Collateral Benefits of Active Soil Depressurization for VI Mitigation

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Alison Maxwell
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1 Collateral Benefits of Active Soil Depressurization for VI Mitigation William J. Angell Midwest Universities Radon Consortium University of Minnesota Vapor Intrusion Exposures The Challenges, Needs for and Benefits of Long- Term Stewardship 24th Annual International Conference on Soil, Water, Energy, and Air March 18,

2 Background (1:2) Globally, active soil depressurization (ASD) is the primary control strategy for radon mitigation (ASD employs a fan) o o o ASD for radon control was inspired by the use of blowers used to control landfill gases The primary benefit of ASD is reduction of indoor radon exposure and thus, reduce the risk of lung cancer A secondary benefit of ASD is reduction of indoor moisture levels that can cause mold contamination and condensation-related decay Passive soil depressurization (PSD) may be used in new construction (PSD uses no fan) 2

3 Background (2:2) If installed according to U.S. standards: o ASD achieves 80 to 99% reductions of indoor radon concentrations in existing homes o PSD achieves about a 55% reductions of indoor radon concentrations in new homes (Angell 2012) o We assume similar reductions on indoor contaminated of concern associated with VI If ASD is installed for VI control, are there collateral impacts? o Obviously, reduction in indoor radon exposure and thus, in rates of lung cancer o There is evidence ASD may also reduce indoor moisture concentrations that may result in mold and condensation-related decay 3

4 In Perspective: Risk of Radon Exposure Radon reduction is collateral since it comes free with VI mitigation Radon is a Group 1 carcinogen o Occupational and residential radon exposure have been linked to risk of lung cancer For the general population in the U.S., residential radon exposure carries a risk of: 7:1,000 at 48 Bq/m 3 Radon cancer risk is 100 to 1,000 (1.3 pci/l) times greater than most VI 23:1,000 at 150 Bq/m 3 (4 pci/l) scenarios There is limited evidence that radon exposure carries additional risks, e.g., leukemia 4

Radon Control and Reduction of Lung Cancer (1:4) Use of passive and active soil depressurization in new and existing houses for VI control have a significant collateral benefit by reducing indoor

5 Radon Control and Reduction of Lung Cancer (1:4) Use of passive and active soil depressurization in new and existing houses for VI control have a significant collateral benefit by reducing indoor radon concentrations and thus, public heath burden related to radon-related lung cancer While indoor radon concentrations vary from house to house, the benefit of radon control will be greater in higher radon risk areas 5

6 Rn Control and Lung Cancer: A U.S. EPA Perspective In its reporting to the Office of Management and the Budget, U.S. EPA uses a matrix to estimate the impact of residential radon mitigation: o One premature death from radon-induced lung cancer is prevented each year for 1,543 homes that are mitigated Considering the primary service life of homes is about 100 years, this impact is ultimately much greater Use of ASD for VI control will have collateral benefits at lesser scale than that of radon-focused mitigation 6

7 Rn Control and Lung Cancer: A Second Perspective Gray (2009) and Steck (2010, 2011) examined cost-effectiveness of residential radon control o As part of the WHO International Radon Project, Gray constructed a model to examine the cost-effectiveness of public policy focused on two risk reduction options in an area of the UK where >5% of homes had indoor radon concentrations >200 Bq/m 3 (5.4 pci/l): Passive radon control in all new homes versus Finding existing homes >200 Bq/m 3 (5.4 pci/l) and active radon control in existing homes >200 Bq/m 3 (5.4 pci/l) Gray concluded that focusing on new homes was more cost-effective national policy than focusing on finding and mitigating existing homes with elevated indoor radon 7

8 Rn Control and Lung Cancer: A Third Perspective o Steck examined the cost-effectiveness of a radon risk reduction policy option focusing on mitigating all homes in two states (IA, MN) with a high proportion of homes with indoor radon concentrations >150 Bq/m 3 (4 pci/l) In these states, most of the radon-related lung cancer occur at concentrations above the U.S. EPA action level 150 Bq/m 3 (4 pci/l) Steck examined the number of lung cancers prevented over 74 years and the long-term cost of universal mitigation and he concluded universal mitigation in these two high radon states appeared to be a cost-effective method of saving lives 8

9 ASD Used for VI Control Appears to have Indoor Moisture Control Benefits While further research is needed, it appears that active soil depressurization used for VI control may collateral benefits by reducing moisture in basements and thus, lessening: o Asthma and respiratory problems o Condensation-related decay However, these potential collateral benefits are difficult to quantify 9

ASD Impact on Indoor Moisture For about 2 decades, there have been anecdotal reports that ASD reduced basement humidity, dampness, and musty odors o o Asthma and respiratory problems have been

10 ASD Impact on Indoor Moisture For about 2 decades, there have been anecdotal reports that ASD reduced basement humidity, dampness, and musty odors o o Asthma and respiratory problems have been associated with indoor dampness as well as condensation-related mold and structural decay To investigate the potential for multi-pollutant control of ASD, U.S. EPA initiated a research project in 2004 through Auburn University and Environmental Building Sciences, Inc. 10

11 EPA ASD Moisture Study Houses (Turk, 2007) Full basements o 2 block wall o 1 poured wall Moisture problems but no liquid water Reconfigurable ASD installed and cycled on/off 1 to 14 days and monitored over 12 to 18 months 11

12 EPA ASD Moisture Study Houses (Turk, 2007) Field tests and measurements o Air flow in and out of basement ~ outdoors, soil, upstairs PFT tracer gas ventilation tests, differential pressures, Soil gas/radon/moisture entry potentials, air leakage area ASD velocity pressures/flows, win speed an direction, + o Temperature and water content of air ~ outdoors, basement, soil, upstairs o Moisture storage and diffusion About 115 parameters recorded every hour at each house 12

13 EPA ASD Moisture Study Houses (Turk, 2007) As expected, ASD dramatically reduced indoor radon 13

14 EPA ASD Moisture Study Houses (Turk, 2007) Moisture extraction in gallons (kg) per day House Full ASD SSD Only Dehumidifier Percent ASD Exhaust from Basement PA01 13 (49) 10 (37) 46 PA02 15 (58) 13 (49) 72 PA03 19 (71) 11 (42) 1-4 (4-15) 72 14

15 EPA ASD Moisture Study Houses Summary o ASD caused significant reductions in basement moisture during non-summer months ASD impact on moisture related to many factors including Leakage of outdoor air into the houses due to ASD exhaust of basement air o ASD robustly controls indoor radon concentrations 15

16 References Angell, W 2012 Radon Control in New Homes: A Meta-Analysis of 25 Years of Research, Proceeding of the 2012 International Radon Symposium, Las Vegas, NV: American Association of Radon Scientists and Technologists Turk, B 2007 Moisture Impacts of ASD Radon Mitigation Powerpoint presentation. Turk, B and Hughes, J 2007 Exploratory Study of Basement Moisture During Operation of ASD Radon Control Systems Las Vegas, NM: Environmental Building Sciences, Inc. Turk, B and Hughes, J 2009 Movement and Sources of Basement Ventilation Air and Moisture During ASD Radon Control Las Vegas, NM: Environmental Building Sciences, Inc. 16

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