Excessive smoking also causes cancers of the mouth, lip, pharynx, larynx, esophagus, pancreas, bladder, kidney and stomach (Rockhill & Colditz, 7). Smoking is also related to increased risk for colon cancer. Tobacco is known to contain at least 50% carcinogenic chemicals, which cause cancer within the body when inhaled. Another most prevalent cancer is that of the breast and causative factors are associated with higher average fat consumption besides earlier onset of menstrual periods, lower number of children and later age of first pregnancy (Hunter & Willett, 17). Greater fat intake is also associated with higher chances of colon cancer (Hunter & Willett, 19). Hormonal imbalance has been diagnosed as the cause for most cancers related to reproductive system in women. In women, hormonal imbalance is also associated with obesity and therefore obesity as the cause for cancers related to ovaries, breast, and endometrium. However, most of the oncology professionals believe that the causes for ovarian cancer are unknown and that chances of ovarian cancers are high in women that did not undergo pregnancy during their fertile period. Other causes include exposure to carcinogenic chemicals, diet, family history, infections, and even obesity (Balch, 290). Cancer caused by smoking can result in tumor growth in specific organs, which results in dysfunction of the organs.