PAHs and metals in the soils of inner-city and suburban New Orleans, Louisiana, USA

Environmental Toxicology and Pharmacology 18 (2004) 243–247

PAHs and metals in the soils of inner-city and suburban New Orleans, Louisiana, USA Howard W. Mielke∗ , Guangdi Wang, Christopher R. Gonzales, Eric T. Powell, Bin Le, V. Nancy Quach College of Pharmacy, Xavier University of Louisiana, 1 Drexel Drive, New Orleans, LA 70125, USA Received 7 January 2003; accepted 13 November 2003 Available online 12 October 2004

Abstract Representative soil samples of an inner-city and suburban community (n = 19 each) are evaluated for 16 polycyclic aromatic hydrocarbons—PAHs (naphthalene, acenaphthylene, acenaphthene, fluorene, phenanthrene, anthracene, fluoranthene, pyrene, benz(a)anthracene, chrysene, benzo[k]fluoranthene, benzo[j]fluoranthene, benzo(a)pyrene, indeno[1,2,3-cd]pyrene, dibenz[a,h]anthracene and benzo[g,h,i]perylene) and nine metals (Pb, Zn, Cd, Mn, Ni, Cu, Cr, Co and V). Surface (2.5 cm deep) samples were air-dried and sieved (2 mm USGS #10). Accelerated solvent extraction was used for PAH preparation prior to analysis with gas chromatography–mass spectrometry. Metals were extracted at a 5:1 ratio of 1 mol nitric acid to soil, shaken at room temperature, centrifuged, filtered and analyzed by inductively coupled plasma-atomic emission spectrometry (ICP-AES). Total PAHs (median 2927 ng g−1 versus 731 ng g−1 ) and the total metals (median 1323 ␮g g−1 versus 183 ␮g g−1 ) summarize differences (P < 0.0001) between the inner-city and suburb, respectively. A strong association exists between PAHs and metals for all 38 soil samples (correlation coefficient = 0.831, P < 0.00001). In terms of the specific sites of accumulation, both PAHs and metals show the same pattern: busy streets > foundations > residential streets > open areas. This study provides real-world data about various chemical mixtures which may be a factor of possible health disparities in sensitive populations, especially children, in different communities of New Orleans. © 2004 Elsevier B.V. All rights reserved. Keywords: Chemical mixtures; Urban environment; Risk assessment; Health disparities

1. Introduction Information about the quantities and associations of mixtures of metals and organic compounds is critical for toxicological assessment. Previous studies surveyed and mapped the entire metropolitan area of New Orleans for nine metals (Pb, Zn, Cd, Mn, Ni, Cu, Cr, Co and V) (Mielke et al., 2000). Large differences in metals exist between inner-city and suburban communities. A follow-up study evaluated metals and PAHs of selected soil samples (n = 27) from different parts of the city and showed a strong and significant associ∗

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ation between metals and PAHs (correlation 0.78, P = 4.9 × 10−4 ) (Mielke et al., 2001a). Building on previous research, this study evaluates two communities, one inner-city and the other suburban to determine the quantities of 16 polycyclic aromatic hydrocarbons (naphthalene, acenaphthylene, acenaphthene, fluorene, phenanthrene, anthracene, fluoranthene, pyrene, benz(a)anthracene, chrysene, benzo[k]fluoranthene, benzo[j]fluoranthene, benzo(a)pyrene, indeno[1,2,3-cd]pyrene, dibenz[a,h]anthracene and benzo[g,h,i]perylene) and nine metals (Pb, Zn, Cd, Mn, Ni, Cu, Cr, Co and V). The purpose is to assess the underlying chemical environment in communities and evaluate how they relate to the exposure of sensitive populations living in different residential locations of metropolitan New Orleans.

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2. Materials and methods

vide sample material for extraction and analysis of PAHs and metals.

2.1. Soil collection 2.2. PAH extraction, cleanup and analysis The census tracts of New Orleans were the basis for stratifying the collection of soil samples. There are 286 census tracts in metropolitan New Orleans. Of these census tracts, two were selected for this study, census tract 78 located in inner-city and 203.01 located in suburban New Orleans (see Fig. 1). The soil samples collected (n = 19 for each tract for a total n = 38) were from the following four types of residential community sites where children could play: four soil samples were collected from the public right-of-way within 1 m of the busiest roads of the census tract; nine samples were collected on the public right-of-way within 1 m of ordinary residential streets; three samples were collected from open spaces away from both houses and streets; and three samples were collected within 1 m of house foundations. All samples were collected from the soil surface (top 2.5 cm), taken to the laboratory, air-dried and sieved (2 mm USGS #10 screen). Each collected soil sample was divided to pro-

Accelerated solvent extraction (ASE) was used to extract PAHs for analysis with gas chromatography–mass spectrometry (GC–MS). Triplicates of 1 g sub-samples were extracted and analyzed for each soil sample. Extraction parameters were adapted from Dionex application note 313 (Sunnyvale, CA) with some modifications (Wang et al., 1999). Post-extraction cleanup procedures included evaporating the extract to approximately 2 mL under a nitrogen stream. The concentrated extracts were then loaded into solid phase extraction cartridges containing 2 g florisil and dried for 5 min. PAHs were eluted from the column with 10 mL methylene chloride using a vacuum manifold. Prior to GC–MS analysis the collected eluent was evaporated down to 1 mL followed by the addition of internal standards. The GC–MS was operated using the selected ion-monitoring mode

Fig. 1. A map of the distribution of MMA (i.e., multiple metal accumulation or sum of the soil metals) in New Orleans. The tables summarize the findings by listing the percentiles of the totals (see Tables 1 and 2) of metals (in ␮g g−1 ) and PAHs (in ng g−1 ) for the suburb and inner-city census tracts of New Orleans.

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tests). Descriptive statistics about the results from each site are displayed as percentiles.

for calculating the chromatographic peak area of each PAH (Wang et al., 1999). 2.3. Metal extraction and analysis

3. Results

Metals were extracted using a 5:1 ratio of 1 mol L−1 nitric acid to soil, shaken for 2 h at room temperature, centrifuged (1000 × g for 15 min), and filtered (Mielke et al., 1997). Metal ions in the extracts were determined using inductively coupled plasma-atomic emission spectrometry (ICP-AES).

3.1. Differences of PAHs and metals between the inner-city and the suburban census tract Tables 1 and 2 show the percentiles of the analytical results for PAHs and metals, respectively. Note the large ranges for each of the PAHs and the metals indicated in the tables. Note also from Tables 1 and 2 that without exception the amounts of each individual PAH and each metal were highest in the innercity and lowest in the suburbs. The Mann–Whitney rank sum test results between the inner-city and suburban soil sample sets are <0.0001 for both PAHs and metals.

2.4. Statistical treatment The metals and PAHs do not have normal frequency distributions, and thus nonparametric statistical methods were used (percentiles, Spearman correlation and Mann–Whitney

Table 1 Percentiles of polycyclic aromatic hydrocarbons (PAHs) in an inner-city (78) and suburban (203) census tract of New Orleans Tract 78

A

B

C

D

E

F

G

H

I

J

K

L

M

N

O

P

PAH78

Min 10% 25% Median 75% 90% Max Tract 203

1 8 20 31 39 82 129 A

0 1 8 12 36 58 152 B

2 2 5 10 18 24 86 C

0 1 3 7 13 17 65 D

21 46 96 148 270 338 463 E

2 10 23 42 66 113 163 F

33 71 129 353 779 1002 1398 G

45 61 94 368 710 906 1236 H

24 63 93 213 416 538 587 I

33 35 57 164 340 562 670 J

89 107 154 317 463 721 868 K

20 33 86 175 262 415 551 L

123 163 196 314 490 579 656 M

199 215 260 391 587 732 762 N

118 125 150 206 271 316 359 O

126 138 164 225 405 511 625 P

906 1147 1880 2927 5164 7026 7285 PAH203

Min 10% 25% Median 75% 90% Max

0 0 0 0 0 3 17

0 0 0 0 0 5 13

0 0 0 0 0 11 22

0 0 0 0 0 3 3

0 5 9 12 26 53 166

0 0 0 0 4 10 45

0 14 23 30 66 137 612

0 13 22 30 58 123 522

1 2 4 11 18 43 230

0 3 11 17 29 60 319

61 64 72 79 97 112 389

0 4 7 12 25 38 197

113 114 119 127 136 145 345

156 163 168 178 199 206 411

102 105 107 111 121 128 214

96 96 97 106 114 126 302

527 615 663 731 889 1167 3753

N = 19 for each census tract. Units are in ng g−1 . Key for polycyclic aromatic hydrocarbons: A, naphthalene; B, aenaphthylene; C, acenaphthene; D, fluorene; E, phenanthrene; F, anthracene; G, fluoranthene; H, pyrene; I, benz(a)anthracene; J, chrysene; K, benzo(b)fluoranthene; L, benzo[k]fluoranthene; O, dibenz[a,h]anthracene; M, benzo(a)pyrene; N, indeno[1,3,3-cd]pyrene; P, benzo[g,h,i]perylene; total PAHs. Table 2 Percentiles of metals in an inner-city (78) and suburban (203) census tract of New Orleans Pb

Zn

Cd

Mn

Ni

Cu

Cr

Co

V

Sum of metals

Tract 78 Min 10% 25% Median 75% 90% Max

163 192 420 656 1323 3631 10300

83 131 234 373 784 1041 4818

1.2 1.9 2.5 3.6 4.9 7.0 17.3

57 78 110 134 223 257 327

5.2 6.8 8.0 10.0 15.1 17.3 21.8

16 16 20 32 60 81 113

1.5 1.9 2.3 3.4 5.9 10.4 15.6

2.1 3.3 4.3 5.8 7.0 8.1 10.6

3.3 3.7 4.5 6.0 8.0 8.9 13.1

392 545 840 1323 2036 4846 15498

Tract 203 Min 10% 25% Median 75% 90% Max

5 5 8 12 26 131 165

12 13 22 33 52 83 208

1.0 1.0 1.2 1.6 1.8 2.2 4.4

40 44 50 72 128 144 186

3.1 4.1 4.8 5.5 6.7 8.8 9.4

2 3 4 5 7 11 24

0.7 0.7 0.8 1.0 1.2 1.5 5.9

2.1 2.3 2.6 3.5 3.9 4.3 5.3

1.4 1.5 1.7 2.6 3.4 3.5 3.9

72 86 112 183 218 320 559

N = 19 for each census tract. Units are ␮g g−1 .

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The quantity of PAHs found in the inner-city compared with the suburbs differs depending on the chemical species of the PAH, and overall, the ratio for the sum of PAHs is 4. That is, the medians of the sum of the PAHs in the inner-city are four times higher than the median of the sum of PAHs in the suburbs. For individual chemical species of PAHs, the ratios vary considerably. For example, in the case of the higher molecular weight molecules such as benzo(a)pyrene the ratio was 2.5, and below the overall factor of 4. On the other hand the difference in the medians of the lower molecular weight PAHs such as benz(a)anthracene is 19.4 or nearly five times larger than the overall ratio of 4. Likewise, the quantities of metals vary between the innercity compared with metals in the suburban census tract. The overall sum of metals differs by a ratio of 7.2. Most of the metals differ by a ratio of around 2 as in the case of Cd, Mn, Ni, Co and V. The ratio is slightly larger for Cr (3.4), Cu (6.4) and Zn (11). Pb and Zn show the largest difference; the median quantity of Pb in the inner-city is 55 times larger than the median amount of Pb in the suburb and the median quantity of Zn is around 11 times larger in the inner-city than in the suburbs. 3.2. The associations between PAHs and metals in the inner-city and suburban census tract Another characteristic demonstrated by these data are the associations between PAHs and metals in the two census tracts. Initial results of the Spearman test of association for the inner-city, indicated a weak association (correlation coefficient = 0.43, P = 0.065) between PAHs and metals in the inner-city. By trimming the three foundation samples from the dataset and reanalyzing the remaining 16 samples, the results changed to a significant association (correlation coefficient = 0.57, P = 0.021) between PAHs and metals in the inner-city of New Orleans. In the case of the suburban community there was a significant association between PAHs and metals (correlation coefficient = 0.45, P = 0.050) for all 19 samples in the dataset. Combining all 38-paired PAH and metal results provides the strongest association (correlation coefficient = 0.831, P < 0.00001).

Table 3 Median PAH concentrations stratified by residential collection sites for the combined data of the inner-city and suburban census tracts PAH

Busy streets

Residential streets

Open areas

Foundation samples

A B C D E F G H I J K L M N O P PAH

10 6 1 1 133 38 266 237 145 111 319 95 255 322 208 237 2469

8 0 4 0 29 8 107 97 41 42 112 34 141 202 126 125 1061

2 5 4 3 21 7 82 67 28 32 94 24 144 205 123 122 975

8 9 5 3 77 10 105 78 51 40 105 72 163 233 128 137 1188

8

18

6

6

N ng g−1 .

Units are Key for polycyclic aromatic hydrocarbons: A, naphthalene; B, aenaphthylene; C, acenaphthene; D, fluorene; E, phenanthrene; F, anthracene; G, fluroanthene; H, pyrene; I, benz(a)anthracene; J, chrysene; K, benzo(b)fluoranthene; L, benzo[k]fluoranthene; M, benzo(a)pyrene; N, indeno[1,3,3-cd]pyrene; O, dibenz[a,h]anthracene; P, benzo[g,h,i]perylene; total PAHs.

Table 4 Median metal concentrations stratified by local residential collection sites for the combined data of the inner-city and suburban census tracts Metal

Busy streets

Residential streets

Open areas

Foundation samples

Pb Zn Cd Mn Ni Cu Cr Co V MET

196 266 4 126 10 23 3 5 4 646

168 110 2 125 7 13 2 4 3 468

86 52 2 112 8 11 1 4 4 289

251 155 2 114 6 12 2 4 4 527

8

18

6

6

N

3.3. The quantities of PAHs and metals as a function of site in the community The four local sites collected were busy streets, residential streets, open areas and foundations. The data were combined for both the inner-city and suburban census tract and stratified by local collection sites. Tables 3 and 4 list the results of the medians of each local site by percentiles. The largest medians are found along busy streets and the ranking for the remaining sites are foundations > residential streets > open areas. Note that the same overall trend exists for both PAHs and metals. The most pronounced trend is for PAHs. Busy streets have over twice the quantities of PAHs as foundation soils, the second largest PAH containing soil. Vehicle exhaust is the

Units are

␮g g−1 .

major source PAHs in residential communities. Note that as traffic volumes change from busy streets to residential streets, the amount of PAHs also changes in the direction expected.

4. Discussion Results of Mann–Whitney tests indicate strong differences between inner-city and suburban soils for both PAHs (P < 0.0001) and metals (P < 0.0001). Spearman product moment correlation reveals that overall the PAHs and metals in soils collected from the inner-city and suburban New Orleans

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exhibit a strong association (correlation coefficient = 0.831, P ≤ 0.00001). In general then, the quantities of metals and PAHs are positively and significantly related, and these results are in agreement with previous work that showed the same chemical relationship in urban soils (Mielke et al., 2001a). Fig. 1 illustrates the significant differences in accumulated mixture of PAHs and metals between an inner-city and suburban residential community. These data provide realworld information about amounts and mixtures of PAHs and metals in soils of different communities of New Orleans, and they represent a starting point for assessing possible health effects of chemical mixtures in the built environment. The results of this study also indicate that the quantity of metals next to foundations in the inner-city diminishes the association between PAHs in the inner-city. Most of the inner-city housing of New Orleans was built prior to 1950 when most paint contained large quantities of Pb and other metals. The soils around these homes were contaminated due to deterioration or to deliberate removal without any attempt to capture the paint residue (Mielke et al., 2001b). When the foundation samples are removed from the sample set, then the association between soil PAHs and metals becomes strong and significant. This study indicates that there are large differences in the chemical qualities of different places in the urban environment. Because New Orleans’ climate is relatively mild with a limited cold season, the city is not subject to large amounts of fuel consumption for heating purposes. Also, the climate is conducive to degradation of the low molecular weight PAHs and climate may explain why the ratio of these compounds is different in the two census tracts when compared to the high molecular weight PAHs. Automotive byproducts are a common denominator for many observations for both PAHs and metals. The motor vehicle is increasingly recognized as a contributor to air pollution. Motorized vehicle emissions are strongly associated with health problems as shown by research on how proximity to roads affects mortality (Hoek et al., 2002). Brunekreef and Holgate (2002) reviewed the health consequences of air pollution and demonstrate a strong association between air pollution, asthma and chronic obstructive pulmonary disease. The PAHs and metals exhausted as fine particles by motor vehicles are deposited in and accumulate in soil. Comparing busy streets with residential streets in the inner-city and in the suburbs provides evidence about the importance of motor traffic as a source of soil PAHs and metals. Empirical evaluation demonstrated a strong association between children’s Pb exposure and the amount of Pb in soil at a community scale in New Orleans and Thibodaux, Louisiana (Mielke et al., 1997). The association was elaborated in a follow-up paper on New Orleans (Mielke et al., 1999). Johnson and Bretsch (2002) also assessed the relationship between soil lead and childhood exposure in Syracuse, New York and found “striking similar results to those obtained by Mielke et al. (1999)”. The similarity of results in two cities located in different climates suggests that chil-

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dren’s physiology and behavior naturally predisposes them to Pb exposure and as we have shown, soil is an important source of Pb exposure (Mielke and Reagan, 1998). If a major source of Pb exposure for children is soil, then the results of this study suggest that, in addition to Pb exposure, children are subject to a mixture of PAHs and a suite of metals. Given the large difference in the chemical mixture of PAHs and metals between surface soils from an inner-city and suburban community of New Orleans, and in more detail, between busy streets and residential streets, it is safe to hypothesize that location of residence plays a major role in community health. Further research is needed to more fully assess this hypothesis in light of the health disparities that may exist in different communities of New Orleans. Acknowledgements Research on metals was funded by the ATSDR/MHPF cooperative agreement #U50/ATU398948, and PAHs research was funded by DOD Grant #DSWA01-97-1-0028 and DOE Award #DE-FG21-93EW-53023 to Xavier/Tulane Center for Bioenvironmental Research. References Brunekreef, B., Holgate, S.T., 2002. Air pollution and health. Lancet 360 (9341), 1233–1242. Hoek, G., Brunekreef, B., Goldbohm, S., Fischer, van den Brandt, P., Piet, A., 2002. Association between mortality and indicators of trafficrelated air pollution in the Netherlands: a cohort study. Lancet 360 (9341), 1203–1209. Johnson, D.L., Bretsch. J.K., 2002. Soil lead and children’s blood lead levels in Syracuse, NY, USA. Environ. Geochem. Health 24 (4), 375–385. Mielke, H.W., Gonzales, C.R., Smith, M.K., Mielke, P.W., 2000. Quantities and associations of lead, zinc, cadmium, manganese, chromium, nickel, vanadium, and copper in fresh Mississippi alluvium and New Orleans alluvial soils. Sci. Total Environ. 246 (2–3), 249–259. Mielke, H.W., Wang, G., Gonzales, C.R., Le, B., Quach, V.N., Mielke, P.W., 2001a. PAH and metal mixtures in New Orleans soils and sediments. Sci. Total Environ. 281 (1–3), 217–227. Mielke, H.W., Powell, E., Shah, A., Gonzales, C.G., Mielke, P.W., 2001b. Multiple metal contamination from old house paints: consequences of power sanding and paint scraping in New Orleans. Environ. Health Perspect. 109, 973–978. Mielke, H.W., Dugas, D., Mielke, P.W., Smith, K.S., Smith, S.L., Gonzales, C.R., 1997. Associations between lead dust contaminated soil and childhood blood lead: a case study of urban New Orleans and rural Lafourche Parish, Louisiana, USA. Environ. Health Perspect. 105 (9), 950–954. Mielke, H.W., Smith, M.K., Gonzales, C.R., Mielke, P.W., 1999. The urban environment and children’s health: soils as an integrator of lead, zinc and cadmium in New Orleans, Louisiana. USA Environ. Res. 80 (2), 117–129. Mielke, H.W., Reagan, P.L., 1998. Soil is an important source of childhood lead exposure. Environ. Health Perspect. 106 (Suppl. 1), 217–229. Wang, G., Lee, A., Lewis, M., Kamath, B., Archer, R., 1999. Accelerated solvent extraction and gas chromatography/mass spectrometry for determination of polycyclic aromatic hydrocarbons in smoked food samples. J. Agric. Food Chem. 47, 1062–1066.