How harmful is aluminium?
Here is a link to the Public Health Statement for Aluminum produced by the Centers for Disease Control and Prevention (CDC) in the United States.  There is much more information on the web page but the following are some of the more pertinent points to your question.

Potential Health Effects

Workers


  Workers who breathe large amounts of aluminum dusts can
  have lung problems, such as coughing or changes that show up in chest
  X-rays. The use of breathing masks and controls on the levels of dust
  in factories have largely eliminated this problem.
  
  Some workers who breathe aluminum-containing dusts or aluminum fumes
  have decreased performance in some tests that measure functions of the
  nervous system.


Humans


  Oral exposure to aluminum is usually not harmful. Some studies
  show that people exposed to high levels of aluminum may develop
  Alzheimer’s disease, but other studies have not found this to be true.
  We do not know for certain that aluminum causes Alzheimer’s disease.
  
  Some people who have kidney disease store a lot of aluminum in their
  bodies. The kidney disease causes less aluminum to be removed from the
  body in the urine. Sometimes, these people developed bone or brain
  diseases that doctors think were caused by the excess aluminum.
  
  Although aluminum-containing over the counter oral products are
  considered safe in healthy individuals at recommended doses, some
  adverse effects have been observed following long-term use in some
  individuals.


Some regulation and recommendations:


Drinking water



  The EPA has recommended a Secondary Maximum Contaminant Level (SMCL)
  of 0.05–0.2 mg/L for aluminum in drinking water. The SMCL is not based
  on levels that will affect humans or animals. It is based on taste,
  smell, or color.



Consumer products



  The FDA has determined that aluminum used as food additives and
  medicinals such as antacids are generally safe.
  
  FDA set a limit for bottled water of 0.2 mg/L.



Workplace air



  OSHA set a legal limit of 15 mg/m3 (total dust) and 5 mg/m3
  (respirable fraction) aluminum in dusts averaged over an 8 hour work
  day.