Clearing the air with indoor plants

G Magazine

It’s time to bring your green thumb indoors. With our homes and offices harbouring astounding levels of pollution, the humble pot plant will help you breathe easy once more.

Indoor plants

Indoor plants can improve air quality and your wellbeing by taking up carbon dioxide and replacing it with oxygen, as well as helping kick-start a process to remove other toxic gases from the room.

Credit: iStockphoto

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It's an all-too-common misconception that pollution is exclusively an outdoor problem. Are our indoor spaces really the safe haven from emission-spewing cars and industrial smokestacks that we think they are? The
scary truth is that levels of some pollutants are, in fact, highest indoors.

With most Australians spending 90 per cent of their time indoors, between offices and homes, indoor air pollution is bound to take its toll on our collective mental and physical health. The CSIRO estimates the cost of poor indoor air quality in Australia to be as high as $12 billion a year due to illness and decreased productivity.

One solution is neither high-tech nor expensive, and it comes straight back to nature. Indoor plants can
improve air quality and your wellbeing by taking up carbon dioxide and replacing it with oxygen, as well as helping kick-start a process to remove other toxic gases from the room.

Allergic to work?

"We've all had the experience indoors when we feel a little bit headachy, perhaps a little bit giddy, and if it gets worse than that, an irritation in your throat, eyes or nose... all these effects of indoor pollution are what's known as sick building syndrome," says Margaret Burchett from the Plant Environmental Quality Group, based at the University of Technology in Sydney.

Indoor air contaminants include volatile organic compounds (or VOCs), carbon dioxide, carbon monoxide, nitrogen oxides and fine particulates, to name just a few.

The high concentrations of pollutants indoors is "partly due to the air coming in from outside with all the pollution it contains, mixing with the [chemical toxins from] indoor materials," says Burchett. And while outdoor air pollution, including vehicle and industrial emissions, is regulated, there are no enforceable limits to indoor air contaminants.

Brand-new buildings can cause sick building syndrome because of all the new furniture, fittings and surface finishes. That 'new smell' from fresh wall paint, newly laid carpets and brand-new furniture might seem 'clean', but the chemicals behind the smell are toxic. Breathing these VOCs into your lungs can not only make
you feel unwell in the short-term but, over a longer period, may cause respiratory diseases and cancer.

People living or working in older buildings are also at risk because materials used to be made from more toxic substances than they are today, and while the VOC emissions gradually decrease over time, most synthetic materials will continue to emit low levels of pollutants for their entire life. Electrical items such as computers and TVs will emit VOCs whenever the plastic casing becomes warm.

While air-conditioners filter dust, mould spores and pollens from the air, they don't remove VOCs and other gases. And if they're not regularly cleaned and maintained, indoor air quality deteriorates further. Add carbon dioxide from everyone breathing in a crowded office, or at home from burning gas appliances such as cooktops, and you have a heady cocktail that could make you feel more than a little woozy.

Sucking it up

There are currently no national guidelines for safe levels of VOCs indoors. In 1993 Australia's National Health and Medical Research Council recommended 500 parts per billion (ppb) VOCs as a goal, but this has since been rescinded. Some people start to feel unwell when levels exceed 200 ppb, says Burchett. She and her team found that, in offices where the concentration of VOCs was close to 450 ppb, placing three or more plants in the room reduced the levels to 100 ppb.

Basic biology taught us all that the leaves of plants take in carbon dioxide and expel oxygen. But what's less commonly known is that often it's the soil - or more specifically, the bacteria in the soil - that does the hard work of removing toxins from the air. Soil microbes will jump into action when they notice toxins at levels as low as 50 ppb.

"The leaves aren't so much what take up large quantities of VOCs. They will, but comparatively more slowly than the micro-organisms in the soil. Both the leaves and soil microbes will also take up nitrogen oxides," says Burchett. However this doesn't mean you can just plonk a pot of soil on your desk to filter the air: "There's a symbiotic relationship with the plants and the microbes for the VOCs."

Making it work for you

If you have visions of vines swallowing up your telephone and pots covering every surface, think again. A surprisingly small amount of greenery makes a big difference. A British study of thousands of homes noted that, if a house had six or more pot plants, it had a third less nitrogen oxides in the air than houses without any indoor plants. The Green Building Council Australia acknowledges the inclusion of indoor plants in its Green Star ratings system and recommends a minimum of a 300 ml pot per two workstations.

The greater the surface area of the leaves on the plant, the more carbon dioxide it will be able to take out of the air. However, when it comes to lowering levels of VOCs, different types of plants are similarly effective because it's the normal bacteria in the potting mix that does most of the work.

Most importantly, choose plants that will work with the current light and space restrictions of your home or office. "There are a myriad of plants that are very good indoors," says Stuart Swaddling, managing director of TPR group, a national supplier for tropical plant rentals.

Swaddling recommends you look at how much light is available before you make your selection. "There are plants that will do very well in low light conditions; Janet Craig is one that can basically live in a cupboard. But any flowering plants need to be as close as possible to a window, so long as it's not direct sun."

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