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Rachel Lane August 26, 2014 15:30-17:00 RGN 3248. Applications: Epidemiology, Radiation and Health Department of Epidemiology and Community Medicine Faculty of Medicine University of Ottawa. Question 1. Ionizing radiation and cancer in professions such as aircrew and healthcare workers

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rachel lane august 26 2014 15 30 17 00 rgn 3248

Rachel LaneAugust 26, 201415:30-17:00RGN 3248


Epidemiology, Radiation and Health

Department of Epidemiology and Community Medicine

Faculty of Medicine

University of Ottawa

question 1
Question 1

Ionizing radiation and cancer in professions such as aircrew and healthcare workers

Radiation protection of aircrew exposed to cosmic radiation and patients exposed to thoracic imaging procedures

The principles of radiological protection:

Justification, Optimisation of Protection and Application of Dose Limits

Linear no-threshold (LNT) assumption for radiation protection purposes (around 5% per Sv)

Occupational dose limit: 20 mSv/year

Public dose limit: 1 mSv/year

Doses should be kept “as low as reasonably achievable” (ALARA principle) taking into account economic and social factors

International System of Radiological Protection (ICRP 60, 1991)

sources and distribution of average radiation exposure to the world population
Sources and Distribution of Average Radiation Exposure to the World Population

WHO, 2014


radiation risk models
Radiation Risk Models

CNSC, 2013: http://www.nuclearsafety.gc.ca/eng/resources/health/linear-non-threshold-model/index.cfm

cosmic radiation exposures in aircrew
Cosmic Radiation Exposures in Aircrew

Cosmic Radiation:

Altitude, Latitude (geomagnetic latitude effect), Flight Time

In 1991, the International Commission on Radiological Protection Publication 60 (1991) identified airline flight crew as an occupational exposed group

Justification, Optimisation, Dose Limits

Natural background: 2.4 mSv/year

Public dose limit: 1 mSv/year

Occupational dose limit: 20 mSv/year

Aircrew can receive low doses from cosmic radiation at levels similar to radiation-exposed occupational groups

a range of 0-6 mSv per year

cumulative exposures of ~ 80 mSv in a career

aircrew health effects of radiation
Aircrew: Health Effects of Radiation

Lower rates of all-cause mortality, overall cancer, and lung cancer compared to the general population (healthy worker effect)

Increased rates of female breast cancer and malignant melanoma compared to the general population

Indication of increased brain cancer among pilots and prostate and leukemia among aircrew compared to the general population

These excesses are not likely related to cosmic radiation but may be due to circadian rhythm, reproductive factors, lifestyle and other risk factors.

do aircrew need radiation protection
Do Aircrew Need Radiation Protection?


Regulatory: 1996 European Commission has developed and implemented regulations to protect their aircrew

Voluntary: Transport Canada have guidance measures for managing aircrew’s exposure to cosmic radiation, and aircrew are monitored and dose records are recorded, however; they are currently not regulated in Canada

With increases in air travel, planes flying at greater altitudes and over longer distances, transpolar routes, and changes in fuselage materials, radiation protection regulations and dose monitoring of aircrew is crucial

medical workers health effects of radiation
Medical Workers: Health Effects of Radiation

British radiologists, US radiologic technologists, and medical diagnostic workers in China exposed to X-rays

< 1950: radiation equipment was less sophisticated and radiation protection less stringent so occupational radiation exposures were higher (~ 50 mGy)

Elevated risk of leukaemia, breast cancer and melanoma and nonmelanoma skin cancers and circulatory disease and eye cataracts

> 1950: improvements in radiation technology and stringent radiation protection resulted in consistent decreasing occupational radiation exposures

No evidence of an increase in cancer or non-cancer mortality

breakdown of annual doses by job category for all of canada 2007
Breakdown of Annual Doses by Job Category for all of Canada, 2007

2007 Preliminary Analysis: National Dose Registry, 2007

Estimated Annual Collective Effective Dose of Ionizing Radiation due to Diagnostic Medical Examinations, 1997-2007

(Adapted from (3), Table 4 of IV. Scientific Report to GA)

trend in radiation exposure from diagnostic radiology
Trend in Radiation Exposure from Diagnostic Radiology

(Adapted from (3), Table 2 of IV. Scientific Report to GA)

high doses from medical imaging and widespread use pose public health cancer risk
High Doses from Medical Imaging and Widespread Use Pose Public Health Cancer Risk
  • Medical exposures largest artificial source of radiation (98%) and is growing at a remarkable rate
  • Between 1980 and 2006, the annual per-capita effective radiation dose in the United States nearly doubled
  • Almost all of this increased dose came from exposure through medical imaging (especially CT), which increased by about 600 percent
  • CT scans give extremely detailed images doses per procedure can be 50-500 times greater dose than standard X-rays and can range from 1.5 - >25 mSv
  • Multiple procedures can quickly be at levels of observed cancer effects
  • Patients are not regulated

(Figure adapted from Mettler et al., Radiology 253(2), 2009)

do patients need radiation protection yes
Do Patients Need Radiation Protection? Yes!

2006 Ontario Health Technology Advisory Committee (OHTAC )

2007 Recommendations Report of the Diagnostic Imaging Committee for Computed Tomography

2012 ICRP Publication 105 focusing on radiological protection in medicine was published which consolidates the current advice

OHTAC Recommendations

General CT Recommendations

Create CT Radiation Safety Committee

Healing Arts Radiation Protection Act/Regs (CT)

CT Scatter Testing and Inspections

Radiation Dose Reduction Recommendations

Develop best practices

Collect and analyse radiation dose information across Ontario

Diagnostic Reference Levels (UK and US)

Guidelines for patient shielding

Develop training program for CT medical staff


Radiation Risk and Protection in Perspective

  • Patients
  • Justification
  • Optimization
  • Reference Levels
  • Workers
  • Justification
  • Optimization
  • Dose Limits