The concept behind bamboo clothing isn’t so much that it’s tough it’s that it grows really fucking fast and doesn’t require as much water (which means you can also grow it in more places). So it’s cheaper to grow but also cheaper to harvest and ultimately a lot more environmentally friendly.

The chemicals used to process bamboo into the type of fiber used in clothing aren’t really a big deal (sodium hydroxide aka “caustic soda”) and have relatively straightforward (and safe) disposal processes. So if the fibers are processed in the West you can assume that regulations will require safe disposal of waste. They’re not exotic or new enough to be of much concern.

However, if it’s made in a 3rd world country with heavy corruption of regulatory agencies (e.g. India and Bangladesh) and/or completely inadequate enforcement/policing (e.g. China) that’s a very real problem. Though not so much a global pollution problem like global warming as much as it’s a local pollution problem.

TL;DR: Bamboo is all around way better for the environment than cotton.