Household air is more polluted than office air and school air, and those who spend much of their time at home, such as children and home workers, receive a proportionately higher dose of home air carcinogens than the general population. Infants are particularly susceptible to indoor air pollution due to their low body weight and continuous exposure to indoor air. Researchers have ranked the cancer risks of indoor air volatile organic carcinogens (VOCs). The highest risk VOCs were benzene, chloroform, formaldehyde, 1,3-butadiene, carbon tetrachloride, acetaldehyde, 1,4-dichlorobenzene (PDCB), naphthalene, perchloroethylene, and ethylene dichloride. VOCs that exceeded acute exposure standards were acrolein and formaldehyde (during cooking) and chloroform (during showering).
Indoor plants have been widely touted as having the ability to remove air pollutants from indoor air.
This approach is known as the “green liver” concept and is a central idea of the field of phytoremediation, the use of plants to remove xenobiotic pollutants from the environment. Early studies of air detoxification by household plants found that formaldehyde was removed from the air of chambers containing spider plants. Other researchers reported that soil or water alone could explain the removal. Subsequently, controlled pure culture plant experiments showed that plants can assimilate and metabolize formaldehyde from the air.
As we like to keep the air in our homes as clean as possible, sometimes we use HEPA air filters to keep offending allergens and dust particles at bay. But some hazardous compounds are too small to be trapped in these filters. Small molecules like chloroform, which is present in small amounts in chlorinated water, or benzene, which is a component of gasoline, build up in our homes when we shower or boil water, or when we store cars or lawn mowers in attached garages. Both benzene and chloroform exposure have been linked to cancer.
Researchers have genetically modified a common houseplant to remove chloroform and benzene from the air around it.
Researchers at the University of Washington have genetically modified a common houseplant — pothos ivy — to remove chloroform and benzene from the air around it. The modified plants express a protein, called 2E1, that transforms these compounds into molecules that the plants can then use to support their own growth.
The team decided to use a protein called cytochrome P450 2E1, or 2E1 for short, 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 turned on when we drink alcohol. So it’s not available to help us process pollutants in our air.
The researchers made a synthetic version of the gene that serves as instructions for making the rabbit form of 2E1. Then they introduced it into pothos ivy so that each cell in the plant expressed the protein. Pothos ivy doesn’t flower in temperate climates so the genetically modified plants won’t be able to spread via pollen.
The researchers then tested how well their modified plants could remove the pollutants from air compared to normal pothos ivy. They put both types of plants in glass tubes and then added either benzene or chloroform gas into each tube. Over 11 days, the team tracked how the concentration of each pollutant changed in each tube.
For the unmodified plants, the concentration of either gas didn’t change over 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.
In order to detect these changes in pollutant levels, the researchers used much higher pollutant concentrations than are typically found in homes. But the team expects that the home levels would drop similarly, if not faster, over the same time frame.
Plants in the home would also need to be inside an enclosure with something to move air past their leaves, like a fan.
The team is currently working to increase the plants’ capabilities by adding a protein that can break down another hazardous molecule found in home air: formaldehyde, which is present in some wood products, such as laminate flooring and cabinets, and tobacco smoke.