Quote Originally Posted by Ole
[...] There is good reason to believe that most high-performance lenses made today contain one or more Lanthanum-glass elements, but they are not emphasised to the same degree due to the unfortunate association with radioactivity in the minds of many photographers (and lens reviewers).
Supposedly Zeiss changed the compound formula for the 38mm Biogon in order to comply with new strident pollution control regulations. Do you know if that has anything to do with Lanthanum-glass?