Team finds high concentrations of combustion- and friction-derived magnetic air pollution nanoparticles in human hearts in Mexico City
An international team led by Professor Barbara Maher, of Lancaster University in the UK, has found that iron-rich, magnetic combustion- and friction-derived nanoparticles (CFDNPs), which are abundant in particulate air pollution, are highly abundant in the hearts of young urban residents with lifelong exposure to high concentrations of particulate air pollution above current USEPA standards.
A 2016 study by Professor Maher and colleagues found abundant magnetite nanoparticles in brain tissue; magnetite is toxic and has been implicated in the production of reactive oxygen species (free radicals) in the human brain, which are associated with neurodegenerative diseases including Alzheimer’s disease.
Solid CFDNPs in air pollution are characterized by the abundant presence of strongly magnetic, iron-rich particles which condense and/or oxidize upon airborne release, often retaining a rounded or spherical shape as they cool. These magnetic nanospheres are abundant in urban airborne PM, and are released from a wide range of PM sources, including transport (road exhaust and brake-wear, rail and metro), metal processing and power generation plants.
In Mexico City, residents are exposed year-round to airborne PM concentrations above the National Air Ambient Quality Standards (NAAQS) for the US; both the PM2.5 annual air quality standard of 12 μg/m3 and the 24-hr standard of 35 μg/m3 have been exceeded for the last two decades.
In the new study, Maher and her colleagues used magnetic analysis and transmission electron microscopy (TEM) to identify heart CFDNPs and measured oxidative stress (cellular prion protein, PrPC), and endoplasmic reticulum (ER) stress (glucose regulated protein, GRP78) in 72 subjects age 23.8 ± 9.4y: 63 Mexico City residents and 9 controls.
Magnetite/maghemite nanoparticles displaying the typical rounded crystal morphologies and fused surface textures of CFDNPs were more abundant in MMC residents’ hearts. NPs, ∼2–10 × more abundant in exposed vs controls, were present inside mitochondria in ventricular cardiomyocytes, in ER, at mitochondria-ER contact sites (MERCs), intercalated disks, endothelial and mast cells.
Erythrocytes were identified transferring ‘hitchhiking’ NPs to activated endothelium. Magnetic CFDNP concentrations and particle numbers ranged from 0.2 to 1.7 μg/g and ∼2 to 22 × 109/g, respectively. Co-occurring with cardiomyocyte NPs were abnormal mitochondria and MERCs, dilated ER, and lipofuscin. MMC residents had strong left ventricular PrPC and bi-ventricular GRP78 up-regulation.
The health impact of up to ∼22 billion magnetic NPs/g of ventricular tissue are likely reflecting the combination of surface charge, ferrimagnetism, and redox activity, and includes their potential for disruption of the heart’s electrical impulse pathways, hyperthermia and alignment and/or rotation in response to magnetic fields. Exposure to solid NPs appears to be directly associated with early and significant cardiac damage.—Calderón-Garcidueñas et al.
The organelles and structures containing abundant NPs displayed substantial abnormality. The subjects also have significant neurovascular unit damage and evolving Alzheimer’s disease.
Failure to compensate for chronic myocardial inflammation, oxidative and ER stress possibly resulting from incursion of iron-rich, magnetic, redox-active NPs may prime the development of pathophysiological CV states in children and young adults in polluted environments. Identification of magnetic CFDNPs in the heart tissue of children and young adults provides an important novel layer of information for the understanding of CVD pathogenesis and emphasizes the urgent need for prioritization of particulate air pollution control. Exposure to iron-rich combustion- and friction-derived nanoparticles is a modifiable risk factor for the development of cardiovascular diseases. This study substantially advances the case for global efforts to reduce exposure to particulate matter air pollution and, specifically, to regulate the ultrafine fraction.—Calderón-Garcidueñas et al.
Lilian Calderón-Garcidueñas, Angélica González-Maciel, Partha S. Mukherjee, Rafael Reynoso-Robles, Beatriz Pérez-Guillé, Carlos Gayosso-Chávez, Ricardo Torres-Jardón, Janet V. Cross, Imad A.M. Ahmed, Vassil V. Karloukovski, Barbara A. Maher (2019) “Combustion- and friction-derived magnetic air pollution nanoparticles in human hearts,” Environmental Research doi: 10.1016/j.envres.2019.108567