There's an understandable tendency to associate air pollution with the outdoors. But indoor air pollution also presents a threat to human health. Fortunately, there's a pleasant potential solution.
Certain houseplants could combat the potentially harmful effects of volatile organic compounds (VOCs) — a main category of these pollutants. In fact, researchers say that some plants are better than others at removing particular harmful compounds from the air. With the right plant, indoor air could become cleaner and safer.
"Buildings, whether new or old, can have high levels of VOCs in them, sometimes so high that you can smell them," says Vadoud Niri, PhD, leader of the study.
VOCs are compounds like acetone, benzene and formaldehyde that are emitted as gases and can cause short- and long-term health effects when inhaled. They can come from paints, furniture, copiers and printers, cleaning supplies and even dry-cleaned clothes.
"Inhaling large amounts of VOCs can lead some people to develop sick building syndrome, which reduces productivity and can even cause dizziness, asthma or allergies," Niri says.
The most common solution is to install ventilation systems that cycle in air from outside. There are also methods that can remove these compounds, using adsorption, condensation and chemical reactions.
However, Niri wanted to find a cheaper, simpler tool to remove VOCs. Using plants to remove chemicals from indoor air is called biofiltration or phytoremediation. In addition to carbon dioxide, plants can take up gases such as benzene, toluene and other VOCs. NASA began studying this option in 1984 and found that plants could absorb these airborne compounds via their leaves and roots.
Since then, other studies have looked at how plants phytoremediate specific compounds, such as the carcinogen formaldehyde, in a closed space. Most of these studies focused on the removal of single VOCs by individual plants from the ambient air. Niri wanted to compare the efficiency and the rate of simultaneous removal of several VOCs by various plants.
To test this, Niri and his team built a sealed chamber containing specific concentrations of several VOCs. They then monitored the VOC concentrations throughout several hours with and without a different type of plant in the chamber. For each plant type, they noted which VOCs the plants took up, how quickly they removed these VOCs from the air and how much of the VOCs were ultimately removed by the end of the experiment.
The researchers tested five common house plants and eight common VOCs, and they found that certain plants were better at absorbing specific compounds. For example, all five plants could remove acetone — the pungent chemical that is abundant at nail salons — from the air, but the dracaena plant took up the most, around 94% of the chemical.
"Based on our results, we can recommend what plants are good for certain types of VOCs and for specific locations," Niri says. "To illustrate, the bromeliad plant was very good at removing six out of eight studied VOCs — it was able to take up more than 80% of each of those compounds — throughout the 12-hour sampling period. So it could be a good plant to have sitting around in the household or workplace."
Niri says the next step in the research is to test these plants' abilities in a real room, not just a sealed chamber. He would eventually like to put plants in a nail salon throughout the course of several months to see whether they can reduce the levels of acetone to which the workers are exposed.
The team presented its research this week at the 252nd National Meeting & Exposition of the American Chemical Society (ACS). Check out the following animation, which explains the findings: