Corrosive? Aluminium Oxide? I moved into a house that has a light fitting that has been made out of an old food 'tin' can.

The light hadn't worked since moving in. On trying to remove it the glass of the bulb pulled straight out into my hand. There is a white powder on the bulb and also the wire towards the bulb.

It also looks in a structure like mould or mildew, as the 'white' is also up the wire and on the beam that the light lead is hanging from.

What is the powder? Is it dangerous, as in corrosive to other materials as it fell onto the floor and myself? Or is it possible that it is more a mould?
IMO this might be tungsten(VI) oxide, $\ce{WO3}$, which is fairly non-toxic, unless you consume it spoonwise.

From the look of this DIY setup I would doubt the quality of the light bulb itself was superb, and most likely one wouldn't use a fancy lamp anyway. So, the glass enclosure could be breached and some point, and the inner inert atmosphere (Argon/Nitrogen) was substituted with air. When hot tungsten filament oxidizes, it produces tungsten oxides which evaporates/scatters from the filament as white smoke:

$$\ce{2W + 3O2 -&gt; 2WO3}$$

Actually, bulky $\ce{WO3}$ is yellow, but being dispersed in a form of tiny crystals, tugsten(IV) oxide has pale-yellow or white color depending on the fraction.

Anyway, I would get rid of this can enclosure and buy a decent light source, mainly from an aesthetic point of view.

P. S. Here is a funky experiment showing what could happen in your case: https://www.thenakedscientists.com/get-naked/experiments/light-bulbs-liquid-nitrogen