Air Purifying Plants: Truth vs. Myth
For years, we've heard that houseplants can purify the air in our homes, removing harmful toxins and creating a healthier living environment. The image of a lush, green indoor jungle scrubbing the air clean is certainly appealing. But how much of this is fact, and how much is simply a well-circulated myth? Let's dig into the science behind air-purifying plants, separating truth from fiction, and explore practical ways to improve your indoor air quality.
The NASA Clean Air Study: Where the Myth Began
The idea that houseplants can purify air largely stems from the NASA Clean Air Study conducted in 1989. This research, led by NASA in collaboration with the Associated Landscape Contractors of America (ALCA), aimed to find ways to clean the air in sealed environments like space stations. The study found that certain common houseplants could remove volatile organic compounds (VOCs) such as formaldehyde, benzene, and trichloroethylene from the air in controlled, sealed chambers (National Wildlife Federation).
This groundbreaking research sparked widespread interest in the potential of houseplants as natural air purifiers. Lists of "top air-purifying plants" began circulating, touting the ability of these plants to eliminate toxins and improve indoor air quality. Some of the plants tested in the NASA study include Variegated snake plant / mother-in-law's tongue (Sansevieria trifasciata laurentii), English ivy (Hedera helix), Peace lily (Spathiphyllum 'Mauna Loa'), Chinese evergreen (Aglaonema modestum), Bamboo palm (Chamaedorea seifrizii), Red-edged dracaena, marginata (Dracaena marginata), Cornstalk dracaena, mass cane/corn cane (Dracaena fragrans 'Massangeana'), Weeping fig (Ficus benjamina), Barberton daisy, gerbera daisy (Gerbera jamesonii), Florist's chrysanthemum, pot mum (Chrysanthemum morifolium), Janet Craig (Dracaena deremensis "Janet Craig"), and Warneckei (Dracaena deremensis.
The Catch: Replicating NASA's Results in Your Home
While the NASA study provided valuable insights, it's crucial to understand the context in which it was conducted. The experiments took place in small, sealed chambers, which don't accurately represent the conditions in a typical home or office. In these sealed environments, the plants demonstrated a significant ability to remove VOCs. However, real-world conditions are far more complex.
Subsequent research has shown that the air exchange rate in most buildings is much higher than in the sealed chambers used in the NASA study. This means that outdoor air is constantly entering and diluting the concentration of indoor pollutants. To achieve the same level of air purification as demonstrated in the NASA study, you would need an impractically large number of plants – potentially hundreds or even thousands – per square meter of floor space (American Lung Association).
A 2019 meta-analysis looking at decades of research found that you would need 10 to 1000 plants per square meter to reach the same benefits seen in the older research studies. The researchers concluded that the natural ventilation of the building removes more VOCs than the plants themselves (Saint-Gobain).
Truth: Plants Offer *Some* Air Quality Benefits
Despite the limitations of the "air-purifying plant" myth, it's important to acknowledge that plants do offer some benefits to indoor air quality. While they may not be the powerhouse purifiers we once thought, they still contribute to a healthier environment in several ways:
- VOC Removal: Plants can absorb certain VOCs through their leaves and transport them to their roots, where microbes in the soil can break them down. A study in Frontiers showed that plants can absorb and purify aromatic organic compounds, such as toluene (C7H8), benzene (C6H6), and formaldehyde (CH2O), at 350–1,200 µg per 100 cm2 of the leaf area per day (Frontiers).
- Carbon Dioxide Reduction: Through photosynthesis, plants absorb carbon dioxide and release oxygen. While the impact on overall air quality might be small, this process can still contribute to a fresher, more breathable indoor environment.
- Humidity Regulation: Plants release moisture into the air through transpiration, which can help increase humidity levels, especially in dry indoor environments.
- Aesthetic and Psychological Benefits: Plants enhance the aesthetic appeal of a space and can reduce stress and improve mood (CO2 Meter).
Myth: Plants are a Substitute for Proper Ventilation
Perhaps the most significant myth surrounding air-purifying plants is the idea that they can replace proper ventilation. Plants cannot compensate for inadequate airflow or the buildup of pollutants from sources like cleaning products, building materials, and combustion appliances.
Ventilation is Key: Ensuring good ventilation is the most effective way to improve indoor air quality. This involves bringing in fresh outdoor air to dilute and remove indoor pollutants. Open windows and doors when weather permits, and use exhaust fans in kitchens and bathrooms to remove moisture and odors.
Mechanical Ventilation: In some cases, mechanical ventilation systems may be necessary to provide adequate airflow. Heat recovery ventilators (HRVs) and energy recovery ventilators (ERVs) can exchange indoor and outdoor air while minimizing energy loss.
Practical Tips: Maximizing the Benefits of Plants (and More)
While houseplants alone won't magically transform your home into an air purification sanctuary, you can still incorporate them into a holistic approach to improving indoor air quality. Here's how:
1. Choose the Right Plants
While the quantity of plants is more important than the specific species, some plants have been shown to be more effective at removing certain VOCs than others. Some popular choices include:
- Snake Plant (Sansevieria trifasciata): Effective at removing formaldehyde, benzene, xylene, toluene, and nitrogen oxides (CO2 Meter).
- Spider Plant (Chlorophytum comosum): Known for its ability to remove formaldehyde, xylene, and toluene (CO2 Meter).
- Peace Lily (Spathiphyllum): Removes formaldehyde, benzene, trichloroethylene, xylene, and ammonia (CO2 Meter).
- English Ivy (Hedera helix): Effective at removing formaldehyde, benzene, xylene, and toluene (CO2 Meter).
- Bamboo Palm (Chamaedorea seifrizii): Effective at removing formaldehyde, benzene, trichloroethylene, and xylene (CO2 Meter).
2. Increase Plant Density
To have any noticeable impact on air quality, aim for a higher density of plants. A general guideline is to have at least one medium-sized plant (8-10 inch pot) for every 100 square feet of space (East River Nursery).
3. Combine Plants with Other Strategies
Houseplants should be just one component of a comprehensive indoor air quality strategy. Consider these additional measures:
- Ventilation: Open windows and doors regularly to allow fresh air to circulate. Use exhaust fans in kitchens and bathrooms.
- Air Purifiers: Invest in a high-quality air purifier with a HEPA filter to remove particulate matter, allergens, and other pollutants.
- Reduce VOC Sources: Choose low-VOC or zero-VOC paints, cleaning products, and furniture.
- Regular Cleaning: Dust and vacuum regularly to remove allergens and pollutants.
- Control Humidity: Maintain a humidity level between 30% and 50% to prevent mold growth.
4. Maintain Your Plants
Healthy, well-maintained plants are more effective at removing pollutants. Provide adequate light, water, and nutrients to keep your plants thriving.
Understanding VOCs: What Are You Really Trying to Remove?
Volatile organic compounds (VOCs) are gases emitted from various everyday products and materials. They can contribute to indoor air pollution and potentially pose health risks.
Common Sources of VOCs:
- Paints and varnishes
- Cleaning products and disinfectants
- Building materials (e.g., adhesives, particleboard)
- Furniture and upholstery
- Air fresheners
- Cosmetics and personal care products
Health Effects of VOCs:
- Eye, nose, and throat irritation
- Headaches
- Dizziness
- Respiratory problems
- Some VOCs are known or suspected carcinogens
By understanding the sources and health effects of VOCs, you can take steps to minimize your exposure and improve your indoor air quality.
Conclusion: Plants as Part of a Bigger Picture
The truth about air-purifying plants is more nuanced than the popular myth suggests. While they may not be a magic bullet for indoor air pollution, they can contribute to a healthier environment when combined with other strategies such as proper ventilation, air purifiers, and source control.
Embrace the beauty and potential benefits of houseplants, but don't rely on them as your sole means of improving indoor air quality. By taking a holistic approach, you can create a cleaner, healthier, and more enjoyable living space.
Next Steps:
- Assess your home's ventilation: Ensure adequate airflow by opening windows and using exhaust fans.
- Identify potential VOC sources: Choose low-VOC products and materials whenever possible.
- Consider an air purifier: Research and invest in a high-quality air purifier with a HEPA filter.
- Strategically place houseplants: Select plants known for their air-purifying properties and distribute them throughout your home.
- Monitor your indoor air quality: Use an air quality monitor to track pollutant levels and assess the effectiveness of your efforts.