PotPourri Ray Copes MD MSc Director Environmental and Occupational Health Public Health Ontario Associate Professor University of Toronto Objectives 1Quick Review The EMS What sources contribute to population exposure to ionizing radiation How many radiation agents have been rev ID: 554418
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Slide1
Radiation Exposure PotPourri
Ray Copes, MD, MSc
Director, Environmental and Occupational Health
Public Health Ontario
Associate Professor, University of TorontoSlide2
Objectives
1)Quick Review – The EMS. What sources contribute to population exposure to ionizing radiation? How many radiation agents have been reviewed by IARC and what are their ratings?
2)
Radon – How risky is radon? What are we doing about it?
3) Do cell phones cause cancer? How can you reduce exposure to RF? Slide3
Electro Magnetic SpectrumSlide4
Ionizing vs. Non-ionizing effectsSlide5
Average Annual Ionizing Radiation Dose to US Residentsfrom
Upton, 2010
Source
Dose (
mSv
)
% of Total
Radon
1.9
31
Cosmic
0.27
4
Terrestrial
0.28
4
Internal
0.39
7
Total Natural
2.84
46
X-ray
Dx
2.4
39
Nuclear Med
0.8
13
Consumer Products
0.1
2
Occup
,
Nucl
,
Misc
0.05
<1
Total Artificial
3.35
54Slide6
Radiation agents reviewed in the International Agency for Research on Cancer’s (IARC) monograph series from
Samet
2011
6
Agent
Group
IARC Monograph Volume No.
Year
Ultraviolet radiation
1
40, 55
1986, 1992
Radon-222 and its decay products 143, 781988, 2001Ultraviolet radiation A (NB: Overall evaluation upgraded from 2B to 2A with supporting evidence from other relevant data)2A551992Ultraviolet radiation B (NB: Overall evaluation upgraded from 2B to 2A with supporting evidence fromother relevant data)2A551992Ultraviolet radiation C (NB: Overall evaluation upgraded from 2B to 2A with supporting evidence from other relevant data)2A551992Solar radiation 1551992X- and Gamma (γ)-Radiation 1752000Radium-224 and its decay products 1782001Radium-226 and its decay products 1782001Radium-228 and its decay products 1782001Radioiodines, short-lived isotopes, including iodine-131, from atomic reactor accidents and nuclear weapons detonation (exposure during childhood)1782001Radionuclides, α-particle-emitting, internally deposited (NB: Specific radionuclides for which there is sufficient evidence for carcinogenicity to humans are also listed individually as Group 1 agents)1782001Radionuclides, β-particle-emitting, internally deposited (NB: Specific radionuclides for which there is sufficient evidence for carcinogenicity to humans are also listed individually as Group 1 agents) 1782001Magnetic fields (extremely low-frequency) 2B802002Magnetic fields (static) 3802002
Classification of carcinogenic hazards to humans:
Group 1: Carcinogenic to humans.
Group 2A: Probably carcinogenic to humans.
Group 2B: Possibly carcinogenic to humans.
Group 3: Not classifiable as to carcinogenicity to humans.
Group 4: Probably not carcinogenic to humans
.Slide7
RadonWorth getting excited about? Slide8
Increase in lung cancer risk per 100 Bq m-3 increase in measured radon concentration in 13 European case-control studies
Source:
Darby
et al. 2005 [28].
8Slide9
Risk of Developing Radon Related Lung Cancer
Copes R , Scott J CMAJ 2007;177:1229-1231
©2007 by Canadian Medical AssociationSlide10
.
Copes R , Scott J CMAJ 2007;177:1229-1231
©2007 by Canadian Medical AssociationSlide11
What About Workplaces?
Care taken with definition of ‘dwellings’
OSH regulator has jurisdiction
‘Normal occupancy’ set at 4 hours/day
Some workplaces may have more than 200
Bq
/m3
At grade or below, also consider potential contribution from water in unusual work settings (e.g. hatcheries)
Some dwellings are work places and worker exposure will be reduced as well as residents (e.g. schools) Slide12
12Slide13
What is being done?
Health Canada cross country survey year 2 complete not yet released
Federal sector buildings being tested
Provincial interest ‘variable’ (e.g. BC school testing)
Resources available for homeowners to test and remediate at their expense
Little concerted pressure or publicity
Burden of illness not widely appreciated even by PH staff
Second only to smoking as preventable cause of lung cancer
Estimated 5-10% of lung ca. radon attributable. Slide14
Does cell phone use cause cancer?
May 2011 IARC meeting, 30 scientists 14 countries to assess carcinogenicity of RF electromagnetic fields.
Frequency 30kHz-300GHz.
Sources: cell phones, cordless phones, Bluetooth, amateur radio, dielectric and induction heaters, pulsed radar, broadcast antennas, medical applications.
The ‘hazard’ isn’t new, the applications are.
Does one apply the Precautionary Principle to new hazards or new applications? Slide15
RF Exposures
Workers –highest exposures are near field
Public – Use of transmitters held close to the body, can give greater dose to brain than work exposures
Exposures from cell phone base stations, TV, radio, Bluetooth are all orders of magnitude lower than cell phones
New 3G phones emit 100 times less RF than GSM phones
For energy deposition to brain, cell phone use is unique Slide16
Ionizing vs. Non-ionizing effectsSlide17
Exposure Standards for RF
Based on tissue heating as mechanism for adverse effects
Canadian (Safety Code 6) and international
stds
(ICNIRP) similar
Critics argue limits set on tissue heating are not stringent enough
Regulatory bodies argue lack of consistency in research with non-thermal end points and whether there is link to ‘
adverse
’ effects on health.
Despite proliferation of wireless technologies, measurements done in community settings are typically small fraction of current limits Slide18
Evidence for Carcinogenicity of RF?
Time trend, case-control, cohort studies
Time trend – surveillance data have
not
indicated evidence of increase in
gliomas
or other
tumours
of interest potentially linked to cell phone use
While some interpret as reassuring, this is a relatively insensitive indicator of risk
IARC considered one cohort and 5 case-control studiesSlide19
Cell Phone studies
Danish cohort
– 257
gliomas
in 420,095 subscribers between 1982 and 1995, subscriber incidence close to national average
.
INTERPHONE
-
2708
glioma
cases, 2972 controls
OR 0.81 (95% CI 0.70 -0.94) for ever versus never users For highest decile of exposure OR 1.40 (95% CI 1.03-1.89) Suggestion of increased risk for ipsilateral and temporal lobe tumours (where RF dose would be greatest) Hardell -pooled analysis based on cases ascertained up to 2003.
OR glioma >1 year of use 1.3 (95% CI 1.1-1.6) increasing to 3.2 (95% CI 2.0-5.1) for >2000h useIpsilateral use assoc w/ higher risk, cordless phones similar Sato – some evidence ipsilateral risk of acoustic neuromaSlide20
Animal Studies
40 studies assessing RF
incl
7 2-year rodent bioassays
Increase in total
tumours
in 1 of 7 chronic bioassays
2/12 studies with
tumour
prone animals showed increase cancer incidence
1/18 studies using initiation-promotion protocol
4/6 co-carcinogenesis studies showed increase in cancer after exposure RF and a known carcinogen Slide21
Conclusion?
Inconsistencies across studies; recall, selection bias possible; inadequate observations to meet latency
Findings cannot be dismissed as reflecting bias alone.
Human evidence ‘limited’, animal evidence ‘limited’
IARC Classification 2B ‘possibly carcinogenic’ supported by ‘large majority’ of the working group.
This is based on exposure from
cell phone use
.
“In reviewing studies that addressed the possible association between environmental exposure to RF-EMF and cancer, the working group found the available evidence insufficient for any conclusion”.
Slide22
Reducing RF Exposure
Cell phone use dominates exposures
Can reduce exposure through:
- reducing use
-texting
-selection of phone with lower SAR
-use of speaker, headset
-avoid use where there is weak signal
Unclear whether this reduces risk of adverse effectsPotential for exposure reduction in other settings less clear, although using wireless laptops on desk rather than lap may also be effective Slide23
Lessons?
Pressure to do ‘premature epidemiology’.
Easy to ignore pretty good epidemiology when outrage is low.
Discomfort with uncertainty.
Tension between ‘Precaution’ versus adoption of beneficial (to whom?) new technologies.
Controversy fueled by increased access to information and misinformation.
Internet can serve as an ‘amplifier’ of minority or fringe views.
Lack of public trust in regulators and experts. Slide24
Thank you
Questions?