[pvaldes]

I assume that the list from less toxic to more toxic is:

silica -> iron -> aluminum -> copper

With a logarithmic scale unit between each step or so. We ingest and tolerate much more aluminum than copper in our daily journey and we could drink water with much more iron oxide dissolved on it than aluminum oxide without suffering permanent problems

[hgomersall]

You should be careful of leaded glass, I've read research that shows it leaches into the liquid it contains (this is a problem in e.g. decanters where the acidic wine sits for several days).

[kwhitefoot]

How careful? Everything is a trade-off, without numbers on the quantities, extraction rates, and what levels are tolerable for short or long-term exposure we can't make a reasoned choice.

[robotomir]

Where's titanium on that scale?

[adrian_b]

Titanium in perfectly pure form is very reactive and it would be dangerous in contact with organic matter.

Fortunately, it is pretty much impossible to come in contact with pure titanium, because whenever it is exposed to air it becomes immediately covered with titanium dioxide.

The ratio between electric charge and radius of the titanium ions is such that titanium dioxide is one of the least soluble oxides. It is practically inert in water or blood.

This inertness of the titanium dioxide ensures that titanium is one of the safest materials for making implants that will have to stay forever in a human body or for making objects that will be in contact with food.

While glass remains the best food-contact material, titanium is a decent choice for applications where glass might break, e.g. spoons.

On that scale, titanium would be placed between silicon and iron. It should be kept in mind that the position on that scale actually refers to the behavior of the oxides, not of the pure elements, because all the elements mentioned are oxidized quickly in air and they are oxidized even faster in a living body.

Titanium dioxide is more inert than silicon dioxide, so less of it can become dissolved, but once the two oxides are dissolved, the silicon dioxide is safer, because most living cells have mechanisms to deal with it.