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In the midst of the energy crisis of the 1970s, those in the building industry placed a high priority on energy consumption and conservation. As a result, both old and new buildings were made more energy efficient. Coinciding with these measures, came a change in the use of natural building materials and furnishings to a more widespread use of synthetic materials. While a tightly sealed building is more energy efficient, it quickly became apparent that trapped within these structures were a mix of emissions of volatile organic chemicals (VOCs) from chemically formulated personal care products, carpeting, fabrics, pesticides, business machines, bioeffluents (emitted in the human breathing process) and airborne microbes. All of these factors teamed together to create a chemical pea soup and resultant complaints of poor indoor air quality (IAQ). Only recently have many physicians begun to associate the increase in respiratory problems with exposure to poor indoor air quality. Once the correlation was accepted, litigation began to wind its way through the courts against building owners, architects and others in the building industry. As a result, insurance companies have paid millions of dollars in damages. However, little progress has been made in mitigating the causes of poor indoor air quality. Sources of Chemical Emissions can be found in the
following chart.
Current IAQ Methods The building industry has struggled with indoor air quality problems since buildings were made more energy-efficient. After almost 30 years of only limited success, the building industry's primary form of remediation is increased ventilation rates. Inherent problems with increased ventilation are: (1) reduced energy-efficiency (2) an assumption of clean outside air and (3) increased vulnerability to bio-terrorism. Only recently have we begun to realize the added risk posed by increased ventilation. Even a small amount of highly pathogenic microbes and/or toxic chemical agents introduced into air intake ducts could quickly contaminate large portions of a building and its inhabitants. The September 11, 2001 terrorist attack on the World Trade Center in New York City should have been a wakeup call for the building industry. Adjacent buildings were saturated by dust and debris much of which was introduced through the ventilation system. Currently, the rapidly spreading SARS virus is again exposing some of the possible vulnerabilities of building ventilation systems. The building industry must accept the need to internally purify, revitalize and recycle air. This is important for energy savings and to reduce the vulnerability of indoor air to biological and/or chemical agents that could be present in the outdoor air.
NASA and Indoor Air Pollution In 1973 during the Skylab III mission, NASA identified 107 volatile organic chemicals (VOCs) that were emitting (offgassing) from synthetic materials inside the spacecraft. As a result, NASA realized that indoor air pollution in any tightly sealed structure could present health-related problems and should be addressed. In 1989 EPA reported to the U.S. Congress that they had detected more than 900 VOCs in the air of public buildings. As part of its research into "closed ecological life support systems," NASA began to study the cleansing powers of nature through the synergestic reactions taking place between plants and their root microbes. In 1984 NASA first published studies demonstrating that interior plants could remove VOCs from sealed test chambers. In a progressive step up, NASA had constructed a tightly sealed building termed the "Biohome" This structure was made with synthetic materials and engineered to achieve maximum air and energy closure. The interior walls of the Biohome consisted of molded plastic panels with 30-cm of fiberglass insulation providing a thermal insulation value of R-40. It was equipped to provide a fully functional habitat suitable for one person. The remainder of the interior space housed a network of bioregenerative components using plants whose basic end products were reclaimed wastewater, potable water and purified air. While the Biohome was not a completely closed system, many valuable lessons were learned. The Biohome was equipped with monitoring ports in each outside door for sampling air from inside this tightly sealed structure. Before plants were added, mass spectrometer/gas chromatograph (mass spec/GC) analyses of the indoor air showed high levels of VOCs offgassing from interior synthetic materials. Upon entering the building, one experienced severe burning of the eyes and respiratory discomfort, both classic symptoms of "sick building syndrome." Interior foliage plants were placed throughout the living quarters to evaluate their ability to remove VOCs outgassed from the newly constructed and furnished facility. A small prototype fan-assisted plant filter was also placed in the living quarters. This plant filter had the VOC removal capacity of 15 standard potted plants. Air quality was again tested using mass spec/GC analyses. Results showed that most of the VOCs had been removed. The ultimate test was the fact that one no longer experienced the symptoms of "sick building syndrome." This was the first "real world" application using interior plants to alleviate indoor air pollution. Later, a student lived in the Biohome with no IAQ complaints. Waste recycling studies where the student's waste (cooking, bathroom, etc.) was treated and recycled within the wastewater treatment/food production section of the Biohome. (See Figures 1 and 2.)
FIGURE 1.
FIGURE 2.
Ecology Gardens Having many plants in an indoor environment is a common occurrence in hotels, offices and restaurants. A visit to Opryland Hotel in Nashville or hotel chains such as Embassy Suites will confirm the euphoric indoor environment created by interior plants. The missing link, however, is that the clean air from the plant-filled spaces is not normally introduced into the surrounding rooms. However, hospitals in Japan are adding plants to take advantage of their air-cleaning properties. Takenaka Garden Afforestation, Inc. of Tokyo is adding "Ecology Gardens" in hospitals. It is a well-established fact that living plants have a beneficial psychological effect on humans. Studies have shown that patients in hospitals experience shorter recovery times when plants are present. Studies by NASA and other scientists have also produced documented evidence that interior plants and their root-associated microbes can remove harmful chemicals from sealed chambers. Studies also show that interior plants may reduce the levels of airborne microbes in the ambient air.
For More Information See Reference page. See also the NASA Technical Report Server. This link provides technical reports written by Dr. B. C. Wolverton while employed with NASA at the John C. Stennis Space Center in Mississippi. Click on the "NASA Technical Report Server" link above. At the search window, type wolverton into the box to gain access to a number of reports (most are downloadable in PDF format). For more information see Dr. Wolverton's book entitled, "How To Grow Fresh Air -- 50 Houseplants that Purify Your Home or Office," (Penguin, 1997 - U.S. Version). Dr. Wolverton rates each plant for its ability to remove chemical vapors, ease of growth and maintenance, resistance to insect infestation and transpiration rates. This book was originally published as "Eco-Friendly Houseplants" (Weidenfeld & Nicolson, 1996) and has been translated into ten languages.
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