With their stiff leaves and large spiky flowers, bromeliads can add drama to a plant stand or window sill. They are not the flashiest of houseplants. Still, some pollution scientists are ready to give them raves. Their new data show these plants are superstars when it comes to cleaning the air.
Paints, furniture, photocopiers and printers, cleaning supplies and dry-cleaned clothes can all release a family of toxic gases into indoor air. As a class, these gases are known as volatile organic chemicals, or VOCs. Inhaling a number of them can cause dizziness, allergic reactions — even asthma. Long-term exposure might lead to liver damage, kidney damage or cancer.
This is important because people often can’t smell these chemicals. They also can't stop breathing when a room’s air becomes polluted, notes Vadoud Niri. He is a chemist at the State University of New York at Oswego. And once VOCs enter a room’s air, there’s no way to pull them out again. People can’t vacuum them out.
But certain types of greenery can suck the pollutants up, which keeps them safely away from us.
A single bromeliad houseplant can remove at least 80 percent of six different VOCs from the air inside a 76-liter (20-gallon) container, Niri found. In tests, other houseplants also filtered out VOCs. But none performed as well as the bromeliad.
Niri presented his group’s new data on August 24 at the annual meeting of the American Chemical Society in Philadelphia, Pa.
Not a surprise
In the 1980s, scientists with the National Aeronautics and Space Administration, or NASA, investigated houseplants' ability to cleanse the air of VOCs. All of the tested plants pulled out at least some VOCs.
But in those tests, each plant was exposed only to one type of VOC at a time. In the real world, indoor air contains a mix of them. So Niri and his colleagues wanted to know what would happen if plants were exposed to a mix of VOCs.
His team exposed five common houseplants — a bromeliad, Caribbean tree cactus, dracaena (Dra-SEE-nuh), jade plant and spider plant — to eight common VOCs. Each plant lived for a while with these pollutants in the 76-liter container (about the size of a car's gas tank).
Certain plants were better than others at removing a particular VOC. For instance, all five plants removed acetone (ASS-eh-tone) — a smelly VOC in nail polish remover. But after 12 hours, the dracaena had cleared out 94 percent of this gas — more than any of the other plants.
Meanwhile, the spider plant removed VOCs most speedily. Once placed inside the container, VOC levels started to fall within one minute. But this plant didn't have staying power.
The bromeliad did. After 12 hours, it had removed more VOCs from the air than any other plant. The two VOCs that it could not filter out — dichloromethane and trichloromethane — were also ignored by the other plants. So in this regard, it was no worse than the others.
Webe Kadima is a chemist who also works at the State University of New York at Oswego. She studies medicinal plants but did not work with Niri on this experiment. Part of her work involves understanding what various plant components do. These include enzymes, which are molecules made by living things to speed up chemical reactions.
Plants absorb VOCs from the air, she explains. Those gases enter through stomata (Stoh-MAA-tuh) — tiny openings in plant leaves and stems. Once inside, the plant's enzymes break down the VOCs into smaller, harmless chemicals.
"The bottom line is that plants contain molecules that let them clear VOCs from the environment," says Kadima.
Of course, a house, or even a bedroom, is much bigger than the container Niri and his team used. But their work suggests people might breathe easier if they can figure out what type and how many plants it takes to clean the air in a room. This is important because indoor air usually has three to five times greater concentrations of VOCs than outdoor air.
Niri says he plans to test how many houseplants it takes to clean the air in an average-size room. After that, he will repeat the experiment in a nail salon. With all those bottles of nail polish and remover, the air in those salons tends to have high levels of VOCs, he notes.
While special air filtering machines might do the same job as green plants, they cost a lot more, Niri says. And they are nowhere near as pretty as a bromeliad. Especially one in bloom.
(for more about Power Words, click here)
acetone A chemical produced by the body that is detectable in people’s breath. It’s also an extremely flammable liquid solvent used, for example, in nail polish remover.
asthma A disease affecting the body’s airways, which are the tubes through which animals breathe. Asthma obstructs these airways through swelling, the production of too much mucus or a tightening of the tubes. As a result, the body can expand to breathe in air, but loses the ability to exhale appropriately. The most common cause of asthma is an allergy. It is a leading cause of hospitalization and the top chronic disease responsible for kids missing school.
cancer Any of more than 100 different diseases, each characterized by the rapid, uncontrolled growth of abnormal cells. The development and growth of cancers, also known as malignancies, can lead to tumors, pain and death.
carbon The chemical element having the atomic number 6. It is the physical basis of all life on Earth. Carbon exists freely as graphite and diamond. It is an important part of coal, limestone and petroleum, and is capable of self-bonding, chemically, to form an enormous number of chemically, biologically and commercially important molecules.
chemical A substance formed from two or more atoms that unite (become bonded together) in a fixed proportion and structure. For example, water is a chemical made of two hydrogen atoms bonded to one oxygen atom. Its chemical symbol is H2O. Chemical can also be an adjective that describes properties of materials that are the result of various reactions between different compounds.
chemical reaction A process that involves the rearrangement of the molecules or structure of a substance, as opposed to a change in physical form (as from a solid to a gas).
enzymes Molecules made by living things to speed up chemical reactions.
extract (v .) To separate one chemical (or component of something) from a complex mix.
filter (in chemistry and environmental science) A device which allows some materials to pass through but not others, based on their size or some other feature. (in physics) A screen, plate or layer of a substance that absorbs light or other radiation or selectively prevents the transmission of some of its components.
molecule An electrically neutral group of atoms that represents the smallest possible amount of a chemical compound. Molecules can be made of single types of atoms or of different types. For example, the oxygen in the air is made of two oxygen atoms (O2), but water is made of two hydrogen atoms and one oxygen atom (H2O).
NASA See National Aeronautics and Space Administration
organic (in chemistry) An adjective that indicates something is carbon-containing; a term that relates to the chemicals that make up living organisms. (in agriculture) Farm products grown without the use of non-natural and potentially toxic chemicals, such as pesticides.
pollutant A substance that taints something — such as the air, water, our bodies or products. Some pollutants are chemicals, such as pesticides. Others may be radiation, including excess heat or light. Even weeds and other invasive species can be considered a type of biological pollution.
toxic Poisonous or able to harm or kill cells, tissues or whole organisms. The measure of risk posed by such a poison is its toxicity.
volatile Chemical that easily evaporates.
Meeting: V. Niri et al. Monitoring volatile organic compound removal by common indoor plants using solid phase microextraction and gas chromatography-mass spectrometry. 252nd National Meeting & Exposition of the American Chemical Society. August 24, 2016. Philadelphia, Pa.