NASA’s Favorite House Plants for Space Stations and You

Space. The final frontier. These are the voyages of the Starship Enterprise, its five year mission…

the-earth-in-spaceWith those now famous words, every episode of Star Trek began its weekly story. The show envisioned an incredible future with humans traveling to the limits of the universe. They had fancy communicators, which some 40-odd years later actually resembled our flip phones. They also had computers in which you placed pre-programmed discs to get things done, much like we do with CDs and DVDs. Yes, Star Trek hit an awful lot of things pretty close to the mark – but in one respect they missed it completely. If you watch the reruns of classic and Next Generation episodes you will notice that you almost never see any house plants. In a science fiction TV show that small subtlety may not seem very odd, but in reality it sure would be strange. At least according to NASA, Pennsylvania State University, the University of Georgia, and other respected institutions it would be quite strange indeed.

So now go ahead and take a deep breath. Fill your lungs. Now consider that breath – how was the air quality? Good? Bad? Do you really have any idea at all?

Having good indoor air quality is very important, especially since many of us spend so much time inside our homes. In the 1980s a common trend started to emerge across Europe, the United States and Canada in new buildings which had been built with energy efficiency in mind. The trend involved a number of symptoms seen in the people who worked in these buildings. Symptoms such as allergies, asthma, headaches, and loss of concentration were noted in person after person. The phenomenon was eventually linked to poor indoor air quality and became known as “Sick Building Syndrome” or SBS. Since then, health officials have been concerned about indoor air quality because of the chronic health risks and the financial costs to society. Poor indoor air quality has also been linked to health problems in children. Asthma has reached epidemic proportions among multiple age groups within the Western world and is considered the most common chronic disease in urban-dwelling youngsters. We now understand that if energy-efficient construction is not carefully designed to maintain indoor–outdoor air exchange, one unintended consequence can be increased concentrations of indoor air pollutants.

Most people have heard that house plants are good for your health because they can clean, filter and purify the air of various toxins and pollutants. A lot of people know that this has been proved by scientific research and testing, although most people don’t know about the actual studies or which plants are best for the job. Have you ever wondered whether house plants actually make a real difference in your indoor air quality? Well, it turns out that this is not just some crazy claim, this is actually rocket science! Reliable data on “plant-mediated indoor air quality” is available from experiments conducted by Pennsylvania State University, the University of Georgia, and others – but it all started with the U.S. National Aeronautics and Space Administration, better known as NASA.

As NASA researchers explored the possibilities of long-term human habitation in space, much like the conditions for the crew of the Enterprise on Star Trek, they quickly learned that the air in a tightly sealed space capsule or a large space station would quickly become contaminated with volatile organic compounds (VOCs, as NASA calls them) and other chemicals released by the materials used to manufacture the capsule interior. This problem, as it turns out, is comparable to the situation in newly constructed energy-efficient buildings, as we discussed above.

So, yes, clean air is important in our homes and offices, and it is important in interstellar travel too. During the late 1980s NASA began studying house plants as a means of providing purer and cleaner air for space stations and biospheres. NASA proposed that if humans traveled to inhospitable planets then small biospheres would need to be built in order to support human life, much like a spacecraft provides a suitable environment for its passengers as thy travel through space. The issue, however, was that at the time our “rocket ships” could only be used for short periods due to the quick build up of volatile organic chemicals, coming from both the people on board and the craft’s equipment and machinery. At first it was thought that air cleaners with HEPA filters would be the answer, but the problem with these units is that they are often bulky and heavy. This isn’t a concern in most homes, but it is a major concern when dealing with the size and weight restrictions associated with space travel. Further, filtration systems and air purifiers do not reduce the levels of all indoor air pollutants. Some methods of filtration can actually aggravate the problem. One study, published in 2008 in the American Journal of Public Health, showed that some air purifiers raise indoor concentrations of ozone above the safety levels established by the U.S. Environmental Protection Agency.

Between 1980 and 1984, NASA proved that plants in sealed test chambers that were exposed to volatile organic chemicals could remove those chemicals from the air. The chemicals plants could filter included formaldehyde, which is found in or used to produce a multitude of everyday household products, from fabrics and furniture to tobacco smoke and gas stoves. Numerous scientific studies have shown that formaldehyde is dangerous to human health, and in 2011 the U.S. National Toxicology Program went as far as to label it a “human carcinogen.” In 1984, many universities were excited by NASA’s findings and began to fund significant research to examine house plants and their air-purifying capabilities.

House Plants to the Rescue!

A more gentle alternative to bulky air filtration systems could very well be found the use of simple house plants. So, sure, that potted fern is pretty, but did you know that it can also spruce up the air quality in your home, biosphere, or spacecraft?! Plants are famously adept at absorbing gases through pores on the surfaces of their leaves. It is this very skill that facilitates photosynthesis, the process by which plants convert light energy and carbon dioxide into chemical energy to fuel their own growth. But in addition to the basic photosynthesis that removes carbon dioxide and returns oxygen to the air, house plants can remove toxins from air, soil, and water in at least two important ways. First, they can metabolize many toxic chemicals, releasing harmless byproducts. And second, they can incorporate toxins such as heavy metals into plant tissues, thus sequestering them safely out of harm’s way.

Early on, the NASA research determined that plants could remove toxic chemicals from indoor air. Initially, they were looking for ways to cleanse the atmosphere inside future space stations and biospheres. The study was the first of its kind, and is still cited today in literature discussing the health benefits of house plants on air quality. You will be able to find an interesting NASA study on the subject at: ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19930073077.pdf.

In the study, NASA used sealed test chambers that were injected with chemicals commonly found in interior spaces. Scientists studied dozens of house plant species to determine which, if any, could reduce toxins in the air. The rocket scientists concluded that house plants were indeed highly effective at removing harmful substances from indoor atmospheres. They published a list of preferred species, along with specific chemicals that each plant was most efficient at cleansing from the air.

Now, most of us don’t travel on spaceships or live in biospheres or space stations – but that doesn’t mean that this information is useless to us. On the contrary, it has great meaning. As it turns out, our own homes contain the very same unhealthy chemicals that NASA was determined to filter from the air of its space stations. These toxins are present in many materials that we use every day, such as paints, plastics, carpeting, and furniture. They can also be found in the various materials used to build, fill, clean, and maintain our homes. Contaminants from all of these sources “off gas” or “gas out” as they age. The slow release of toxic fumes from these materials pollutes the air in our homes and over time can cause harm to each of us, often beginning with the most vulnerable; the youngest and oldest inhabitants in our homes.

Some common indoor chemicals of concern are: benzene, found in plastics, nylon, dyes and detergents; toluene, used in paints, coatings, dyes, adhesives and fragrances; xylene, in cleaning products, printing ink, rubber and leather; formaldehyde, which is very common and found in plastics, resin, adhesives, furniture, insulation, fabrics, carpeting, and many building materials; and trichloroethylene, used in adhesives, cleaners and degreasers.

These noxious chemicals are invisible to us mere mortals so we cannot see them as they poison our indoor air, thus we do not know that they are there and we do not know when they need to be combated. House plants however, do not need to know, nor do they care that pollutants abound – they just go along doing what nature has made them to do, day after day. These wonderful gifts of our Earth have been shown to cleanse the air of many chemicals, especially those listed above that are of most concern to us. Simply by their very existence, they work to make our environment better and healthier.

It begins to sounds wiser and wiser to have plenty of house plants around, doesn’t it?

The scientists and researchers who studied the air-purifying quality of plants suggest one or two plants for every 100 square feet of indoor space. For greatest impact, they recommend at least 10 to 18 house plants in most homes. The suggestion is based on sizable plants growing in pots 10 to 12 inches in diameter.

Some house plant types filter certain chemicals from the air, but not others. Topping the list are plants that cleanse the widest array of indoor pollutants.

Here are a dozen house plants NASA recommends for indoor air purification:

1. Peace lilies ranked highest at cleansing nearly all chemicals floating around in today’s home air. These were the most effective plants at removing benzene, formaldehyde, xylene, toluene and trichloroethylene from the atmosphere. Peace lilies are common in both homes and offices and perform well even in low-light conditions. They can be located several feet away from a window.
2. Sanseveria, called snake plant, performed second highest, removing nearly all air contaminants. This was good news because they’re not only easy to grow but long-living, with plants commonly reaching ages of 25 to 40 years old. Being a succulent, they are tolerant of occasional neglect (That makes them perfect for me!).
3. Palms including areca, lady and bamboo types. Avoid soggy soil, and watch for spider mites.
4. Golden pothos, also called devil’s ivy, is a rapid-growing vine useful for hanging baskets or anywhere trailing plants are needed.
5. Several types of dracaenas made the list, including marginata, Warnecki and Janet Craig types.
6. English ivy has a classic appearance. Occasionally washing the foliage will reduce its susceptibility to spider mites.
7. Chrysanthemums and gerbera daisies are effective purifiers, but they are difficult to maintain as house plants, other than enjoying them occasionally as blooming gift plants from the florist.
8. Spider plant has long been recognized as an air cleanser.
9. Aloe Vera is also called medicine plant. It is a good air cleaner and good for first aid too.
10. Ficus, the weeping fig becomes tree-like as it grows.
11. Chinese Evergreen does well in low light.
12. Philodendron air cleaners include both the vining heartleaf and selloum types.

There may be some high-ranking house plants on the list that you really don’t care for, but there may be others that you love further down the list. So keep in mind that you should select plants for your home or office that you actually enjoy. The list will simply illustrate that if you keep the plants above, there is hard scientific proof that they will clean the air in your home or office, thus earning the official stamp that they “are good for your health” as a result. In the end it would seem that having house plants in our homes is not only a great way to relax and enjoy nature, but that it really is “rocket science” after all!

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  • Dale says:

    Have any low light food or herb producers been tested for air cleaning ability, plants such as ginger, turmeric, winter tomatoes, etc?

  • Alice J Haslam says:

    Thanks for reminding me about the air cleaning ability of certain houseplants. In my recent focus on vegetables, I have gotten away from houseplants. I believe that my new carpet has been causing some air quality issues in my house, and I am anxious to give this solution a try. I am unable to open my windows most of the year due to the air conditioning.

    1. Joe Urbach says:

      Hi, I am glad that this article has helped you.
      I am not able to open my windows most of the year just like you and so I always keep a houseful of these plants in my home. They are like a beautiful air filter that I never have to change!

  • Michael says:

    Checking the ASPCA list, almost all are listed as toxic in some way. Would be nice to find something that cleans the air well but can be pruned and fed to animals. Though perhaps as a compost.

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