Agenda Item #7

July 17,2012

Public Hearing

MEMORANDUM

July 13,2012

TO:

FROM:

County Council

Robert H. Drummer, Senior Legislative Attorney

Amanda Mihill, Legislative

Attorney~O

SUBJECT:

Public Hearing:

Bill 21-12, Erosion, Sediment Control and Stormwater

Management - Coal Tar Pavement Products

Bill 21-12, Erosion, Sediment Control and Stonnwater Management - Coal Tar Pavement

Products, sponsored by Councilmembers Rice, Navarro, EIrich, Riemer, and Ervin was

introduced on June 19, 2012.

A

Transportation, Infrastructure, Energy & Environment

Committee worksession is tentatively scheduled for July

26

at

2

p.m.

Bill 21-12 would prohibit the use and sale of coal tar pavement products in the County and

require enforcement by the Department of Environmental Protection. Attached on ©5 is a recent

study describing the problems caused by polycyclic aromatic hydrocarbons (PAHs) released into

the environment through the use of a coal tar pavement product. Coal tar and coal-tar pitch are

Group

1

carcinogens and the Environmental Protection Agency classifies

7

PAH compounds as

probable human carcinogens.

This packet contains:

Bill 21-12

Legislative Request Report

American Chemical Society Study

F:\LAW\BILLS\1221 Erosion, Sediment Control-Coal Tar\Public Hearing Memo,Doc

Circle

#

1

4

5



Bill No.

21-12

Concerning: Erosion, Sediment Control

and Stormwater Management - Coal

Tar Pavement Products

Revised: June 5, 2012 Draft No. -'--__

Introduced:

June 19,2012

Expires: .

December 19, 2013

Enacted: _ _ _ _ _ _ _ _ __

Executive: _ _ _ _ _ _ _ _ __

Effective: _ _ _ _ _ _ _ _ __

Sunset Date: -!..!.No:::,:n..:::e:...-_ _ _ _ __

Ch. _ _, Laws of Mont. Co. _ __

COUNTY COUNCIL

FOR MONTGOMERY COUNTY, MARYLAND

By: Councilmembers Rice, Navarro, EIrich, Riemer, and Ervin

AN

ACT to:

(1)

(2)

(3)

(4)

prohibit the use and sale of coal tar pavement products in the County;

require enforcement by the Director ofthe Department of Environmental Protection;

amend the titles of Chapter 19; and

generally amend the County laws regarding water quality.

By amending the titles of Chapter 19 and adding

Montgomery County Code

Chapter 19, Erosion, Sediment Control and Stonn Water Management

Article VI. General.

Section 19-68

By renumbering

Montgomery County Code

Chapter 19, Erosion, Sediment Control and Stonn Water Management

Article VI. General.

Sections 19-68 and 19-69

Boldface

Underlining

[Single boldface brackets]

DQuble underlining

[[Double boldface brackets]]

* *

*

Heading or defined term.

Added to existing law by original bill.

Deletedfrom existing law by original bill.

Added by amendment.

Deletedfrom existing law or the bill by amendment.

EXisting law unaffected by bill.

The County Council for Montgomery County, Maryland approves the following Act:



BILL

No. 21-12

1

Sec. 1. The titles in Chapter 19 are amended, a new Section 19-68 is

added, and Sections 19-68 and 19-69 are renumbered as follows:

Chapter 19, Erosion, Sediment Control and [Storm Water] Stormwater

Management.

2

3

4

5

6

*

*

19-68. Coal tar pavement products.

*

*

*

*

Article II. [Storm Water] Stormwater Management.

7

8

9

10

11

12

ill

Definitions.

As used in this Section:

Coal tar pavement product

means

~

material that contains coal tar and is

intended to cover an asphalt or concrete surface, including

or parking area.

~

driveway

l3

14

Director

means the Director of the Department of Environmental

Protection or the Director's designee.

@

Use gfcoal tar pavement products prohibited.

15

16

17

ill

ill

A person must not use

~

coal tar pavement product in the County.

Both the property owner and the applicator have violated this

Section if

~

coal tar pavement product is applied to an asphalt or

concrete surface on the property.

18

19

20

21

Sale.

A person must not sell or offer for sale

~

coal tar pavement product

in the County.

Enforcement.

The Director must:

22

23

24

25

26

ill

publish

~

list of alternative products for use on asphalt and

concrete that do not contain coal tar; and

ill

generally enforce this Section.

[19-68] 19-69. Authority of department of environmental protection.

27

*

*

*

f:\law\bills\1221 erOSion, sediment control-coal tar\bill4.doc

o



BILL

No.

21-12

28

[19-69] 19-70. Violations.

Any violation of this Chapter is a Class A violation.

However,

29

30

notwithstanding Section 1-19, the maximum penalty for a civil violation of Article I

is $1,000 for an initial or repeat offense. Each day a violation continues is a separate

offense.

31

32

33

*

Approved:

*

*

34

35

Roger Berliner, President, County Council

Date

36

Approved:

37

Isiah Leggett, County Executive

Date

38

This is a correct copy ofCouncil action.

39

Linda M. Lauer, Clerk of the Council

Date

f:\law\bills\1221 erOSion. sediment control-coal tar\biIl4.doc



LEGISLATIVE REQUEST REPORT

Bill 21-12

Erosion, Sediment Control and Storm water Management

-

Coal Tar Pavement Products

DESCRIPTION:

Bill 21-12 would prohibit the use of coal tar pavement products in the

County and require the Department of Environmental Protection to

enforce this law.

Coal tar and coal-tar pitch are Group 1 carcinogens and the

Environmental Protection Agency classifIes 7 polycyclic aromatic

hydrocarbons (P AH) compounds as probable human carcinogens. Of

all known PAH sources, the highest concentrations are in coal tar and

related compound creosote.

To prohibit the use of coal tar pavement products.

Department of Environmental Protection

To be requested.

To be requested.

To be requested.

To be researched.

Bob Drummer, 240-777-7895

To be researched.

PROBLEM:

GOALS AND

OBJECTIVES:

COORDINATION:

FISCAL IMPACT:

ECONOMIC

IMPACT:

EVALUATION:

EXPERIENCE

ELSEWHERE:

SOURCE OF

INFORMATION:

APPLICATION

WITHIN

MUNICIP ALITIES:

PENAL TIES:

Class A violation.

f:\law\bills\1221 erosion, sediment control-coal tar\legislative request report.doc



InYIRonnu:nml

{lienee

iTe

Clinol

ogg

and E. Spencer Williams.l

tU.S. Geological Survey, Austin, Texas 78754, United States

*Minnesota Pollution Control Agency, St. Paul, Minnesota 55155-4194, United States

§University of New Hampshire, Durham, New Hampshire 03856, United States

IICity of Austin, Austin, Texas 78767, United States

.lBaylor University, Waco, Texas 76798, United States

pubs.acs.org/est

'M"'.

Coal-Tar-Based Pavement Sealcoat and PAHs: Implications for the

Environment, Human Health, and Stormwater Management

Barbara

J.

Mahler/'* Peter

C.

Van Metre/ Judy

1.

Crane/ Alison W. Watts,§ Mateo Scoggins,

II

• INTRODUCTION

Driveways and parking lots are common features of cities,

suburbs, and small towns. Most single-family residences in the

U.S. have paved driveways, and we encounter parking lots at

multifamily reSidences, schools, offices, and commercial busi­

nesses. Most people in developed countries, when outdoors,

probably spend as much time walking on pavement as on any

other type of surface.

There are differences among paved surfaces, however. Most

pavement is concrete or asphalt. The asphalt pavement of many

parking lots, driveways, and even some playgrounds in North

America is sprayed or painted with a black, shiny coating

referred to as "sealcoat," "pavement sealant," or "driveway

sealer" (Figure lA). Sealcoat is marketed as improving

pavement appearance and increasing pavement longevity.1 In

addition to making pavement black, however, one type of

commonly used pavement sealcoat contains refined coal tar and

is a potent source of polycyclic aromatic hydrocarbons

(PAHS).2-B

The contribution of pavement sealcoat to PAH

contamination of soils, lakes, and homes has only recently been

recognized.

4 ­ 6

Coal-Tar-Based Sealcoat: A Newly Identified Source of

PAHs.

The two primary sealcoat product types on the market

are refmed coal-tar-pitch emulsion and asphalt emulsion. Coal­

tar pitch, a known (Group

1)

human carcinogen,9 is the residue

remaining after the distillation of crude coal tar (a byproduct of

the coking of coal), and contains about 200 PAH compounds.

to

Most coal-tar-based sealcoat products consist of 20-35% coal­

tar pitch as the binder. Asphalt is the residue remaining after

the distillation of crude oil and

is

the binder in asphalt-based

sealcoat products. Although the two sealcoat product types are

similar in appearance, PAH concentrations in coal-tar-based

sealcoat are about 1000 times higher than those in asphalt­

based sealcoat

ll

(Table

1).

In the U.S., coal-tar-based sealcoat is used primarily east of

the Continental Divide, and asphalt-based sealcoat is used

primarily west of the Continental Divide.

3

Coal-tar-based

sealcoat also is used in Canada. 12 Geographic differences in use

in North America likely are a historical and economic artifact of

the location of most coal-tar-distillation plants near steel mills,

which historically were (and are) in the central and eastern

United States. An estimated 8S million gallons (320 million

liters) of coal-tar-based sealcoat are used annually in the

United States.

ll

The pavement sealcoat issue has been evolving since 2000,

when PAH concentrations were discovered to be increasing in

many urban lakes across the United States,lS even as

concentrations of other contaminants like lead, f.0lychlorinated bi­

phenyls (PCBS), and DDT were decreasing. 6,17

This

was an

apparent reversal from earlier reports that PAH concentrations in

the U.S. were decreasing in re1.0nse to reduced emissions from

power plants and industries.IB,1 The earlier studies, however, had

focused on lakes in undeveloped watersheds, whereas the upward

trends in P

AHs

were in lakes in urban and suburban watersheds.

This

meant, first, that reductions in PAH emissions caused

by

changes in home-heating and power-generation technology had

been eclipsed in urban areas by some other urban source of

PAHs,15 and second, that

this

other source

was

specific to urban

and suburban areas.

A breakthrough in understanding urban sources of PAHs

came in 2003, when staff with the City of Austin, TX, noted

elevated PAH concentrations

(LPAH

16

>

1000 mg/kg)

in some sediment samples collected from small tributaries

and drainages in largely residential areas?O Concentrations of

PAHs this high are typical of contaminated soils at some

manufactured gas plant Superfund sites,21 but cannot be

accounted for

by

common urban sources (e.g., tire wear, vehicle

emissions, asphalt)? City of Austin staff connected the dots and

hypothesized that the source of the elevated PAHs was particles

eroded from parking lots that were coated with coal-tar-based

sealcoat. 22 Since that time, an understanding has emerged of

relations between coal-tar-based pavement sealcoat and PAHs

in the environment.

Published: January 24, 2012

dx.doLorgI10.1021/es203699xiEnviron.

Sci.

Technol.

2012. 46, 3039-3045

• . ACS Publications

©

2012 American Chemical Society

3039



Environmental Science

&

Technology

.,"'.

Figure

1.

PAHs from coal-tar-based pavement sealcoat are transported by different pathways to various environmental compartments. Once dry, the

sealcoat product (A), which contains high concentrations of PAHs, is abraded into a powder and becomes part of the dust on

th~

pavement (B).

That dust is transported by storm runoff (C) to stormwater management devices (D) or to receiving stream.s and lakes (E).

~arking

lot dust also

adheres to tires (F) that track it onto unsealed pavement, and wind and runoff transport the dust to nearby soils (G). Dust particles

~so

are

tr~cked

on shoes into residences, where they become incorporated into house dust

(H).

Volatile PAHs in coal-tar-based sealcoat are released mto the aIr (1).

PAH concentrations associated with each compartment and literature sources are provided in Table

1.

WHAT ARE POLYCYCLIC AROMATIC HYDRO­

CARBONS (PAHS)? PAHs are a large group of

organic compounds composed of two· or more fused

. benzene rings arranged in various configurations. Those

with a low molecular weight (two or three benzene

rings)

tend to be more volatile, soluble, and biodegrad­

able than those with a higher molecular weight (four or

more benzene rings). PAHs occur naturally in coal and

petroleum products and are formed by the incomplete

combustion of organic matter, from fossil fuels to wood

to cigarettes. PAHs have many urban sources, including

used motor oil, automobile exhaust, industrial atmos­

pheric emissions, tire particles, and asphalt.

l3Il4

PAHs

always occur as a mixture of different PAH compounds,

and are ubiquitous in the urban environment. Of all

known PAH sources, the highest concentrations are in

coal tar and the related compound creosote. Most

laboratories analyze only a subset of PAHs, and

concentrations of total PAHs are reported as the sum

of the subset analyzed as described in Table

1.

(Figure IB). Concentrations ofPAHs in fine particles (dust) on

pavement with coal-tar-based sealcoat are hundreds of times

higher than those in dust on concrete pavement or on asphalt

pavement that is unsealed or that has asphalt-based sealcoae- s

(Table 1). PAHs in dust on sealcoated pavement in the central

and eastern

u.s.

are about 1000 times higher than in dust on

sealcoated pavement in the western U.S., supporting anecdotal

reports of geographic differences in product use

3

(Figure 2).

Stormwater runoff transports abraded sealcoat particles off

sealed pavement (Figure IC, Table 1). The PAH concentration

measured in particles in runoff from parking lots with coal­

tar-based sealcoat (3500 mg/kg) was 65 times higher on

average than the concentration in particles in runoff from

unsealed asphalt and cement lots? Concentrations in unfiltered

stormwater runoff from coal-tar-sealcoated pavement are

particularly elevated during the months following sealcoat

application. The mean l:PAH

16

in stormwater runoff from a

coal-tar-sealcoated parking lot during the 3 months follOwing

sealcoat application was 1357 Jl.g/L and the 3-month

mea~

during the following two years ranged from 17 to 116 Jl.g/L.

This relatively elevated concentration persists for years-the

median l:PAH

18

in stormwater runoff from a parking lot in

Madison, WI, 5 years after the last application of coal-tar-based

sealcoat,

was

52 Jl.g/L.

25

That concentration is about 10 times

higher than that in runoff from a mixed-use strip mall, arterial

street, and unsealed parking lot (4.8-5.7 Jl.g/L), more than 20

times higher than in runoff from a minor arterial street and a

commercial rooftop (1.8-2.4 Jl.g/L), and about 1000 times

~her

than in runoff from a residential feeder street (0.05 flg/L).

In many communities, the first stop for stormwater runoff is

a stormwater-retention pond or other stormwater-management

device (Figure ID), where suspended sediment and associated

contaminants settle out. Stormwater ponds are designed to

efficiently collect sediment-associated contaminants, which

creates an unintended problem for many mUnicipalities because

£)

PAHs accumulate in pond sediment.

In

5 of 10 ponds sampled in&

the Minneapolis-St. Paul, MN, metropolitan area, concentrations

3040

dx.doLorg/l0.1021/es203699xl

Environ. 5ci. Technol.

2012,46,3039-3045

Migration of PAHs from Sealcoated Surfaces into the

Environment_

Sealco'\t doesn't remain on the pavement sur­

face indefinitely, and different applicators recommend reappli­

cation from every 1 to 2 years (e.g., ref 23) to every 3 to 5 years

(e.g., ref 24). Tires and snowplows, in particular, abrade the

friable sealcoat surface into fine particles.

S,ll

The overall annual

loss of sealcoat from parking lots in a warm climate

is

about 2.4%

of total sealcoat applied, with wear being most rapid (about

ll

5% per year) in driving areas. Higher wear rates have been

noted in a cold-weather climate? The mobilized sealcoat particles

and associated PAHs are transported to various environmental

compartments (Figure I, Table 1).

The first compartment is the dust on the pavement surface

itself, generated as the sealcoat

is

abraded from the surface



Environmental Science

&

Technology

'MWN

(median

Of

mean)

mcoal·

tar-based

sealcoat

.or

Table

1.

Concentrations of PAHs as Reported in the Literature for Environmental Compartments Shown

in

Figure

1,

and

Definitions of PAH Summations Used

,

,

'.

,-

. ' compartment '.

e~vkon~enbl

.

(Figure 1)

A

PAHroncentration

affected. medium

pAijCl:lncehqation(m~cliart·

.•or

mean) 1n

asphaltseal.::"at,

affeq.~.

. ..

medi!llIl,or .assoclat¢d with unsealj'd!

.

. ,pavemell.t

. .

sUI1mlati'Dn~

~PAH'6

~PAHI2

sealcoat products

pavement dust

66000

2200

4760

685

50

II

mg/kg

mg/kg

mg/kg

mg/kg

mg/kg

11,22

B

3

4

9

<I

54

2

~AH'6

~PAH16

~AH,z

5

2

7

c

D

runoff, particles

runoff, unfiltered water

b

stormwater-management-device

sediment

lake sediment

C

tires

3500

71

~PAH16

52

646

5

2

0.4

~PAH'8

EPAH 16

flg/L

flg/L

mg/kg

mg/kg

mg/kg

mg/kg

mg/kg

ng/m

3

25

5

6

5

E

F

G

33

1380

3

2

soU

d

105

129

1320

138

297000

5680

5

H

settled house dust

air (0.03 m from pavement),

3-8

years after sealing

air (1.28 m from pavement),

3-8

years after sealing

air (0.03 m from pavement), 1.6 h

after sealing

air (1.28 m from pavement), 1.6 h

after sealing

S

66

26

4

28

28

29

29

66

26

a:EPAH n is the sum of concentrations of the 12 parent PAH (naphthalene, acenaphthylene, acenaphthene, fluorene, phenanthrene,anthracene,

f1uoranthene, pyrene, benz[a]anthracene, chrysene, benzo[a]pyrene, and dibenz[a,h]anthracene), which are those PAHs used in computation of the

probable effects concentration (PEC) sediment-quality guideline,41 less 2-methylnaphthalene. :EPAH

I6

is

the sum of the concentrations of the

16

priority pollutants identified by the

U.S.

Environmental Protection

Agency,'~l

equal to the sum of :EPAH

I2

and concentrations of

benzo[b]f1uoranthene, benw[ghiJperylene, benzo[k]fluoranthene, and indeno[l,2,3-cd]pyrene. :EPAH

I8

is equal to :EPAH

I6

plus concentrations

of I-methylnaphthalene and 2-methylnaphthalene. :EPAH

CMB

is the sum of concentrations of phenanthrene, anthracene, fluoranthene, pyrene,

benz[aJanthracene, chrysene, benzo[a ]pyrene, benzo[b ]f1uoranthene, benzo[ghi]perylene, benzo[k]f1uoranthene, indeno[ 1,2,3-cd]pyrene, and

benw[e]pyrene. :EPAH

a

is the sum of concentrations of phenanthrene, anthracene, 4,5-methylphenanthrene, I-methylphenanthrene, f1uoranthene,

pyrene, chrysene, and benw[b ]f1uoranthene. On the basis of PAH data from primarily combustion sources presented in Mahler et

a1/

:EPAH 12 is

about 70-75% Of:EPAH

I6•

kPAHIB is similar to :EPAH

I6,

as the additional compounds in the summation either are not detected or are detected at

very low concentrations?·2S bCollected >3 months after sealcoat application. cMeans fur urban lakes with >70% PAH from sealcoat and 0-20% from

sealcoat. dConcentration in soil adjacent to a sealed parking lot.

Figure 2. PAHs in dust swept from sealcoated parking lots show a

striking geographic difference. PAH concentrations in dust from

parking lots in central and eastern

U.S.

cities, where coal-tar-based

sealcoat is commonly used, are about 1000 times higher than in the

western

U.S.,

where asphalt-based sealcoat

is

more commonly used.

Concentrations are the sum of 12 PAHs (:EPAH1J, in mg/kg. (Figure

adapted from ref 3, Figures 1 and 2).

of P AHs in sediment exceeded Minnesota's Level 2 Soil

Reference Value of 3 rng/kg benzo[aJpyrene

e~uivalents

(BaPeq), greatly increasing the cost for disposal? Even a

small amount of sealcoated pavement can be the dominant source

of PAHs to sediment that collects in storrnwater-rnanagement

3041

devices, as demonstrated at the University or New Hampshire

Storrnwater Center.s Sediment collected from a storrnwater­

management device receiving runoff from a parking lot with

coal-tar-based sealcoat contained ::EPAH

16

of

393-1180

mg/kg;

sediment in devices receiving mixed runoff (4% sealed pavement

and

96%

unsealed pavement) contained

61-638

mg/kg ::EPAH I6;

and sediment in a device in the center of an adjacent unsealed lot

contained less than 4 mg/kg ::EPAH16.

5

Some sealcoat particles that are not trapped by storrnwater

ponds or other collection devices are transported down streams

and rivers to lakes, where they are deposited in lake sediment

(Figure IE). Do the PAHs associated with the particles

constitute a majority of PARs in urban lake sediments, and

might coal-tar-based sealcoat account for many of the upward

trends in PAHs reported by Van Metre et

al.?15

An

initial

indication comes from a comparison of PAH ratios, or

"fIngerprints", of the dust collected from parking lots in nine

U.S. cities to that of PAHs in sediment from lakes in the same

watersheds.

3

In the central and eastern U.S., PAR fIngerprints

of lake sediment and dust from sealcoated parking lots were

similar, and were different from fIngerprints of lake sediment

and dust in the western U.S., reflecting regional differences?-;\

in sealcoat product type used. A more sophisticated source0

apportionment method-a statistical approach that quantifies

dx.doi.orgI10.10211es203699x I

Environ.

Sci.

Technol.

2012.46. 3039-3045



Environmental Science

&

Technology

the contribution of sources with known PAH profiles to an

environmental receptor-was used to quantify the contribution

of identified urban PAH sources to PAHs in bed sediment in

40

U.S. urban lakes.

6

Coal-tar-based sealcoat was estimated to

contribute about one-half of the PAHs in the lake sediment,

when averaged across the 40 lakes; vehicle-related sources and

coal combustion also were important contributors. PAH

concentrations in lake sediment and the proportion contributed

from coal-tar-based sealcoat were greater in the central and

eastern U.S. than in the western U.S. Using sediment cores,

trends in PAHs were investigated for eight urban lakes; of the

six with significant upward trends, source apportionment

indicated that coal-tar-based sealcoat was the cause of the

trend in all six of them.

Turning our attention back to sealed pavement, dust from

pavement with coal-tar-based sealcoat contaminates nearby

unsealed pavement, with concentrations decreasing with

distance from the sealed pavement.

s

A petrographic analysis

of dust from unsealed pavement in Fort Worth, TX, found that

coal-tar pitch was the dominant

(92%)

source of PAHs in the

dust.s Particles are transported by adhesion to vehicle tires and

by wind from sealed to unsealed

surfaces-~PAHI6

in particles

swept from tires driven over sealed lots were

400

times higher

than in particles swept from tires driven over unsealed 10ts

S

(Table

I,

Figure IF). Transport of abraded coal-tar-based

sealcoat particles by wind and tires might be one reason why

PAH concentrations in dust from unsealed parking lots in

the central and eastern U.S. (median

~PAH12

27

mglkg), where

coal-tar-based sealcoat is predOminantly used, are Significantly

higher than those in dust from unsealed parking lots in the

western U.S. (median

~PAH12

O.S

mg/kg), where the asphalt­

based product is predominantly used.

3

P AHs in particles abraded from coal-tar-based sealcoat also

are transported by wind, runoff, and snow removal to nearby

soils (Table 1, Figure IG).

~PAHI6

in surface soil adjacent to

coal-tar-sealed lots at the University of New Hampshire was as

high as

411

mg/kg, and concentrations decreased with distance

from the sealed lot to less than 10 mg/kg.s The highest

concentrations were measured in areas where snow was piled

adjacent to the lots during the winter months-snowplows

were scraping the seal coat off with the snow. PAHs in surface

soils from commercial areas in Fort Worth, TX, were

dominantly (88%) from coal-tar pitch.

S

PAHs from pavement sealed with coal-tar-based sealcoat can

contaminate the indoor environment (Figure IH) as well as the

outdoor environment. In a study in Austin, TX, apartments

with parking lots with coal-tar-based sealcoat had

~PAHI6

in

house dust that was

2S

times higher, on average, than

~PAHI6

in house dust from apartments with parking lots with other

surface

~es

(concrete, unsealed asphalt, or asphalt-based

sealcoat) (Table 1). The presence or absence of coal-tar-based

sealcoat on the apartment complex parking lot was strongly

correlated with PAH concentrations in house dust. Although

tobacco smoking, candle and incense burning, and barbecue

and fireplace use have been suggested to affect PAH

concentrations in house dust, Mahler et al.

4

found no relation

between any of these and PAH concentrations in the house

dust. Concentrations of individual P AHs in house dust

collected from apartments in Austin adjacent to pavement

with coal-tar-sealcoated parking lots were about

140

times

higher than those measured in a study of house dust in

California. 27 Lower concentrations of PAHs in house dust in

California are consistent with the very low concentrations of

3042

lijiW*

PAHs measured in pavement dust in the western U.S. (Figure

2),

where coal-tar-based sealcoat is not commonly used.

In addition to contaminating stormwater, sediment, soil, and

house dust, PAHs from coal-tar-based sealcoat contaminate air

(Figure 1I). Several of the lower molecular weight PAHs in

coal-tar-based sealcoat are volatile, which is why sealed parking

lots and driveways frequently give off a strong smell. A recent

study

28

reported that the

flux

of

~PAHg

from in-use parking

lots with coal-tar-based sealcoat of various ages (mostly more

than

3

years old) was

60

times higher than that from unsealed

9

pavement on average. A second stud/ reported that

~P

AHg in

air just after sealcoat application was hundreds to thousands of

times higher than that above unsealed parking lots (Table

1),

and that one-quarter to one-half of the PAHs in the applied

seal coat were lost to the atmosphere during the first

16

days

following application. A mass balance indicated that

LP

AHg

emissions from new applications of coal-tar-based sealant each

year are larger than annual vehicle emissions of PAHs for the

29

U.S.

Biological Concerns.

The detrimental effects of PAHs on

3D

terrestrial and aquatic ecosystems are well documented. For

example, when fish are exposed to PAHs, they exhibit chronic

effects, including

fin

erosion, liver abnormalities, cataracts, skin

tumors, and immune system impairments leading to increased

susceptibility to diseaseY When benthic macro invertebrates­

insects and other organisms that live at the bottom of rivers and

lakes and that make up the base of the aquatic food chain­

are exposed to PAHs, they are susceptible to a number of

detrimental effects, including inhibited reproduction, delayed

emergence, sediment avoidance, and mortality.31 The most

important mechanism by which acute effects occur in benthic

invertebrates is a nonspecific narcosis-like mode of action that

32

results in the degradation of cell membranes. Ultraviolet

(UV)

radiation greatly increases the toxicity of PAHs in a wide

.

.

.

vanety

0

f

aquatic orgamsms.33-36

As

the importance of coal-tar-based seal coat as a source of

PAHs has emerged, several studies have looked at potential

biological effects of this particular source of PAHs. When

sediment was spiked with coal-tar-based sealcoat to provide a

range of environmentally relevant PAH concentrations, frogs

(XenopU$ laevis)

had stunted growth or delayed development at

30

mg/kg

~PAHI6'

and complete mortality occurred at the

highest treatment of

300

mg/kg

~PAHI6.37

Salamanders

(Ambystoma maculatum)

and newts

(Notophthalmus viridescens)

exposed to sediment contaminated with coal-tar-based sealcoat

at PAH concentrations similar to the highest treatment in

the frog study had stunted growth, difficulty swimming or

righting themselves, and liver problems.

38,39

These effects were

3s

magnified by the addition of

UV

light. At the community

level, macro invertebrate communities exposed to sediment

spiked with coal-tar-based sealcoat had Significant decreases in

species abundance and richness at

~PAHI6

concentrations

exceeding

300

mg/kg.4{l Similarly, in a study of urban streams,

aquatic invertebrate communities downstream from parking

lots with coal-tar-based seal coat suffered losses of abundance

and diversity along a gradient of increasing total P AH con­

centration, starting near the

~PAH~~

Erobable effects concen­

tration (PEe) value of

22.S

mg/kg. . I These studies demon­

strate that PAHs in sediment contaminated by coal-tar-based

sealcoat are bioavailable and that environmentally relevant con­

centrations adversely affect amphibians and benthic commun-

~

ities, two robust indicators of aquatic ecosystem health. The

\9J

finding of adverse biological effects to biota when exposed to

dx.doi.orgI10.1021Ies203699x

I

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&

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sediment with PAH concentrations near the PEC has wide­

spread relevance: Of the 40 U.S. urban lakes investigated by

Van Metre and Mahler/ sediment in the nine lakes with the

greatest mass loading of PAHs from coal-tar-based sealcoat had

concentrations of PAHs that exceeded the PEe.

Human-Health Concerns.

Coal tar and coal-tar pitch are

listed as Group 1 (carcinogenic to humans) carcinogens,9 and

the U.S. EPA currently classifies seven PAH compounds as

probable human carcinogens (Group B2): benz[aJanthracene,

benzo[a ]pyrene, benzo[b]fluoranthene, benw[k]fluoranthene,

chrysene, dibenz[a,h]anthracene, and indeno[ l,2,3-cdJ­

pyrene.

42

Coal tar itself is a powerful mutagen: The muta­

genicity index for coal tar is about 1000 times that of asphalt

cements.

43

However, although coal-tar-based sealcoat has been

on the market since at least 1960/ little has been published

to date about the contribution of the sealcoat to PAH expo­

sures and the associated potential for adverse human-health

outcomes.

The elevated concentrations of PAHs in house dust, soil, air,

water, and sediment associated with coal-tar-based sealcoat

raise the possibility of several complete exposure pathways for

humans. Incidental ingestion of house dust and soil is

particularly relevant for small children, who

~t

their hands

and objects into their mouths. A recent study reported that

children living in homes adjacent to pavement with coal­

tar-based sealcoat likely are exposed to about 14-fold higher

doses of PAHs through ingestion of house dust than are

children living in residences adjacent to unsealed pavement,

and that exposure from ingestion of PAH-contaminated house

dust is estimated to be more than double that from diet, even

under conservative assumptions. Ingestion of contaminated soil

is another way that children might be exposed to PAHs from

coal-tar-based sealcoat, particularly given that ingestion rates of

soil typically exceed those of house dust.

45

Incidental ingestion

of dust directly from sealed pavement also might be important,

because the extremely high concentrations of PAHs measured

in these materials (Table 1) could translate to substantial doses

from miniscule exposures. On a long-term basis, nondietary

ingestion of PAH-contaminated house dust and soil likely are

the most important routes of exposure, but a complete human­

health risk analysis is required before the cancer risk associated

with ingestion of these media can be quantified.

Other routes of exposure to coal-tar-based seaicoat, in addition

to ingestion, might have implications for human health. Relatively

high acute exposures might occur from inhalation of wind-blown

particles or fumes that volatilize from sealed parking lots,

especially during sealcoat application. Sealeoat applicators, in

particular, might be subject to substantial inhalation exposures,

but such exposures have not yet been characterized. Other

potential routes include skin contact with sealcoat and abraded

sealcoat particles and contaminated soil, sediment, dust, and

water. Such exposures likely would be relatively infrequent and

short-term. However, PAHs are readily absorbed through the

skin,46 and circumstances that increase the frequency or

magnitude of exposure events, such as daily activity on pavement

treated with coal-tar-based sealcoat, might be associated with

increased cancer risk.

Regulatory and Retail Actions.

Research to date, as

documented here, provides a compelling weight-of-evidence

that coal-tar-based sealcoat products are an important source of

PAHs to our environment. A patchwork of actions has been

taken to either ban or restrict the use of coal-tar-based sealcoat

in the United States. The fIrst ban was implemented by the City

3043

of Austin, TX, in 2006.

47

As

ofJanuary 2012, IS municipalities

and two counties in four states (Minnesota, New York, Texas,

and Wisconsin), the District of Columbia, and the State of

Washington had enacted some type of ban, affecting nearly 10.4

million people.

48

Other local and state jurisdictions have used

voluntary or limited-use restrictions for certain groups (e.g., city

48

government) to discourage the use of coal-tar-based sealcoat.

Minnesota, in particular, has been actively engaged in this issue

after municipalities contacted state agenCies and the Minnesota

Legislature for assistance addressing PAH-contaminated storm­

water pond sediment.

49

Costs for disposing of this sediment

could reach $1 billion

if

PAHs in sediment in just 10% of the

estimated 20 000 municipal stormwater ponds

in

the Minneap­

olis-St. Paul, MN, metropolitan area exceed Minnesota's Level 2

human-health risk-based Soil Reference Value of 3 mg/kg

BaPeq50 (Donald Berger, Minnesota Pollution Control Agency,

written communication, 2011). The Minnesota Legislature passed

a bill in 2009 that provides small grants to local governments for

use in treating or disposing of contaminated sediment in storm­

water ponds, provided that the governments restrict the use of

undiluted coal-tar-based seaicoat.

49

As

ofJanuary 2012, 13 muni­

cipalities had passed ordinances and three mUnicipalities have

received grants for remediation of stormwater ponds.

Several national and regional hardware and home-improvement

retailers have voluntarily ceased selling coal-tar-based driveway­

sealer products.

48

Some private applicators have chosen to use

only asphalt-based sealcoat (e.g., refs 51,52). Many profeSSional

sealcoating companies in areas unaffected by bans or restric­

tions use coal-tar-based sealcoat, however, and coal-tar-based

sealcoat products are readily available online for purchase by

homeowners.

No action has been taken at a federal level to restrict the use

of coal-tar-based sealcoat. Coke product residues, such as coal

tar, are not classified as hazardous waste under the Resource

Conservation and Recovery Act

if

the product is recycled.

S3

This exemption allows coal-tar pitch to be used in the

production of aluminum (""'95% of use), commercial carbon,

built-up roofing, and pavement sealcoat.

S4

Because PAHs are a ubiquitous and persistent class of urban

contaminants, a decade or more might be required to assess .the

effectiveness of bans, restrictions, and/or changes in the retail

availability of coal-tar-based sealcoat on reducing PAH

concentrations in urban water bodies. Research on trends in

the occurrence of PCBs and DDTs supports this concern.

FollOwing national bans on use of PCBs and DDT in the 19705,

it was 10-15 years before concentrations in lakes and reservoirs

decreased by one_half.

17,55

Unlike these chemicals, all sources of

PAHs in urban watersheds will not be eliminated by banning

coal-tar-based sealcoat. However, reductions in PAH loads over

time might be sufficient to provide more options for disposal of

dredged material from stormwater ponds and navigation

channels and reduce risk to terrestrial and aquatic ecosystems

and human health.

•

AUTHOR INFORMATION

."".

Corresponding Author

*E-mail: bjmahler@usgs.gov.

Notes

The authors declare no competing financial interest.

dx,doLorgf10,1021/e,203699xl Environ,

Sci,

Techno!.

2012, 46, 3039-3045



Environmental Science

&

Technology

•

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