Hello: The dip tube is polypropylene. It’s a cousin of polyethylene, which milk jugs are made of. I’ve not heard of any health concerns related to dip tubes. If your water is not heated enough, Legionnaires could be a concern. It behaves like pnumonia.
Note that I’m a plumber, not a doctor or a lawyer. Do be careful of associations. The sun comes up when the rooster crows, but the rooster crowing does not necessarily cause the sun to rise… But, if you’re sick and your doctor can’t find the cause, possibly another doc or a specialist is in order?