It can show correlation but not causation.
Exactly. There are millions of people with Alzheimers that don't have high traces aluminium, so I don't see how they can claim causation from one person with high aluminum level. Futhermore, this person had extreme levels of exposure that cannot be related to a person that may have small exposure to aluminium.
Aluminum is the 3rd most abundant element on earth and occurs naturally in the body in small amounts.