Polycyclic Aromatic Hydrocarbons in Houston Parks After Hurricane Harvey

Abstract

Unprecedented inland precipitation and catastrophic flooding associated with Hurricane Harvey potentially redistributed contaminants from industrial sites and transportation infrastructure to recreational areas that make up networks of green infrastructure, creeks, and waterways used for flood control throughout the Greater Houston Area. Sediment samples were collected in parks located near the Buffalo Bayou watershed 1 week after Hurricane Harvey made landfall and again 7 weeks later. Total concentrations of the U.S. Environmental Protection Agency's (EPA's) 16 priority polycyclic aromatic hydrocarbons (PAHs) were measured in each sample at both time points. Diagnostic ratios were calculated to improve understanding of potential sources of PAHs after flooding. Diagnostic ratios suggest vehicular traffic to be a potential source for PAHs in parks. Although the concentrations of PAHs in all samples were below EPA actionable levels, given that no background values were available for comparison, it is difficult to quantify the impact flooding from Hurricane Harvey had on PAH concentrations in Houston parks. However, given the high frequency of flooding in Houston, and the concentration of industrial facilities and transportation infrastructure adjacent to recreation areas, these data demonstrate that PAHs were still present after unprecedented flooding. This study may also serve as a baseline for future efforts to understand the environmental health impacts of disasters.

INTRODUCTION

Hurricane Harvey made landfall on the Texas coast on August 26, 2017, as a Category 4 hurricane with sustained winds of 215 km/hour.¹ Hurricane Harvey became the wettest tropical storm to make landfall in the United States, with up to 1538.7 mm of rain measured in Nederland, Texas, and large portions of the Greater Houston Area (GHA) experiencing 1-in-1000-year flooding.² Estimates from the National Oceanic and Atmospheric Administration suggest that the total damage resulting from Hurricane Harvey could be as high as $180 billion.³ Unprecedented flooding like that associated with Hurricane Harvey can result in multiple exposures for individuals in affected communities. These include potential exposure to harmful chemicals transported by floodwater from industrial facilities and transportation infrastructure to nearby parks and recreation areas. Understanding the potential exposure to contamination in parks and recreation areas after disasters is important because these areas may play an important role in community disaster recovery. For example, after Hurricane Katrina, researchers in New Orleans demonstrated that access to public parks was an instrumental part of community resilience and recovery from the impacts of natural disasters.⁴ To our knowledge, no other studies have addressed this potential.

This study focused on improving understanding of potential post-Hurricane Harvey contamination in four parks flooded by Hurricane Harvey and located near the Buffalo Bayou watershed. During nondisaster times, parks and recreational areas provide public health benefits through access to physical activity and green spaces, as well as ecosystem services that include the moderation of heat and reduction of air pollution.^5,6 Postdisaster, parks can help with coping, providing opportunities for social interaction, access to physical activity, and an escape for those living in affected neighborhoods.⁷ However, in nondisaster times, residents of environmental justice communities have access to fewer parks, and those that are available are smaller and have fewer and lower quality amenities.⁸ Access to parks for residents of environmental justice neighborhoods may also be interrupted due to direct (e.g., flooding, wind damage) and indirect (e.g., use of parks for Federal Emergency Management Agency trailers or for staging trash and storm debris) disaster impacts.⁹ After a disaster, access to parks in environmental justice neighborhoods can be differentially interrupted by contamination associated with agricultural run-off, bacteria from sewage overflows, and contaminated sediment from nearby industries and other sites that store contaminants.^10,11,12

Hurricanes and associated flooding disproportionately affect residents of environmental justice communities.¹³ In Hurricane Harvey, the extent of flooding was greatest in neighborhoods with more non-Hispanic black residents and higher rates of poverty.¹⁴ Similar research in Miami,¹⁵ the Charlotte/Atlanta megaregion,¹⁶ and Galveston, Texas,¹⁷ has demonstrated greater flood risks in neighborhood with higher economic instability and greater percentages of non-Hispanic blacks and Hispanics. Inequities in flood exposure are also directly related to postdisaster needs, such as the need for environmental risk assessments¹⁸ and assessments of potential health risks.¹⁹ These may include potential exposure to contaminants from toxic site incidents,²⁰ in floodwater,²¹ as well as chemical contaminants mobilized in soils and sediments redistributed by flooding.^22,23,24

Four recreational areas, Addicks Reservoir, Meyers Park, Tony Marron Park, and Mason Park, were selected with input from the Houston Health Department whose staff were among the initial responders to Hurricane Harvey flooding. All parks are city parks, two of the parks (Tony Marron and Mason Park) are located in proximity to the Manchester/Harrisburg Super neighborhood, which includes the Manchester neighborhood, an environmental justice community. All study areas are located inside or adjacent to a tributary to the Buffalo Bayou watershed, a system of creeks and streams that crosses the GHA beginning in the Addicks and Barker Reservoirs and terminates in the Houston Ship Channel (Fig. 1). The 85.3 km long Buffalo Bayou has a watershed area of ∼1295 km² and is part of a system of green infrastructure used to reduce the impacts of flooding in the GHA.²⁵ However, over the past 50 years, Buffalo Bayou has become highly urbanized, with >450,000 residents living in the 80% of Bayou area that has been developed.²⁶

FIG. 1.

Map of Harris County portion of Greater Houston Area Bayou System.

Addicks Reservoir was constructed by the Army Corp of Engineers in the 1940s to mitigate flooding.²⁷ The area includes a 104.2 km² park with a drainage area of 183 square miles and recreational facilities for community use, including baseball fields, soccer fields, picnic locations, and playgrounds.²⁸ Addicks Reservoir received >838.2 mm of rain after Hurricane Harvey, which forced the City of Houston to release levees, flooding several West Houston neighborhoods.²⁹ Meyers Park is a 0.73 km² park in northwest Houston located on the Cypress Creek watershed, which drains into Buffalo Bayou.³⁰ Available recreational areas include soccer fields, basketball courts, playgrounds, nature trails, and fishing ponds.³¹ Tony Marron Park is a 0.08 km² park located in southeast Houston across Buffalo Bayou from a nonferrous metal and electrical waste recycling facility. The park offers walking trails, playgrounds, and soccer fields and received 889 mm of rain after Hurricane Harvey.^32,33 Mason Park is a 0.42 km² park located in southeast Houston along the Brays Bayou, a major tributary of Buffalo Bayou. Established in 1930, Mason Park has a community center, baseball and softball fields, walking trails, and playgrounds and received 889 mm of rain after Hurricane Harvey.^34,35

Polycyclic aromatic hydrocarbons (PAHs) are chemicals that form as a result of the incomplete combustion of organic matter and comprise multiple aromatic rings^36,37). Organic matter is further broken down into three categories for determination of PAH source: pyrogenic, petroleum, and biomass. PAHs are typically ubiquitous in the environment due to the multiple forms of exposure including vehicular traffic, cooking, and other combustion sources.³⁸ Chronic exposure to PAHs in the workplace has been shown to have adverse human health outcomes, such as increased incidence of lung, skin, and bladder cancer.³⁹ The U.S. Environmental Protection Agency (EPA) has designated 16 PAHs as priority pollutants. Little is known about the potential health impacts of PAH exposure in recreational settings, with most of the recommendations and standards from the federal government involving workplace exposures rather than community or recreational exposures.⁴⁰

Neither Harris County nor the City of Houston has well-defined chemical profile backgrounds for parks and recreation areas. This lack of background data makes understanding potential changes to the chemical profiles of parks after natural disasters such as floods more difficult. To improve understanding of potential postdisaster recreational exposure to PAHs through park-based sediment, we describe the distribution of PAHs at multiple time points after a major flooding event and identify potential sources.

METHODS

Sample collection and analysis

Sediment samples were collected longitudinally, 1 week and 7 weeks after Hurricane Harvey impacted the GHA. When the first samples were collected 1 week after Hurricane Harvey, many locations across Houston and Harris Counties were still submerged by floodwater and some roads remained impassable. Therefore, sediment collection could only be completed in park locations where there was little or no standing water. Four sediment samples were collected from Mason Park, four from Tony Marron, four from Meyers Park. There were five samples taken at the Addicks Reservoir on the first sample collection. The latitude and longitude of each collection site were recorded using Google Map's Global Positioning System (Mountainview, CA) (Fig. 2). A new pair of nonpowder nitrile gloves was used for each sample. Samples were collected in 227.3 mm glass jars using a metal trowel, which was rinsed after each collection. The collection jars were filled ∼75% full due to the saturation of the soil. Sediment samples in the second round were collected in November 2017, 7 weeks after Hurricane Harvey made landfall, at the same geocoded locations using the same methods with one exception, the Addicks Reservoir. One of the original sample sites had been paved over since the first sampling at the Addicks Reservoir, so a sample was collected near the original site. After collection, samples were stored in a cooler for transport from the Houston area to the Texas A&M School of Public Health (SPH) in College Station, Texas, ∼144.8 km. Once the samples arrived at SPH, they were placed in a −20°C freezer for storage. Frozen samples were freeze dried at SPH and transported to TDI-Brooks International in College Station, Texas, for analysis using gas chromatography mass spectrometry (GC-MS). Output data were analyzed using Microsoft Excel (Redmond, WA), Systat Sigmaplot V12.5 (San Jose, CA), and R (R Core Team).

FIG. 2.

Maps of the parks and sampling locations.

Extraction of sediments for aromatic and saturated hydrocarbons

An automated extraction apparatus (Dionex ASE200 Accelerated Solvent Extractor EPA Method SW-846 3545) is used to extract various organics from 2 to 20 g of predried samples. The extractions are performed using methylene chloride solvent inside stainless-steel extraction cells held at elevated temperature and solvent pressure. The extracts dissolved in the solvent are then transferred from the heated extraction cells to glass collection vials containing activated copper granules to minimize matrix interference during quantitative determinations. The extracts are subjected to silica gel/alumina columns to remove biogenic organic material that can cause positive interference with this method. The extracts are then concentrated to a final volume of 1 mL using an evaporative solvent reduction apparatus. Final extracts are submitted for determination of aromatic and saturated hydrocarbon analytes and synthetic based drill mud.⁴¹

Determination of aromatic hydrocarbons by selected ion monitoring: GC-MS

This quantitative method is for the determination of PAHs and their alkylated homologues in extracts of sediment and biological tissue (Modified SW-846 8270D). Quantitation is performed by an Agilent, model 6890 Gas Chromatograph and model 5973 Mass Spectrometer Detector (GC/MS) operated in selected ion monitoring mode. The gas chromatograph is temperature programmed and operated in splitless mode. The capillary column is a J&W Scientific DB-5MS (60 m long by 0.25 mm ID and 0.25 μm film thickness) or equivalent. Carrier flow is controlled by electronic pressure control. The carrier gas is helium at a flow rate of 1 mL/minute. The temperature of the injection port is 285°C and transfer line is 290°C. The initial oven temperature is 60°C, the ramp rate is 7°C/minute to a final oven temperature of 310°C and held for 22 minutes. The autosampler is capable of making 1–5 μL injections. The mass spectrometer is capable of scanning from 35 to 500 amu every second or less, utilizing 70 volts electron energy in electron impact ionization mode. The data acquisition system allows continuous acquisition and storage of all data during analysis and capable of displaying ion abundance versus time or number of scans.

Calibration solutions are prepared at six concentrations ranging from 0.02 to 1 μg/mL by diluting a commercially available solution containing the analytes of interest (typically NIST SRM 1491). For each analyte of interest, a relative response factor (RRF) is determined for each calibration level. All six response factors are then averaged to produce a mean RRF for each analyte.

An analytical set consists of standards, samples, and quality control samples. Each extraction batch is analyzed as an analytical set including samples and the following quality control samples: method blank, matrix spike, matrix spike duplicate, and standard reference materials.^42,43

Diagnostic ratios

Potential sources of PAHs can be identified based on the calculation of ratios between different PAH concentrations in sediment samples.^44,45 The concentration of anthracene is compared with the combined concentrations of anthracene and phenanthrene (A/A+P). If this ratio is >0.1, this is indicative that the PAHs come from pyrogenic or combustion sources, such as those formed in the crude oil maturation process or other similar process.⁴⁶ If the value is <0.1, it indicates that the source of the PAHs in the sediment most likely originates from petroleum products in sediment rather than combustion sources. The ratio of the concentration of fluoranthene to fluoranthene and pyrene (F/F+P) can also be used to assess the source of PAHs. Values from this ratio fall into three potential source categories: <0.4 is indicative of a petrogenic source, ratios between 0.4 and ≥0.5 indicate petroleum combustion as the source, and ratios >0.5 indicate combustion of biomass. Similarly, ratios of the concentration of indeno(1,2,3-c,d)pyrene and benzo(g,h,i)perylene (I/B) of <0.2 indicate a potential petrogenic source, ratios ≥0.2 and ≤0.5 indicate petroleum combustion, and ratios >0.5 indicate grass, wood, or coal combustion.⁴⁷ A ratio of benzo(a)anthracene to chrysene <0.2 indicates a petrogenic source, a ratio ≥0.2 and ≤0.35 is indicative of coal or petroleum combustion, whereas a ratio >0.35 is indicative of combustion or vehicular emission. Finally, the ratio of benzo(a)pyrene to benzo(g,h,i)perylene can indicate whether the source for the PAHs in sediment is vehicular emissions or nontraffic emissions. A ratio <0.6 indicates nontraffic emissions, whereas a ratio >0.6 is indicative of vehicular emissions.

Toxic equivalent factors

Both the United States and Canada have established contamination concentration levels for PAHs using the toxic equivalent factor (TEF). The TEF is used to describe the potential toxicity of a chemical with no known toxicity value based on the chemical structure in relation to a chemical with a similar chemical structuring that has known toxicity information. For the 16 priority PAHs, the EPA uses benzo(a)pyrene as the TEF for other PAHs. The TEF maintains the same units as the total mass (ng/g). TEFs for the PAH concentrations were calculated to better understand potential exposure risk to individuals who use disaster impacted parks frequently. Using TEFs, contamination levels are divided into three categories: <100 ng/g is defined as uncontaminated, >100 ng/g and <1000 ng/g is defined as slightly contaminated, and between 1000 and 10,000 ng/g is defined as significantly contaminated, which may pose human health risk.

Statistical analyses

One-way analysis of variance (ANOVA) statistical tests were used to identify pairs of samples from the same locations collected at different time points after Hurricane Harvey landfall where there were statistically significant (α = 0.05) differences between total concentrations, categorized either by the number of rings or by TEF, between the samples from the same location at the two time points.

RESULTS AND DISCUSSION

In three of the four park sampling locations, the total concentration of PAHs (ng/g) declined between the first and second sample collection (Fig. 3B). The one exception was Tony Marron Park, where total PAH concentration more than doubled between 1 week after Hurricane Harvey and 7 weeks after Hurricane Harvey.

FIG. 3.

(A) Total PAH concentration comparison between the individual parks, PAHs are organized by number of rings. (B) Percentage composition of PAHs per park, organized by number of rings. PAHs, polycyclic aromatic hydrocarbons.

More than 70% of the PAHs present in the park sediment samples collected 1 week after Hurricane Harvey comprised either four-ring PAHs or five/six-ring PAHs (Fig. 3B). Samples taken 7 weeks after Hurricane Harvey landfall also predominantly comprised four-ring (44%), five/six-ring (23%), and three-ring (26%) PAH structures. Both Addicks Reservoir and Tony Marron Park samples indicated an increase in the percentage of three-ring PAHs from the first sample collection (1.3%) to the second (16.2%). In both the Addicks Reservoir and Meyers Park samples, two-ring PAHs were ∼10% in the first sample and 20% in the second sample. For all other parks, two-ring PAHs comprised <10% at both sampling times. ANOVA results showed that each individual park in the study was statistically unique as shown in Supplementary Tables S1 and S2.

One week after Hurricane Harvey, 4 of the 18 samples collected across the four parks had an A/A+P ratio of <0.1 (Fig. 4). Three of these samples were located in Meyers Park (0.06, 0.04, and 0.08) and one was located in Mason Park (0.10). Three of 18 samples had an F/F+P ratio between 0.4 and 0.5, indicative of petroleum combustion. Two of the three (0.49 and 0.50) samples were collected at the Addicks Reservoir and the other (0.46) was from Meyers Park. All other samples collected 1 week after Hurricane Harvey had F/F+P ratios that indicated biomass combustion as the main source for PAHs. Of the samples collected 1 week after Hurricane Harvey, five had an I/B ratio between 0.2 and 0.5 (Fig. 3B). Four of these five (0.48, 0.48, 0.39, and 0.47) samples were from Addicks Reservoir and one (0.48) sample was from Meyers Park.

FIG. 4.

Diagnostic ratios used to predict potential sources of environmental PAH concentrations in sediment. Sample 1 was taken 1-week post-Hurricane Harvey and sample 2 was taken 7 weeks after Hurricane Harvey made landfall. (A) Ratio anthracene/(anthracene + phenanthrene) and the ratio fluoranthene/(fluoranthene + pyrene). (B) Ratio fluoranthene/(fluoranthene + pyrene), and the ratio indeno(1,2,3-cd)pyrene/(indeno(1,2,3-cd)pyrene combined + benzo(g,h,i)perylene). (C) Ratio benzo(a)anthracene/(benzo(a)anthracene + chrysene), and the ratio benzo(a)pyrene/benzo(g,h,i)perylene.

In the second round of samples, only one sample from Meyers Park had an A/A+P ratio <0.1. The A/A+P ratio for all other samples was indicative of combustion as the primary source of PAH concentration in park sediment. Of the later samples, six had F/F+P ratios between 0.4 and 0.5, indicating petroleum combustion as the potential source. Three of these samples (0.47, 0.44, and 0.44) were collected at Addicks Reservoir, two (0.43 and 0.47) samples were from Meyers Park, and one (0.45) sample was from Mason Park. All other samples had an F/F+P ratio of >0.5, indicating the source of PAHs in the parks was the combustion of biomass. Three of the second round samples had I/B ratios between 0.2 and 0.5. Two (0.49 and 0.48) samples were in Addicks Reservoir and one (0.50) sample was in Meyers Park, indicating that the source of PAHs in Addicks Reservoir and Meyers park may be petroleum combustion. All other samples from both sampling times had I/B ratios >0.5, pointing to biomass combustion as the source for the majority of the samples.

Both of the ratios presented in Figure 3C are used to predict whether the source of the concentration of the PAHs is likely to be vehicular emissions or another source of emission. Seven days after Hurricane Harvey made landfall, eight of the samples contained a ratio between 0.2 and 0.35, including three samples (0.2899, 0.3462, and 0.3428) from Addicks Reservoir, three samples (0.2953, 0.2905, and 0.2911) from Meyers Park, and two samples (0.3466 and 0.3319) from Mason Park. Two months after Hurricane Harvey made landfall, 10 samples contained a ratio between 0.2 and 0.35: 4 samples (0.3416, 0.2891, 0.3079, and 0.2996) from Addicks Reservoir, 4 samples (0.3009, 0.2769, 0.3416, and 0.3303) from Meyers Park, and 2 samples (0.3000 and 0.3259) from Mason Park. These samples are all indicative of coal or petroleum combustion as a potential source for the PAH concentrations in the samples. No samples contained a ratio <0.2, and all other samples contained ratios >0.35, indicating combustion or vehicular emissions as possible sources. All of Tony Marron Park sample ratios indicate combustion or vehicular emission as the potential source for the PAHs in the sediment samples.

Seven weeks after Hurricane Harvey made landfall, nearly all samples contained ratios >0.6, indicating vehicular emissions as the main source of PAHs in the sediment samples. Only three samples contained ratios <0.6: one sample (0.5989) from Addicks Reservoir and two samples (0.4424 and 0.4775) from Meyers Park. These three ratios indicate that nontraffic emissions were the potential source for the PAHs in these sediment samples. All ratios are displayed in the Supplementary Table S3.

PAHs with more rings tend to have higher TEF values. When converting the total PAH concentrations to TEF values, both Addicks Reservoir and Tony Marron Park showed significant differences between the first and second samples. For three-ring PAHs, there were no significant differences at any park, whereas the TEF was different only at Mason Park. For four-ring PAHs, there were significant differences for both total concentration and TEF at both Addicks Reservoir and Mason Park. For five/six-ring PAHs, there were statistically significant differences for total concentration at both Addicks Reservoir and Mason Park, but differences in TEF were only found in the two Mason Park samples.

Figure 5 shows the total PAH concentrations converted to TEF values. Addicks Reservoir had the highest TEF relative to the other parks at both sampling time points. Only the Addicks Reservoir samples reached the level of slightly contaminated at both sampling periods. The contamination level of all other parks fell <100 ng/g, indicating that the sediment samples were uncontaminated.

FIG. 5.

Toxic equivalent factor concentration at each park location across two sampling points.

Little is known about the baseline levels of PAHs in recreational areas in the GHA, although the area is home to >40% of the nation's petrochemical industrial capacity and an extensive rail and highway transportation infrastructure. Although TEFs across all parks sampled were well below the threshold for significant contamination, Addicks Reservoir sediment samples collected after Hurricane Harvey had PAHs levels that could be characterized as slightly contaminated. This could be due to several factors, including the park's large size and the timing of the release of water after Hurricane Harvey to prevent a possible breech in the levees. However, the potential for negative health impacts from chronic exposure to PAHs makes it important to continue to improve our understanding of potential ongoing exposures among Houston residents using parks and how these exposures may be impacted by a natural disaster.

Although it is difficult to attribute the PAHs in Houston parks to a direct source, vehicular traffic may be the most important contributor to the PAH concentrations. The Houston Metropolitan Area is home to >6 million residents living in an area about the size of the State of New Jersey. Therefore, Houston has ample vehicular traffic,⁴⁸ which can be a main source of PAH deposition onto sediment.^49,50 The lack of zoning in Houston has had a major impact on its land use and urban development, with the City of Houston having more freeway kilometers and higher transportation costs than any comparable region of the United States.^51,52 The high traffic volume in the City of Houston is consistent with the diagnostic ratios, which identified combustion sources for PAHs. The parks sampled in this study, similar to most of the GHA, are relatively proximate to major highway infrastructure, and the four-, five-, and six-ring PAHs that comprised a majority of the PAHs identified in these samples are indicative of vehicular sources. Therefore, it may be that the two- and three-ring PAHs, weighing less than their heavy counterparts, traveled farther from the road than the heavier PAHs. In general, diagnostic ratios in more samples predicted petroleum combustion sources in the second round of sampling compared with the first round, which may capture increases in vehicular traffic around the GHA as roads reopened and disaster recovery began.

Nearly all sediment samples collected 7 days after Hurricane Harvey made landfall, except for three samples collected in Meyers Park, were indicative of pyrogenic sources. Meyers Park is located in the northwest Houston suburb of Spring and is, therefore, not located in proximity to petroleum sources; potentially petroleum mixtures were deposited in the area as the floodwaters rose and subsided after Hurricane Harvey. The second round of sampling indicated that only one sample contained the ratio for a petrogenic source; this sample was again located in Meyers Park. Major sources of petrogenic origin to PAH contamination come in the form of oil spills as well as underground and above ground storage tanks leaks and motor oil and gasoline leaks.⁵³ Since Meyers Park is not located in proximity to storage tanks, these sources may have included oil and gas leaks from automobiles using the parks' extensive parking areas for youth sports tournaments and other events ∼2 months after Hurricane Harvey.

With the vast amount of water brought by Hurricane Harvey, the deposition of mobile chemicals from the petrochemical industry lining the Buffalo Bayou to the parks in this study was a distinct possibility. However, Figure 5 shows that after Hurricane Harvey, the parks all contained PAHs at below actionable levels. Figure 3 shows that some parks increased in their overall PAH concentration from the first sampling period to the second sampling period, whereas others decreased in overall concentration. Large deposits of sediment from Hurricane Harvey, up to 1.83 m in some areas, were also deposited in many parks, although we did not sample this sediment as part of this project.⁵⁴ With so little known about the PAH makeup of the sediment in these parks before Hurricane Harvey, these initial results displaying below actionable concentrations are promising for the communities using these parks. Future research should continue monitoring the sediment PAH levels to better understand their distributions and to help assess the future impacts of flooding and other natural disasters to park sediment.

Hurricane Harvey was unique in that it was primarily an inland precipitation event; potential contaminants were, therefore, washed downstream with freshwater through the Houston Ship Channel to the Galveston Bay as opposed to the more typical concern that storm surge could mobilize contaminants inland to the city's neighborhoods from Galveston Bay.^55,56 Although all PAH concentrations and their TEFs were below actionable levels, residents of the GHA still express concerns about the potential for pollution and contamination associated with flooding that results from a natural disaster.⁵⁷ As described earlier, parks can play an important role in community resilience in postdisasters settings⁵⁸ and Mason and Tony Marron Parks are close to the environmental justice neighborhood of Manchester, which is frequently impacted by both natural and technological disasters. Making information on potential PAH exposures in parks available to residents can bring the community one step closer to ensuring a safe park experience after flooding disasters.

CONCLUSION

Residents using parks and other recreation areas after flooding should still exercise caution and best judgment when using a park after a major disaster, even if in this particular flood, the concentration of PAHs in the sediment was not high enough to prevent park usage. Because there are no data on background levels of PAHs in sediments in the GHA, this research helps to describe a baseline for future disaster events. Future studies may target additional parks and sampling locations to begin to develop a library of baseline chemical profiles to improve our understanding of the potential for environmental contamination as a result of natural disasters in large urban areas at high risk.

DISCLAIMER

The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.

AUTHOR DISCLOSURE STATEMENT

No competing financial interests exist.

FUNDING INFORMATION

Research reported in this publication was supported by the National Institute of Environmental Health Sciences of the National Institutes of Health under Awards P42 ES027704 and T32 ES026568. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the article.

SUPPLEMENTARY MATERIAL

Supplementary Table S1

Supplementary Table S2

Supplementary Table S3