They recruited six households in York, who all live in similar modern homes with similar outdoor air quality and placed an air sampler in each house for five days to tell us which homes had the highest amounts of chemicals, and what those chemicals were.
Each household kept a diary of what household products they used over the five day period and how often they used them.
They also tested for formaldehyde in three of the six households.
Lab studies show that for every two molecules of limonene released in the air, one molecule of formaldehyde is formed. Formaldehyde is a known secondary product of fragrance chemicals when they react in the air. It is a carcinogen (a cancer-causing chemical) and can cause skin irritation and respiratory symptoms.
The programme said research suggests that houseplants could possibly have powerful chemical-absorbing properties but this research has predominantly been carried out in the lab, with some evidence that it could work in an office. It has not been carried out in the home.
They placed four houseplants in each of the volunteer families’ houses for four weeks, then took new air samples at the end of the experiment to see whether the plants had any effect on the indoor air pollution in each home.
The plants were: Chlorophytum(Spider plant), Dracaena (Dragon tree), Scindapsus (Golden Pothos), Hedera helix (English Ivy).
The results showed instead of the plants reducing the levels of fragrance chemicals in the homes - the limonene actually increased but the most likely explanation was because it was November there were lots of candles and fewer open windows.
Since limonene reacts in the air to make formaldehyde, the programme expected the formaldehyde to rise as well. But levels of formaldehyde actually fell in all three of the homes measured (in contrast to the rising limonene), while the plants were in there.
They concluded: "The results of our very small experiment suggest that the plants could have played a role in reducing the levels of formaldehyde in our families’ homes."
One study in 2010 tested 86 species of plant for their effectiveness in absorbing formaldehyde, and found 9 to be excellent absorbers:
- Osmunda japonica (Japanese royal fern)
- Selaginella tamariscina
- Davallia mariesii (squirrel’s foot fern)
- Polypodium formosanum (grub fern)
- Psidium guajava (common guava)
- Lavandula spp (lavender)
- Pteris dispar
- Pteris multifida (spider fern)
- Pelagonium spp. (geranium)
Other studies have looked at a wider range of chemicals, and house plant species which have excellent all-round absorbing ability seem to be:
- Hemigraphis alternate
- Hedera helix (English ivy)