Green and Variegated Rhapis palms, Cycads, Rhapis excelsa

Plants and formaldehyde within the building envelope

THE AUTHOR

Jessica Wilkins – wilkins.jessica@saugov.sa.gov.au – has a Bachelor of Architecture and a Bachelor of Design Studies from the University of Adelaide, and is presently working as an Environmental Project Officer with the Building Asset Services branch of the South Australian Department for Administrative and Information Services (DAIS). She has a strong interest in environmentally sound design – especially within the built environment.

This paper on indoor air quality is specifically about office buildings. The reason for this is that, according to the US Environmental Protection Agency, office buildings exceed other building types with regard to concentrations of Hazardous Air Pollutants. In the study referred to, the other building types monitored were hospitals and nursing homes, and the air pollutants specifically measured were trichloroethylene, benzene, xylene, and formaldehyde, which are all Volatile Organic Compounds (VOCs).

VOCs are emitted (off-gassed) from various internal sources and are then essentially trapped within the building envelope, along with us, the building occupants. We average over 90% of our time indoors – in virtual confinement within this mix of pollutants. This paper is also specifically about formaldehyde (as opposed to the other pollutants) as, among those measured, formaldehyde was by far the most predominant chemical found in each of the building types and, within offices, was measured at 0.173 micrograms per litre. Formaldehyde is emitted from a number of sources including adhesives, carpeting, ceiling tiles, fabrics, floor coverings, paints, particleboard, plywood and upholstery. On 15 June this year (2004), the International Agency for Research on Cancer (a branch of the World Health Organisation) updated formaldehyde from "probably carcinogenic" to "carcinogenic to humans", based on new information from studies of persons exposed to it.

Formaldehyde’s effects on human health are now known to range from mild eye and nose irritation to lung and nerve damage, birth defects and cancer. Levels of formaldehyde are likely to be highest in new or newly refurbished spaces that have not been designed according to ecologically sustainable principles. Owing to the many factors that contribute to the level of formaldehyde in a space (e.g., the number and concentration of sources and the amount of natural ventilation), and the factors that contribute to rates of off-gassing (e.g., temperature, humidity and time), the actual level will vary from office to office, from day to day. While not 100% accurate for every office space, the US EPA’s measurement of 0.173 micrograms per litre is, however, a useful generic figure to indicate approximate overall exposure. This generic figure is of interest because former NASA scientist Bill Wolverton has found that there are a variety of indoor plants that remove formaldehyde from the air, and he has established a removal rate in micrograms per hour for the best performers.⁶In a 1989 NASA experiment, formaldehyde was introduced into a sealed Plexiglas chamber containing plants and potting soil, and the level subsequently measured at 6 and 24 hours.

The following Table below shows the best performing commonly grown indoor plants and the rates at which they remove formaldehyde from surrounding air. These plants are all available from nurseries and garden shops in Australia.

^{Removal of Formaldehyde from Sealed Chambers by Plants Grown in Potting Soil} Common Name	Botanical Name	Removal Rate (Micrograms/Hour)
Boston fern	Nephrolepis exaltata ‘Bostoniensis’	1863
Dwarf date palm	Phoenix roebelenii	1385
Bamboo palm	Chamadorea seifrizii	1350
Janet Craig	Dracaena deremensis ‘Janet Craig’	1328
English ivy	Hedera helix	1120
Weeping fig	Ficus benjamina	940
Peace lily	Spathiphyllum ‘Clevelandii’	939
Areca palm	Chrysalidocarpus lutescens	938
Corn plant	Dracaena fragrans ‘Massangeana’	938
Lady palm	Rhapis excelsa	876

Using this information, it is possible to calculate how many of particular types of indoor plants you should have around you in an office environment in order to breathe cleaner air. There are 1000 litres of air in a cubic metre. Therefore by determining how many litres of air there are in your office and multiplying by 0.173 micrograms per litre, it is possible to estimate the amount of formaldehyde in the space and the number of plants needed to remove it. According to Bill Wolverton, since figures in the table were determined for a sealed-chamber environment, the figure determined should be doubled to account approximately for continuous off-gassing, diffusion, etc.⁽⁵⁾

^{While the
table suggests which plants might best be used to remove formaldehyde as
the most prominent indoor air pollutant, various other plants are better
at removing the less prevalent but nonetheless undesirable chemicals.
For example, gerberas, English ivy and peace lilies are good at removing
benzene and trichloroethylene. Therefore, a selection of different
plants, rather than a room full of Boston fern, is the best approach. If
enough plants are introduced to remove the formaldehyde, then the other
pollutants should also be removed as well. In selecting appropriate
plants for a particular office, it is also important to consider their
varying light requirements as offices can differ significantly in light
level depending, for example, on type of lighting and whether natural
light is available.

Boston Fern}

^{“Since man’s existence on Earth
depends upon a life support system involving an intricate relationship
with plants and their associated micro organisms, it should be obvious
that when he attempts to isolate himself in tightly sealed buildings
away from this ecological system, problems will arise.”(6)}

^{Another benefit to consider is
the effect of nature on the human psyche; there are studies to support
that being in the presence of plants can result in a reduction of
stress, an increase in productivity, and an increase in mental
awareness.(7) While there are many factors that would influence the
accuracy of the formaldehyde removal formula, it cannot be denied that
our existence must always be balanced by the presence of plants and
trees – and it makes sense to keep them around us within the building
envelope.}

PLANTS & INDOOR AIR QUALITY

How to Grow Fresh Air – 50 Houseplants that Purify Your Home or Office –

Book available from Penguin Books

Most city dwellers spend 90% of their lives indoors, which means that good indoor air quality is vital for good health. How pure is the air you breathe? Plants produce the oxygen that makes life possible, add precious moisture, and filter toxins from the atmosphere. Houseplants can perform these essential functions in your home or office with the same efficiency as a rainforest in our biosphere. In research designed to create a breathable environment for a NASA lunar habitat, scientist and author Dr. B.C. Wolverton discovered that houseplants are the best filters of common pollutants such as ammonia, formaldehyde, and benzene. Hundreds of these poisonous chemicals can be released by furniture, carpets, and building material, and then trapped by closed ventilation systems, leading to the host of respiratory and allergic reactions now called Sick Building Syndrome. This illustrated book shows how to grow and nurture 50 plants as accessible and trouble-free as the tulip and the Boston fern, and includes many beautiful but commonly found varieties not generally thought of as indoor plants. He also rates each plant for its effectiveness in removing pollutants,

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