A new study published in the Proceedings of the National Academies of Science claims to have found alarmingly high levels of pollution-derived magnetic nanoparticles in the brains of urban study participants, leading to renewed worry about the effects of smog on billions of people around the world. The study is not the final word on the origin or effects of these particles, and its results probably need to be replicated at a larger scale, but they’re serious enough to warrant major attention.
The study was conducted by taking brain tissue samples from just 38 people, 9 from Manchester and 29 from Mexico City, and ages ranged from three to 92. These people all died from fatal accidents, not neurological problems, with brains relatively intact, and samples of their frontal cortex were treated to extract magnetic material for analysis. The team found high levels of nanoparticles made of a mineral called magnetite. More importantly, they found evidence that these nanoparticles were taken up from air polluted by industrial processes.
Magnetite has been known to occur in the brain, but its origin was argued to be mostly natural — we create our own magnetite particles. However, these particles differ in structure from those we know are released industrial combustion processes, which tend to release magnetite as perfect spheres called high-temperature magnetite nanospheres. These spheres are formed in just about any industrial process involving combustion, tiny molten droplets of magnetite that get released from the heating of iron and which quickly cool and lock into their distinctive spherical shape.
This team’s analysis of the magnetic content of their brain samples concludes that they are atmospheric in origin. These people’s brains are laced with magnetite they’ve inhaled from their urban environment. The implication is that these nanoparticles, which are generally no bigger than a virus, are passing through the blood-brain barrier, which is designed specifically to filter out environmental contaminants just like this.
What’s the upshot of this study? Well, that’s beyond the scope of this study. But magnetite is inherently dangerous in certain concentrations since it’s reactive enough to spur the creation of so-called “free radicals.” These strong oxidizing molecules, usually derived from oxygen hijacked from cellular respiration pathways, have become public enemy number one among health aficionados. While they’re not as all-powerful as some fad diets would have you believe, they are a legitimate health concern. Especially in developing brains, the constant “oxidative stress” applied to neurons by higher-than-normal levels of radicals could have major consequences.
That leads to the most sensational implications of this study: Smog may be linked to Alzheimer’s Disease. Heightened levels of magnetite in the brain has previously been implicated in causing, or perhaps exacerbating the symptoms, of Alzheimer’s, and one of the study’s authors has made anecdotal references to Alzheimer’s-like morphology in the child tissue samples he examined. As she herself points out, though, this is far from definitive.
Whether or not the Alzheimer’s connection bears out specifically, the basic danger of harm is real enough to warrant further investigation. It raises an alarming question: If this is a pressure that has been increasing since the beginnings of the industrial revolution, have we been subject to increasing neurological damage as a result? We might ask how such a thing could go undetected for so long — but the answer could be that it has affected so many people for so long that its symptomatic effects have gone unnoticed in comparisons between individuals and even between time periods.
Or, perhaps this study has found a real pollutant with few real effects — after all, there is no real standard for the concentration at which atmospheric magnetite nanoparticles become a health problem. Still, it’s alarming to consider the idea that such a widespread environmental factor as airborne pollution could have been contributing an additive to our brains for so long, and stay hidden until 2016.