The word "contaminated" refers to something that is polluted, tainted or infected. The antonyms for more contaminated are "cleaner," "purified," "sanitized," "sterile," "immaculate," and "uncontaminated." When these words are used to describe something, they indicate that it is free from impurities, bacteria or harmful substances. For example, a purified water source can be considered an antonym for more contaminated water source. Essentially, the antonyms for more contaminated offer a range of options to describe something that is free from any form of pollution or infection, which is vital to health and safety.