results in an estimated range of dioxin TEQ load of 0.67-1.2 ng/m2. The estimated dioxin TEQ load of 0.67-1.2 ng/m2 using literature data (37, 38) falls within the range of mean concentrations obtained from our study, although the estimated comparison value has a number of limitations. The conversion from mass per mass to a common metric of mass per area required employing an estimate of the average dust load in a residential dwelling. This value can vary considerably depending on housekeeping habits and may under- or overestimate the dust load. In addition the Christmann et al. study collected samples from households that contained furniture treated with a wood preservative, which may have biased the results high. Finally, the Christmann et al. study employed a vacuum sampling method, whereas our study used wipe samples. An additional comparison was made from literature values reported from a sampling event that occurred after cleaning following a transformer fire in an office building. The mean TEQ (ND ) one-half detection limit) concentration of 0.99 6488

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ng/m2 from NYSDOH (39) is higher than the range of reported mean concentration from our study. The combination of these two studies as comparison values indicates that the range of values found in our study are similar or lower than those reported in the literature. PAHs in Settled Dust. None of the 113 wipe samples (80 from residential areas and 33 from common areas) analyzed for PAHs showed detectable levels above the detection limit of 290 µg/m2. The midpoint value would be 145 µg/m2 (equal to the arithmetic mean using one-half of the detection limit for samples that were reported below the detection limit). The literature search did not identify studies that reported surface loading (mass per unit area) of PAHs in settled dust in residential dwellings; however, comparisons to literature values can be made if the conversion approach similar to that in the discussion for dioxin was adopted. Chuang et al. (40) reported that the sums of concentrations of the seven B2 PAHs ranged from 10 to 300 µg/g in carpet-embedded dust collected in the living areas of eight homes in Columbus, OH. Applying the dust loading range of 0.5-0.9 g/m2 from Rodes et al. (38) to these concentration values would result in an estimated range of surface loading for PAHs of 5-270 µg/m2. The caveats noted in the previous dioxin discussion regarding the conversion of concentration values to surface loading values also apply in this instance. Analytes with Limited Comparison Studies. As indicated earlier, several analytes did not have literature values that could be used for direct comparison, specifically, SVF in settled dust and alpha-quartz in air and settled dust. The data reported here for these analytes may be useful for future hazardous site evaluations as there is a paucity of data reported in the literature for these analytes. In addition, these data may help better characterize residential indoor environments for health-related studies or for cleanup programs in response to indoor contamination. As shown in Table 5, building-related materials that were included in this study (i.e., cristobalite, tridymite, gypsum, and portlandite) were infrequently detected in settled dust, and none were detected in the air. Detection limits for these compounds were established from parameters based upon the ultimate sensitivity of the analytical equipment (X-ray Diffractometer) and the sample preparation protocols detailed in each specific analytical method. To achieve lower detection limits applicable for estimating background concentrations for these analytes, major modifications to the analytical procedures or the sampling methods would have to have been made. Differences between Residential and Common Spaces. There were some differences observed between the residential spaces and the common spaces, both in frequency of detection and in the measured concentrations. A variety of factors may influence these differences, such as activity patterns, amount of foot traffic, type, and frequency of cleaning. These factors may differ between these spaces, and some combination of these factors may be responsible for this observation. Although there are physical and usage differences between residential and common spaces, the overall results were similar for the two types of spaces. Therefore, assessing exposure to contaminants in indoor environments, at least in this limited study, the results for the two different spaces were combined to estimate concentrations to which an individual may be exposed on a daily basis. In summation, we initiated this study due to the limited historical background concentrations on building-related materials and combustion byproducts in residential dwellings. We characterized concentration ranges for select building-related materials and combustion byproducts that were identified in WTC-related dust. This provided insight into preexisting concentrations in residential dwellings for

these analytes prior to the collapse of the WTC. Where historical data were available, a comparative analysis showed general agreement with these background values reported in the literature.

Acknowledgments The U.S. Environmental Protection Agency (EPA) is grateful for the generous contribution of the Manhattan residents who provided access to EPA to sample their dwelling units and of the building owners who provided access to the common space areas used in this study. The authors thank Messrs. Joseph D. Rotola, Richard N. Koustas, and Pat Evangelista for their thoughtful comments on this manuscript. This project was designed and implemented by EPA with the support of the Indoor Air Work Group of EPA’s Indoor Air Task Force. The work group organizations directly involved in the development of the project included the following: the New York City Department of Environmental Protection, New York City Department of Health and Mental Hygiene, New York City Mayor’s Office of Environmental Coordination, New York City Office of Emergency Management, New York State Department of Health, the Agency for Toxic Substances and Disease Registry, the Occupational Safety and Health Administration, EPA’s Office of Solid Waste and Emergency Response, and EPA Region 2. EPA acknowledges the assistance of New York City’s Housing and Preservation Department for its assistance in identifying study locations. The study was funded by the U.S. Federal Emergency Management Agency through an interagency agreement with partial support provided by EPA. This manuscript has been reviewed and approved for release by EPA. Approval does not signify that the contents necessarily reflect the views and policies of EPA, nor does mention of trade names, commercial entities, or commercial products constitute endorsement or recommendation for use.

Nomenclature f/cm3

fibers per cubic centimeter, airborne asbestos fibers via PCM analysis

s/cm3

structures per cubic centimeter, airborne asbestos structures via TEM analysis

s/cm2

structures per square centimeter, surface loading of asbestos structures or SVF

s/L

structures per liter, airborne SVF

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Received for review December 29, 2003. Revised manuscript received September 1, 2004. Accepted September 14, 2004. ES035468R