Is Bitcoin bad for the environment?
No, bitcoin is rather an improvement on the already delapitated environmental disaster caused by other mining activities, bitcoin mining is environmentally friendly and also brings about solving the harmful effect caused by other mining activities through the use of waste energy polluting the environment into a reusable means for bitcoin mining.
Is Proof of Work a security?
Proof of work is a security and that's why it's more different from proof of stake, any mining procedure that involves been decentralized is a secured process and this is only found with bitcoin and not other crytpos which are centralized currencies and have the same centralized mining process wgich is proof of stake.