1. Lisa Gregory, PhD AARST Symposium October 2, 2018
Investigation of Radon Decay Products: Case Studies and Review of Key Scientific Literature
Lisa Gregory, PhD
AARST Symposium
October 2, 2018
2018 International Radon Symposium™

2. Outline 2018 International Radon Symposium™
Radon Decay Product (RPD) Background
Important Factors
Alpha Particles
Working Levels
Literature Review
Case Study 1
Case Study 2
Summary
Recommendations
Questions
2018 International Radon Symposium™

3. Radon Decay Product Background
RDPs come from the radioactive decay (“breakdown”) of radon gas.
A portion of these RPDs “plate out” and attach to surfaces and are not inhaled.
The other portion of these RDPs stay suspended in the air and may be inhaled.
Some inhaled RDPs release alpha particles in lungs that can damage lung tissue and cause cancer.
Half Life
Radon-222
3.8 Days
α γ
Polonium-218
3 Minutes
α γ
Lead-214
27 Minutes
β γ
Bismuth-214
Ones in red are the inhalable RDPs that can release alpha/beta/gamma particles and damage lung tissue. Lead is stable.
Polonium has a half life of 3 minutes and appears to be considered more dangerous than the other RDPs (perhaps due to short half life or the release of alpha particles). Will try to find more info about it.
Can try to find better picture of RDP breakdown chain but this is based on Doug’s.
19.7 Minutes
β γ
Polonium-214
.0096 Seconds
α γ
Lead-210
19.4 Years
2018 International Radon Symposium™

4. Important Factors 2018 International Radon Symposium™
The potential that someone may experience damage to lung tissue by an alpha particle is directly related to the amount of suspended RDPs that are inhaled and reach the lung tissue.
Once RDPs adhere to lung tissue, the probability that irreparable damage may occur increases with:
Shorter half-life
Higher energy alpha particles
Thinner protective layer of lung surface epithelial cells
Lower genetic resilience
Random: It’s only by chance whether the alpha particle hits the DNA of a sensitive cell and causes damage.
2018 International Radon Symposium™

5. Alpha Particles are the “Bad Guys”
Isotope
Half-life
Alpha Particle Energy
Penetration into Lung Tissue
radon-222
3.8 days
5.49 Mev
41 microns
polonium-218
3 minutes
6.00 Mev
48 microns
polonium-214
164 micro-sec
7.69 Mev
71 microns
2018 International Radon Symposium™

6. Alpha Particles are the “Bad Guys”
Mucus layer (~10 microns thick)
Epithelial layer (40-80 microns thick)
Basal epithelial cells frequently divide and are sensitive to development of cancer
Alpha particles with higher energy penetrate further and have greater probability of causing double strand DNA breaks
DNA double strand breaks are hard to repair
DNA α
2018 International Radon Symposium™

7. RDP Equilibrium Factor
The Equilibrium Factor (EF) is the ratio of suspended RDPs to the total RDPs produced by radon gas.
EFs were originally determined by uranium mining studies that measured both radon and RDP working levels (WL).
Different organizations assume different EFs.
Currently, the EPA and World Health Organization assume an EF of 40%.
40%
Airborne
Breathable
Measureable
Radon-222
RDPs
Plated Out
Not Breathable
Not Measurable
Should this also be replaced with Miner RDP study info? EF is pretty important as we talk about plate-out quite a bit but these folks may already know this info…
Mention that using know working levels and an assumed EF is how we now have our 4 pCi/L guidance. NO one was even looking at radon concentration before 1984.
EPA uranium miner technical report.
60%
2018 International Radon Symposium™

8. Equilibrium Factor Assumptions
EF = 0.4
EF = 0.5
EF = 1.0
40% Suspended
Current EPA protocol
World Health Org.
50% Suspended
Past EPA protocol
100% Suspended
OSHA assumption
2018 International Radon Symposium™

9. Working Level (WL)
RDPs concentration measured in WL is a true measure of actual exposure to radiation
WL was developed in the 1950s and is commonly used to measure RDP exposure by underground miners
One WL refers to the concentration of RDPs in equilibrium with 100 pCi/L of radon
A WL of 0.02 is referred to in U.S. law as the “not to exceed” radiation level
Radon levels are not accurate measures of exposure to radiation and the guidance of 4.0 pCi/L is not in codified in law
2018 International Radon Symposium™

10. 2018 International Radon Symposium™

11. Literature Review
2018 International Radon Symposium™

12. AARST Protocol (2014) 2018 International Radon Symposium™
AARST and EPA used to have more information regarding RDPs. This information was removed for awhile.
The most recent AARST protocol has included RDP measurement info.
Current protocol tells how RDPs can be used to further characterize home and room conditions.
Says that RDP measurements alone do not tell you everything and cannot be solely used to assess mitigation needs.
This info has been historically absent.
2018 International Radon Symposium™

13. Seasonal Behavior of RDPs (2014)
Essential to characterize attached vs. unattached RDPs
Observed highest RDP dose during winter and lowest during Spring
We see similar seasonal findings between RDP dose and radon concentration
Due to seasonal differences of aerosol particle sizes and RDP dose
The place where this experiment occurred (Japan) has warm spring followed by a rainy season, then a humid/less rainy summer and a mild autumn.
Seasonal variation occurs with radon concentration, RDP dose, and aerosol particles.
-Radon concentration: Higher in winter due to poor ventilation, stack effect, and rooms staying closed. Reverse in spring and summer
-RDP dose: highest in the winter and lowest in the summer. Influenced by both radon concentration and RDP working levels.
-Aerosol particles: their size and distribution is needed for accurate assessment by the lung dose model. Particles are bigger in warm/humid/moist weather (hygroscopic particles grow as they move through moist air) so they are less likely to enter into lungs. Less moisture in winter leads to small particles which can be more easily inhaled.
Effective dose is based on the widely accepted lung dose model which assumes affective RDP dose based on particle size and density as well as radon and RDP concentration.
Moderate radon/RDPs/dosage in rainy season may be attributed to reduced ventilation greater radon entry due to rainstorms, and short-term tests.
2018 International Radon Symposium™

14. Deposition of Radon Progeny (1997)
Investigates the concept of RDP plate-out and the use of different deposition models
Homogeneous turbulence model
Higher fan speeds increase air turbulence and therefore RDP deposition rates
Changes in air temperature can also cause mixing and higher deposition rates
Concluded that increased air circulation lowered working levels, thereby lowering EF
Cheng used different velocity profiles in order to compare RDP deposition rates.
Homogeneous turbulence model: assumes that at the center of a room the air is well mixed and aerosol concentration is uniform. Supported by many laboratory studies.
Aerosols were a mixture of fine and ultrafine silver and latex particles.
Danger can come from RDPs attaching to dust, entering lungs, and shooting alpha particles. In areas with no dust however, air flow is totally beneficial.
2018 International Radon Symposium™

15. Effect of Air Cleaners on Radon Progeny (1996)
Suggests there are three main ways to control RDPs
Prevent radon infiltration
Dilute radon/RDPs inside the house
Directly remove RDPs
Utilized a model to reflect nasal/oral RDP deposition
Most air cleaners alone are insufficient to reduce RDPs
They can greatly reduce aerosols
Combination of air movement and air cleaners can work well in reducing RDPs
One study, Rudnick et al (1983) suggests that air cleaning systems may increase radon risk so the EPA did not endore air cleaners as a viable option.
UPDATE: upon reading the abstract, the Rudnick article seems rather favorable for using cleaners and fans to reduce RDPs…odd.
Findings show that air cleaners pose no risk in increasing radon or RDP concentration (something that seems to be a common misconception)
Dosimetric model: rapidly evolving model. Considers respiratory tract, nasal and oral deposition.
2018 International Radon Symposium™

16. Case Studies 2018 International Radon Symposium™
Both case studies were performed at the Naval Warfare Center in Carderock, Maryland.
2018 International Radon Symposium™

17. Lowering RDP Risk 2018 International Radon Symposium™
The primary goal of radon mitigation is to reduce Radon Decay Product (RDP) exposure.
Reduce radon gas concentration (“source” method)
Direct reduction of RDPs (“direct” method)
Methods for lowering RDPs that do not affect radon gas concentrations include:
Increasing air circulation
Increasing air filtration
These methods can be useful for areas that are unsuitable for traditional radon mitigation techniques.
2018 International Radon Symposium™

18. Study Descriptions
“Mini” studies were performed in two separate rooms at a military installation after short-term radon tests resulted in elevated radon levels.
Studies investigated effects of HVAC or air filtration/ movement on radon and RDPs.
Purpose of these studies were to investigate radon and RDPs in response to variable conditions and to determine effectiveness of HVAC alterations as a radon mitigation approach.
2018 International Radon Symposium™

19. Office X First floor office located over slab on grade.
Initial short-term test showed radon was elevated compared to adjacent rooms.
Office X: 12.3 pCi/L
Adjacent rooms: <4.0 pCi/L
Each office had its own HVAC unit located on exterior wall.
We were told the HVAC unit was plumbed to fresh air.
We were told that occupant sometimes turned off his HVAC unit.
2018 International Radon Symposium™

20. Office X: Case Study 1 Hypothesis 1:
We measured continuous radon and continuous RDPs with HVAC ON for two days and then OFF for two days. This study ran from Wednesday December 6th to Monday December 11th 2017.
If the HVAC is bringing fresh air into the room, then when the HVAC is ON ___________________________________.
Radon and RDPs will increase
Radon and RDPs will decrease
Radon and RDPs will remain the same
Radon and RDPs will have variable responses
Hypothesis 1:
Move hypo title
2018 International Radon Symposium™

21. Office X: Case Study 1 Hypothesis 2:
If the assumed equilibrium factor of 50% is correct, then an increase of radon over 4 pCi/L will be associated with an RDP level ___________ than 0.02 WL.
greater
lower
the same as
impossible to predict
Hypothesis 2:
2018 International Radon Symposium™

22. Office X: Case Study 1 Results
Talk about this graph:
-Operation of HVAC unit is drawing sub-grade radon into the room
-In both cases, we see that RDPs are below guidance
--When HVAC is on, high air circulation is causing RDPs to plate out
--When HVAC is off, lower radon activity is resulting in fewer RDPs in the room
Conventional radon mitigation thought would have you say that turning off the HVAC would be the most beneficial for the room. But that’s not necessarily the case.
Mention EF

23. Office X: Case Study 1 Conclusions: Investigate HVAC! Action Item?
HVAC was NOT bringing fresh air into office.
HVAC seemed to be “mining” radon gas from under slab.
Investigate HVAC!
RDPs were way under the action level of 0.02 WL even with radon concentrations almost at 8.0 pCi/L.
Actual EF was much lower than assumed EF when HVAC ON.
Action Item?
Remember you have 2 questions that you’re asking here. They will fade in when you click forward.
Why?
Because increased air circulation from the HVAC fan was causing more RDP plate out to surfaces!

24. Office X: Investigate HVAC
Fresh air intake blocked!
Talk about this graph:
-Operation of HVAC unit is drawing sub-grade radon into the room
-In both cases, we see that RDPs are below guidance
--When HVAC is on, high air circulation is causing RDPs to plate out
--When HVAC is off, lower radon activity is resulting in fewer RDPs in the room
Conventional radon mitigation thought would have you say that turning off the HVAC would be the most beneficial for the room. But that’s not necessarily the case.

25. Unit Ventilator pulling soil gas into unit!
Air gap to soil!
Talk about this graph:
-Operation of HVAC unit is drawing sub-grade radon into the room
-In both cases, we see that RDPs are below guidance
--When HVAC is on, high air circulation is causing RDPs to plate out
--When HVAC is off, lower radon activity is resulting in fewer RDPs in the room
Conventional radon mitigation thought would have you say that turning off the HVAC would be the most beneficial for the room. But that’s not necessarily the case.

26. Radon was reduced to 0.9 pCi/L with HVAC ON!
Office X
Solution:
Unblock air intake
Seal opening
Retest using CRM
Talk about this graph:
-Operation of HVAC unit is drawing sub-grade radon into the room
-In both cases, we see that RDPs are below guidance
--When HVAC is on, high air circulation is causing RDPs to plate out
--When HVAC is off, lower radon activity is resulting in fewer RDPs in the room
Conventional radon mitigation thought would have you say that turning off the HVAC would be the most beneficial for the room. But that’s not necessarily the case.
SOLUTION WORKED!
Radon was reduced to 0.9 pCi/L with HVAC ON!
2018 International Radon Symposium™

27. Room Y
Small, basement room with smaller sublevel accessible through door that typically stays open.
Room unsuitable for traditional mitigation.

28. Case Study 2: Room A37
Results support the idea that RDP reduction is possible through increased air flow and filtration
Working levels were much lower than expected given radon concentration and assumed EF
If RDPs and radon were analyzed together, invasive mitigation may not be needed

29. Room Y: Case Study 2 Hypothesis 1: 2018 International Radon Symposium™
Measure continuous radon and continuous RDPs for two days under normal conditions and then with fan and filters ON for four days. Study ran from Monday with HVAC ON for two days and then OFF for the rest of the trial. Study ran from Monday 26 February to Monday 3 March 2018.
If air filtration and circulation increase RDP plate out, then RDP measurements will _____________________.
increase
decrease
exhibit no change
Hypothesis 1:
I don’t think this description is true
2018 International Radon Symposium™

30. Room Y: Case Study 2 Hypothesis 2: 2018 International Radon Symposium™
When fan/filter are OFF, if there are relatively high radon levels than RDPs should be relatively ____________.
high
low
no different
Hypothesis 2:
2018 International Radon Symposium™

31. Room Y: Case Study 2 Power-on Power-out Talk about this graph
RDPs are always below action levels but drop to below detectable limits when the air cleaners and fans are turned on.
Gap in RDP data is from a power outage but we see that once power is restored, RDPs are detectable again but still well under EPA guidance while radon spikes.
Weather: Average for this week was around 55 degree high and 38 degree low. Quite chilly. There was some light rain on Friday and Saturday which may have affected radon?
Can also discuss the slight cyclical appearance of RDP working levels at the beginning of the graph.
Power-on
Power-out

32. Room Y: Case Study 2 Conclusions:
Power outage resulted in reduction of negative pressure in room as evidenced by greatly reduced radon levels.
Room has definite radon issue (space is under negative pressure).
Action Item?
Investigate HVACs!
Air filter/movement reduced RDPs to below detectable levels (similar to the air outside) even in the presence of high radon levels.
Room conditions are extremely amenable to RDP plate out.
Why?
Talk about this graph:
-Operation of HVAC unit is drawing sub-grade radon into the room
-In both cases, we see that RDPs are below guidance
--When HVAC is on, high air circulation is causing RDPs to plate out
--When HVAC is off, lower radon activity is resulting in fewer RDPs in the room
Conventional radon mitigation thought would have you say that turning off the HVAC would be the most beneficial for the room. But that’s not necessarily the case.
Very large surface to volume ratio and
the air movement from ceiling unit.

33. Room Y Investigations

34. Takeaways from these studies
HVAC investigation/alteration is a cheap radon mitigation technique that can work to fix radon issues in work spaces.
The military has spaces that are not suitable for traditional mitigation techniques, which are often costly and require penetrations through floors and/or walls.
Consider measuring RDPs and using air movement/ filtration as a relatively cheap and easy technique to ensure the space poses no risk even in the presence of radon levels above 4.0 pCi/L.
Consider measuring RDPs as a standard practice in any space with high radon levels just to confirm the RDP WLs. We have had difficulty finding a space with RDP WL even close to 0.02 WL. Showing low WLs can protect the office owner against possible litigation.
The unique situations here are the HVAC drawing in radon (so we turned it off) and A37 not being suitable for radon mitigation.
2018 International Radon Symposium™

35. Recommendations
2018 International Radon Symposium™

36. Questions?
2018 International Radon Symposium™