Houseplants that clean the air

People generally rely on High Efficiency Particulate Air (HEPA) filters to keep out harmful allergens and dust particles from air in their homes.

However, molecules of some hazardous compounds are too small to be trapped in common HEPA filters, such as small molecules like chloroform or benzene that are present in chlorinated water and in gasoline. These small particles bypass HEPA filters and build up in our homes when we shower or boil water, or when we park our vehicles in garages attached to homes. Both benzene and chloroform exposure have been linked to cancer.

Researchers at the University of Washington in the US have now genetically modified a common houseplant, pothos ivy, to remove chloroform and benzene from the air around it.

The team decided to use a protein referred to as 2E1, which is present in all mammals, including humans.

In our bodies, 2E1 turns benzene into a chemical called phenol and chloroform into carbon dioxide and chloride ions. But 2E1 is located in our livers and is thus not available to help us process pollutants in our air. Meanwhile, plants use carbon dioxide and chloride ions to make their food, and they use phenol to help make components of their cell walls.

The researchers made a synthetic version of the gene that serves instructions for making 2E1 and then introduced it into pothos ivy, so that each cell in the plant expressed the protein.

They specifically selected pothos ivy because it is a robust houseplant that grows well under all sort of conditions.

To find out the effectiveness of the modified plants in removing pollutants from the air, researchers placed both modified and normal pothos plants under glass tubes and then exposed them to either benzene or chloroform gas.

On measuring the concentration of each gas in the glass tube over a 11-day period, the researchers found that for the unmodified plants, the concentration of either gas did not change over the test time. But for the modified plants, the concentration of chloroform dropped by 82 percent after three days, and it was almost undetectable by day six. The concentration of benzene also decreased in the modified plant vials, but more slowly: By day eight, the benzene concentration had dropped by about 75 percent.

Though the researchers used much higher pollutant concentrations in their test than are typically found in homes, the team expects that the home levels of pollutants would drop similarly, if not faster, over the same time frame. They also noted that plants in the home would probably need the assistance of a fan to circulate air past their leaves in order for them to be effective.

The research team is currently working to increase the plants’ capabilities by adding a protein that can break down formaldehyde, another hazardous molecule found in home air, and present in some wood products, such as laminate flooring and cabinets, and in tobacco smoke.

These are all stable compounds, so it is really hard to get rid of them. “Without proteins to break down these molecules, we would have to use high-energy processes to do it. It is so much simpler and more sustainable to put these proteins all together in a houseplant,” said the researchers.