1. Influence of Attached Garages on Indoor VOC Concentrations in Anchorage Homes Stephen S. Morris, P.E. Municipality of Anchorage Department of Health and Human Services

2. Acknowledgements Anne Schlapia, Matt Stichick and Larry Taylor – MOA DHHS John Freeman, Phil Kaluza, Ginny Moore – ABSN Sally Liu, Tim Gould, Dave Hardie and Timothy Ting University of Washington

3. Background

4. A previous Anchorage study sparked interest in a further investigation of the influence of attached garages on air quality inside Anchorage homes.

5. Architectural, Behavioral, and Environmental Factors Associated with Indoor VOCs in Anchorage Homes (1995) Sampled 137 homes for BETX between December 1994 and February 1996 Sampled 137 homes for BETX between December 1994 and February 1996 Summa canisters deployed in living space of homes for 24 hours Summa canisters deployed in living space of homes for 24 hours Documented architectural, behavioral and environmental characteristics of each home sampled Documented architectural, behavioral and environmental characteristics of each home sampled

6. The most important factor influencing [benzene] and other BTEX compounds was the presence of an attached garage. Cigarette smoking was not an important factor in determining benzene concentration in living space of the home. The presence of an attached garage was the single most important variable associated with elevated benzene inside the home.

7. Comparison of Mean Benzene Concentrations in Single Family Homes 1994-1996 Anchorage Study 18.0 6.8 3.2 0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 16.0 18.0 20.0 garage with parked cars N = 46 garage w/o parked cars N = 16 no attached garage N = 14 [benzene] ppb

8. Data suggested that attached garages increase in-home exposure to benzene five-fold. Incremental increase in lifetime exposure cancer risk was approximately 1 in 6,000.

9. Benzene content (3.9%) and volatility of Alaska gasoline is higher than most of the U.S.

10. We wanted to explore the mechanisms responsible for elevated benzene in homes with attached garages.

11. Study Objectives Measure VOC concentrations in a representative sample of 50 Anchorage homes with attached garages to assess personal exposures. Measure VOC concentrations in a representative sample of 50 Anchorage homes with attached garages to assess personal exposures. Measure garage to house air infiltration rates. Determine architectural / mechanical factors affecting the amount of air entering house from the garage. Measure garage to house air infiltration rates. Determine architectural / mechanical factors affecting the amount of air entering house from the garage. Identify possible strategies for reducing in-home VOC exposures through modification of architectural features, mechanical systems and/or modification of personal behaviors. Identify possible strategies for reducing in-home VOC exposures through modification of architectural features, mechanical systems and/or modification of personal behaviors.

12. How much garage air infiltrates into the home and what are the responsible mechanisms? How much garage air infiltrates into the home and what are the responsible mechanisms? How high are benzene and other VOCs inside the garage and what sources are responsible? How high are benzene and other VOCs inside the garage and what sources are responsible?

13. We narrowed study scope to include non- smoking, detached single family homes with attached garages only. Simplified analysis of air exchange rates. Simplified analysis of air exchange rates. Eliminated other possible confounding variables. Eliminated other possible confounding variables. Confined sampling to winter season when previous study showed VOC concentrations were highest. Confined sampling to winter season when previous study showed VOC concentrations were highest.

14. House selection

15. A representative sample of Anchorage homes was selected for sampling. Used Anchorage municipal property tax database to characterize housing stock by age and square footage. Used Anchorage municipal property tax database to characterize housing stock by age and square footage. Selected proportional number of houses in each sampling bin. Selected proportional number of houses in each sampling bin.

16. Age and size distribution of detached single family homes with attached garages in Anchorage. Resultant sampling profile (50 home target)

17. Tracer gases were used to estimate air exchange rates between garage and house.

18. A PMCH tracer gas source emitter was deployed in each house and a PDCH source in each garage. The emission rate of each source was known. PMCH PDCH house garage

19. Capillary absorption tubes (CATs) were deployed in the house and garage to measure concentrations of PMCH and PDCH over a 24-hour period. PMCH PDCH CATCAT CATCAT

20. Mass balance approach was used to compute air exchange rates between garage and house, house and outside, and garage and outside.

21. Four simultaneous equations were developed to estimate 4 unknown flows from measured [PMCH] and [PDCH] and the known emission rates of the two tracer gases. Q GA Q GL Q LG Q LA PMCH PDCH Simultaneous equations could be solved and flow rates Q GL, Q GA, Q LG, and Q LA could be computed for each house.

22. The proportion of air in the house coming from the garage could be easily derived. Proportion of house air coming from garage = Q GL /(Q GL + Q AL ) PMCH PDCH Q AL Q GL

23. VOC sampling methodology

24. ATD tubes were used to collect VOC samples in the house and garage. ATD tubes were used to collect VOC samples in the house and garage. Samplers were deployed in active living space in home, typically in living room. Samplers were deployed in active living space in home, typically in living room.

26. Ambient CO measurements were used to estimate outdoor concentrations of BTEX and butadiene. Relationship Between Outdoor [CO] and [benzene] y = 1.7858x + 1.6288 R 2 = 0.5882 0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 0.00.51.01.52.02.53.0 Outdoor [CO] ppm Outdoor [benzene] ppb

27. VOC results

28. Summary of In-house VOC Concentrations Nmeanmedianmax 1,3-butadiene460.730.446.26 benzene 457.605.1635.49 carbon tetrachloride460.080.090.13 chlorobenzene460.140.090.62 ethylbenzene462.511.659.34 methylene chloride462.790.3573.16 napthalene460.140.081.20 o-xylene462.982.1511.21 toluene4618.8912.9181.73 trichloroethene440.030.020.49 m,p-xylene466.925.1933.78

29. Distribution of Benzene Concentrations Inside Homes with Attached Garages 22 12 6 2 1 0 2 0 5 10 15 20 25 0 to 5 ppb 5 to 10 ppb 10 to 15 ppb 15 to 20 ppb 20 to 25 ppb 25 to 30 ppb >30 ppb Number of Homes

30. For benzene and other BTEX compounds, mean concentrations in the house were approximately 5 times higher than outside. Garage concentrations were 10 to 15 times higher than outside.

31. Mean Benzene 7.60 26.08 1.66 0.00 5.00 10.00 15.00 20.00 25.00 30.00 HouseGarageOutdoor ppb

32. Toluene 18.89 61.35 5.42 0.00 10.00 20.00 30.00 40.00 50.00 60.00 70.00 HouseGarageOutdoor o-Xylene 2.98 8.50 0.72 0.00 1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00 9.00 HouseGarageOutdoor Ethylbenzene 2.51 6.51 0.46 0.00 1.00 2.00 3.00 4.00 5.00 6.00 7.00 HouseGarageOutdoor m,p- Xylene 6.92 21.82 1.44 0.00 5.00 10.00 15.00 20.00 25.00 HouseGarageOutdoor

33. Data Analysis and Discussion

34. Garage to house infiltration rates varied considerably among homes sampled. Homes with forced air furnaces in the garage had higher infiltration rates than homes with other heating configurations.

36. Comparison of Median Infiltration Rates Proportion of House Air Originating from Garage 36.7% 17.0% 18.4% 0% 5% 10% 15% 20% 25% 30% 35% 40% 45% Forced Air Furnace in Garage N = 15 Forced Air Furnace in House N = 5 Hydronic N=11

37. Although the [CO] in many garages was high immediately after vehicle start-ups, exhaust emissions do not appear to be the primary source of VOCs in the garage.

38. House 30 0 10 20 30 40 50 11121314151617181920212223 0123456789 Hour of Day [CO] ppm House Garage Outside

39. CO vs benzene in garage R 2 = 0.2729 0 20 40 60 80 100 120 0.002.004.006.008.0010.0012.0014.0016.0018.00 CO (ppm) benzene (ppb)

40. There was a stronger relationship between CO and butadiene concentrations.

41. CO vs butadiene in garage R 2 = 0.4111 0 1 2 3 4 5 6 7 8 0.002.004.006.008.0010.0012.0014.0016.0018.00 CO (ppm) butadiene (ppb)

42. The data do not show a significant association between the benzene level in the garage and: The number of vehicles parked in the garage; The number of vehicles parked in the garage; The age of the vehicles in the garage; or The age of the vehicles in the garage; or The number of trips originating from the garage. The number of trips originating from the garage.

43. Evaporative emissions may be a more important source than exhaust emissions.

45. Comparison of Benzene Concentration in the Garage 32.3 7.6 0.0 5.0 10.0 15.0 20.0 25.0 30.0 35.0 Garage Used for Gasoline Equipment Storage N = 23 Garage Not Used for Gasoline Equipment Storage N = 8 median [benzene] ppb

46. Having an elevated level of benzene in the garage was a good indicator that benzene levels in the house would also be high.

47. Garage Benzene vs. House Benzene y = 0.2789x + 0.4748 R 2 = 0.7291 0 5 10 15 20 25 30 35 40 020406080100120 measured benzene in garage measured benzene in house (ppb)

48. The benzene concentration in the house could be precisely predicted from the garage concentration if the air exchange rate between the garage and house was known.

49. [benzene L ] = [benzene A ] x Q AL /(Q GL + Q AL ) + [benzene G ] x Q GL /(Q AL + Q GL ) PMCH PDCH Q AL Q GL [benzene A ] [benzene G ] [benzene L ] ?

50. Computed vs. Measured House Benzene y = 0.9224x + 0.6102 R 2 = 0.9563 0 5 10 15 20 25 30 35 40 0510152025303540 measured benzene in house computed benzene in house (ppb)

51. 27% of air from garage 73% of air from outside [benzene] = 1.4 ppb [benzene] = 29.8 ppb Outside air garage [benzene] = 8.8 ppb house The “average” Anchorage house…. - benzene concentration is 6 times higher than outside - 27% of air in the house comes from garage - over 90% of benzene in house comes from the garage

52. BTEX concentrations dropped considerably between 1994-96 study and 2003-2004 study Comparison of In-home BTEX Concentrations 1994-94 study vs. 2003-2004 study 0.0 5.0 10.0 15.0 20.0 25.0 30.0 35.0 40.0 BenzeneTolueneEthylbenzenem,p-Xyleneo-Xylene ppb 1994-96 Study2003-2004 Study

53. Phase 2 – Evaluation of Mitigation Strategies

54. Candidate Strategies Remove gasoline-fueled equipment from garage. Remove gasoline-fueled equipment from garage. Modify forced air systems placed in garages to reduce air infiltration Modify forced air systems placed in garages to reduce air infiltration Ventilate garage to reduce VOC concentrations Ventilate garage to reduce VOC concentrations Lower benzene content in gasoline Lower benzene content in gasoline