Indoor Vapour Inhalation Risks from a Leaded

Gasoline Additive (1,2-Dichloroethane) that

Still Contaminates Groundwater

By: Karl Bresee, B.Sc., PBD, P.Biol. &

Nino Devdariani, B.Sc., M.Env.Sc.

Intrinsik Corp.

April 5, 2017

Fairmont Banff Springs, Banff

Outline

• History and use in gasoline

• Environmental fate and partitioning

• Environmental quality guidelines

• Case Study #1

• Case Study #2

• Indoor air sources

• Toxicology

• Conclusion1,2-Dichloroethane (DCA)

C2H4Cl2

History and Use in Gasoline

• DCA was used as “lead

scavenger”

• Since 1990, Canada’s

Gasoline Regulations

limit concentrations of

lead in gasoline

• DCA encountered at

historically impacted

gasoline sites

Environmental Fate and Partitioning

Property Value Reference

Molecular weight 98.96 g/mol SRC 2013

Henry’s law constant 0.00118 atm-m³/mol SRC 2013

Vapour pressure 78.9 mmHg SRC 2013

Water solubility 8,600 mg/L SRC 2013

Half-life in groundwater

23 years

1-30 years

GOC 1994

ATSDR 2001

Volatile

Soluble

Persistent

Environmental Fate and Partitioning

• Fugacity modeling (US EPA 2012)

Environmental

MediaAir (%) Water (%) Soil (%) Sediment (%)

Released to air 97 2 <1 <1

Released to water 16 84 <1 <1

Released to soil 26 4 70 <1

GROUNDWATER

• Groundwater quality guidelines (μg/L) (AEP 2016)

Environmental Quality Guidelines

Land Use

Human Health Ecological Receptors

Vapour InhalationPotable Water Aquatic Life

Coarse Fine

Residential 10 170 5 100

Commercial 130 1,200 5 100

SOIL VAPOUR

• Soil vapour quality guidelines (<1 m depth) (μg/m³)

INDOOR AIR

• Inhalation exposure limit: 0.4 μg/m³ (AEP 2016)

Environmental Quality Guidelines

Land UseHuman Health

Vapour Inhalation

Residential 40

Commercial 140

Case Study #1

• Village in southern Alberta

• Commercial land use

• Property developed prior to 1929 as hardware store

and gas bar

• Source is former underground storage tanks (USTs)

and pump island

• Petroleum hydrocarbons investigated in soil,

groundwater, soil vapour and sub-slab vapour

Case Study #1

• Shallow

(<1 m)

soil

vapour

samples

Land Use

Vapour Inhalation

Soil Vapour

Guideline (μg/m³)

Residential 40

Commercial 140

Case Study #2

• Community in Calgary, Alberta

• Residential land use

• Source is nearby former gasoline station

– Decommissioned and USTs removed in mid-1990s

• Petroleum hydrocarbons investigated in soil,

groundwater, soil vapour and indoor air of homes

Case Study #2

Case Study #2

• DCA measured

in groundwater

• 42 monitoring

wells

• 302 samples

• Groundwater

depth 5 to 10 m0

50

100

150

200

250

300

350

Gro

un

dw

ate

r C

on

cen

tra

tio

n (μ

g/L

)

Sample Date

Indoor Vapour Inhalation Groundwater Guideline DCA

Case Study #2

• DCA analyzed

in soil vapour

(1 to 6 m

depth)

• 45 locations

• 90 samples

• Detection limit

0.4 μg/m³ 0.1

1

10

100

So

il V

ap

ou

r C

on

ce

ntr

ati

on

(μ

g/m

³)

Sample Date

Indoor Vapour Inhalation Soil Vapour Guideline DCA

<0.4 (n=44) <0.4 (n=45)

Case Study #2

• DCA

analyzed in

indoor air

• Detection limit

0.4 μg/m³

• Sub-slab

sample non-

detect

(<0.4 μg/m³)0.05

0.5

5

Summer2014

Fall 2014 Summer2015

Summer2016

Winter 2017 Indoor Air -Canada

(GOC 1994)

Indoor Air -USA (US

EPA 2011)

Outdoor Air- Calgary

Air

Co

nc

en

tra

tio

n (μ

g/m

³)

<0.4 <0.4

Inhalation Exposure Limit DCA

Case Study #2 Indoor Air

Indoor Air Sources

• DCA found in automotive products, oils, greases

and lubricants and miscellaneous products (Sack et

al. 1992)

• DCA also found in cleaning agents, pesticides,

glued wallpaper and glued carpet (Wallace et al.

1987)

• North American residences average detection

frequency 13.8% (US EPA 2011)

Indoor Air Sources

• A recent study conducted in the United States found that

consumer products, namely molded plastic holiday

ornaments manufactured in China, were the primary

sources of DCA in indoor air (Doucette et al. 2009)

• In one home, the room in which molded plastic

ornaments were stored had a DCA concentration of 82

μg/m³, while in other rooms of the house concentration

ranged from 0.41 to 12 μg/m³

Indoor Air Sources

• Chamber

study used to

measure

emission rates

from

consumer

products

Toxicology

• DCA carcinogenic via ingestion (US EPA 1987)

• Oral slope factor = 0.091 per (mg/kg/day)

• Inhalation unit risk was calculated from oral data

• Inhalation unit risk = 2.6E-05 per (μg/m³)

Toxicology

• Acceptable

benchmark

incremental cancer

risk = 1.0E-05 (i.e.,

1 in 100,000)

• 0.4 μg/m³ DCA is

associated with

1.0E-05 risk of

cancer (AEP 2016) 1.0E-07

1.0E-06

1.0E-05

1.0E-04

1.0E-03

1.0E-02

1.0E-01

1.0E+00

0 1 2 3 4 5 6 7 8 9 10 11

Incre

men

tal C

an

cer

Ris

k

Air Concentration (μg/m³)

DCA Vinyl Chloride Benzene

Toxicology - Uncertainty

• Extrapolating from oral to inhalation exposure

• No consideration by US EPA for potential differences in

metabolism between oral and inhalation exposures,

internal exposure, mode of effect or key toxicological

endpoints

• An evaluation of pharmacokinetics and mode of action

after oral and inhalation exposure should be undertaken

to ensure that it is appropriate to use oral values for

inhalation exposures (CCME 2014)

Conclusions

• Consider DCA as a chemical of concern for sites

with old gasoline impacts

• Always collect sub-slab and/or soil vapour

samples when analyzing indoor air to address

background indoor sources

• Health risks need to be interpreted cautiously

due to toxicological uncertainty

Questions?

ReferencesAEP (Alberta Environment and Parks). 2016. Alberta Tier 1 Soil and Groundwater Remediation Guidelines.

ATSDR (Agency for Toxic Substances and Disease Registry). 2001. Toxicological Profile for 1,2-Dichloroethane.

CCME (Canadian Council of Ministers of the Environment). 2014. A Protocol for the Derivation of Soil Vapour Quality Guidelines for Protection of Human

Exposures Via Inhalation of Vapours.

Doucette, W.J., Hall, A.J. and Gorder, K.A. 2009. Emissions of 1,2-Dichloroethane from holiday decorations as a source of indoor air contamination. Ground

Water Monitoring & Remediation, 30(1):65-71.

GOC (Government of Canada). 1994. Canadian Environmental Protection Act. Priority Substances List Assessment Report. 1,2-Dichloroethane.

Sack, T.M., Steele, D.H, Hammerstrom, D. and Remmers, J. 1992. A survey of household products for volatile organic compounds. Atmospheric Environment,

26A(6):1063-1070.

SRC (Syracuse Research Corporation). 2013. FatePointers Search Module. Website: http://esc.syrres.com/fatepointer/search.asp.

US EPA (United States Environmental Protection Agency). 1987. Integrated Risk Information System (IRIS) Chemical Assessment Summary. 1,2-

Dichloroethane; CASRN 107-06-2. Website: https://cfpub.epa.gov/ncea/iris/iris_documents/documents/subst/0149_summary.pdf.

US EPA (United States Environmental Protection Agency). 2011. Background Indoor Air Concentrations of Volatile Organic Compounds in North American

Residences (1990-2005): A Compilation of Statistics for Assessing Vapor Intrusion. Office of Solid Waste and Emergency Response. EPA 530—R-

10-001.

US EPA (United States Environmental Protection Agency). 2012. Estimation Program Interface Suite™ for Microsoft® Windows, v 4.11. United States

Environmental Protection Agency, Washington, D.C., USA.

Wallace, L.A., Pellizzari, E., Leaderer, B., Zelon, H. and Sheldon, L. 1987. Emissions of volatile organic compounds from building materials and consumer

products. Atmospheric Environment, 21(2):385-393.

Figures: https://upload.wikimedia.org/wikipedia/commons/1/12/1,2-dichloroethane-eclipsed-side-3D-balls.png,

https://www.flickr.com/photos/gamersincepong/4987129907, Doucette et al. 2009