The Collaborative International Dictionary of English v.0.48:

Unpolluted \Unpolluted\
   See polluted.

WordNet (r) 3.0 (2006):

unpolluted
    adj 1: free from admixture with noxious elements; clean;
           "unpolluted streams"; "a contaminated lake" [syn:
           uncontaminated, unpolluted]

Moby Thesaurus II by Grady Ward, 1.0:

41 Moby Thesaurus words for "unpolluted":
   bleached, bright, clean, cleanly, dainty, dirt-free, fair,
   fastidious, fresh, immaculate, kosher, nonpolluted,
   of cleanly habits, pure, ritually pure, shiny, smut-free, smutless,
   spotless, stainless, sweet, tahar, tubbed, unadulterated,
   unbesmirched, unblemished, unblotted, undefiled, unmuddied,
   unsmirched, unsmudged, unsoiled, unspotted, unstained, unsullied,
   untainted, untarnished, well-scrubbed, well-washed, white,
   whitened