Indoor Pollutants are a great threat to health than outdoor pollutants
Per the Environmental Protection Agency (see reference):
- Americans, on average, spend approximately 90 percent of their time indoors,1 where the concentrations of some pollutants are often 2 to 5 times higher than typical outdoor concentrations.2
- People who are often most susceptible to the adverse effects of pollution (e.g., the very young, older adults, people with cardiovascular or respiratory disease) tend to spend even more time indoors.3
- Indoor concentrations of some pollutants have increased in recent decades due to such factors as energy-efficient building construction (when it lacks sufficient mechanical ventilation to ensure adequate air exchange) and increased use of synthetic building materials, furnishings, personal care products, pesticides, and household cleaners.
Pollutants and Sources
Typical pollutants of concern include:
- Combustion byproducts such as carbon monoxide, particulate matter, and environmental tobacco smoke.
- Substances of natural origin such as radon, pet dander, and mold.
- Biological agents such as molds.
- Pesticides, lead, and asbestos.
- Ozone (from some air cleaners).
- Various volatile organic compounds from a variety of products and materials.
Most pollutants affecting indoor air quality come from sources inside buildings, although some originate outdoors.
Indoor sources (sources within buildings themselves).
Combustion sources in indoor settings, including tobacco, wood and coal heating and cooking appliances, and fireplaces, can release harmful combustion byproducts such as carbon monoxide and particulate matter directly into the indoor environment.
Cleaning supplies, paints, insecticides, and other commonly used products introduce many different chemicals, including volatile organic compounds, directly into the indoor air.
Building materials are also potential sources, whether through degrading materials (e.g., asbestos fibers released from building insulation) or from new materials (e.g., chemical off-gassing from pressed wood products). Other substances in indoor air are of natural origin, such as radon, mold, and pet dander.
Outdoor sources: Outdoor air pollutants can enter buildings through open doors, open windows, ventilation systems, and cracks in structures. Some pollutants come indoors through building foundations. For instance, radon forms in the ground as naturally occurring uranium in rocks and soils decays. The radon can then enter buildings through cracks or gaps in structures.
Harmful smoke from chimneys can re-enter homes to pollute the air in the home and neighborhood. In areas with contaminated ground water or soils, volatile chemicals can enter buildings through the same process.
Volatile chemicals in water supplies can also enter indoor air when building occupants use the water (e.g., during showering, cooking).
Finally, when people enter buildings, they can inadvertently bring in soils and dusts on their shoes and clothing from the outdoors, along with pollutants that adhere to those particles.
Other Factors Affecting Indoor Air Quality
In addition, several other factors affect indoor air quality, including the air exchange rate, outdoor climate, weather conditions, and occupant behavior.
The air exchange rate with the outdoors is an important factor in determining indoor air pollutant concentrations. The air exchange rate is affected by the design, construction, and operating parameters of buildings and is ultimately a function of infiltration (air that flows into structures through openings, joints, and cracks in walls, floors, and ceilings and around windows and doors), natural ventilation (air that flows through opened windows and doors), and mechanical ventilation (air that is forced indoors or vented outdoors by ventilation devices, such as fans or air handling systems).
Outdoor climate and weather conditions combined with occupant behavior can also affect indoor air quality. Weather conditions influence whether building occupants keep windows open or closed and whether they operate air conditioners, humidifiers, or heaters, all of which can affect indoor air quality. Certain climatic conditions can increase the potential for indoor moisture and mold growth if not controlled by adequate ventilation or air conditioning.
Effects on Human Health
Health effects associated with indoor air pollutants include:
- Irritation of the eyes, nose, and throat.
- Headaches, dizziness, and fatigue.
- Respiratory diseases, heart disease, and cancer.
The link between some common indoor air pollutants (e.g., radon, particle pollution, carbon monoxide, Legionella bacterium) and health effects is very well established.
- Radon is a known human carcinogen and is the second leading cause of lung cancer.4, 5
- Carbon monoxide is toxic, and short-term exposure to elevated carbon monoxide levels in indoor settings can be lethal.6
- Episodes of Legionnaires' disease, a form of pneumonia caused by exposure to the Legionella bacterium, have been associated with buildings with poorly maintained air conditioning or heating systems.7, 8
- Numerous indoor air pollutants—dust mites, mold, pet dander, environmental tobacco smoke, cockroach allergens, particulate matter, and others—are “asthma triggers,” meaning that some asthmatics might experience asthma attacks following exposure.9
While adverse health effects have been attributed to some specific pollutants, the scientific understanding of some indoor air quality issues continues to evolve.
One example is “sick building syndrome,” which occurs when building occupants experience similar symptoms after entering a particular building, with symptoms diminishing or disappearing after they leave the building. These symptoms are increasingly being attributed to a variety of building indoor air attributes.
Researchers also have been investigating the relationship between indoor air quality and important issues not traditionally thought of as related to health, such as student performance in the classroom and productivity in occupational settings.10
Another research area that is evolving is “green building” design, construction, operation, and maintenance that achieves energy efficiency and enhances indoor air quality.
How Plants Combat Indoor Air Pollutants
A famous study conducted by Dr Wolverton, a scientist commissioned by NASA to research and study the effects of houseplants on air quality in contained spaces produced some of the most popular and commonly referenced research papers about the topic.
See the NASA research here:
When NASA announced that houseplants could filter pollutants, dangerous bacteria, and viruses from the air, people were understandably ecstatic. As a result, an extensive study on houseplants' capacity to filter the air in residences and workplaces was conducted.
We've included a link to Dr. Wolverton's book, "How to Produce Fresh Air," on Amazon below if you want to learn more about his research, the experiments, or how he came up with his ranking.
Below is the list of the top 50 houseplants for air cleaning according to NASA and Dr. Bill Wolverton.
The List of 50 Effective Houseplants:
According to Dr. Wolverton, the following list is organized according to the effectiveness of plants in a typical home. As a result, the first plant on the list (the Areca Palm) is the most effective, while the 50th plant (the Kalanchoe) is the least effective.
- Areca Palm (Chrysalidocarpus lutescens)
- Lady Palm (Rhapis excelsa)
- Bamboo Palm (Chamaedorea seifrizii)
- Rubber Plant (Ficus robusta)
- Dracaena "Janet Craig" (Dracaena dermensis)
- English Ivy (Hedera helix)
- Dwarf Date Palm (Phoenix roebelenii)
- Ficus "Alii" (Ficus macleilandii)
- Boston Fern (Nephrolepis exaltata "Bostoniensis")
- Peace Lily (Spathiphyllum)
- Corn Plant (Dracaena fragrans)
- Golden Pothos (Epipremnum aureum)
- Kimberley Queen Fern (Nephrolepis obliterata)
- Pot Mum (Chrysanthemum morifolium)
- Gerbera Daisy (Gerbera jamesonii)
- Dracaena "Warneckei" (Dracaena dermensis)
- Dragon Tree (Dracaena marginata)
- Red Emerald Philodendron (Philodendron erubescens)
- Syngonium (Syngonium podophyllum)
- Dumb Cane (Dieffenbachia "Exotica Compacta")
- Parlor Palm (Chamaedorea elegans)
- Weeping Fig (Ficus benjamina)
- Schefflera / Umbrella Plant (Schefflera arboricola)
- Wax Begonia (Begonia Semperflorens)
- Lacy Tree Philodendron (Philodendron selloum)
- Heart-Leaf Philodendron (Philodendron Oxycardium)
- Snake plant / Mother-in-Law's Tongue (Sansevieria trifasciata / laurentii)
- Dumb Cane (Dieffenbachia camilla)
- Elephant Ear Philodendron (Philodendron domesticum / tuxla)
- Norfolk Island Pine (Araucaria heterophylla)
- King of Hearts (Homalomena wallisii)
- Prayer Plant (Maranta leuconeura "Kerchoveann")
- Dwarf Banana (Musa cavendishii)
- Christmas Cactus (Schlumbergera buckleyi)
- Easter Cactus (Schlumbergera gaertneri)
- Oakleaf Ivy (Cissus rhombifolia "Ellen Danika")
- Lily Turk (Liriope spicata)
- Dendrobium Orchid (Dendrobium)
- Spider Plant (Chlorophytum comosum)
- Chinese Evergreen (Aglaonema)
- Anthurium (Anthurium andraeanum)
- Croton (Codiaeum variegatum pictum)
- Poinsettia (Euphorbia pulcherrima)
- Dwarf Azalea (Rhodedendron simsii "Compacta")
- Peacock Plant (Calthea makoyana)
- Aloe Vera (Aloe barbadensis)
- Cyclamen (Cyclamen persicum)
- Urn Plant (Aechmea fasciata)
- Moth Orchid (Phalaenopsis)
- Kalanchoe (Kalanchoe blossfeldiana)