I think people are possibly confusing a few things here.  Firstly,
the white powder is not lead.  Therefore it is not lead dust and
breathing it in will not result in lead poisoning.

Secondly, lead is one if the most stable substances on this planet
and has extremely high resistance to corrosion.  That is why it is
used on roofs, ancient buildings, etc.

Thirdly, if the white powder were oxidation, i.e. lead oxide, it
would not be white as lead oxide is not white.

Fourthly, lead oxide is actually not poisonous unless ingested in
a largish quantity.

So what is the white powder?  I think it is basic lead carbonate
or white lead.  Again, that compound is only toxic in larger
concentrations.

So the only problem is that the tubing slowly disintegrates as it
converts the lead to lead carbonate.  To prevent this, coat the inside
with lacquer.  It is not that hard to do.

Don't blow the powder out unnecessarily as it will expose fresh lead
to the atmosphere and result in more disintegration of the precious
tubing.

I would not hesitate using new lead tubing as the advantages are huge.
But the cost can be prohibitive.

Bernt Damm
Sydney