Chemicals in coal-tar based driveway sealants: environmental behaviour andimplications for indoor environment quality

8/12/2019 Chemicals in coal-tar based driveway sealants: environmental behaviour andimplications for indoor environment quality

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Chemicals in coal-tar baseddriveway sealants :

environmental behaviour andimplications for indoor

environment quality

Jiping Zhu 1,* , Elaine Easson 2 , Yong-lai Feng 1 and Gordon Cockell 21: Exposure and Biomonitoring Division, Health Canada, Canada2: Sector Strategies Division, Risk Management Bureau, HealthCanada, Canada*: Corresponding email: [email protected]


2/18


3/18

Rationale for the study

Initiated from needs in risk assessmentQuinoline and biphenyl are measurable inindoor air but have no obvious indoor sources.coal tar-based driveway sealants might be oneof the outdoor sources

PAHs were added to the studyPAHs present in coal-tarFew studies on emission characters of PAHs

PAHs in sealcoat vs. indoor dust(Mahler et al. Parking lot sealcoat: an unrecognized source

of urban polycyclic aromatic hydrocarbons. Environ SciTechnol. 2005, 39, 5560-5566.)


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Methods (1)

Headspace analysis5 g in 5-ml vial (48 h), inject 1 ml to GC/MS

Concentrations in products0.2 g extracted with 4 ml of 1:1 DCM/CAN

Leaching testMaterial placed in 500-ml separating funnelEluted with waterEluate extracted with DCM


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Method (2)

Emission estimationo Total weight loss of product over timeo

Residual concentrations at variousevaporation timeso Net loss of chemical = emission rate


6/18

Results (1): Concentrations

Product #1 #2 #3 #4

Quinoline 9 (100) 8 (19) 5 (58) 6 (98)Biphenyl 75 (100) 50 (39) 21 (136) 26 (135)

Quinoline 1.63 (91) 0.42 (69) 0.06 (77) 35 (11)Biphenyl 99 (13) 48 (22) 14 (64) 226 (22)

Naphthalene 977 (16) 345 (20) 59 (131) 2087 (17)Acenaphthene 9541 (18) 2385 (10) 1189 (61) 14734 (22)Benzo(a) pyrene 1878 (5) 498 (8) 204 (58) 2274 (19)

Headspace Conc. (g/m3)

Products Conc. (g/g)

Concentrations of target chemicals in headspace and in products(mean value (relative standard deviation))

It confirmed the presence of quinoline and biphenyl in coal-tarbased driveway sealant as we suspected.


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Results (2): Emission tests

Weight loss over time

0

5

10

15

20

25

0 50 100 150 200 250 300

Evaporation Time (hour)

S a m p

l e W e i g h

t ( g )

6.366.38

6.406.426.446.46

6.486.50

6.526.54

20 70 120 170 220 270

Weight loss over time

0

5

10

15

20

25

0 50 100 150 200 250 300

Evaporation Time (hour)

S a m p

l e W e i g h

t ( g )

6.366.38

6.406.426.446.46

6.486.50

6.526.54

20 70 120 170 220 270

Lineardecrease

ca. 75%evaporated

in 24 h

Initial wt:22.3 g

6.5 g at 24 h


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Residue levels (g/g) of target compounds in samples atvarious evaporation times

SamplesEvap. Time

(h)Material

(g) Naphthalene Quinoline Biphenyl Acenaphthene Benzo(a) pyrenePan #1 24 0.234 3210 2.89 273 8781 1667Pan #2 48 0.191 3064 2.73 278 8983 1747Pan #3 72 0.331 3017 2.61 266 8235 1579Pan #4 96 0.223 2791 3.09 254 8425 1658Pan #5 192 0.323 2798 2.78 245 8265 1645Pan #6 264 0.196 2742 4.15 242 8366 1664

Chemical remained in the product (mg) = Conc (ug/g) xremaining weight (g) / 1000Evap. Time

(h)

Samples

(g) Naphthalene Quinoline Biphenyl Acenaphthene Benzo(a) pyrene24 6.569 21.09 0.019 1.79 57.7 10.9548 6.451 19.76 0.018 1.79 57.9 11.2772 6.427 19.39 0.017 1.71 52.9 10.1596 6.424 17.93 0.020 1.63 54.1 10.65

192 6.410 17.94 0.018 1.57 53.0 10.55264 6.400 17.55 0.027 1.55 53.5 10.65

-17% -14% -7% -3%


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Amount of chemicals (ug) remained in theproducts (24 h 270 h)

1000

10000

100000

0 50 100 150 200 250 300

Evaporation Time (h)

A m o u n t

( u g

) r e m a

i n e

d i n t h e

p r o

d u c

t s

Biphenyl Naphthalene Acenaphthene Benzo(a) pyrene


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Calculation of emission profile

EF (g/g/h) = dC/dt = C/t (C1 -C2)/(t1-t2)

Evap Area = 3.14 x (0.0605 m) 2 = 0.0115 m 2

0.01

0.10

1.00

10.00

0 50 100 150 200 250 300

Evaporation times (h)

E m

i s s

i o n

f a c t o r

( u g

/ g / h )

Biphenyl

Naphthalene

Acenaphthene

Benzo(a) pyrene


11/18

Rough estimation of time needed for thechemicals to emit from products

Naphthalene Biphenyl Acenaphthene Benzo(a) pyrenemg/Kg at 24 h 3210 273 8781 1667Emissio factor (mg/Kg/h) 0.5 0.05 0.5 0.05Time need to evaporate all (days) 267 227 732 1389

Some considerations:

Product labelling: 15 Kg / 40 m 2 = 0.38 Kg/m 2 Our experiment: 0.0223 Kg/0.0115 m 2 = 1.9 Kg/m 2 Ours is 5 times thinker than normal application, so the actualEF would be 5 times greater;

On the other hand, the 0.5 or 0.05 EF estimation is higherthan actual EF especially at later emitting times.


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Results (3): Leaching tests

Water

Material

Receiver


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Percentage of chemicals leached from thematerials (%) in 5 hours .

Collection time Quinoline Biphenyl Naphthalene Acenaphthene Benzo(a) pyrene24 h 7.67 0.3 0.93 1.01 0.0005348 h 6.51 0.26 0.99 0.91 0.0004572 h 9.22 0.31 1.13 1.28 0.00059

96 h 9.11 0.47 1.71 1.64 0.00064192 h 9.45 0.4 1.27 1.46 0.0009264 h 11.73 0.38 1.38 1.34 0.00061Mean 8.95 0.36 1.23 1.27 0.00062

Water solubility(mg/L, 25C) 6100 6.94 31 3.94 0.00162

% leached: naphthalene > acenaphthene > benzo(a)pyrene

1% leach of BaP requires 3086 hours or 128 days!


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Amount of chemicals in leaching solutions(g/L) over long term of repeated leaching.

0.01

0.10

1.00

10.00

100.00

1000.00

0 2 4 6 8 10 12 14 16

Leaching time (day)

C o n c e n

t r a

t i o n

i n l e a c h e

d s o

l u t i o n

( u g

/ L )

Naphthalene Quinoline Biphenyl Acenaphthene Benzo(a) pyrene

Almost no change in concentractions in leaching solution for BaP.


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Increase of concentration in leached solution asa function of pH value of leaching water .

0.01.0

2.0

3.0

4.0

5.0

6.0

7.0

8.0

9.0

7 6 5pH in leaching water

C o n c

( u g

/ L ) i n

l e a c

h e d s o

l u t i o n Quinoline

Biphenyl


16/18

Conclusions

Quinoline and Biphenyl are present incoal-tar based sealantsPAHs are major ones in these products

Emission quite slow, especially for BaP(low vapour pressure)Once product is dry (after 24 h), theleach ability of chemicals remain similar

over timeLeaching proportional to water solubility,very little of BaP leached out


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Implications linkage to indoorenvironment

Emission will be present long afterthe product is dry and will last forweeks and monthsOff-gas could be carried into indoorenvironment by windHuman traffic is a more prevalentvenue of chemicals entering indoorsas chemicals will remain in theproduct for a long time


18/18

Acknowledgement

Christine Levesque of HealthCanada for technical assistance.

The study was funded byGovernment of Canada.

Documents

Chemicals in coal-tar based driveway sealants: environmental behaviour andimplications for indoor environment quality