Some Effects of Weak Magnetic
Fields on Biological Systems and
Potential Health Effects
Frank Barnes
1.
Department of Electrical, Computer, and Energy
Engineering, University of Colorado, Boulder,
Colorado
Acknowledgement
Ben Greenebaum
Lucas Portelli
Carlos Martino
Aditya Kausik
Cynthia Bingham
Aly Ashraf
Many students and friends from all across the
field.
Outline of Talk
1. Some History
2. Hypothesis
3. Some Background Experiments and
Theory
4. Reasoning for Hypothesis
5. Possible implications for long-term
exposures to weak magnetic fields
Some History
• 1. Debate on Thermal vs Non-thermal Health
effects from radar back to at least 1960s.
• 2. Wertheimer, N., and E. Leeper.1979.
• 3. Cordless phones, cell phone, WiFi
• 4. In all cases problems in going from the
physics through the chemistry to the biology
to possible health effects.
Hypothesis
Radical Pair Model:
Radical pairs form with electron spins in S or T States.
Changing pair’s energy states and spins polarization
change the recombination rate and radical
concentrations, with downstream consequences.
Proposal:
1. The AC magnetic field, BAC, at frequencies
corresponding, to the Zeeman Energy Level
differences can change in the populations
distribution.
2. Transitions can also occur at level crossings or Zero
External Field.
3. BDC changes can change recombination rates
Radical Pairs in S or T States
Pair Spin = 0
Pair Spin = 0
Pair Spin = 1
Oxygen Radical O2• 1. Oxygen radical
Background Experiments
1. Decreases in cell growth in fibrosarcoma HT1080 cells for
magnetic fields less than 18 µT.
(Martino, et al. Bioelectromagnetics pp:1 to 7 (2010)
2. Decreases in cancer incidence in mice and rats
(Boorman, et al., Toxicol. Pathol., 27, 267–278, 1999)
3. Increase in cell growth rates with RF and an increase in
H2O2 Concentrations of 50%
(Usselman et al. PLOS ONE 2014)
4. Measured changes in free radical concentrations
(M. Lantow et.al. Radiat Environ Biophys (2006)DOI 10.1007/s00411-006-
5. The Interphone Study.
(International Journal of Epidemiology 2010;39:675–694)
0038-3)
On Average, My Temperature Is Just
Right!
• 1
Background In Physical Chemistry and
Magnetic Fields
• 1. Most of the work has been done at magnetic
field levels that are large compared to the earth’s
magnetic field of ≈ 45µT (23 to 65µT)
• 2. Kaptein [1968], Kaptein and Oosterhoff [1969],
many others, and Woodward et al. [2001],
• 3. Reviews by Steiner and Ulrich [1989], Grissom
[1995]
• 4 Book by Hayashi [2004] very good theory
• 5. Adair [1999]
Theory for Allowed Energies
•
•
1. The
Hamiltonian for a radical pair
(1)
• where
and are the electron and nuclear Zeeman terms, depending
upon the interaction between the external magnetic field B and the
electronic and nuclear magnetic moments, respectively. These terms take
the form µ•B, where µ depends on the appropriate net angular
momentum. The total angular momentum is characterized by F for low
external fields, the net electronic angular momentum is J = L + S, the sum
of the orbital and spin angular momenta, and the nuclear spin is
characterized by I. Hex is the exchange term; Hss is the electron–electron
dipolar coupling term between the members of the pair; and Hsi is the
hyperfine coupling term, that is, the interaction of the nuclear moment
with the local field due to the electronic motion, depending on J•S.
• Add
for coupling between nuclear spins in large molecules.
Theory
• 1. For magnetic fields with Bext >>45µT the spins
react with Bext and the electron spins are
independent of the nuclear spins to first order.
• 2. For Bext<< 45µT the electron and nuclear spins
are coupled and the quantum number is given by
F = I +J where is given by J= L +S
• 3. In the case of large B we have noise from
coupling to the background and large line widths
• 4. For small B we have the inertia of the nucleus
and narrow line widths.
The Energy Level Diagram for D2
Energy Levels for NO
• 1
• Figure 4. Energy level diagram and complete spectrum
of the 𝐽 = 1/2 → 3/2 rotational transition of the 2∏1/2
state of N14O16. From Gallagher et al., [1954]
Energy Levels for NO
•
Figure 5. Energy level diagram of the J=3/2 level of the 2∏1/2 state of N14O16. Stage (a) is in the
absence of magnetic field. Stage (b) shows the magnetic levels considering only molecular effects.
Stage (c) adds magnetic hyperfine splittings. Stage (d) includes the nuclear electric quadrupole IJ
coupling and shows the nine transitions ∆MJ=±1, ∆MI=0. Arabic indices on the transitions
correspond to the labeling of the observed absorption lines. [from Beringer and Castle, 1950]
Energy Levels of Free Radicals
• Energy Levels have electron and nuclear Zeeman terms that
depend on the magnetic moments, of the electrons and
nuclei, the external magnetic field and the alignment of the
angular momentum along the net field at that location,
𝝁 •𝑩
• At low field the nuclear, electronic, and molecular rotational
angular momenta are coupled and Zeeman energy depends
on 𝝁𝑭 •B. Where F is total magnetic momentum; F=J+I, I is the
nuclear angular momentum, J = L + S + j is net electronic one;
L is net orbital, S is net spin, j is rotational.
• At higher fields, L, S, J, I couple separately to B.
• Internal couplings within the radical molecule primarily set
level energies for any B.
Hypothesis Theory
1. Relative S and T state of newly-formed free radical pairs
depends on relative orientation of the radicals’ electronic
angular momenta J.
2. Allowed Zeeman transitions include changes between
electron and nuclear spin orientations with respect to the
applied magnetic fields.
3. Applying weak AC magnetic field to radical in one Zeeman
level stimulates transitions between energy levels if
hf = ΔE.
4. If two levels have same energy, spontaneous transitions
can occur subject to some other restraints.
5. Changing relative S or T state of a pair changes
recombination probability, resulting in change in radical
concentration, with downstream consequences.
Recombination for Radicals
Background Theory + Experiments
Growth of P815 Mastacytoma Cells
Bdc=38µT f= 60Hz (Bingham 1996)
RF Absorption Spectra
From Woodward et al., 2001
Population Saturation
Population difference of states in AC field is
n1
n12 
1   2 B1T2T1
Where 𝒏𝟏 is population of one state, 𝜸 =
𝝁𝑭
𝟐 𝝅 is the gyromagnetic ratio, B1 is the AC
𝒉𝒇
magnetic flux density, T1 is the relaxation time
between states and T2 is the nuclear spin
relaxation time (Bovey et al., 1988).
Free Radical Concentrations
• T2 may be seconds long
• T1 is typically in the range from 10-6 to
• 10-10sec
• Assuming T2 is seconds or longer, T1 is 10-6 10-10 sec for transition between the S and T
states of the radical pair, and γ = 1.933 x 107
for the nuclear spin transition, then
B1 = 2.68 x10-5 to 2.68x10-9 T to reduce Δn12
by a factor of 2.
Some Examples of Radical
Concentration Changes
• Usselman et al. show that for rat pulmonary
arterial smooth muscle cells (rPASMC).
• 1. RF exposures at 7MHz and 10µTRMS for
3days in a BDC= 45µT lead to decreases of
45% in O2 -*and an increase in H2O2=50%
• 2. Enhanced cellular proliferation by up to
40% on day 2 and 45% on day 3 in
proportion to the SMF control group
Some Effects of H2O2
• 1. H2O2 is both a signaling molecule and can be
destructive by conversion to radicals that lead
to the modifications of DNA and lipids.
• 2. It can stimulate growth in cancer cells at low
concentrations and lead to killing them in
high concentrations.
• 3. The generation of ROS and H2O2 is a normal
part of the metabolic process.
• 4. ROS produced via normal cell metabolism
modify approximately 20,000 bases of DNA
per day in a single cell.
A Positive Example of Concentration
Changes
• 1. Arendash et.al show exposures of
transgenic mice destined to develop
Alzheimer’s-like cognitive impairment to
0.25 W/kg at MHz reduced brain amyloidβ (Aβ) deposition through Aβ antiaggregation actions and increased brain
temperature during exposure periods
Variations in growth rates of E.coli
with Static Magnetic Fields
Effects Of Periodic Signals
• 1. Cell often communicate with periodic pulses
or signals. This gives a better signal to noise,
S/N, than a straight amplitude signal for
things like gene expression.
• 2. Examples Ca+2 and the circadian rhythms with
temperature pulses
• 3. Signals close to the natural oscillation
frequency can pull the period and the closer
you are to the natural frequency the smaller
the signal needed to get phase locking.
Variations In the Growth Rate of Human Fibrosarcoma HT1080
Cells with ΔT=+/- 1.25oC and ΔB≈+/- 100µT
1.2
Normalized cell counts for 4 hour exposure with varying temperature pulses
Cell counts of exposed samples normalized
using counts of control sample
1
0.8
0.6
0.4
0.2
0
7s oscillation
13s oscillation
Normalized Initial Count
20s oscillation
Normalized Final Count
25s oscillation
Variations In the Growth Rate of Human Fibroblast Cells with
ΔT=+/- 1.25oC and ΔB≈ +/- 100µT
1.2
Normalized cell counts for 4 hour exposure with varying temperature pulses - Fibroblast cells
Cell counts of exposed samples normalized
using counts of control sample
1
0.8
0.6
0.4
0.2
0
7s oscillation
13s oscillation
Normalized Initial Count
20s oscillation
Normalized Final Count
25s oscillation
Variations in NADPH Concentrations
for HD1080 Cells
Variation in NADPH levels with frequency for temperature oscillations
18
NADPH concentration (pmol/well)
16
14
12
10
8
6
4
2
0
7s oscillation
20s oscillation
Seeding control
Incubator control
25s oscillation
Exposed
Radicals in Biology
• Reactive oxygen (ROS) and nitrogen (NOS) free
radicals occur as a part of the metabolic processes .
• NO may be used as a signaling molecule that leads to
a cascade of events that amplify the signal.
• The body has a normal operating range for free
radicals and magnetic fields can lead to biologically
significant events when they take these concentration
ranges outside their normal range.
• This may mean we see health effects only when the
concentrations go outside the range where the
feedback and repair process can compensate for the
induced changes.
Free Radical Concentrations
• Free Radical concentrations vary by more than an order of
magnitude in time as show below.
• Normally these concentrations return to the baseline level. Resistive
stimulations over long periods of time can lead to a rise in the
baseline level we can in turn lead to aging, cancer etc. (Droge 2002)
Conclusions -1
1. Low level magnetic fields can lead to both
increases and decreases in the concentration
levels of free radicals such as ROS and NOS.
2. These effects will be a function of the frequency
of the of the AC fields, the angle between the AC
and DC magnetic field, the amplitudes and the
pulse repetition rates.
3. The biological effects of these fields will be a
function of time and depend on other stress in the
biological system
Conclusions -2
1. This hypothesis is consistent with experimental and
theoretical results, including both observed increases
and decreases in free radical concentration and
experimental changes in the growth rate of some cancer
cells, E.-Coli and some tumor growth rates.
2. It may also explain why we see little or no health
effects for short term exposure and different effects for
long term exposures.
3. More work will need to confirm or disprove this
hypothesis. Additional mechanisms may also be
operative.
Random Motion of Human Neutrophils
Positive Chemotaxis
15
20
5
1
10
Neutrophil Motion with RF at 900MHz, E≈ 1V/M
Parallel to Chemical Gradient and B≈20nT
Positive Chemotaxis
43 - Ending
35- RF Removed
33
1 – Starting Point
22
'
5
8
15
Speed with and Without RF at 900MHz, E≈ 1V/M
Parallel to Chemical Gradient and B≈20nT
Under RF Field
Velocity (microns/min)
Without RF Field
Temperature (oC)
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