Radon 101 Plus

Radon Fundamentals

William J. AngellUniversity of Minnesota

© 2012 Board of Regents University of Minnesota

andand Persistent Questions

aboutaboutRadon and Weatherization

Affiliations and Disclosures

W.J. Angell– Professor of Housing,

College of Design, University of Minnesota• Director, Midwest Universities Radon Consortium

– Chair, Prevention and Mitigation Working Group, International Radon Project, World Health Organization

– Immediate Past President, American Association of Radon Scientists and Technologists

– Director, United Kingdom’s Radon Council. . . and long ago, Chairman of the Board,

Natural Resources Corporation

Pretest

1. Today, there are more homes with elevated radon than 25 years ago

True or False or Maybe or Sometimes or It Depends2. More U.S. lung cancer deaths are the result of exposure to

radon in homes with radon concentrations below EPA’s Threshold for Action than those above

True or False or Maybe or Sometimes or It Depends3. New houses have lower radon concentrations than older

houses True or False or Maybe or Sometimes or It Depends

4. The risk of lung cancer caused by indoor radon exposure requires years of exposure

True or False or Maybe or Sometimes or It Depends

Radon 101 Plus

This session will provide an overview of the following:

1.What is radon?

2.What is the evidence of radon health effects?

3.How does radon enter our homes?A. Who is responsible for indoor radon concentrations?

B. What is the relationship between energy conservation and indoor radon concentrations?

4.How do we control indoor radon concentrations?A. Mitigation in existing houses

B. The real story behind radon prevention in new homes

1. What is Radon?

• Radon is a radioactive gas – Part of the Uranium238 decay chain– As radon decays, it releases energy and mass and it

decays into a series of four short-live decay products• The decay products are the major source of health risk

– Outdoor radon concentrations are naturally occurring . . . • . . . but indoor radon concentrations are largely the

result of human actions . . .– . . . Stay tuned, more later . . .

U.S. Radon Measurement Units

• One picoCurie per liter (pCi/L) is 2.22 disintegrations per minute within a liter– This comes from the fact that one Curie is 37 billion

disintegrations per second (disintegrations per second [dps])

– One picoCurie is one trillionth of a Curie, or 0.037 decays per second• There are 60 seconds in a minute:

60 x .037=2.22, or 1 pCi/L is 2.22 dpm• Thus, a 1,000 sq. ft. home with 4 pCi/L = almost 2

million radioactive decays per minute

Marie Curie (1867-1934)

Polish physicistMarie coined the term

radioactivity in 1898 and she is the first woman to earn the

Noble prize

Another Take at the Concept of pCi/L

• For reference, a golf ball is about 1.6 inches in width– If the golf ball was shrunk to 1.3 inches and if it was Radium226, it

would weigh about 1 pound

• Take a ball bearing of 0.28 inches diameter and if it was Radium226, it would weigh about 1 gram which would produce 1 Curie of radioactivity– Now take this ball bearing, and cut it into a million pieces

– Now take 1 of these million pieces and cut it into a million pieces

– One of these pieces would produce

• One picoCurie/Liter of radioactivity . . .

• . . . or 2.2 radioactive disintegrations per minute

Hidden

2. What is the Evidence of Radon Health Effects

• First, what are the health effects of radon?– Lung cancer is the strongest documented risk– Some forms of leukemia have been associated

with miner radon exposure in ecological studies• Case-control or cohort studies are needed

– Multiple sclerosis has been associated with indoor radon exposure in one ecological study

Notes:• Cohort studies measure radon concentrations and track the exposed population

into the future to assess the frequency of lung cancer • Case control studies compare the multi-year radon concentrations in homes of

lung cancer victims versus non- lung cancer victims• Ecological studies are not used for risk assessment

Evidence from Miner Cohort Studies

• More than 20 underground miner studies in U.S., Canada, Europe, Australia, and China• 24 years ago, radon and its short-lived radon decay products were

classified as a known human carcinogenic • The U.S. National Cancer Institute (NCI) pooled data from 11

studies with over 60,000 miners Linear dose-response, i.e., RDP exposure and lung cancer relationship

increased with increased exposure Little credible evidence for a threshold effect In later years,

Higher risk associated with exposure received at low rates Increased risk for nonsmokers confirmed

• Miner studies irrefutably document radon risk

Lifetime Lung Cancer Death Risk per Person (based on miner data; out of 1,000; 2003)

20201010 88 44 2 2 1.31.3

36 1815 7 4 2

260150120 62 32 20

Never Smokers

CurrentSmokers

GeneralPopulation

110 56 45

23 (1:50)

12 7

pCi/LpCi/L

Note: Compared with EPA’s earlier risk assessment, the current risk assessment for never smokers increased from 2 to 7/1,000 and smokers from 29 to 62/1,000

Evidence from Residential Case-Control Studies

• More than 40 residential case-control studies of indoor radon exposure and lung cancer– Data has pooled from

• 7 North American studies (2005)• 13 European studies (2004)• 2 Chinese studies. . . and these pooled studies lead the World Health

Organization to recommend a radon reference level one third lower than the current U.S. 4 pCi/L

action level – The pooled data from these studies is currently being

analyzed and this analysis will be the most compelling risk assessment of indoor radon in our lifetime

0 5 10 15 200

1

2

3 IA CT MO-1 UT MO-2 Winn NJ-1

Od

ds

ra

tio

Radon concentration (x), pCi/L

Results of Results of Major Major Radon Radon Studies of Studies of Lung Lung CancerCancer

0 5 10 15 200

1

2

3

Od

ds

ra

tio

Radon concentration (x), pCi/L

NA pooled RRsEPAEPA

GansuShenyang China pooled RRs

Pooled European RRs

Pooled miners

© 2011 Board of Regents University of Minnesota

Radon Compared to Other RisksRadon Compared to Other Risks (EPA 2010 A Citizen’s Guide

to Radon; EPA; Consumer Product Safety Commission, 2003; CDC. Unintentional non–fire-related carbon monoxide exposures—United States, 2001-2003. MMWR Morb Mortal Wkly Rep. 2005;54[2]:36-39 )

3. How Radon Enter Homes

• First, it is a question of source– The vast majority of indoor radon originates from the soil

and geology under the home– Seldom are the following significant sources:

• Emanation of radon from building materials • Water from private drilled wells

• Second, it is a question of driving forces– Air pressure difference between the indoors and the soil is

the primary transport mechanism• Pathways through the soil and the foundation are usually

not major determinants of indoor radon concentrations

Radon Entry and Concentrations

Uranium

Radium

Radon100s - 100,000s pCi/L – 1,000s to 1,000,000 Bq/m3

1.3 pCi/L U.S. annual

average indoors in

homes (living areas) – about 50 Bq/m3

0.4 pCi/L U.S.

annual average

outdoors – about

15 Bq/m3

pCi/L is a unit of radon radioactivity (or ‘activity’) concentration

U.S. Radon Zone Map: Radon Sources+

Map based on Map based on

1.1. Geologic factorsGeologic factors

2.2. Aerial surveys ~ Aerial surveys ~ uranium prospectinguranium prospecting

3.3. Results of home Results of home surveyssurveys

4.4. Home foundation typeHome foundation type

5.5. Soil surveys Soil surveys

Expected average short term Radon (pCi/L):

Red = Zone 1 > 4.0 High probability

Orange = Zone 2 > 2 < 4.0

Yellow = Zone 3 < 2.0 Low probability

Areas of high and low radon may be found in any zone

Indoor Radon in a Community

Source: Mike Mudrey, 2005, UW-Madison

Test Results < 4 pCi/L

4 - 10 10 - 12 12 - 16 16 – 20 20 – 30

>30

The Lesson

• Radon maps are relatively poor indicator of indoor radon concentrations in any building

• Radon concentrations vary – House to house– Apartment to apartment– School classroom to classroom

• The only way to know the radon concentration– Is to measure

• Each house• Each apartment• Each school classroom

So, Why the Variation?

• Each house in ground contact has a distinct connection with the soil, in large part, due to subtle differences in air pressure relationships between the indoors and the soil

• What about ventilation differences and indoor radon concentrations?– Or the elephant in the energy conservation

community• Does air sealing increase indoor radon concentrations?

Can Air Tightening Increase Indoor Radon Concentration? (1:2)

• The short answer is yes. Some of the studies reveal:– Radon concentrations tended to increase with decreases in

ventilation rates according to a study by Hollowell (1980) in 17 houses with energy saving features

– Average 42% increase in radon concentrations over pre-weatherization concentrations were observed in a study by Offermann (1981) of ten State of Washington homes receiving weatherization retrofits with an average air leakage reduction of 32%

– The more airtight energy efficient group had six month winter indoor radon concentrations 3.2 times greater than that of the conventional group in a study of 14 New York State energy efficient homes (11 of which were solar) and 13 conventional homes in by Fleischter (1982)

Can Air Tightening Increase Indoor Radon Concentration? (2:2)

• The better answer is that it is more complex than simply air tightness– “. . . in evaluating the effects that a change in the air-exchange

rate may have on the indoor radon concentrations, one must consider the change in radon entry rate that may result” according to a study by Nazaroff (1985) were a Chicago area home that was monitored for five months

– “It appears that the major cause of the observed differences in indoor radon concentration is variation from one house to another is the rate at which radon enters houses from its sources" according to Nero (1983) in a concurrent study of indoor radon concentrations and infiltration rates in 17 energy efficient houses and 84 conventional houses

Three Forthcoming Papers

1. A study in a very large county in a northeast U.S. state that compares pre- and post-weatherization indoor radon concentrations in about 70 homes

2. A U.S. DOE study of about 450 homes in about 38 states that compares pre- and post-weatherization indoor radon concentrations

3. A paper I am co-authoring with a colleague that compares pre- and post-weatherization indoor radon concentrations above 4 pCi/L in about 1,200 houses

1. NE U.S. Weatherization & Rn Study

• One county, about 70 homes– 2 to 4 day Rn tests in basements

• QC: 100% duplicates, 3% blanks, 4 spikes– Weatherization air tightening:

• 60% had air exchange rates that declined < 30%• 40% had air exchange rates that declined > 30%. . . But did not see a relationship between air-tightening

and changes in indoor radon concentration. . . Probably because of the small size of the study

• Study involved about 500 houses (75%) and mobile homes (25%) in 35 states– 7 day tests– QA/QC followed EPA guidance

• The study is in the final review stage– It is expected to be released soon (not later than June)

• It is inappropriate for me to comment on the findings and conclusion of the report

• . . . But I will say the findings appear to be consistent with the findings I will discuss in the next few slides

2. U.S. DOE WAP and Radon Concentrations

3. Forthcoming Weatherization & Rn Paper

Site/EPA Zone

TotalHouses Tested

FinalAir-

ChangeRate/ Hour

Homes BeforeWeatherization Mitigation Need After Weatherization

Less Than

4 pCi/L

4 pCi/L or

More

MitigationNow

Required

Mitigation No Change in Status

Mitigation No Longer Required

Mitigation Still

RequiredL/1 149 0.15P/1 139 0.2B/1 81 0.3Y/2 333 0.4W/2 487 0.7All/

1 and 2 1188 0.4

Y/2Control 265 0.8

Uncertainty Versus Do No Harm

• Of course. all studies have uncertainty and we could spend a lot of effort debating uncertainty

• But I argue, why leave low-income families with a major environmental toxicant when:– It costs so little to fix the problem and . . . – . . . nationally, less than 10% of houses will need

mitigation• Of course, some local weatherization programs will have

a higher proportion of houses that will need to be fixed and some will have a lower proportion

So Who is Responsible for Indoor Radon Concentrations ?

• The architect or designer of the house or building– EPA recommendations since at least 1975– ASTM E 1465 since 1990– IRC Appendix A since 1995

• The builder– Same as above plus NAHB recommendations since 1987

• To a degree, the occupant(s) doing “normal” things• Those who modify the house or building, e.g.,

– Basement groundwater control contractors– Energy conservation contractors/programs

• . . . and those modify house to soil air pressure relationships

4. How do we Control Indoor Radon Concentrations?

• In existing houses, the radon mitigation work horse is active soil depressurization (ASD) – Meaning we use a fan to

• Reverse the air pressure differences between the house and the soil

• Lower the radon concentration in the soil

• In new houses, passive soil depressurization or ASD may be used– Passive depressurization relies upon thermal buoyancy

in the vent stack to control indoor radon concentrations

30

Active Soil Depressurization Active Soil Depressurization (ASD; Existing Houses)(ASD; Existing Houses)Active Soil Depressurization Active Soil Depressurization (ASD; Existing Houses)(ASD; Existing Houses)

Inline fan outside conditioned spaceInline fan outside conditioned space Discharge away from potential Discharge away from potential

exposure exposure

Performance indicatorPerformance indicator LabelingLabeling

Suction of subslab materialSuction of subslab material 3 to 4” PVC or equivalent pipe3 to 4” PVC or equivalent pipe

Operating instructionsOperating instructions Post mitigation testing Post mitigation testing

© 201 1 Board of Regents University of Minnesota

Passive Soil Depressurization (PSD; New Houses)

• Nine studies over the past 24 years– 458 houses in 14 states– 12 to 59% radon reduction with an open vent pipe

compared to a capped vent pipe (control)• PSD installed, according to EPA recommendations or

ASTM E1465, produced greater radon reduction (~50%)– Two of the studies compared PSD and ASD

• NAHB (1994) reported 47% radon reduction with PSD versus 86% with ASD

• PA (1999) reported 87% (total?) radon reduction when adding a fan to PSD systems

What About Sealing as a Radon Control Technique?

• Not recommended as a stand alone radon control technique– World Health Organization– U.S. Environmental Protection Agency– Health Canada

• Important as a component of ASD – Improves the effectiveness and efficiency of ASD systems– Reduces ASD energy penalties

• Leakage of conditioned air into the system• Smaller fan is often feasible

– . . . and critically important to PSD

Why Does It All Matter?

Cancer Survivors Against Radon (CanSAR) Founders

. . . Because There Victims

Quiz

• Who is this kid in the 1950s holding a Micro-R (gamma) meter?– Hint: the kid is somewhere in

this room today

Thank You