1. Understanding Exposure Calculations Radon Bq/m³ Levels and mSv Dose/Year Comparisons CARST 7th Annual Ottawa, Ontario April 24, 2018
Disclaimer: Please try these comparisons at home and let me know if you come up with something different!
Greg Baytalan B.Sc., C.P.H.I.(C)
Specialist Environmental Health Officer
Interior Health Authority
Thank you for opportunity to provide update to the presentation provided to City Council last April.

2. Workplace Radon

3. Radon Units
USA measurement is picocurie (pCi) 1 pCi/l = 2.22 disintegrations/min/liter International Systems (S.I.) measurement Becquerel (Bq) 1 Bq/m³ = 1 disintegration/second/m³ (disintegration = 1 alpha particle release) 1 pCi = Bq Commonly used units conversion in air 1 pCi/l = 37 Bq/m³

4. Radon Guideline, Action Levels, Reference Level
Canada Guideline 200 Bq/m³ (5.4 pCi/l)
(Health Canada recommends lowering radon levels to as low as reasonably achievable)
USA EPA Action Level 4 pCi/l (148 Bq/m³)
(EPA recommends homeowners consider mitigation if levels between 2 & 4 pCi/l (74 & 148 Bq/m³) found
WHO Reference Level 100 Bq/m³
(WHO recommends countries adopt a 100 Bq/m³ reference level)

5. Health Canada Cross-Country Home Radon Survey
2009 – 2011, 18,081 participants, 13,976 followed through for 77.3% participation
% above the 200 Bq/m³ Canadian Guideline varied provincially, with New Brunswick the highest 24.8, Manitoba 23.7, BC 7.9%
But, cross-country high readings, localized hot spots; BC Kootenay-Boundary 29.3% above Guideline; check your local health district
BC Lung Radon Aware Castlegar survey, 59% of homes >200 Bq/m³ (158 test kits)

6. Canadians typically Spend 90% of time indoors (Canadian Lung Association)
We get comfortable in our homes, yet high radon could be lurking within
Highest BC House I’m Aware of; Slocan Valley Rental House
Neighbour suggested testing…
Basement 37,000 Bq/m³
Main Floor 7,800 Bq/m³
Post Mitigation by IRPS Ltd.,
Basement 29 Bq/m³
Main Floor 22 Bq/m³

7. Radon is natural, but what isn’t natural is the way we build…

8. ↑↑↑↑↑
Stack
Effect
Natural Resources Canada, licensed under the Open Government Licence – Canada  

9. Radon in the Workplace
BC Occupational Health & Safety Regulationhttps://
Section 7.18(2) Division 3, Radiation Exposure does not apply to natural background radiation, except as specified by the Board
Naturally Occurring Radioactive Material (NORM)
Section 7.19 Workers exposure to ionizing radiation not to exceed 20 mSv/year effective dose (pregnancy 4 mSv/year)

10. Radiation Comparisons – Briefly
Canada Ave. Effective Dose 1.8 mSv/yr of which 0.9 mSv is inhalation (Winnipeg is 3.2 mSv from inhalation alone)
Typical Chest X-ray 0.1 mSv, CT 10 mSv
Cross-Canada flight 0.02 mSv
N. Iran 260 mSv/yr (natural background)
Canada effective dose limit for the public is 1 mSv/yr (can’t exceed 1 mSv/yr above the normal background, if > 1 in work performance, then fall into nuclear worker category)
Nuclear worker effective dose 50 mSv/yr and 100 mSv in 5 consecutive years

11. Comparisons Continued
Reporting & monitoring demonstrates the average annual effective dose to the most exposed nuclear worker to be 5 mSv/yr
Average risk of Cancer in Canada is about 25%
Scientific consensus of 4% increase per 1000 mSv (exposure = % = 29%)
By design, if nuclear worker received the max. allowable dose (20 mSv/yr on ave.) every year for 50 years = 1000 mSv thereby limiting their workplace risk to 4%
It is a violation of law for a radiation worker to exceed annual dose limit, admin. & control alarms sound at 1/10th the limit

12. Comparisons Continued
At Fukushima maximum effective dose was 679 mSv; 6 workers received >250 mSv
Expectation of 5 mSv/yr requires wearing of dosimeter
Big issue if a nuclear worker receives 10 mSv dose
“working level” (WL) used for the calculation of lung exposure to alpha particle energy release (Mega Electron Volts (MeV))
1 working level month (WLM) = 1 WL exposure for 170 hours

13. Comparisons Continued
WLM enables calculation of mSv/yr dose
100 pCi/L = 3700 Bq/m³ = 1 WL at perfect equilibrium ratio (impossible to have 1:1 decay products and radon ratio)
By definition
pCi/L x 1 WL/100 pCi/L = WL
Or…0.01 WL = 1 pCi/L
0.4:1 generally used for indoor radon, 0.6 in dusty environments
Assuming 0.4 Equilibrium Factor (EF 40% attached DP)

14. Formula X Bq/m³ exposure for Y hrs/mth (or hrs/mth, hrs/yr)
Bq/m³ x 1 pCi/L/37Bq/m³ = x pCi/L
Again
By definition pCi/L x 1 WL/100 pCi/L = WL or…0.01 WL = 1 pCi/L
WL x 0.4 EF = WL at 0.4 Equilibrium Factor
hrs/mth exposure at WL
WL x hrs/mth/170 = WLM
WLM x 12 = WLM/yr
(4 WLM corresponds to an effective dose of 20 mSv at 5 mSv/WLM)

15. Formula Continued
Convert to mSv/yr exposure International Commission of Radiation Protection (ICRP) applied a 5 multiplication factor to the WLM/yr exposure for lung exposure WLM/yr x 5 mSv/WLM = mSv/yr But, new revised January 2018 ICRP Document #137 uses a 10 multiplication factor Now WLM/yr x 10 mSv/WLM = mSv/yr
Last 6 slides includes information from the Canadian Nuclear Commission website
and communication with Radiation Safety Institute of Canada, National Laboratories, Saskatoon

16. Exposure Comparisons Keep in mind:
Canada effective dose limit for the public is 1 mSv/yr (can’t exceed 1 mSv/yr above the normal background, if > 1 in work performance, then fall into nuclear worker category)
BC OH&S Regulation, Section 7.19 Workers exposure to ionizing radiation not to exceed 20 mSv/year effective dose (pregnancy 4 mSv/year)

17. Examples
7800 Bq/m³ for 24 hrs/day 365 days/yr 7800 Bq/m³ x 1 pCi/L/37Bq/m³ = 211 pCi/L 211 pCi/L x 1 WL/100 pCi/L = 2.11 WL 2.11 WL x 0.4 = WL (at 0.4 Eq.Factor) If 730 hr/mth at WL WL x 730/170 = 4.29 WLM 4.29 WLM x 12 = 51.5 WLM/yr (4 WLM corresponds to an effective dose of 20 mSv at 5 mSv/WLM) 51.5 WLM/yr x 5 mSv/WLM = mSv/yr 51.5 WLM/yr x 10 msV/WLM = mSv/yr

18. Exposure Comparisons Continued
At 3156 Bq/m³ for 7.5 hrs/day 5 days/wk
= mSv/yr at 5 Factor
= mSv/yr at 10 Factor
At 1173 Bq/m³ for 7.5 hrs/day 5 days/wk
= 6.71 mSv/yr at 5 Factor
= mSv/yr at 10 Factor
At 300 Bq/m³ for 6 hr/day 5 days/wk
= 1.37 mSv/yr at 5 Factor
= mSv/yr at 10 Factor
Aligns with effective dose values presented by Dr. John Harrison, ICRP
300 Bq/m³ at home ~7000 hrs = 14 mSv/yr
300 Bq/m³ at work ~2040 yrs = 4 mSv/yr

19. See what you get; do some exposure scenarios & include Total Daily Exposure…
- Indoor radon contributes a significant portion of the annual radiation dose, and the workplace may be a large portion of this dosage. - It is therefore reasonable for radon to be on the agenda of workplace building maintenance, and within Occupational Health & Safety provisions. - Awareness testing at work places serves to promote testing at home and indoor leisure environments.

20. Thank You Greg Baytalan greg.baytalan@interiorhealth.ca
(250) ext