7 minute read
The Health Benefits of Growing Plants Indoors
BY ANNE GIBSON
With more people spending time at home and mindful of health in 2020, it’s time to reflect on the indoor environment and how that impacts our wellbeing. Research studies in recent years have revealed plants can have a positive effect on indoor air quality, how we feel both mentally and physically, and mitigate a wide range of potential health issues.
Where Potential Dangers Lie Figures from 2019 reveal over 86% of Australians live in urban areas and spend an average of 90% of their time indoors - either at home or work. According to the Nursery and Garden Industry Australia (NGIA), “Indoor air is generally more polluted than outdoor air due to Volatile Organic Compounds (VOCs) produced by furnishings, carpets, paints, and outdoor VOCs (mainly fuel emissions) trapped indoors.”
VOCs are carbon-containing chemicals that evaporate into the air at room temperature. Some of these toxic gases are easily identifiable from their distinctive smell. Cigarette smoke is an obvious one, and most of us recognize that ‘new car’ or ‘new carpet’ scent, but other emissions are odorless. Some of the worst offenders include newly manufactured products, like curtains and flooring, building products, marker pens, varnishes, adhesives, synthetic fabrics, cleaning agents, craft products, scents, and sprays. Office electronics like new computers and printers may emit a variety of VOCs, according to a US Berkeley study.
Common VOCs found in our homes include benzene, formaldehyde, toluene, acetone, and styrene. Higher levels of VOCs occur with new products, and off-gassing gradually reduces over time. However, if new VOC-containing products are regularly introduced, concentrations can build up significantly, particularly in warm, poorly-ventilated rooms. Unfortunately, it’s virtually impossible to avoid all off-gassing. Even if a product no longer smells, it could still be emitting VOCs.
Health Impacts of Poor Indoor Air Quality
Polluted indoor air contaminated by VOCs is recognized as a major cause of building-related health conditions, including headaches, nausea, lethargy, nose and throat irritation, and loss of concentration. Few people likely suspect an invisible enemy may be contributing to their health issues.
The United States Environmental Protection Agency (US EPA) has identified indoor air quality (IAQ) as one of the top five environmental hazards. Research studies have revealed that pollutants indoors might be two to five times, and sometimes over 100 times higher than outdoors (US EPA, 1993).
Normal outdoor carbon dioxide levels range between 300 and 500ppm. Indoors, the average CO2 concentration levels range between 500 and 1,500ppm (Seppänen, 2006), primarily from human respiration. Disturbingly, one study (Satish et al., 2012) revealed that rational thinking and reasoning ability reduced at 1,000ppm CO2 concentration levels. Another study (Bluyssen, 2009) showed occupants could suffer from suffocation and tightness in the chest with exposure to CO2 levels at 800ppm or higher.
Indoor Plants to the Rescue
There are positive low-cost solutions – and plants hold the key! Indoor plants not only absorb all types of urban air pollution, but an ever-increasing body of evidence confirms they also promote positive mental and physical wellbeing benefits. The findings from a three-year study, “Greening the Great Indoors for Human Health and Wellbeing”, conducted by the University of Technology Sydney (UTS) are significant. A series of tests were performed before and after plants were positioned in offices. The results showed people in offices with plants experienced:
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• 58% reduction in depression/dejection;
• 44% reduction in anger/hostility
• 38% reduction in fatigue;
• 37% reduction in tension/anxiety;
• 30% reduction in confusion;
• 4.5% increase in vigor.
The research provides strong evidence to support the use of plants in work environments to reduce stress and improve performance. Impressively, just one office plant was enough to make all the difference.
Plants Help Improve Wellbeing
Plants can relax and energize us, improve our mood, enhance productivity, and aid concentration. The results from many research works confirm that people find plants an effective mechanism for coping with stress just by being around them. A greener space is not only a cleaner one to live in, but provides a practical strategy for mental health. In our homes, plants can give a sense of connection to nature that lifts the spirits and makes us feel more relaxed.
Plants Help Remove VOCs and Reduce CO2
In one of the UTS studies, CO2 concentrations were reduced by 10% in an air-conditioned building and by 25% in a naturally ventilated building – another significant improvement in IAQ. Air conditioning indoors is used for temperature control and to refresh the air by removing CO2 to acceptable levels (a maximum of 1000 ppm). During the UTS office plant testing period, it was observed that just three people talking over 10 minutes in an office could increase CO2 concentrations to 800 ppm. Indoor plants could potentially play a major role in reducing CO2 levels under the extra-ventilation cut-in point for air conditioning systems.
In terms of reducing VOCs, the UTS research revealed that after an initial period where the plants acclimatise to the unique VOCs in the room, the potting mix bacteria in conjunction with the plant consistently remove VOCs on an ongoing basis. Residual concentrations of VOCs are removed to insignificant levels (< 20 ppb), which is below the detection limits of the gas chromatography instrumentation.
Test results from multiple studies revealed that indoor plants were able to consistently remove VOCs and CO2 within 24 hours regardless of the plant species, whether they were in small or largesized pots, in light or dark, in air-conditioning or not. What’s even more impressive, is when the VOC levels increased, the rate of removal rose in response to the challenge. The research revealed, “the bacteria involved (Burchett et al., 2009) are among the normal decomposing microorganisms of soil/potting mixtures, and similar to those routinely cultured for use in bioremediation of oil spills and groundwater contamination.” An invisible workforce we can employ to improve our health!
The type of plant species used for indoor air phytoremediation is not significant, but rather, it is a healthy microbe population that needs to be cultivated (Leahy and Colwell, 1990). Keeping indoor plants, regardless of species, well-maintained in a moist, well-drained and pH-balanced potting mix rewards us with clean air and healthier homes and workplaces. A win-win!
Loving our Indoor Plants
It’s clear from this evidence that plants not only play a beneficial role in our outdoor gardens by providing us with greenery, food, and a place to find peace and relaxation, but they also contribute valuable ecosystem services indoors for human health. Indoor gardening is becoming many people’s go-to activity – not only as a hobby to green our homes but also as a way to improve wellbeing through sensory engagement with plants and soil.
I have plants in every room of our home including on our desks, bedrooms (where CO2 accumulates overnight as we sleep) and in our living spaces. Not only do they make the house more beautiful to look at by greening our indoor spaces, but they are effectively part of our ‘health insurance’ plan!
List of indoor plant species UTS laboratory-tested for VOC removal:
• Aglaonema modestum (Chinese Evergreen) (Fam. Araceae)
• Chamaedorea elegans (Parlour Palm) (Fam. Palmae)
• Dracaena deremensis ‘Janet Craig’ (Fam. Dracaenaceae; prev. Liliaceae) Dracaena marginata (Fam. Dracaenaceae; prev. Liliaceae)
• Epipremnum aureum (syn. Scindap(s)us aureus) (Pothos; Devil‘s Ivy) (Fam. Araceae)
• Howea forsteriana (Kentia palm) (Fam. Palmae)
• Philodendron ‘Congo’ (Chinese Clone) (Fam. Araceae)
• Sansevieria trifasciata (Mother-in-law‘s tongue) (Fam.Ruscaceae/Dracaenaceae) Schefflera ‘Amate’ (Queensland Umbrella Tree) (Fam. Araliaceae)
• Spathiphyllum ‘Petite’ and ‘Sweet Chico’ (Peace Lily) (Fam. Araceae) Spathiphyllum ‘Sensation’ (Peace Lily) (Fam. Araceae)
• Zamioculcas zamiifolia (Zanzibar; ZZ) (Fam. Araceae)
They were all found to be equally effective in removing a standard dose within about 24 hours after a week of acclimatization (induction) to exposure to the VOC.
My houseplants get a weekly ‘spa bath’ treatment with a soak in liquid seaweed for trace elements. They are rotated outdoors for a brief ‘holiday’ in the sun to boost photosynthesis every fortnight and soak up the mineral-rich rain to wash off any dust. I can honestly say my houseplants are thriving and even flowering indoors. They’re like members of our family now and deserve a little TLC in return for the positive health and wellbeing benefits they contribute. Perhaps yours do too?
BIO
Anne Gibson, The Micro Gardener, is an author, speaker and urban garden community educator on the Sunshine Coast, in Queensland, Australia. Anne is passionate about inspiring people to improve health and wellbeing, by growing nutrient-dense food gardens in creative containers and small spaces. Anne regularly presents workshops, speaks at sustainable living events, coaches private clients and teaches community education classes about organic gardening and ways to live sustainably. She has authored several eBooks and gardening guides. Anne shares organic gardening tips and tutorials to save time, money and energy on her popular website - TheMicroGardener.com.