Biological effects of small air ions: a review of findings and methods.

A wide variety of effects of exposure to small air ions have been reported, but these are difficult to evaluate because of limitations in experimental design and control. These limitations are discussed, and trends in the literature are reviewed. It is concluded that small air ions are likely to have biological effects, that these effects may be related to polarity, and that where effects occur they are likely to be small in magnitude and difficult to detect reliably.