Air pollution is on the rise—and some of the most concerning contaminants are in our own homes. Seemingly innocuous household items like shower heads, paint cans, and plywood paneling can all leak cancer-causing pollutants into the air we breathe. Because closed doors make for poor ventilation, these chemicals have a way of building up indoors, often spiking to levels up to 10 times higher than outdoor concentrations.
By these numbers, the future of easy breathing looks a little bleak. But now, scientists reveal that the fight for clean indoor air may just have acquired a new and powerful ally: the humble houseplant.
A study published today in the journal Environmental Science & Technology reports that a genetically modified strain of ivy may be able to leach dangerous carcinogens like benzene and chloroform out of air. Though the technique is still in its infancy, these plants could someday provide a sustainable way to deliver cleaner air to homes around the world.
“We’re still in the early stages of what we can do with engineered plants,” says Patrick Shih, a synthetic biologist at the University of California Davis who was not involved in the new study. “It’s really exciting to see that more people are thinking in this direction, outside agriculture… and this could be a very cool application to make the household less dangerous.”
Pioneering the effort is Stuart Strand, an environmental engineer at the University of Washington. For decades, Strand has been investigating new and sustainable ways to combat indoor air pollution, which remains largely unaddressed. Compounds like chloroform can emanate from chlorinated tap and shower water, and others such as benzene are present in tobacco smoke, furniture, and fuel that may be stored in attached garages.
Homes have been found to harbor both of these chemicals at levels that could increase cancer risk to residents, especially infants, young children, and others who spent a lot of time in the home. The few methods that exist to sponge up these contaminants, like adsorption by activated carbon, aren’t always ineffective, and can be financially impractical or energetically expensive. Instead, Strand thinks part of the next big solution might already be a modern indoor mainstay.
Golden pothos (Epipremnum aureum), a low-maintenance ivy often seen dangling from household pots, may seem simple at first glance. But like many other plants, golden pothos can act as a blank genetic canvas eager for paint: Its DNA is easily manipulated, and, because plants make their own energy, they’re remarkably sustainable. “Plants are marvelous high-energy environments,” Strand adds. “They produce lots of sugars, and those are available to power all kinds of reactions.”
And one of those reactions could involve detoxifying air. But plants aren’t naturally hardwired with this superpower. So Strand and his team selected a gene that could confer this ability to golden pothos. Their gene of choice codes for a protein called cytochrome P450, which is found in many species across the tree of life, including humans. In mammalian livers, cytochrome P450 serves as a microscopic cleanup system for the myriad toxins the body encounters, often rendering them ineffective through the process of oxidation. For instance, cytochrome P450 neutralizes drugs, which is why their effects eventually wear off.
To enhance golden pothos, the team copied a version of cytochrome P450 out of the rabbit genome and inserted it into the plant’s genome. They then sealed the cytochrome P450-producing plants into closed vials containing benzene or chloroform. To Strand’s delight, the ivy sapped the chemicals out of the surrounding air over the course of a week. By the sixth day, chloroform in vials containing plants was barely detectable.
“This is a very interesting first step, and it seems they’ve done a careful job,” says Allison Snow, who studies plant ecology at Ohio State University but was not involved in the new study. “But there needs to be a lot more work to show that this would scale up to make a difference.”
It’s a fair point: The researchers’ initial work was performed in 40-milliliter vials—which can hold just under three tablespoons—that contained only a gram of plant material apiece. That’s a far cry from even a single room in a large household.
But Strand and his team are already planning ahead. Currently, they’re developing a product to maximize the plants’ positive effects in the home. Their hope is to use something similar to a particle filter that will collect and circulate air over the ivy leaves to maximize chemical-to-plant exposure—something akin to “a mini greenhouse in the home,” Strand says.
However, a plant-based filter will need to be very efficient to actually put a dent in the levels of indoor contaminants, says Richard Shaughnessy, a chemical engineer studying indoor air pollution at the University of Tulsa, but who was not involved in the study. Plant-based filters haven’t performed well in the past. What’s more, Shaughnessy adds, this device would need to be built at a practical size and cost, which may be challenging; for instance, some of Strand’s estimates for such a filter could require over 20 pounds of ivy in a single unit. The team would also need to ensure that neither the addition of cytochrome P450, nor exposure to toxins, will have unintended side effects on the ivy’s growth and development—especially in ways that could compromise its efficiency.
If the research progresses, however, benzene and chloroform are only two of many compounds Strand’s team plans to target. Cytochrome P450, while powerful, is ineffective against other potentially cancer-causing contaminants like formaldehyde, which sneaks into houses in the form of wood flooring, glues, particle board, and cigarette smoke. To address this, the researchers plan to introduce additional genes into the ivy, making it something of a Swiss Army knife of decontamination.
Of course, modifications to any living organism may spark concern that the genes could spread to the environment. But because golden pothos doesn’t reproduce well in temperate climates and isn’t edible, some of the typical concerns about GMOs may be more easily allayed, Strand says. All the same, the team is taking precautions before going commercial.
“The list of plants that are engineered is already growing,” Snow says. “There are applications [for these plants] that maybe most people haven’t heard of or thought of that will probably become more common—and maybe this is one of them.”