We now have the first study ever (at the below link) to directly claim that nicotine by itself can cause cancer. Also, we've been listening for years to long-term NRT users both female and male complain of significant hair loss. Now we have photos to show why.   Here's a direct quote from the study's full-text:
 
"We demonstrated for the first time that chronic treatment of A/J mice with an
LD50 dose of nicotine cause carcinogenic transformation of both smooth and
striated muscles as well as transient hair loss. These findings help explain
previous reports of association of childhood rhabdomyosarcoma with parental
smoking (Gruffermanet al., 1982) and earlier onset of hair loss in smokers
(reviewed in (Ortiz and Grando, 2012)). Our results, therefore, should add
nicotine to the list of potential carcinogens present in tobacco products and
raise concern about the safety of long term usage of nicotine replacement
products."

http://www.sciencedirect.com/science/article/pii/S0024320512001890