Two things:

1. You don’t gain anything from worrying.
2. I don’t know any thoracic oncologists who would consider a year of smoking as a teenager to be a likely indicator of future cancer.

Is there a “safe” level of smoking? Absolutely not. But your risk factor goes up with use over time, so assuming that you were not chain smoking non-stop for a year straight, it is doubtful that you damaged the DNA enough to cause a cancer situation.

Going forward, maintain a healthy lifestyle and enjoy living that great life you have cultivated. If — and this is a big if — you ever do develop lung cancer, chances will be that it had nothing to do with your junior year of high school. Sometimes cancers just happen, and this in and of itself is a huge reason for not living in fear or cancer. Be as healthy as you can be, be as happy as you can be and just get on with the business of enjoying life.