he had discovered toxic levels of arsenic in apple juice. This created a backlash led by the FDA and represents a classic example of misunderstanding science and science procedures.
A week before the show aired, the FDA sent the Dr. Oz show a letter explaining arsenic testing in fruit juices and how it worked. The show apparently ignored this information and aired the segment anyway.
Simply put, Dr. Oz was conflating two different tests for arsenic and misunderstanding them both. The level of arsenic he was reporting was total arsenic level rather than distinguishing between the organic and inorganic arsenic. Only inorganic arsenic is harmful and that has been found to be at safe levels in all FDA-approved fruit juices.
For more information:
FDA laboratory methods for arsenic testing in fruit juices
FDA Q&A: Apple juice and arsenic
BBC Health: Arsenic poisoning
Agency for Toxic Substances & Disease Registry (ATSDR): ToxFAQs for Arsenic