Scientists have identified this commonly used sealcoat as a major source of dangerous chemicals in streams and lakes, and as a significant health risk to the public, especially young children. These chemicals, which will are discussed in depth in the webinar, are found in the sediments of nearby lakes and streams from pavements coated with this type of product. Our expert speaker is Dr. Barbara Mahler, a Research Hydrologist with the USGS at the Texas Water Science Center. She is part of the Contaminant Trends in Lake Sediments (CTLS) team, which uses cores of sediments from lakes to reconstruct the contaminant histories of watersheds.

1. 1
Coal-Tar-Based Pavement Sealcoat:
Health and Environmental Overview
Barbara Mahler
for
Ohio Environmental Council
30 September 2014

2. NAWQA: Contaminant
Trends in Lake Sediment
2
http://tx.usgs.gov/coring/index.html
Van Metre et al., 2005, Environ. Sci. & Tech.

3. The first clue: City of Austin measures
high PAH in stream sediment
 PAHs >1,500
mg/kg in some
small drainages
in residential
areas
 Probable Effect
Concentration
(PEC) is 23
mg/kg

4. 4

5. Polycyclic aromatic hydrocarbons (PAHs) are
ubiquitous in the urban environment
Benzo(a)pyrene
Pyrene
Naphthalene
5

6. PAHs in urban sources
• Fresh asphalt 1.5
• Weathered asphalt 3
• Fresh motor oil 4
• Brake particles 16
• Road dust 24
• Tire particles 86
• Diesel engine 102
• Gasoline engine 370
• Used motor oil 440
6
All concentrations in mg/kg (means of as many as 6 studies)
Pavement Sealcoat
•Asphalt Based
~ 50
•Coal-tar-based
~70,000

7. Used
motor oil
Coal-tar
sealcoat
=

8. Coal-tar-based sealcoat use
• 85 million gallons per
year (per industry)
• 170 mi2, or 110,000 ac
covered

9. Contaminants in sealcoat are mobile
9

10. 10
Sealcoat PAH transport pathways
Mahler et al., ES&T, 2012

11. 5.2
<13
2.1
3,000
570
3,200
3,400
3,200
1,300
Sealed pavement dust
Total PAH (mg/kg)
Unsealed pavement dust
Asphalt Coal tar
8.5
<8.6
0.83
54
24
21
47
30
Van Metre et al., 2009, Environ. Sci. & Tech. 11

12. Decker Lake
2,090 people/km
SPAH 0.76 mg/kg
Lake Anne
2,095 people/km
SPAH 17.0 mg/kg

13. Environmental Forensics: PAH fingerprints
3 ring 4 ring 5-6 ring
0.25
0.2
0.15
0.1
0.05
0
Fraction
12 PAHs
CT dust
Lake Anne
0.25
0.2
0.15
0.1
0.05
0.25
0.2
0.15
0.1
0.05
0
Fraction
12 PAHs
Gas vehicle
Lake Anne
0
Fraction
12 PAHs
Coal
Lake Anne
13
r=0.60
r=0.68
r=0.94
Phe
Anth
Flu
Pyr
BaA
Chry
BbF
BkF
BeP
BaP
IP
BgP
Phe
Anth
Flu
Pyr
BaA
Chry
BbF
BkF
BeP
BaP
IP
BgP
Phe
Anth
Flu
Pyr
BaA
Chry
BbF
BkF
BeP
BaP
IP
BgP

14. PAH sources to U.S. urban lakes
14
Probable Effect
Concentration
Van Metre and Mahler, 2010, STOTEN

15. PAH Trends in New Urban Lakes

16. Effects on aquatic biota
Bommarito et al., 2010, Ecotoxicology
Bommarito et al., 2010, Chemosphere
Bryer et al., 2010, Environ. Poll.
Bryer et al., 2006, Ecotoxicology
Scoggins et al., 2007, J. NABS
16

17. Fish kill, 17 July 2010
Hodge’s Creek, North Carolina

18. Photos from Jupiter Images and Corbis Images, Inc.

19. 23 ground-floor apartments

20. 5.1
9.0
129
4,760
Median total PAH [mg/kg]
n=12 n=11
Mahler et al., 2010, Environ. Sci. Technol.

21. Sealcoat and pre-school ingestion of PAHs
21
B2-PAH dose 250
(ng B2-PAH/kg
Photo courtesy of CLEARCorps Durham, NC
Baby aspirin =0.081 g
Williams et al., Environ. Poll., 2012
200
150
100
50
0
body
weight/day)
Dietary
ingestion
Non-dietary ingestion,
low house-dust
ingestion (0.027 g/d)
Non-dietary ingestion,
high house-dust
ingestion (0.101 g/d)
CT
sealcoat
no
sealcoat
CT
sealcoat
no
sealcoat

22. “Coal tars and coal tar
pitches are known to be
human carcinogens…”
National Institute of Environmental
Health Sciences, USA

23. Coal-tar sealcoat contribution to excess
lifetime cancer risk (central tendency)
23
1:10,000
Williams et al., Env. Sci. Technol., 2012
1.20E-04
1.00E-04
8.00E-05
6.00E-05
4.00E-05
2.00E-05
0.00E+00
Urban background CT sealed
Excess Lifetime
Cancer Risk
soil
house dust
38x
increase in
cancer risk

24. What are effects on
air quality?
24

25. Fluxes (releases) from in-use CT-sealed lots
25
Flux = 1.4 mg/m2 h Flux = 88 mg/m2 h
Unsealed
asphalt
Coal-tar
sealed
Van Metre et al., Chemosphere, 2012

26. Air trends after application
26
50,000
40,000
30,000
20,000
10,000
0
Flux
50,000
45,000
40,000
35,000
30,000
25,000
20,000
15,000
10,000
0 100 200 300 400
SPAH8 flux (ug/m2 h)
time (days)
5,000
0
day-night
regression
measured flux
SPAH ~2.5 g/m2
0 5 10 15 20
SPAH8 (ug/m2 h)
time (days)
R2=0.95
Van Metre et al., Chemosphere, 2012
Van Metre et al., Atm. Environ., 2012

27. Total PAH emissions during drying
27
Annual coal-tar sealcoat use 85 million gal
Area covered ~440 km2
Total PAH emitted during drying 2.5 g/m2
SPAH8 emissions/yr ~1,000 Mg
SPAH16 vehicle emissions, 2010 840 Mg*
* Shen et al., 2011

28. 28

29. PAH concentrations in Lady Bird Lake:
Before and after the ban
29
12,000
10,000
8,000
6,000
4,000
2,000
0
1950 1960 1970 1980 1990 2000 2010 2020
SPAH16 (micrograms per kilogram)
Estimated date of sediment deposition
TWN.1
LBL.4
LBL.1
LBL.2
Surficial bottom sediment
Series6
2006 ban
on coal-tar-based
sealcoat
58%
decrease
Van Metre and Mahler, ES&T, 2014

30. Estimated PAH contribution to Lady Bird
Lake sediment by source type
30
8,000
7,000
6,000
5,000
4,000
3,000
2,000
1,000
0
mean 1998-2006 mean 2012-14
Mass of PAH (mg/kg)
wood
oil
coal
vehicle
CT sealcoat

31. USGS Research on PAHs and Coal-Tar-Based
Pavement Sealant
http://tx.usgs.gov/sealcoat.html
Barbara Mahler, bjmahler@usgs.gov
(512) 927-3566
Peter Van Metre, pcvanmet@usgs.gov
(512) 927-3506

32. References cited in this presentation
• Van Metre, P.C., Mahler, B.J., Wilson, J.T. 2009. PAHs underfoot:
Contaminated dust from coal-tar sealcoated pavement is
widespread in the United States. Env. Sci. Technol., 43:20-25.
• Mahler, B.J., Van Metre, P.C., Crane, J.L., Watts, A.W., Scoggins, M.,
Williams, E.S. 2012. Coal-tar-based pavement sealcoat and PAHs:
Implications for the environment, human health, and stormwater
management. Env. Sci. Technol., 56:3039-3045.
• Van Metre, P.C., Mahler, B.J. 2010. Contribution of PAHs from coal-tar
pavement sealcoat and other sources to 40 U.S. lakes. Sci. Total
Environ. 409:334-344.
• Bommarito, T., Sparling, D.W., Halbrook, R.S. 2010. Toxicity of coal-tar
pavement sealants and ultraviolet radiation to Ambystoma
maculatum. Ecotoxicol. 19: 1147-1156.
32

33. References cont.
• Bommarito, T., Sparling, D.W., Halbrook, R.S. 2010. Toxicity of
coal–tar and asphalt sealants to eastern newts, Notophthalmus
viridescens. Chemosphere 81: 187-193.
• Bryer, P.J., Scoggins, M., McClintock, N.L. 2010. Coal-tar based
pavement sealant toxicity to freshwater macroinvertebrates.
Environ. Poll. 158: 1932-1937.
• Bryer, P.J., Elliott, J.N., Willingham, E.J. 2006. The effects of coal tar
based pavement sealer on amphibian development and
metamorphosis. Ecotoxicol. 15: 241-247.
• Scoggins, M., McClintock, N., Gosselink, L., Bryer, P. 2007.
Occurrence of polycyclic aromatic hydrocarbons below coal-tar-sealed
parking lots and effects on stream benthic
macroinvertebrate communities. J. NABS 26: 694-707.
33

34. References cont.
• Mahler, B.J., Van Metre, P.C., Wilson, J.T., Musgrove, M., Burbank,
T.L., Ennis, T.E., Bashara, T.J. 2010. Coal-tar-based parking lot
sealcoat: An unrecognized source of PAH to settled house dust.
Environ. Sci. Technol. 44: 894-900.
• Williams, E.S., Mahler, B.J., Van Metre, P.C. 2012. Coal-tar pavement
sealants may significantly increase children's PAH exposures.
Environ. Poll. 164: 40-41.
• Williams, E.S., Mahler, B.J., Van Metre, P.C. 2012. Cancer risk from
incidental ingestion exposures to PAHs associated with coal-tar-sealed
pavement. Environ. Sci. Technol. 47:1101-1109.
• Van Metre, P.C., Majewski, M.S., Mahler, B.J., Foreman, W.T., Braun,
C.L., Wilson, J.T., Burbank, T. 2012. PAH volatilization following
application of coal-tar-based pavement sealant. Atmos. Environ. 51:
108-115.
34

35. References cont.
• Shen, H., Tao, S., Wang, R., et al. 2011. Global time trends in PAH
emissions from motor vehicles. Atmos. Environ. 45: 2067-2073.
• Van Metre, P.C., Majewski, M.S., Mahler, B.J., Foreman, W.T., Braun,
C.L., Wilson, J.T., Burbank, T., 2012. Volatilization of polycyclic
aromatic hydrocarbons from coal-tar-sealed pavement.
Chemosphere 88: 1-7.
• Van Metre, P.C., Majewski, M.S., Mahler, B.J., Foreman, W.T., Braun,
C.L., Wilson, J.T., Burbank, T., 2012. PAH volatilization following
application of coal-tar-based pavement sealant. Atmos. Environ. 51:
108-115.
• Van Metre, P.C., and Mahler, B.J. PAH concentrations in lake
sediment decline following ban on coal-tar-based pavement
sealants in Austin, Texas. Env. Sci. Technol.
http://dx.doi.org/10.1021/es405691q
35