Grow Fresh Air at Home

Most of the year we are all tucked away in our homes keeping snug and warm in Winter or cool and comfortable in summer. We sit all sealed up in our nice energy efficient homes. Now is the perfect time of year to go out and fill your home with houseplants. Yes, that’s right, I said houseplants.All locked up in the house or in office buildings we are that much more disconnected with our real roots – nature. At this time of year especially we need to bring a little of the outdoors in.

Need another reason?

How about indoor air pollution? The air inside your home may be as much as 10 times more polluted than the outside air. Today most people will spend as much as 90 percent of their lives indoors. As people spend more time indoors there has been an increase in the number and severity of allergic reactions and other chronic illnesses.

In 1973 NASA found over 300 volatile organic compounds (VOC) in Skylab III. In 1983 the United States Environmental Protection Agency (EPA) found more than 350 VOC in homes for the elderly in Washington, DC. The EPA has done more studies since and now ranks indoor air pollution as one of the top five threats to public health. That’s bad!

A large number of these chemicals have the potential not only for producing allergic reactions, but also cancer and other forms of illness as well. So where is all this coming from? Of the hundreds of toxic chemicals found indoors, the National Aeronautics and Space Agency (NASA) studied three because they were the most commonly found and in greater abundance. These toxins are formaldehyde, benzene, and trichloroethylene (TCE).

The chemical with the greatest human exposure is formaldehyde.

It is found in urea-fromaldehyde foam insulation (UFFI), and particle board or pressed wood products. Many consumer paper products have it as well, such as grocery bags, waxed papers, facial tissues and paper towels. These products give off formaldehyde because they are treated with urea-formaldehyde (UF) resin. This resin is used as a stiffener, wrinkle resister, water repellant, fire retardant, and adhesive binder in floor coverings, carpet backing, and permanent-press clothes. Other sources of UF include many common household cleaning agents, cigarette smoke and heating and cooking fuels such as natural gas and kerosene.

Side Effects

include irritation of the mucous membranes of the eyes, nose, and throat. Formaldehyde combines with protein and can cause allergic contact dermatitis. The most widely reported symptoms from exposure to high levels include irritation of the upper respiratory tract and eyes and headaches. It also causes asthma. The EPA has recently linked a rare throat cancer with long-time occupancy of mobile homes. The main suspect in the cause is formaldehyde which is found in higher concentrations in mobile homes than any other buildings. This is the problem with the FEMA trailers Hurricane Katrina victims are living in. There are high levels of Formaldehyde in them. Formaldehyde is considered a cancer-causing substance by the International Agency for Research on Cancer.

The next culprit studied by NASA is Benzene. It is a commonly used solvent and is found in many basic everyday items such as gasoline, oils, inks, paints, plastics and rubber. It is also used in the manufacture of detergents, explosives, pharmaceuticals and dyes.

Side effects include skin and eye irritation.

Chronic exposure at low levels causes headaches, loss of appetite, drowsiness, nervousness, psychological disturbances, and diseases of the blood system, including anemia and bone marrow disease. Benzene has been shown to cause mutations in cells, adversely affect growth and development of embryos, and a carcinogen in some tests. Benzene may also be a contributing factor in disrupting chromosomal content in cells causing genetic conditions, and may be linked to leukemia in humans. Repeated skin contact causes drying, inflammation, blistering, and dermatitis. Inhalation of high levels has been reported to cause dizziness, weakness, euphoria, headache, nausea, burred vision, respiratory diseases, tremors, irregular heartbeat, liver and kidney damage, paralysis, and unconsciousness. In animal tests inhalation led to cataract formation, and diseases of the blood and lymphatic systems.

Trichloroethylene (TCE)

is the third chemical NASA focused on. It is a commercial product with a wide variety of industrial uses. Over 90 percent of TCE produced is used in metal degreasing and dry-cleaning industries. It is also used in printing inks, paints, lacquers, varnishes and adhesives.

AS far as side effects the National Cancer Institute considers TCE a potent liver carcinogen. Carbon monoxide is another toxin that threatens human health. That is just four out of the over 300 chemicals found in the studies! Most of which had not been identified.

Why all these chemicals?

We have changed the nature of building materials and household furnishings over the last several decades. We use pressed wood and fiber board instead of natural wood. Household furnishings have changed with more pressed board, plastic, and artificial fibers being used. Cleaners, insecticides, glues air fresheners, hair sprays, shoe polish, magic markers, and numerous health care and personal grooming air products add even more synthetic chemicals to the air in our homes.

Add to that sealing our homes, offices, apartments, and hospitals tight to make them more energy efficient and you have a closed environment with toxins trapped inside.

This “Sick Building Syndrome” is attributed to the poor ventilation in these energy efficient, tightly sealed homes and buildings. It cannot be due to microorganisms. Dr. Tony Pickering of the Wythenshawe Hospital near Manchester, England has studied this syndrome extensively. He found that naturally ventilated buildings with high levels of micros had minimal symptoms while mechanically ventilated buildings with low levels of micros had the highest levels of symptoms.

Before you go running out of your home screaming there is some help. First of all energy efficient homes and buildings are a good thing. Natural ventilation is good but if you use central heating and air, as most people do, you need to be sealed in tight to use less energy. That’s good for the environment. Opening up the house on beautiful days when heat or air is not necessary is refreshing. Ideally products and building materials should be off-gassed for a while before being used in homes and buildings. The problem with that is many of these products will release these toxic gases for years. Even better would be no toxic chemicals at all. Until then, what do you do?

Well, we at Earth Council are not surprised at the solution at all. Get in touch with your environment, indoors. The Earth and all of Nature is our support system. It only makes sense that nature will save us in our artificial environments as well. NASA in partnership with the Associated Landscape Contractors of America (ALCA), now called PLANET, found plants to be the easiest and most efficient air filters. Plants will filter out the three toxins mentioned and carbon monoxide as well. The plants’ leaves absorb these organic chemicals and destroy them by a process called “metabolic breakdown”. The chemicals are metabolized and converted into tissue products such as organic acids, sugars, and amino acids.

It is not just the leaves at work cleaning the air. Microorganisms in the soil are capable of biodegrading toxic chemicals. Before you go out and put pots of dirt in your home, rather than worry about possibly killing a plant, the microorganisms need the plant to do their work. When a plant is well established in the soil these microorganisms are activated by the plant root growth. The micros are then able to biodegrade the toxic chemicals.

The capacity of micros to clean the air improves the longer they are exposed to the chemicals. Micros have the ability to genetically adapt. So when they are exposed to such chemicals continuously they increase their ability to utilize toxic chemicals as a food source. This adaptability is currently being used to remove toxic chemicals from wastewater. The plant-root soil zone is the most effective area for removing volatile organic chemicals. Maximizing air exposure to this area by clipping off lower leaves will help in filtering the air.

To make plants even more efficient at their filtering capabilities the researchers developed high efficiency filters using plants and activated carbon. The activated carbon is placed in the specially designed pot near the plant’s roots. A small fan is built into the pot near the bottom. The activated carbon absorbs large quantities of the toxic chemicals and retains them until the plant roots and microorganisms are able to degrade them. The little fan then blows the clean filtered air out. These filters have the VOC (volatile organic compounds) removal capacity of approximately 200 regularly grown plants. They are currently marketed in Japan under the name “EcoPlanter”.

How do plants do all this?

Plants use photosynthesis to live. In order to maintain this process they require a continuous exchange of gaseous substances between the plants leaves and the surrounding atmosphere. Plants give off water vapor and oxygen and take in carbon dioxide. Plants are able to take in other gaseous substances through tiny openings in their leaves called stomates. When plants transpire water vapor through their leaves they pull air down around their roots, an area called the rhizosphere. This supplies their root microbes with oxygen. The microbes utilize not only the air but any chemicals, even toxic ones, found in the air. They breakdown and destroy the chemicals and convert it into a source of food and energy for the plant and themselves. Microbes, such as bacteria, quickly adapt and produce new colonies that are resistant to the toxic chemicals. Because of this adaptation microbes become more efficient at filtering toxins in the air the longer they are exposed to it. Since transpiration is what pulls air down the to the roots and microbes for filtering, the higher the transpiration rate the faster and more chemicals are filtered. Increasing this rate hlelps the filtration of the air. As humidity goes down and temperature goes up the transpiration rate and therefore the filtration rate increases.

So, not convinced yet?

Only recently have physicians begun to associate the increase in respiratory problems with exposure to poor indoor air quality. Tokyo recognizes that it is a well-established fact that living plants have a beneficial psychological effect on humans. They are now adding “Ecology Gardens” in hospitals. Studies have shown that patients in hospitals experience shorter recovery times when plants are present.

If filtering toxins out of the air is not enough for you how about these other benefits.


Plant filtered rooms have 50 to 60 percent less airborne microbes, like mold spores and bacteria, than similar rooms without plants (B.C. Wolverton and J.D. Wolverton, “Interior Plants: Their Influence on Airborne Microbes Inside Energy-Efficient Buildings, Journal of the Mississippi Academy of Science, 1996, 41(3):99-105.) They do it by releasing phytochemicals that suppress these microbes. They possibly do this to protect themselves from being attacked by airborne microbes. So plants help filter out airborne allergens. Some allergy physicians continue to recommend that patients remove all plants from their homes,even though there is no scientific basis for this recommendation.

Feeling Good

Plants have physical as well as psychological benefits. Positive health benefits of negative ions have been known for a hundred years. They have been known to help lift a person’s mood, alleviate depression, and seasonal affective disorder (SAD or winter depression).

Ions are charged particles in the air found in nature in UV light, airflow friction, lighting, falling water and plants. As plants emit water vapors through transpiration they produce negative ions. Waterfalls and tropical forests and crashing waves at the beach produce large amounts of negative ions. It helps explain the good feeling people experience at these places.

We not only do not have these things in our homes, but the synthetic building materials, clothing, furniture coverings and plastics actually remove large numbers of negative ions from the environment. So the chemicals that are off-gassing toxic chemicals are also zapping the negative ions that would keep us healthy and happy. The plastics have a positive static charge that consumes large quantities of negative ions. So there are often very low numbers of negative ions in modern buildings.

Since high levels of negative ions is need for good health and good feelings then large numbers of indoor plants could certainly improve our health and sense of feeling good. The reduction in mold spores and bacteria in the air that helped with allergies were possibly due to the production of negative ions by plants.

Dr. Lohr from Washington State found that houseplants can reduce human stress and increase productivity (Journal of Environmental Horticulture, 1996, 14(2):97-100). This is likely due to the increased number of negative ions produced by the plants. These negative ions not only improve our health, lift our moods and reduce stress, but they cut down on dust inside homes and buildings. Dr. Lohr found in another study (Atmospheric Environment, 1996, 30(14): 2565-2568) houseplants could reduce dust levels in a computer room by 20 percent! So plants cut down on allergies in this way as well, and cut down on dusting time! Humidity

Plants maintain healthy humidity levels inside homes and buildings. Plants regulate humidity levels to control transpiration rates. Higher hujmidity means less transpiration (release of water vapor) from the plant. Too high a humidity means mold growth which is not good for plants or people. Too low a humidity level means very dry air which means more moisture loss from a plant’s leaves and drying of membranes and the respiratory system in humans. Drier air occurs in the winter months. A drier respiratory system makes humans more susceptible to colds, viruses, and allergens. Dry air also damages homes, building materials and equipment. Wood that is too dry cracks and rots, “dry rot”.

Plants maintain humidity levels indoors at a range of 40 to 60 percent which is optimum for humans and plants. While plants are keeping humidity levels down to prevent mold growth at the same time they are suppressing mold spores.

Makes you want to go out and fill your home with plants doesn’t it? Dr. Wolverton, who headed the research at NASA has written a book on the research and the plants recommended for your home. It is How to Grow Fresh Air: 50 Houseplants that Purify your Home or Office by Dr. B.C. Wolverton.

Below are the 50 plants he recommends. They are rated based on their removal of chemical vapors and their ease of care, among other factors. This list starts with the best overall purifier. Parents with children and pet guardians need to take note that many of these plants are toxic if ingested. There are lists below of what plants are safe out of the ones he recommends for pets and children.

None of this is very surprising.

We are so intricately entwined with nature it is not surprising that we get so sick when we live without it. It is also not surprising that it is nature that makes us better. The planet has always supplied us with everything we need to be happy and healthy. Our human egos just make us think we can do better. The best part of the final report from NASA stated “Since man’s existence on Earth depends upon a life support system involving an intricate relationship with plants and their associated microorganisms, it should be obvious that when he attempts to isolate himself in tightly sealed buildings away from this ecological system, problems will arise. Even without the existence of hundreds of synthetic organic chemicals off-gassing into tightly sealed environments, man’s own waste products would cause indoor air pollution problems.” “The answer to these problems is obvious. If man is to move into closed environments, on Earth or in space, he must take along nature’s life support system.” “This joint effort has gone a long way toward reminding man of his dependence on plants for his continued existence and well-being on our planet.”

If plants do this much to clean up our toxic mess indoors, think of what they can do to clean up our outdoor mess. We just need to give them a chance and not keep cutting down these natural air filters and polluting at such rates that the few trees we let live cannot keep up.

And you thought all plants did was produce life giving oxygen.