Infections are responsible for 6% of cancer deaths in developed nations.

You (demographically typical LW reader) may want to look into the HPV vaccine, (and post what you find!) I thought there was no cost-effective-benefit to vaccinating males or older women, but this seems to be wrong. A few credible sources have argued for young men and older women to receive the vaccine.

Some medical tests can also increase exposure to radiation.

Note that dosage varies widely by procedure. This link gives some estimates. They say yearly background dose is about 3mSv. A dental x-ray is quoted at 0.005 mSv, while an abdominal CT scan is 10 mSv, and a few procedures are even higher.