Snot. Dirty ears. Other comments.

Lexan flasks, including those made by Nalgene using the same formula they use for water bottles, are used for medical and enviromental lab work every day. If there was something leeching into the samples, you'd see it as a constant lab contaminant. And we don't see it.

I clean mine with dish soap and warm-hot water, but I put tea in them every winter. Never had anything I could taste or an ill effect. The one time I had an effect, it turned out to be a water source contaminant. As a result, any water from my parent's tap has to be boiled- again, never noticed anything.

I would be more concerned with the HDPE ones, actually.