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Workplace Radon

Understanding Exposure Calculations Radon Bq/m³ Levels and mSv Dose/Year Comparisons CARST 7 th 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)

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Workplace Radon

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  1. Understanding Exposure CalculationsRadon Bq/m³ Levels and mSv Dose/Year ComparisonsCARST 7th AnnualOttawa, OntarioApril 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

  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 = 0.037 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) • https://www.canada.ca/en/health-canada/services/environmental-workplace-health/radiation/radon/cross-canada-survey-radon-concentrations-homes-final-report.html

  6. We get comfortable in our homes, yet high radon could be lurking within Canadians typically Spend 90% of time indoors (Canadian Lung Association) 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  http://open.canada.ca/en/open-government-licence-canada

  9. Radon in the Workplace BC Occupational Health & Safety Regulationhttps://www.worksafebc.com/en/law-policy/occupational-health-safety/searchable-ohs-regulation/ohs-regulation/part-07-noise-vibration-radiation-and-temperature#B0A11CFEA21A41CCB24EA6B7054E8644 • 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 = 25 + 4% = 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 http://nuclearsafety.gc.ca/eng/resources/radiation/introduction-to-radiation/radiation-doses.cfm#2 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 = 0.844 WL (at 0.4 Eq.Factor) If 730 hr/mth at 0.844 WL 0.844 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 = 257.50 mSv/yr 51.5 WLM/yr x 10 msV/WLM = 515.00 mSv/yr

  18. Exposure Comparisons Continued At 3156 Bq/m³ for 7.5 hrs/day 5 days/wk = 18.06 mSv/yr at 5 Factor = 36.12 mSv/yr at 10 Factor At 1173 Bq/m³ for 7.5 hrs/day 5 days/wk = 6.71 mSv/yr at 5 Factor = 13.42 mSv/yr at 10 Factor At 300 Bq/m³ for 6 hr/day 5 days/wk = 1.37 mSv/yr at 5 Factor = 2.74 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) 469-7070 ext. 12273 https://www.interiorhealth.ca/YourEnvironment/RadonGas/Pages/default.aspx

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