We live in increasingly polluted cities, traffic, heating of houses, factory fumes and some types of materials release toxic substances into the atmosphere and this is a possible cause of different symptoms, from allergies, headaches and chronic irritations to more serious diseases such as tumors (Daisey et al, Indoor air, 2003). The problem belongs to all seasons of the year but certainly a peak of pollution occurs in the winter months. What actions can we take to improve the air in the rooms in which we live? Certainly the choice of plants is not only an ornamental question but it can really help to make a difference. In fact, already as of the late 1980s, thanks to a study commissioned by NASA (Wolverton, NTRS, 1989), it has been possible to understand that some types of plants can be a great ally in improving the microclimate of homes by removing toxic if not even carcinogenic substances such as formaldehyde or benzene. Well, in recent years, scientists have continued to study and experiment to look for other plant species, easy to find and useful to improve the quality of air. In particular, research has focused on the impact of these plants on volatile compounds such as formaldehyde, benzene, toluene and xylene, toxic substances easy to find in homes as they are released from paints, lacquers, glues, new furniture, cigarette smoke, pressed wood and insulating materials. Not only that, the scientists tried to understand if the plants analyzed could also influence the levels of particulate levels, which is made up of solid particles and aerosols dispersed in the air and able to incorporate toxic substances into them, thus causing, in those who inhale them, heart and lung problems. But scientists observed also the effects of plants on ozone levels, a type of pollution more typical of the summer period as this gas is formed in the lower layers of the atmosphere when solar radiation hit pollutants already present. Ozone may cause a worsening of respiratory diseases. Finally, also the effect of plants on the levels of nitrogen dioxide has been analyzed. Nitrogen dioxide, or NO2, is a pollutant, whose main source is traffic and which causes an increased risk of contracting infections, respiratory problems and an aggravation of already existing pathologies such as asthma (Samet et al, Toxicol Ind Health, 1990 - Zhang et al, Frontiers in Immunology, 2019). Well, what emerged (Gourdji et al, Environ Pollut, 2018) is that the pines are the best to capture the particulates, for example it is possible to plant in gardens or green roofs, which are the roofs covered with vegetation, the Pinus strobus radiata 'Nana', or eastern white pine, the mountain pine and the Siberian dwarf pine.
Then, always as garden or roof plants, we can mention, according to the same study, the Japanese Maple plant, or palmate maple, useful against ozone, while the magnolias are excellent to reduce the levels of nitrogen dioxide and indirectly also those of ozone.
As for pot plants, on the other hand, the plants of the ficus family are very effective, such as the rubber plant, scientific name ficus elastica, or raphis excelsa, which is a small palm. They are useful to remove volatile compounds such as benzene, toluene, formaldehyde, xylene while they are less useful in removing particulate from internal environments as the levels of this pollutant in the home depend mainly on the quantity present outside (Hong et al, EHT, 2017).