36 and smoker)what could 3 noncalcified lung nodules sizes 6mm- 4mm left lower lobe be? found on ct, what would be next step to identify cause?

Many possibilities.: Noncalcified lung nodules are worrisome, especially if you are a smoker (as you have), & more so if you are a "heavy" smoker (based on number of packs per day, & no of yrs that you've smoked). A nodule could be scar tissue, or the effects of an infection or radiation; however, most worrisome, of course, is lung cancer. To identify cause, next step is usually bronchoscopy (scope to look) & biopsy.