In a time where more and more people suffer from the negative effects of living, working and learning in insufficiently ventilated and smelly buildings, it can’t be stated often enough: plants clean the air. By gaining more knowledge about the air-purifying qualities of specific plants, consumers as well as educational and healthcare institutions could benefit and nurseries and green retailers could earn a bundle. So you would think. Yet the qualities of plants are too little specified in programmes featuring a healthy indoor climate. A missed opportunity.

It all started with NASA

Thankfully in recent years awareness has grown of the dangers of the Sick Building Syndrome: people literally turn ill because of the presence of harmful substances like benzene and formaldehyde in buildings, due to insufficient or closed ventilation systems. A study of the University of Technology in Sydney demonstrated that over 300 volatile organic compounds can be present in the air of office buildings. This gives people headaches, fatigue symptoms and respiratory ailments. In the Netherlands the national institute for public health, RIVM, has compiled norms for outside air quality and there are guidelines for the indoor air quality of schools and houses as well. It is a fact that the air quality is not good in many cases.

During his research for NASA in the 1980s, Bill Wolverton discovered that plants could be used to keep up the air quality in space vessels. This Clean Air Study was the beginning of a lot of studies all over the world which all found that plants are a cheap and effective solution to clear the air in rooms. Especially green plants with a lot of leaves and a fast metabolism appear to have these outstanding air-purifying qualities. These plants can pick up harmful compounds with their leaves and break these down in the plant or via the roots. In the book How to Grow Fresh Air you can read about these plants.

In 2010 Wolverton published the book Plants; Why You Can’t Live without Them that summarizes his scientific research spanning decades. Together with Japanese colleague Takenaka he developed the concept Ecology Garden, meant for the healthcare industry. The concept involves indoor gardens, containing any number of the 50 air-purifying plants that NASA discovered, planted in a special soil. They are already in use in 71 Japanese hospitals.

plants in building

Source: Takenaka Garden Afforestation Inc

On the Internet many lists or top-10 of air-purifying plants can be found. These are all based on the original study by Wolverton for NASA. Check here, here and here, for example.

In the Netherlands research facility Fytagoras investigates the air-purifying capacities of plants, for example by placing them in a closed cupboard, adding toxic substances and measuring the break-down time. Fytagoras developed norms for the efficacy of air-purifying plants and compiled the following list for the society for nurseries Air so Pure: golden cane palm, spathiphyllum, sword fern, ivy, dracaena, cabbage palm ferns and calathea. Please note: the latter is not an easy plant to grow. Based on the Fytagoras study, Noviflora developed the concept Ogreen, for plants that can clean the air from 10 to 30 m3 per plant. These are: philodendron, maidenhair fern, clusia and brake fern. All plants mentioned here are easily obtainable. In other countries market concepts are also developed based on the air-cleaning capacities of plants.

These parties have all executed studies and come up with a list or a top-10, but in order to truly convince policymakers, the results need to be more transparent. This will also allow seed improvement companies and nurseries to decide with which plants they want to improve in order to enhance their air-cleaning qualities.

Little attention for purifying properties of plants in indoor environment policy

Despite positive research results and the market concepts already developed, it should be noted that hardly any mention is made of the opportunities plants can offer in most programmes aimed at improving the interior environment of buildings. In 2013 the National Effort Environment and Health initiated by the Dutch government and focused on the improving of the interior of homes, schools and childcare centres. Part of this Effort are the following programmes: The Healthy School, Fresh Schools. In 2014 the following programme was also explored: Healthy Childcare. The latter does bring up plants outside, but no mention is made of the possible positive effects of indoor planting. And in a recent report of the WHO about the indoor climate of schools plants aren’t mentioned either, as is the case in the deal that was closed this past May: Green Deal: Making school buildings sustainable with the spearhead of achieving a healthy and sustainable learning and working climate for students and teachers.

In all programmes aimed at enhancing the interior environment, the focus is always mostly on CO2 and taking measures for natural and mechanical ventilation. However, according to the national institute for public health, better ventilation in schools is often difficult because there are insufficient windows and outlets since theses are closed to keep out draft, sound pollution or to prevent burglary. For further improvement of the indoor environment of schools, structural changes to the ventilation systems and the school buildings are needed. Understandably these adaptations will cost a lot of public money.

Bringing plants to the attention of policymakers

It is now over 25 years since the appearance of the ground-breaking Clean Air Study by NASA. It is high time to bring these effective and relatively cheap air-cleaners to the attention of national and European policymakers, working on improving the indoor environment. Our professional organization has already brought this to the attention of the Dutch delegation with the European Parliament.

In this respect it is important to give the public transparent and structural access to the research results of the studies into the air-purifying capacities of plants, and especially to which plants give the best result under what circumstances. Because so far the available information is no more than a jumble of lists. This makes it hard for policymakers, interior architects and directors of companies, schools and healthcare centres to see the forest for the trees, when they are looking for the right information.

We feel it would be a huge step forward if the possibilities for using air-purifying plants would be considered for the national Dutch guidelines for a healthy indoor climate. If this could be achieved the Netherlands would be the frontrunner in this respect, as far as we know.

Besides, it would offer new opportunities for Dutch growers, breeders and seed specialists to put plants on the international market that have specific, scientifically proven health benefits, based on publicly accessible research results.