Seat 62K
No. Its fumes caused by oil getting through leaking engine seals into the bleed air system. This alows the vapours to get into the air conditioning and is often refered to as a "sweaty socks" smell.
There is an ingredient added to aircraft engine oil called TCP, and its pretty nasty stuff (it's been used in chemical weapons!). Its is thought that this is the stuff that is casuing the health problems.