Could air purifying plants improve your indoor air quality in Shanghai?
As we spend most of our time indoors, it is critical to keep your indoor air clean.
Apart from outdoor pollution, other pollutants can affect indoor air quality, such as emissions from furniture and building materials, cooking and heating gas, plastics and detergents etc.
If we close windows and doors to prevent outdoor pollution from entering, or to save energy, it is even more critical to ensure indoor air is purified.
One of the most effective air pollution solutions is using air purifiers in your home, but a cheaper, if not so effective, solution is to use air purifying plants.
There are several plant and flower markets in Shanghai where you can find hundreds, if not thousands, of varieties of flowers and plants. These markets house many vendors under one roof, so you can usually get good prices just by doing comparison shopping, even if your bargaining skills aren't so great.
The vendors will arrange delivery, sometimes included for free depending on the amount of your purchase. In case you don't have a green thumb, there are also some vendors that will rent you plants, including a monthly maintenance service, to make sure they are watered correctly.
Besides breathing in carbon dioxide and breathing out oxygen, air purifying plants also absorb other toxins.
There is some controversy about how effectively they do this, with the California Environmental Protection Agency stating in a 2005 report on Air Cleaning Devices for the home that "Houseplants do not effectively remove indoor air pollutants.
"One researcher has reported that certain air purifying plants can remove significant amounts of indoor air pollutants. However, six subsequent reviews, and a study in office buildings and portable office buildings, indicated that houseplants have very little, if any, effect on indoor pollutant levels.
"Small effects might occur, but only with an unreasonably large number of houseplants present, which could easily cause other indoor pollution problems such as excess moisture.” Read their full report here.
There have been, however, several studies that do show plants have many benefits, including purifying our indoor air.
The best-known study of air purifying plants was done by NASA and Dr. B.C. Wolverton in the 1970s and 80s. This study was carried out to find ways to clean air in orbiting space stations, where astronauts would be confined for long periods of time.
Dr. Wolverton went on to do many more of his own studies and published several books on the effectiveness of plants in purifying air.
The NASA study focused on 3 common toxins found in indoor air:
The results of the study showed that some air purifying plants can remove up to 87 percent of some air pollutants within 24 hours. Based on their studies, NASA recommended the use of 15 to 18 good-sized houseplants in a 170 m2 home or office.
Dr. B.C. Wolverton’s list of the 50 most effective air purifying plants, published in his book How to Grow Fresh Air, with rough translations into Chinese, can be found below.
A separate study from the Pennsylvania State University published in an issue of the American Society of Horticultural Science's journal HortTechnology revealed that three common houseplants; snake plant, spider plant, and golden pothos, all showed an ability to reduce ozone, another air pollutant which is becoming a serious issue in Shanghai.
Air purifying plants are known to be very adaptable to their environment, as their air purifying capability increases over time. They learn to convert more of the toxic particles in their new environment into their own food source.
The NASA study also showed that the roots and exposed soil plays a big part in absorbing the toxins, so lower lying leaves and branches should be removed to ensure maximum contact with the air.
Some plants, however, can also be toxic, so you should check the list for non-toxic safe air-purifying plants if you have pets or young children.
Another study published by Dr. Wolverton in 1996 in the Journal of the Mississippi Academy of Science showed that rooms with air purifying plants have 50 to 60 percent less airborne microbes, such as mold spores and bacteria, than similar rooms without plants.
Plants do this partly by reducing humidity levels indoors down to between 40 and 60 percent, the ideal level for humans, thereby helping to prevent mold growth.
Although some people recommend removing plants to reduce allergies, a reduction in mold spores and bacteria in the air could actually have a great benefit to allergy sufferers.
Another way air purifying plants reduce microbes is by releasing negative ions. In an article published in the Journal of Environmental Horticulture, also in 1996, Dr. Lohr, found that houseplants can reduce human stress and increase productivity by releasing negative ions, which have been known for many years to have health benefits to humans.
Ions can improve people’s mood, alleviate depression, and help to cure seasonal affective disorder (SAD, or winter depression).
Ions are charged particles in the air which can be produced by UV light, airflow friction, lighting, falling water and plants. As air purifying plants emit water vapors they produce negative ions. Many products found indoors such as plastics have a positive static charge that consumes large amounts of negative ions.
In another study (Atmospheric Environment, 1996, 30(14): 2565-2568) Dr. Lohr also showed that houseplants could reduce dust levels in a computer room by 20 percent, also helping allergy sufferers.
In a study published in 2011 in the Journal of Environmental Psychology, scientists showed that air purifying plants placed in an office helped to boost the attention span of office workers, showing that greenery has regenerative effects for directed attention.
There is a report extensively distributed around Chinese Social media sites promoting the effectiveness of 14 plants for their air purifying attributes. This report does not list who did the study, and just refers to ‘experts’.
Some of the same or similar plants can be found on the NASA list. You can find the list with a rough translation below.
Caojiadu Flower and Bird Market in Shanghai
Flower and plant market in Shanghai:
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