http://www.appleinsider.com/articles/09/09..._in_europe.html
http://www.pcworld.com/article/172748/can_...on_the_way.html
So I frequently observe people listening to headphones at an unsafely loud level - when I can easily hear what is coming out of their earbuds, for example.
But from a public-health industry-regulation standpoint, regulating volume is much different than regulating parts-per-million of some substance in drinking water. This is because what constitutes unsafe volume is difficult to measure. Sure, we know that a certain decibel-level over a certain time-period ups risk of hearing loss. This is because the volume coming out of an mp3 player depends on two factors:
1) the player's volume-level setting, with some upper limit
2) the loudness of the media being played
Controlling the decibel-level coming out of a portable player is difficult, because the volume level of songs varies significantly. As anyone who uses or understands replaygain knows, albums can be mastered at different apparent-volume levels.
People who use the replaygain standard on their music (which results in the volume being lowered on the vast majority of songs) often have to set the volume level on mp3 players near the top, just to get a sufficient listening level.
If this EU policy is implemented as-is, let alone becoming the de facto worldwide standard, I wonder if people who use replaygain will have to stop doing so. (In my case, I apply mp3gain to files or apply a scalefactor upon encoding mp3's, and I do this because most players aren't replaygain-compatible)