Negative air ions (NAIs) have been discovered for more than 100 years and are widely used for air cleaning. Here, we have carried out a comprehensive reviewing on the effects of NAIs on humans/animals, and microorganisms, and plant development. The presence of NAIs is credited for increasing psychological health, productivity, and overall well-being but without consistent or reliable evidence in therapeutic effects and with controversy in anti-microorganisms. Reports also showed that NAIs could help people in relieving symptoms of allergies to dust, mold spores, and other allergens. Particulate matter (PM) is a major air pollutant that affects human health. Experimental data showed that NAIs could be used to high-efficiently remove PM. Finally, we have reviewed the plant-based NAI release system under the pulsed electric field (PEF) stimulation. This is a new NAI generation system which releases a huge amount of NAIs under the PEF treatment. The system may be used to freshen indoor air and reduce PM concentration in addition to enriching oxygen content and indoor decoration at home, school, hospital, airport, and other indoor areas.

 

Negative air ions (NAIs) have been discovered for more than 100 years. Now, NAI generators are widely available for home or industrial uses. In the meantime, various new technologies were developed and used to further improve NAI generation and reduce the release of its byproduct ozone. However, some controversial results or comments have been reported for the beneficial effect on humans/animals or on reductions in bacterial densities. Here, we have carried out a comprehensive reviewing on NAIs. On the other hand, strong evidence had shown the roles of NAIs in high-efficiently reducing particulate matter (PM) concentration. Thus, more work should be done to further improve NAI release by new methods or devices so that NAIs could be more widely used for air cleaning. Here, we review the generation of NAIs and their effects on humans, animals, and microorganisms. We then discussed the involvement of superoxide ions in biological effects of NAIs. Subsequently, we focused on plant-based NAI generation systems as these are relatively new NAI generation systems with some advantages on traditional corona discharge NAI generators. We also reviewed the air cleaning ability of NAIs, especially in removing PM with diameters less than 10 micrometers (PM10).