Happy 100th Birthday Robert Adair

Are Electromagnetic Fields Making Me Ill?

This Wednesday will be the 100th anniversary of Robert Adair’s birth. I wrote a blog post about Adair recently but he is an important enough figure in biological physics, and in Intermediate Physics for Medicine and Biology, that today I will write about him again. This time I will focus on a difference of opinion between Adair and Joseph Kirschvink about the possible effects of weak electric and magnetic fields in biology. In Are Electromagnetic Fields Making Me Ill? I wrote

One of the first physicists to enter the fray [over the potential hazards of powerline magnetic fields] was Yale physics professor Robert Adair, a member of the National Academy of Sciences who was known for his research on elementary particles called kaons and for his interest in the physics of baseball. In 1991, Adair published an article in the leading physics journal Physical Review investigating the possible mechanisms by which 60-Hz electric and magnetic fields could affect organisms…. Adair concluded that “there are very good reasons to believe that weak [extremely low frequency] fields can have no significant biological effect at the cell level—and no strong reason to believe otherwise” [10].

“Constraints on Biological Effects of Weak Extremely-Low-Frequency Electromagnetic Fields”

Reference 10 is

R. Adair, “Constraints on Biological Effects of Weak Extremely-Low-Frequency Electromagnetic Fields,” Physical Review A, Volume 43, Pages 1039–1048, 1991

Kirschvink responded (“Comment on ‘Constraints on biological effects of weak extremely-low-frequency electromagnetic fields.’” Physical Review A, Volume 46. Pages 2178–2184, 1992)

In a recent paper, Adair [Phys. Rev. A 43, 1039 (1991)] concludes that weak extremely-low-frequency (ELF) electromagnetic fields cannot affect biology on the cell level. However, Adair’s assertion that few cells of higher organisms contain magnetite (Fe₃O₄) and his blanket denial of reproducible ELF effects on animals are both wrong. Large numbers of single-domain magnetite particles are present in a variety of animal tissues, including up to a hundred million per gram in human brain tissues, organized in clusters of tens to hundreds of thousand per gram. This is far more than a “few cells.” Similarly, a series of reproducible behavioral experiments on honeybees, Apis mellifera, have shown that they are capable of responding to weak ELF magnetic fields that are well within the bounds of Adair s criteria. A biologically plausible model of the interaction of single-domain magnetosomes with a mechanically activated transmembrane ion channel shows that ELF fields on the order of 0.1 to 1 mT are capable of perturbing the open-closed state by an energy of kT. As up to several hundred thousand such structures could fit within a eukaryotic cell, and the noise should go as the square root of the number of independent channels, much smaller ELF sensitivities at the cellular level are possible. Hence, the credibility of weak ELF magnetic effects on living systems must stand or fall mainly on the merits and reproducibility of the biological or epidemiological experiments that suggest them, rather than on dogma about physical implausibility.

In his comment, Kirschvink proposed a model of a magnetosome interacting with the earth’s magnetic field that Russ Hobbie and I discuss in Section 9.10 of Intermediate Physics for Medicine and Biology.

What do you think about Kirschvink’s claim that magnetite is found in the human brain? In Are Electromagnetic Fields Making Me Ill? I wrote

Caltech geophysicist Joseph Kirschvink has found magnetite in the brain, which could be the basis of magnetoreception in humans [12]. Experiments to test this hypothesis are difficult; contamination of tissue samples is always a problem, and the mere presence of magnetite does not by itself imply that a magnetic sensor exists.

[12] J. L. Kirschvink, A. Kobayashi-Kirschvink, B. J. Woodford, “Magnetite Biomineralization in the Human Brain,” Proceedings of the National Academy of Sciences, Volume 89, Pages 7683–7687, 1992.

The last sentence of Kirschvink’s abstract particularly interests me: “Hence, the credibility of weak ELF magnetic effects on living systems must stand or fall mainly on the merits and reproducibility of the biological or epidemiological experiments that suggest them, rather than on dogma about physical implausibility.” In one sense it is a truism. Yes, of course, experiments are the final deciding factor in scientific truth. Yet, I’m uncomfortable about characterizing Adair’s analysis as “dogma about physical implausibility.” Adair’s work was based on very basic physics. I suppose you could call Maxwell’s equations and the three laws of thermodynamics “dogma,” but it is a pretty credible dogma.

More recently, Sheraz Khan and David Cohen published a fascinating study about “Using the Magnetoencephalogram to Noninvasively Measure Magnetite in the Living Human Brain” (Human Brain Mapping, Volume 40, Pages 1654–1665, 2019). They observed magnetite primarily in older men, and suggest that magnetite may play a role in neurodegenerative diseases, such as Alzheimers.

Adair published a reply (R. K. Adiar, “Reply to ‘Comment on “Constraints on Biological Effects on Weak Extremely-Low-Frequency Electromagnetic Fields,”’” Physical Review A, Volume 46, Pages 2185–2187, 1992). His abstract says:

Kirschvink [preceding Comment, Phys. Rev. A 46, 2178 (1992)] objects to my conclusions [Phys. Rev. A 43, 1039 (1991)] that weak extremely-low-frequency (ELF) electromagnetic fields cannot affect biology on the cell level. He argues that I did not properly consider the interaction of such fields with magnetite (Fe₃O₄) grains in cells and that such interactions can induce biological effects. However, his model, designed as a proof of principle that the interaction of weak 60-Hz ELF fields with magnetite domains in a cell can affect cell biology, requires, by his account, a magnetic field of 0.14 mT (1400 mG) to operate, while my paper purported to demonstrate only that fields smaller than 0.05 mT (500 mG) must be ineffective. I then discuss ELF interactions with magnetite generally and show that the failure of Kirschvink s model to respond to weak fields must be general and that no plausible interaction with biological magnetite of 60-Hz magnetic fields with a strength less than 0.05 mT can affect biology on the cell level.

I tend to side with Adair’s position in his reply; I, too, am skeptical of weak-field magnetic effects in biology. However, the controversy makes me wonder if magnetic resonance imaging interacting with magnetite in the brain might possibly trigger some sort of effect, especially in the newer high-magnetic-field scanners. The magnetic field in a 4-tesla MRI machine is nearly 10⁵ stronger than the 0.05 mT field of the earth that Adair and Kirschvink are arguing about. I still remain skeptical about MRI effects (see Chapter 2 in Are Electromagnetic Fields Making Me Ill?), but at least this seems to be a more plausible mechanism than interactions with the earth’s magnetic field.

Several important figures in physics applied to medicine and biology were born in 1924: Allan Cormack, Bernard Cohen, Robert Plonsey, and Robert Adair. This week we wish Adair a happy 100th birthday. His work on the effect of weak electric and magnetic fields in biology remains relevant today. I wish he was here to see the latest results.