There are many chronic conditions related to poor blood circulation. They include diabetes, stroke, Parkinson's disease, hypertension, gallstones, senility and others. Reportedly, these conditions are also ameliorated by chelation therapy. And in both cases, rust is harmful. All atoms and molecules have nuclei with electrons flying around them.
Nature likes balance so in most cases the electrons balance out the protons.
But shift happens. Now we have what is called a free radical. And because nature likes balance, free radicals immediately look for an electron to steal. They become scavengers. When that happens, the building code of the cell is altered and cancer may result.