Hello. Taking X-ray is radiation exposure definitely. But at 10 months of ago, taking one X-ray to look for a lung infection does no long term harm.
The pros and cons of taking an X-ray will be analysed by your Pediatrician and only because your baby really required the X-ray it must have been ordered.
So one X-ray has no long term effects!
Health Tips
Whenever you visit a Pediatrician always let the doctor know of previous xrays taken for a child and the time when it was taken.
This way we can decrease the number of X-ray exposures if one was done very recently.