If there were a direct link between Alzheimers and the ingestion of, or
even handling of, copper, then there would be a disease called
"plumber's disease" just like there is "black lung" for coal miners and
mesothelioma for people who worked with asbestos.
In order to make a solder joint, you have to sand the oxide layer off
the copper pipe and brush out the oxide layer on the fitting. That
creates copper dust particles that are small enough to hang in the air
How many plumbers do you know that wear a dust mask when they sand
copper pipe? I don't know of any.
If what that report suggests is true, they could easily prove it be
comparing the rate of Alzheimers amongst retired plumbers with that of
the general population. I doubt they'll find any correlatioin because
plumbers often bring their sons into their business, and if there was a
strong correlation between Altzheimers and copper, then many of the
plumbing companies in major cities where the family owned company has
been in business since the 1950's would have noticed the prevalence of
Alzheimers in their family.