Some years ago, the issue of dioxyn in plastic bottles came to fore. The articles, according to the medical gazette, point to a poisonous chemical that is produced when the plastic drinking bottle is heated. That warning is very apt for cyclists because it is common for them to bring bottles during a ride. And since the riding is done mostly during daytime when the sun is up then the probability of dioxyn to appear in drinking bottles is high.
Honestly, I'm still using plastic bottles sometimes.
Honestly, I'm still using plastic bottles sometimes.