Magnetite Nanoparticle Pollution May Be Linked to Alzheimer’s Disease

            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 plaques^2,5,7. 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 standard^2,5. 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.

7) Wikipedia. "Amyloid beta." 2016. https://en.wikipedia.org/wiki/Amyloid_beta.