Houseplants are, of course, the essence of green, and their presence is beneficial. Their appearance in rooms has been found to purify indoor air.  In addition to eliminating noxious gases and reducing carbon dioxide, plants also produce oxygen and balance indoor humidity, resulting in air that is more like natural outdoor air.
It's the methods used to grow plants that are the problem: The US spends more than $5 billion a year (including outdoor gardening) on fossil-fuel-derived fertilizers that leak chemicals and accelerate the release of nitrous oxide—a greenhouse gas. Insecticides are also dangerous to the environment: The US Environmental Protection Agency (EPA) has classified ingredients such as permethrin as a likely carcinogen.
Related health issues
The EPA cites indoor air pollution as one of the top five public health threats in America due to artificial materials like synthetic fibers and plastic, which emit harmful formaldehyde, trichloroethylene (TCE), benzene, and other volatile organic compounds (VOCs).
In a recent study, the Berkeley National Laboratory in Berkeley, California, found that 40 percent of all office sick days are related to poor indoor air quality and that the presence of plants could save $58 billion per year by preventing sick building syndrome, and save another $200 billion in improved worker performance.
A US National Aeronautics and Space Administration (NASA) study found that certain plants help with specific chemicals—spider plants and golden pothos remove carbon monoxide and formaldehyde and peace lilies are particularly good at eliminating benzene and TCE. The book How to Grow Fresh Air: 50 House Plants that Purify Your Home or Office by B. C. Wolverton offers comprehensive guidance on plant choices.
- volatile organic compounds (VOCs): Elements that significantly vaporize and enter the atmosphere; they can be found indoors in materials like paint and plastics. VOCs can be harmful, contributing in some cases to sick building syndrome, where people suffer health effects from chemicals in the materials in buildings.
- US Environmental Protection Agency - Indoor Air Quality
- Brooklyn Botanic Garden - Drought-Proofing Your Garden: Essential Water-Saving Strategies
- The Green Guide - Leafing the Air Clean
- Care2 Greenliving - Top Ten Houseplants for Cleaner Air
- The Green Home Guide - Choose the Right Air Cleaner for Your Baby’s Nursery
- Time Magazine - Global Warming Survival Guide: Make Your Garden Grow
- Kentucky Division for Air Quality - Indoor Air Quality
- The Green Guide - Air cleaning houseplants
- Cancer Prevention Coalition - Indoor Air Pollution: Cleaning Up Cleaning Habits