Magnetite
(Fe2+/Fe3+),
a dark gray, metallic mineral, most well known for its strongly magnetic
properties, is mined for a variety of industrial and commercial uses. The magnetite
oxide Fe3O4 is a common oxide of iron, and is
predominantly found in sedimentary rock4. Because of iron’s role in biological processes, magnetite is
known to be naturally occurring in human tissues and a number of animals. Notably, it is associated with the
cellular response that allows use of magnets for medical imaging, such as with
Magnetic Resonance Imaging (MRI)2,3. Magnetite in biological tissue exists in the form of nanoparticles,
particles ranging from 1-100 nanometers in size6. Additionally
though, nanoparticles or nanospheres of magnetite can also be formed by high-temperature
combustion or friction, common in fuel processing and usage. The resulting particulate
matter (PM) ultimately contributes to a large portion of the world air polution2.
When exposed to an external magnetic field, magnetite nanoparticles lead to
production of radical oxygen species, and in the case of the biogenic particles
(by way of ß-amyloid), can lead to brain tissue damage in the form of amyloid
plaques2,5,7. Recent research reveals the toxicity of magnetite nanoparticles,
and links them to neurodegenerative diseases, such as Alzheimer’s Disease (AD),
in which oxidative tissue damage and “senile plaque” formation are standard2,5.
While a study3 in 1992 by geophysicist
Joe Kirschvink and coworkers, confirmed
the presence of natural magnetite in the human brain and its ability to
oxidatively damage tissue, it was not until recently, as reported by Maher et
al. at Lancatser University, that externally
formed magnetite particles can enter the human body, and lead to similar
biological harm2.
Due
to the health hazard of the particulate magnetite, and its increasing presence
as a pollutant in urban areas, Maher and her research team used a variety of
analytical techniques such as high-resolution transmission electron microscopy
(HRTEM), electron energy loss spectroscopy (EELS), and energy dispersive X-ray
(EDX), to study the characteristics and levels of magnetite nanoparticles in
human brain tissue. Specifically, postmortem
brains of individuals who had lived in the highly polluted, urban areas of
Mexico City and Manchester, UK were examined. This research2,
published in the Proceedings of the
National Academy of Sciences of the United States of America (PNAS), identified magnetite PM in the brain
samples, and analyzed the samples through crystallographic measurements and
imaging techniques to further understand the particulate properties. While high
levels were seen across ages and residential areas, the highest quantity was
found in a 32-year-old individual from Mexico City. Most of the magnetite
nanospheres found in the frontal cortex tissue were distinguished as round and
spherical in shape, and were often associated with other transition metals such
as Pt, Ni, Co and Cu. These morphological features differed greatly from
natural magnetite crystals, which are smaller, more “angular, cubo-octahedral,”
and are not typically found in the presence of additional metals2. Maher
et al. concluded that these large, spherical magnetite particles result from
external sources, as the geometry, size, and association with other metals,
closely resemble particulate matter (PM) formed by high-heat manufacturing and
vehicle processes. The authors believe that due to the small magnetite PM mass
and diameter, as compared to other common airborne nanoparticles, they may be
overlooked by governmental regulation. However, the high concentration of
magnetite particles, and their contribution to urban air pollution is
concerning due to the uniquely, relatively easy entry into the brain, and
should be a public concern. While the PNAS study found highest PM concentration
in brains from older individuals (>65 y at death), particularly those with Alzheimer’s
disease, there were also markedly high PM concentrations in brains of people younger
than 40-years-old at death. Finally, the authors discussed that the externally acquired
magnetite PM may be correlated to increased “risk” of AD (using previous
studies and controls to support their claims), but were careful to note the
need for much further study to make any decisive conclusions2.
Justin
Worland’s article in TIME, “Toxic Air Pollution Can Penetrate the Brain: Study”1
attempts to summarize the findings in the PNAS publication and links it to
multiple previous studies about pollution. Worland cites Maher’s work as he
describes the negative impacts of pollutants on human health, specifically the
new evidence that particles in the atmosphere can lead to harmful effects on
the brain. The article correctly informs the reader that magnetite particles, a
common urban pollutant, can enter humans through the olfactory nerve (if
<200 nm), and ultimately reach the brain tissue. Worland goes on to describe air pollution as a “top global
health threat,” which is leading to premature deaths worldwide1. He
highlights China and India, with their infamously high air pollution levels,
but also points out the alarmingly high number of deaths in the “comparatively
clean” U.S. and UK, due to anthropogenic air pollution1. Readdressing
Maher’s research, Worland explains the characteristics of the recently analyzed
magnetite particles found in the human brain tissue, noting their difference from
the naturally occurring nanoparticles. Finally, the TIME article states that
the PNAS publication details a potential means by which urban pollution may
cause Alzheimer’s, but Worland, like Maher et. al, is careful to note the need
for further research.
In
general, Justin Worland’s TIME article does a sufficient job presenting important
findings of the PNAS publication. Worland
clearly states how the magnetite nanoparticles enter the brain, and explains
that the high levels of magnetite result from airborne pollution, evidenced by
the unnatural shape and composition of the specific particles examined. Moreover, he does this in a clear and
understandable way, given the complicated nature of the research. While
helpful, however, the article has some shortcomings. . The author’s decision to
gloss over what magnetite is and how it is formed is an immediately apparent
deficiency. While he states that this particle can be a pollutant, the fact that magnetite is
a naturally occurring mineral in both humans and the earth’s surface is completely
ignored, leaving one to conclude that by addressing the human creation of the
pollutant, the problem could be reduced or eliminated. The TIME article also poorly explains the
conclusions drawn from the Maher study by exaggerating the findings and failing to address the
true motivations behind the work. The article’s title, “Toxic Air Pollution Can
Penetrate the Brain: Study,” is immediately followed by the broad statement,
“air pollution contributes to millions of premature deaths each year,” inadvertently
linking the magnetite particles that can enter humans through the olfactory
nerve, to previous and unrelated studies about air pollution and premature
deaths. He glosses over the fact that it is biological redox processes that may
spur degenerative diseases in brain tissue, simply stating that general
particulate pollution exposure could cause
AD. While the PNAS publication
does address premature death due to Alzheimer’s disease, and addresses the
possible link between AD and high levels of magnetite in the brain, it was intended
to prove that the presence of many frontal cortex magnetite nanoparticles have
external origin, rather than biological. Maher explored the correlation between these pollutants and
neurodegenerative damage, but states that their “preliminary” results “warrant
more intensive study” on this topic2. While the TIME article does
address this at the end, the title and bold first sentence unavoidably link the
two statements in the reader’s mind. An additional shortcoming of the TIME
article is the linking to other popular media articles, many of them also in
TIME, which Worland uses to support the facts provided. Many of these other sources use data
found before the PNAS research, and are somewhat unrelated. Interestingly, the
article cited by Worland when discussing the smog issues in China actually
details an air quality improvement in Beijing.
Overall,
while I believe that the TIME article accurately portrays the significant findings
from the peer-reviewed PNAS article in an understandable fashion, Worland adds
additional information and words his statements in way that might misinform the
reader. The PNAS article aimed to identify and characterize the non-biological
source of magnetite in human brain tissue by analytical techniques, while
Worland utilizes the publication to overemphasize the preliminary link between premature
death and pollution, and generalizes the findings on magnetite PM to pollution overall.
With this in mind, I would give Worland’s article a 6 out of 10.
1) Worland,
Justin. "Toxic Air Pollution Can Penetrate the Brain: Study." TIME,
September 6, 2016 http://time.com/4480016/air-pollution-health-effects/.
2) Maher,
Barbara A. "Magnetite pollution nanoparticles in the human brain." Proceedings
of the National Academy of Sciences of the United States of America,
(September 2016).
http://www.pnas.org/content/early/2016/08/31/1605941113.full.pdf.
3) Kirschvink,
Joseph L., Atsuko Kobayashi-Kirschvink, and Barbara J. Woodford.
"Magnetite biomineralization in the human brain." Proceedings of
the National Academy of Sciences of the United States of America 89 (August
1992): 7683-87.
4) Wikipedia.
"Magnetite." 2016. https://en.wikipedia.org/wiki/Magnetite.
5) Price,
Michael. "Industrial air pollution leaves magnetic waste in the
brain." Science, September 2016. DOI: 10.1126/science.aah7262.
6) Mandal,
Ananya. "What are Nanoparticles?." News-Medical.net. 2016. http://www.news-medical.net/life-sciences/What-are-Nanoparticles.aspx.