Indoor Plants and Your Health - January 2023

When you add indoor plants to your home's interior, you add greenery as well as living organisms that provide health benefits. A number of studies have found an association between houseplants and a range of positive psychological and physiological benefits.

Air purification
Researchers have investigated the role of indoor plants for biofiltration, a process that purifies the air. Plants can absorb carbon dioxide in addition to volatile organic compounds (VOCs) such as benzene (found in some plastics, cigarette smoke, fabric softener) and formaldehyde (found in some cosmetics, carpet cleaner and fabric softener). 

NASA carried out a landmark study of plants and air purification in 1989.  Researchers wanted to look at how plants could affect the indoor air quality of a space station and energy efficient buildings with little outside ventilation. According to NASA researcher Dr. Wolverton, indoor air pollution is one of the world’s greatest public health risks. The indoor environment is important since we spend about 80 to 90 percent of our time indoors. Plants found to be most beneficial for the indoor environment include the spider plant and gold pothos, and to a lesser degree the dracaena, philodendrom, ficus, English ivy, peace lily, Chinese evergreen, bamboo and reed palm. The Mother Nature Network website has the complete list of plants from the NASA study. 

Researchers are examining the relationship between a high concentration of VOCs and health problems such as dizziness, asthma, and allergies. The NASA study served as the basis for newer studies including a 2016 study out of the State University of New York where researchers looked at the efficiency and capability of five plants to absorb VOCs - the jade plant, spider plant, bromeliad, dracaena, and Caribbean tree cactus. The lead author, Vadoud Niri, notes that both new and old buildings can have high levels of VOCs. Niri and colleagues placed plants in air-tight chambers with specific concentrations of several types of VOCs. The purification of the air was measured over time and the best plant was Bromeliad plant which cleaned up to 80 percent of the air pollutants in six of the eight VOCs. You can watch a video by the American Chemical Society that describes this study.

Future research will look at ‘real-life’ scenarios instead of lab controlled conditions. While the Environmental Protection Agency reports that there is no clear evidence at this time regarding the number of houseplants needed to remove a significant level of pollutants, NASA suggests placing two or three plants in 8 to 10-inch pots for every 100 square feet for air purification purposes. The most benefit can be gained by having a variety of plants in a room. 

Other benefits of house plants: 
Lowering stress - a study in the Journal of Environmental Psychology found that houseplants can decrease stress levels. 

Positively affecting mood - one study found higher concentration, job productivity and satisfaction in offices with plants when compared to offices without plants.  

Healing for surgery patients - research has found that the process of healing from surgery was improved with plants e.g., fewer painkillers, better physiological responses to tests, less anxiety and fatigue, as well as less time to heal. 

Negatives of houseplants: 

Fungi or bacteria in plants and the soil make them inappropriate in the environment of people with compromised immune systems.  

Plants may not be appropriate for people with allergies. The Berkeley Wellness Letter suggests removing an indoor plant to see if this affects your allergies. 

Pet danger - some plants are poisonous for pets (see the list on the Ontario SPCA website). Some common poisonous plants for pets include sago palms, tulips and azaleas. 

Future research 
Building on small-scale research, a large scale project is exploring the benefits of houseplants in the Netherlands and will be completed in December 2018. Called the Plants for a Good Interior Climate, the project is looking at the effects of ornamental plants on the health and well-being of people in office buildings and care institutions. The researchers are seeking to identify the plants that contribute to air quality, and the influence of the plants on the well-being and health of the building residents.

If you would like to know more about having houseplants in your home or office, check out this presentation by McGill University. To ensure success with plants, look for the right plant for the right spot. For example, the snake plant is a tried and true plant that can tolerate all levels of light and humidity. 

Source: Berkeley Wellness Letter website, David Suzuki Foundation website, Science Alert website, ABC News website, American Forests website, Phys Org website