That might just as easily stem from lead- or barium-doped optical glasses that have been around for, in some cases, centuries. There's a lot more lead glass used in optics than lanthanum glass -- IIRC, the crown glass in a common achromat (as in a doublet loupe or telescope objective) is often leaded. And the glass "mud" from grinding and polishing lead glass is an environmental hazard on the same order as arsenic bearing mine tailings or smelter slag (though of much less volume). I've heard Germany now requires mandatory recycling of glass TV and computer display tubes, as well, with the recycling costs included in initial purchase price (the sane way to do this, IMO), but the result is that the up-front cost increase is partly driving the runaway switch to LCD monitors (which are inferior to CRTs in some significant ways, even though they are light, compact, and use a lot less power -- most notably, with their fixed size display elements, they don't handle multi-resolution display usage at all well in my experience).

Bottom line, lead glass is on the way out, at least in Germany -- and optics isn't the only industry affected.

Lanthanum glass is likely much less affected, since there's a lot less lanthanum in a given glass than there would be of lead in a corresponding crown, and the higher index and lower dispersion of lanthanum glass allow using less or no lead glass in other parts of the lens.