Power frequency electric and magnetic fields

1
Power frequency electric and magnetic fields
probing the health risks
Royal United Hospital, Bath, Medical Physics
Dept, 4th February 2008

• Denis L Henshaw
• H H Wills Physics Laboratory
• University of Bristol

2
Richard Boxs FIELD (February 2004) (Photo
Stuart Bunce, www.richardbox.com)
3
Magnetic field exposure from the electricity
supply

• 1. Chronic exposures
• Average home levels 0.05 mT
• Levels under powerlines can be several mT or
  evens tens of mT
• 2. Short-term exposures
• High magnetic fields are found near appliances
• e. g. Microwaves, vacuum cleaners, hairdryers,
  shavers
• can be tens of mT close to

Epidemiological case-control studies have
demonstrated a doubling of the risk of childhood
leukaemia associated with magnetic field
exposures above 0.3/0.4 mT.
4
Ascertaining how magnetic fields cause adverse
health effects
1. Physics
4. Epidemiology
3. Human Biology
2. Chemistry
Magnetic Fields
(Physical Chemistry)
(Biochemistry)

• Proof that exposure to power frequency MFs
  causes increased risk of certain illnesses,
  requires answers to wide ranging questions
• Physicists would like to know the primary
  interaction mechanism of MFs with
  biological/living systems
• Chemists would like to know how this primary
  interaction affects basic chemistry
• Biologists would like to know how a
  physical/chemical response to MF affects biology
  e.g. through DNA or cellular damage and how this
  may result in increased risk to health
• Epidemiologists would like to demonstrate
  increased risk of a given illness with MF
  exposure by carrying out a series of independent
  epidemiological studies with sufficient resolving
  power to detect an effect and to obtain a robust
  set of positive findings such that an association
  between exposure and increased risk can be
  established.

5
Aetiology of childhood leukaemia

• 500 cases/yr in UK, increased 5-fold since 1900
• 2-hit process initiation in-utero, later
  progression to disease
• Paternal pre-conceptual exposure, maternal and
  foetal exposure in-utero and exposure in
  childhood all areas of interest
• Linked with traffic pollution (exposure to
  carcinogenic PAHs), natural radiation and MFs.
  (In addition, maternal obstetric X-rays generally
  not used today)

6
Childhood leukaemia key epidemiological findings

• Ahlbom et al. (2000) and Greenland et al. (2000)
  doubling of risk above 0.3/0.4 mT average
  exposure.
• International Agency for Research on Cancer
  (IARC) 2001 declares magnetic fields a Class 2B
  possible carcinogen
• 31st March 2004 UK Government sets up the
  Stakeholder Advisory Group on EMF or SAGE. First
  interim Report issued March 2007
• June 2005 Draper et al. find increased risk of
  CL near powerlines in England Wales
• 2007 World Health Organisation (WHO) has said
  precaution against exposure is warranted

7
Review bodies assessments of EMF causation of
various diseases.
Disease IARC 2002 2B NIEHS 1999 2B Calif 2002 2B
1. Childhood Leukaemia Yes Yes Yes
2. Adult Leukaemia Yes Yes
3. Adult Brain Cancer Yes
4. Miscarriage Yes
5. ALS Yes
Class 2B, possible carcinogen US National
Institute of Environmental Sciences
8
California EMF Report 2002 Numbers of reviewed
epidemiological studies and of positive and
significant results.
Meta-analytic OR (95 CI)?
Significant positives number, p-value
Positive studies number, p-value
Number of Studies
Disease
16
3
1.3 (1.0 1.7))
0.011
0.0022
19
1. CL
32
11.5
1.2 (1.12 1.24)
6.5 x 10-9
0.0010
43
2. Adult L
25
6
1.2 (1.1 1.3)
0.00013
0.0011
32
3. A Brain C
27.5
9
2.5 x 10-7
0.0038
37
4. Miscarriage
6
3
1.5 (1.2 1.7)
0.00051
0.063
7
5. ALS
Null hypothesis, result occurs by
chance Amyotrophic Lateral Sclerosis Motor
Neurone Disease
9
Summary of the findings of epidemiological
studies considered by the California Department
of Health Services EMF Report 2002
Disease Studies Positives Significant Positives Significant Negatives
Childhood leukaemia 19 16 3 0
Adult leukaemia 43 32 11 0
9 other diseases 150 110 36 1
Total 212 158 50 1
p-value for total 2.5 x 10-13 4.4 x 10-15
Null hypothesis, result occurs by chance
10
Health and fluctuations in solar and geomagnetic
fields (GM) Review by Palmer et al. Surv
Geophys 27 557-595, 2006

• The Earth has a static magnetic field 48 mT in
  the UK
• However, there are short-term fluctuations
  derived from solar flares
• Of particular interest are fields varying up to
  0.3 mT over a 3 hour period
• Evidence suggests that 10-15 of the population
  were predisposed to possible health effects such
  as cardiovascular health, depression suicide
  and melatonin disruption
• and it is the fluctuations that are of special
  interest

11
4. Epidemiology
1. Physics

• Magnetic field action on free radicals

12
Biophysical mechanisms Radical Pair Mechanism

• Free radicals react with DNA, causing damage
• When two radicals created from one precursor,
  spin states are coupled (½, -½) singlet state
• If the spin of one of the species changes,
  radical pair will have parallel spins triplet
  state

13
Biophysical mechanisms Radical Pair Mechanism

• Pairs assumed only to recombine in singlet state
• Triplets more likely to separate, becoming free
  radicals and be available for reaction for longer
  time
• Low field effects previously degenerate energy
  states resolve (Timmel et al. Mol Phys 95 71-89,
  1998)
• Increases probability of transitions from singlet
  to triplet state of radicals
• Singlet-to-triplet ratio lower, more radicals in
  triplet form longer-lived

14
Biological evidence for the RP mechanism

• Juutilainen et al. (IJRB 82 1-12, 2006) review
  of 65 studies MFs enhance the effects of known
  harmful agents, plt0.0001
• Lupke et al. (Free Radical Res 38 985-993, 2003)
  monocyte cells from cord blood exposed to 1 mT
  fields produce reactive oxygen free radicals

15
Illnesses associated with EMFs Is there a
common factor?

• Childhood leukaemia
• Adult leukaemia
• Adult brain cancer
• ALS
• Depression
• Suicide
• Miscarriage
• Breast cancer

16
Illnesses associated with EMFs Is there a
common factor?

• Childhood leukaemia
• Adult leukaemia
• Adult brain cancer
• ALS
• Depression
• Suicide
• Miscarriage
• Breast cancer

Disruption of Melatonin
17
Melatonin (N-acetyl-5-methoxytrptamine)

• Melatonin is a hormone produced in the pineal
  gland mainly at night
• Ganglion cells in eye (not visual system) signal
  when there is no light pineal melatonin
  produced at night
• Highly protective of oxidative damage to the
  human haemopoietic system
• Reduced levels of melatonin are associated with
  (i) increased cancer risk in animals and in
  humans, (ii) with depression and possibly
  miscarriage

18
Properties of melatonin

• Unlike vitamins C E, melatonin enters cells and
  can act directly on DNA
• By a scavenging cascade one melatonin molecule
  can scavenge up to 10 ROS/RNS (Tan et al J Pineal
  Res. 42 28-42, 2006)

19
Light at Night - Europe in the Present
http//www.ngdc.noaa.gov/dmsp/
20
Light at Night - Europe in the Past
http//www.earthview.mars/safe/
21
The Melatonin Hypothesis Richard Stevens
University of Connecticut 1987

• Exposure to light-at-night or MFs suppresses
  nocturnal melatonin leading to increased risk of
  breast cancer
• Has much support for visible light evidence that
  female night shift workers have elevated breast
  cancer risk (Review by Megdal et al. Eur J Cancer
  41 2023-2032, 2005)
• Womens blood containing normal physiological
  concentrations of nocturnal melatonin prevents
  growth of MCF-7 breast tumours transplanted into
  rats (Blask et al. Cancer Res, 65 1-11, 2005)
• 2007 IARC has classed night shift work as a
  Class 2A, probable carcinogen

22
Magnetic fields and melatonin disruption

• MFs and breast cancer risk controversial small
  increased risk at best
• But, populations exposed to neighbourhood EMFs
  shown melatonin disruption with fields as low as
  0.2 mT (Review by Henshaw Reiter,
  Bioelectromagnetics S7 86-97, 2005)
• Some evidence for a non-linear dose-response
  (just as for light)
• For EMFs, the Melatonin Hypothesis has been
  extended to Childhood Leukaemia melatonin is
  highly protective of oxidative damage to the
  human haemopoietic system and highly protective
  of oxidative damage to the fetus in animals

23
Biophysical mechanisms Animal navigation

• Many animals can detect and use tiny changes in
  the Earths static magnetic field both its
  strength and orientation for navigation
• Robins detect changes of 80 nT (Ritz, 2004) and
  homing pigeons sensitive to 10-20 nT (Wiltschko,
  2005)
• A magnetometer consisting of magnetite particles
  in beak
• A compass in the eye
• Some amphibians have receptors in pineal gland

24
A compass in the eye based on the radial pair
mechanism Review by Wiltschko Wiltschko,
BioEssays, 28 157-168, 2006

• The RPM is in the eye visible light of
  particular wavelengths is required to create the
  RPs.
• The RPM uses arrays of photo-pigments,
  cryptochromes, to detect and amplify the MF
  signal.
• The literature on this subject has undergone
  explosive growth in the last 2 3 years

(www.ks.uiuc.eu/Research/cryptochrome)
25
Are the melatonin and RP mechanisms tied together?
Light
Newly discovered ganglion cell
Pineal gland (regulates melatonin)
MF reception
Light dependent radical pair
Brain (Navigation)
?
EMF
Pineal gland
26
Biophysical mechanisms Relevant metrics

• Key word in many of descriptions is fluctuation
• Appears that (rapid) changes in field cause
  effects
• Many epidemiological and laboratory studies use
  time-weighted average (TWA) field magnitude
• Much information is lost in this way signalling
  spikes, peak values, orientation and polarisation
• False negatives may result
• Determination of correct biological response (if
  any) needs physical measurements of the correct
  field properties

27
But for high voltage powerlines

• What about the electric field?

28
Draper et al. British Medical Journal 2005 330
1290-3 29,081 children with cancer, 9,700 with
leukaemia 1962-1995 (322 leukaemia cases lt600 m)
NB Unlike other studies, this used the birth
address and not the diagnosis address
29
Lowenthal et al. Internal Medicine Journal
2007 854 patients diagnosed with LPD or MPD aged
0-94 years diagnosed in Tasmania 1972-1980
1st 15 years of life
3.23 (1.26-8.29)
4.74 (0.98-22.9)
1st 5 years of life
ORs for ever having lived within 50 and 300 m of
a high voltage power-line compared with never
residing within 300 m and for risk associated by
age of exposure within 300 m.
30
Corona ion hypothesis
14

• Direct fields cannot explain findings of Draper
  and Lowenthal distant from the power lines
• Indirect mechanism could be due to corona ions
  (Fews et al. 1999)
• High voltage line ionises the air and forms
  atmospheric small-ions
• Small-ions attach to pollutant aerosols,
  changing their charge state
• Increased charge on aerosols can lead to
  increased lung deposition

31

• Corona losses can be up to 0.1 mA per metre of
  powerline or up to 6.25 1014 charges per metre
  per second - even if most of these are absorbed
  by the line, there is potentially a high flux
  emitted into the atmosphere
• Corona ion effects have been seen up to 7 km from
  powerlines

32
Lung deposition and electric charge

• ICRP (1994) particle deposition efficiency
• In sub-micron range, not all particles deposited
• Charged particles near conducting surface induce
  a charge on the conductor
• Equivalent to charge of equal magnitude, opposite
  sign, equidistant from surface
• Image force increases chance of lung deposition

33
Charging of inhaled aerosol particles increases
their probability of lung deposition
Cohen et al. (1998) studied the deposition of
singly charged vs. natural charge state 20 and
125 nm particles For singly charged 20 nm
particles, deposition in the airways was 3.4
0.3 times higher than for their natural charge
state. For singly charged 125 nm the
corresponding increased deposition was 2.4 0.3.
(Health Physics 74(5), 554-560)
34
Risk assessment of possible annual excess cases
of ill health in people living near high voltage
powerlines in the UK, as a result of corona ion
and other electric field interactions with air
pollution (Henshaw, Medical Hypotheses, Vol. 59
(1), 39-51, 2002)

Condition Possible excess cases annually in the UK near high voltage powerlines
(i) Lung cancer mortality (ii) Other illnesses associated with air pollution (iii) Childhood leukaemia 200 400 2,000 3,000 2 6
Assumes 30 increased lung deposition Knox et
al. 2005a,b, 2006 childhood cancer air
pollution
35
Corona ion DC electric field measurements

• DC field mill meters used to measure atmospheric
  electric field near power lines
• Work by alternately covering and uncovering a
  sensing electrode
• AC signal received proportional to DC field
  strength

(John Chubb Instrumentation, www.jci.co.uk)
36
Variation in ground level atmospheric E-field
near a 400 kV powerline

• Wilding R. J., 2001. Corona Ions From Powerlines
  and the Implications for Human Health. University
  of Bristol PhD thesis.

37
Corona ion mobility spectrometry measurements

• Concentration and mobility of small ions (lt 1.6
  nm) and nano-aerosols (1.6 30 nm) also measured
  
• Aspiration Condenser Ion Mobility Spectrometer
  (ACIMS)

• Air drawn through cylindrical capacitor
• Voltage on outer cylinder varied stepwise from 0
  to 5 kV
• Charged particles deflect in electric field onto
  central electrode
• Ion current at electrode is converted to a
  mobility spectrum after scan

38
Corona ion mobility spectrometry measurements

• Example measurements made at 275 kV line near
  Cheltenham, Glos.
• Typical outdoor background ion concentrations 200
  250 cm-3
• Elevated to up to 6000 cm-3 downwind
• Ion attachment to aerosols evidenced by
  increasing ve/-ve ratio

  Ratio ve/-ve Ratio ve/-ve
Location aerosol ions
210 m Up 0.9 1.1
75 m Down 1.8 99.1
220 m Down 3.2 8.3
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Aerosol size distribution and charge state
measurements

• Submicron (10 1000 nm) aerosols measured using
  Sequential Mobility Particle Sizer (SMPS)
• Gives aerosol size distribution

• Using two at the same site allows investigation
  of charge state
• Average mobility increased if there is more
  charge on aerosols
• Causes a shift in distribution
• By fitting a theoretical charge distribution to
  measurement, calculate expected modified
  distribution due to charge

40
Can we square the circle with Draper et al.
?(and possibly with Lowenthal et al)

• Knox (2005a, b, 2006) has published three papers
  reporting a series of statistically significant
  associations and dose response information
  between the incidence of childhood cancer and
  sources of petro-chemical air pollution in Great
  Britain
• We can certainly point to powerlines, 400, 275
  and 132 kV which emit sufficient corona to
  explain the finding of Draper et al. (2005) in
  terms of the corona ion model
• What we cannot do is claim that all powerlines in
  England Wales, from 1962 1995 are/were in
  sufficient corona to account for Draper et als
  findings

41
Conclusions

• The is a robust association between exposure to
  magnetic fields and increased risk of childhood
  leukaemia and possibly other illnesses. Causal
  mechanisms are under discussion
• Though much less developed, recent evidence
  suggests that in the case of high voltage
  powerlines adverse health effects may extend much
  further away than from the direct range of either
  the electric or magnetic fields

42
Acknowledgements

• Team members
• Paul Keitch
• Julie Close
• Liz Ainsbury
• Matthew Wright
• Jonathan Ward
• James Matthews
• Alison Buckley
• Andrea Lazenby
• Supported by

Websites www.electric-fields.bris.ac.uk
www.leukaemiaconference.org
www.electric-fields.bris.ac.uk/presentations.html
43
Questions

• Got told people who live near powerlines are of
  lower social class this is not True of Draper,
  and in any case this would lead to LOWER CL
• Got told a study comparing leukaemia in Mexico
  with high natural background radiation in
  Colarado (?) found lower rates in Colarado of
  course it did, there was no correction for air
  pollution!