What is it about making methamphetamines that is so toxic?

Just curious..I was reading and article on court tv today about a guy caught cooking meth and they had to have a hazmat team clean up what he was making..I've heard this before that it's really bad and that some houses have to be destroyed. Is it just the chemicals they use? What are the ones that they use that are so toxic?

: http://alcoholdrugstreatment.info/what-is-it-about-making-methamphetamines-that-is-so-toxic