This latest research finds billions of nanoparticles from exhausts and industrial processes are in our hearts, brains and probably every organ of our bodies. Further details on this can be seen in the Guardian article here
This paragraph is the significant one in the abstact of the original research paper:
The health impact of up to ∼22 billion magnetic nanoparticles (NPs) per gram of ventricular heart 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. Identification of strongly magnetic CFDNPs in the hearts of children and young adults provides an important novel layer of information for understanding CVD pathogenesis emphasizing the urgent need for prioritization of particulate air pollution control.