Potted plants can remove the pollutant nitrogen dioxide indoors

Nitrogen dioxide (NO₂) is a significant pollutant in both outdoor and indoor environments with exposure linked to serious respiratory illnesses, decreased lung function and airway inflammation. Here, we investigate whether potted plants can contribute as a simple and cost-effective indoor air pollution mitigation technique. Our study investigates the ability of the combination of the three plant species Spathiphyllum wallisii ‘Verdi’, Dracaena fragrans ‘Golden Coast’ and Zamioculcas zamiifolia with two different growing media to remove in situ concentrations (100 ppb) of NO₂ in real-time at two typical indoor light levels (0 and 500 lx) and in ‘wet’ and ‘dry’ growing media conditions. All studied ‘growing medium–plant systems’ were able to reduce NO₂ concentrations representative of a polluted urban environment, but to varying degrees. The greatest NO₂ removal measured inside a 150 L chamber over 1-h period in ‘wet’ growing media at ~ 500 lx was achieved by D. fragrans. When accounting for dilution, this would correspond to a removal of up to 3 ppb NO₂ per m² of leaf area over the 1-h test period and 0.62 ppb per potted plant over the same period when modelled for a small office (15 m³) in a highly polluted environment. Depending on building ventilation rates and NO₂ concentration gradients at the indoor-outdoor interface that will vary massively between polluted urban and rural locations, potted plants offer clear potential to improve indoor air quality—in particular in confined indoor spaces that are poorly ventilated and/or located in highly polluted areas.