Is it bad to breath fumes produced when machining cast iron,aluminium and other steels?

yep

yep
what are the side effects?

a lot of different metals that get into you body which are not elements that your body can consume will get deposited in the joints , aluminum is linked to alzheimer's , burning some if not most stainless steels are lethal if you take in to many fumes ,etc etc i'm sure if you google search you can get all sorts of info ,