THE AIR in modern homes and offices is pretty clean, but not as clean as it might be. Often, it contains small amounts of volatile, toxic, organic compounds such as benzene, formaldehyde, butadiene, carbon tetrachloride, naphthalene and chloroform. Chronic exposure to these is a bad thing, so clearing them out of the air people breathe is widely accepted as worthwhile. Finding an effective way to do so has proved difficult. But Stuart Strand, Long Zhang and Ryan Routsong, of the University of Washington, in Seattle, think they have succeeded. As they report in Environmental Science and Technology, their method involves splicing a gene from a rabbit into a popular indoor plant nicknamed Devil’s vine—a type of ivy that is so called because it is famously difficult to kill.
The idea of employing plants, both unmodified and transgenic, to de-pollute the atmosphere inside buildings has been around for decades—but has met with only qualified success. One experiment involving unmodified spider plants, for example, showed that they are indeed capable of scrubbing formaldehyde from the air. The drawback is that to make much of a difference in a space as large as a house would require turning most of the rooms into spider-plant forests. Tobacco plants fitted with a bacterial gene for a formaldehyde-destroying enzyme were three times more effective at formaldehyde scrubbing than those without it. The trouble in their case was that tobacco plants flower indoors, and their pollen can thus spread genetically engineered material (about which some people are paranoid) to unexpected places. Dr Strand, Dr Zhang and Mr Routsong thus sought something suitably transgenic, but that does not flower indoors.
The plant they settled on was Devil’s vine, precisely because of its robustness. The gene they picked was for cytochrome P450 2E1, a mammalian enzyme that oxidises a wide range of volatile organic compounds, including benzene, chloroform, trichloroethylene and carbon tetrachloride. With the help of a bacterium, they were able to ferry the rabbit version of the gene into the plant’s chromosomes, and thus to engineer a type of Devil’s vine capable of producing cytochrome P450 2E1.
To test the effectiveness of their idea, the researchers put their modified ivy to work inside chambers filled with air containing high levels of either benzene or chloroform. The plants performed well, reducing benzene levels from 2,000 milligrams per cubic metre to 250 over the course of eight days, and chloroform levels from 800 to near zero over the course of 11. Unmodified versions of Devil’s vine, tested for comparison, reduced benzene only from 2,000 to 1,400 milligrams per cubic metres over the same eight-day period, and had no statistically significant effect on chloroform levels at all. Genetically modified Devil’s vine may thus prove the answer to the question of how to clean up household air—though perhaps it might be marketed under a slightly different name.