The results of Sylvie Fink's autopsy showed only ONE abnormal finding.She was found to be completely healthy at the time of her autopsy except for an EXTREMELY high, 45% level of methemoglobin in her blood at the time of death.
Elevated levels of methemoglobin in the blood are caused when the mechanisms that defend against oxidative stress within the red blood cell are overwhelmed and the oxygen carrying ferrous ion (Fe2+) of the heme group of the hemoglobin molecule is oxidized to the ferric state (Fe3+). This converts hemoglobin to methemoglobin, resulting in a reduced ability to release oxygen to tissues and thereby hypoxia. Mayo Clinic.
In a nut shell,one of the things that can bring on this condition is ingesting a strong oxidizing agent such as chlorine dioxide.
Since her autopsy was otherwise NORMAL this was the MOST likely cause of her death.