Would radiation from x-rays etc of the legs or knees (lower body) increase my risk of salivary cancer? i had some radiation as a kid but only of lower body, not the head. i understand that most tumors are benign anyways but was wondering about this?

All x-rays can hit your genes and DNA and cause cancer. Including those that come from our sun. But risk is thought to be small but not zero. Discuss with you health care team and look at Wikipedia. Or pay $20 for a one month sub to uptodate and read the current state of the are discussion of the risk.

X-ray exposure to the lower body in childhood would not increase your risk of salivary gland cancer. You can reduce your risk of cancer by adopting healthy habits: Eat a mostly vegetarian diet, avoid alcohol, tobacco and street drugs, avoid excessive exposure to sun, exercise 30 minutes each day, drink enough water so your urine is mostly colorless. Wish you good health!