Using pot plants to clean indoor air

Polluted indoor air, air contaminated by Volatile Organic Compounds (VOCs), are a major cause of headaches, nausea, concentration loss and other `building-related illnesses. Previous laboratory research by the Plants and Environmental Quality Group at the University of Technology, Sydney (UTS) has shown that the `pot plant system (plants-and-potting-mix combination) can daily eliminate several times the Australian maximum exposure concentrations of the common VOCs benzene and n-hexane

Teriparatide treatment exerts differential effects on the central and peripheral skeleton: results from the MOAT study

The central and peripheral skeleton was characterised using imaging techniques during 104 weeks of teriparatide treatment. Teriparatide exerts differential effects on the central and the peripheral skeleton. Overall, we did not observe a change in total body bone mineral. Our conclusions are constrained by the study limitations. INTRODUCTION: Teriparatide stimulates bone formation and resorption and therefore can cause bone gain and loss. We simultaneously characterised the central and peripheral skeleton using imaging techniques to better understand the mechanism of action of teriparatide. METHODS: Postmenopausal, osteoporotic women (n = 20, 65.4 ± 5.5 years) were recruited into a 104-week study of teriparatide. Imaging techniques included DXA, quantitative computed tomography (QCT), and high-resolution peripheral quantitative computed tomography (HR-pQCT). RESULTS: Total lumbar spine areal bone mineral content (aBMC) (+ 11.2%), total lumbar spine areal bone mineral density (aBMD) (+ 8.1%), subregional thoracic spine aBMD (+ 7.5%), lumbar spine aBMC (+ 23.5%), lumbar spine aBMD (+ 11.9%), pelvis aBMC (+ 9.3%), and pelvis aBMD (+ 4.3%) increased. However, skull aBMC (- 5.0%), arms aBMC (- 5.1%), legs aBMC (- 2.9%), and legs aBMD (- 2.5%) decreased. Overall, we did not observe a change in total body bone mineral. Increases in L1-L3 volumetric BMD (vBMD) (+ 28.5%) occurred but there was no change in total proximal femur vBMD. Radius and tibia cortical vBMD (- 3.3 and - 3.4%) and tissue mineral density (- 3.2 and - 3.8%) decreased and there was an increase in porosity (+ 21.2 and + 10.3%). Tibia, but not radius, trabecular inhomogeneity (+ 3.2%), and failure load (+ 0.2%) increased, but cortical thickness (- 3.1%), area (- 2.9%), and pore volume (- 1.6%) decreased. CONCLUSIONS: Teriparatide exerts differential effects on the central and the peripheral skeleton. Central trabecular vBMD (L1-L3) is improved, but there is a concomitant decrease in peripheral cortical vBMD and an increase in porosity. Overall, we did not observe a change in total body bone mineral. We acknowledge that our conclusions may be speculative and are constrained by the technical limitations of the imaging techniques used, the lack of a control group, and the small sample size studied

Interaction between plant species and substrate type in the removal of CO2 indoors

Elevated indoor concentrations of carbon dioxide [CO2] cause health issues, increase workplace absenteeism and reduce cognitive performance. Plants can be part of the solution, reducing indoor [CO2] and acting as a low-cost supplement to building ventilation systems. Our earlier work on a selection of structurally and functionally different indoor plants identified a range of leaf-level CO2 removal rates, when plants were grown in one type of substrate. The work presented here brings the research much closer to real indoor environments by investigating CO2 removal at a whole-plant level and in different substrates. Specifically, we measured how the change of growing substrate affects plants’ capacity to reduce CO2 concentrations. Spathiphyllum wallisii 'Verdi', Dracaena fragrans 'Golden Coast' and Hedera helix, representing a range of leaf types and sizes and potted in two different substrates, were tested. Potted plants were studied in a 0.15 m3 chamber under ‘very high’ (22000 lux), ‘low’ (~ 500 lux) and ‘no’ light (0 lux) in ‘wet’ (> 30 %) and ‘dry’ (< 20 %) substrate. At ‘no’ and ‘low’ indoor light, houseplants increased the CO2 concentration in both substrates; respiration rates, however, were deemed negligible in terms of the contribution to a room-level concentration, as they added ~ 0.6% of a human’s contribution. In ‘very high’ light D. fragrans, in substrate 2, showed potential to reduce [CO2] to a near-ambient (600 ppm) concentration in a shorter timeframe (12 hrs, e.g. overnight) and S. wallisii over a longer period (36 hrs, e.g. weekend)

Removal of benzene by the indoor plant/substrate microcosm and implications for air quality

The quality of the indoor environment has become a major health consideration, since urban-dwellers spend 80-90% of their time indoors, where air pollution can be several times higher than outdoors. 'Indoor' potted-plants can remove air-borne contaminants such as volatile organic compounds (VOCs), over 300 of which have been identified in indoor air. In this study a comparison was made of rates of removal of benzene, as model VOC, by seven potted-plant species/varieties. In static test-chambers, high air-borne doses of benzene were removed within 24 h, once the response had been stimulated ('induced') by an initial dose. Removal rates per pot ranged from 12-27 ppm d -1 (40 to 88 mg m -3 d -1) (2.5 to 5 times the Australian maximum allowable occupational level). Rates were maintained in light or dark, and rose about linearly with increased dose. Rate comparisons were also made on other plant parameters. Micro-organisms of the potting mix rhizosphere were shown to be the main agents of removal. These studies are the first demonstration of soil microbial VOC degradation from the gaseous phase. With some species the plant also made a measurable contribution to removal rates. The results are consistent with known, mutually supportive plant/soil-micro-organism interactions, and developments in microbially-based 'biofilter reactors' for cleaning VOC-contaminated air. The findings demonstrate the capacity of the potted-plant microcosm to contribute to cleaner indoor air, and lay the foundation for the development of the plant/substrate system as a complementary biofiltration system

The potted-plant microcosm substantially reduces indoor air VOC pollution: II. Laboratory study

Indoor air-borne loads of volatile organic compounds (VOCs) are usually significantly higher than those outdoors, and chronic exposures can cause health problems. Our previous laboratory studies have shown that the potted-plant microcosm, induced by an initial dose, can eliminate high air-borne VOC concentrations, the primary removal agents being potting-mix microorganisms, selected and maintained in the plant/root-zone microcosm. Our office field-study, reported in the preceding paper, showed that, when total VOC (TVOC) loads in reference offices (0 plants) rose above about 100 ppb, levels were generally reduced by up to 75% (to < 100 ppb) in offices with any one of three planting regimes. The results indicate the induction of the VOC removal mechanism at TVOC levels above a threshold of about 100 ppb. The aims of this laboratory dose-response study were to explore and analyse this response. Over from 5 to 9 days, doses of 0.2, 1.0, 10 and 100 ppm toluene and m-xylene were applied and replenished, singly and as mixtures, to potted-plants of the same two species used in the office study. The results confirmed the induction of the VOC removal response at the lowest test dosage, i.e in the middle of the TVOC range found in the offices, and showed that, with subsequent dosage increments, further stepwise induction occurred, with rate increases of several orders of magnitude. At each dosage, with induction, VOC concentrations could be reduced to below GC detection limits (< 20 ppb) within 24 h. A synergistic interaction was found with the binary mixtures, toluene accelerating m-xylene removal, at least at lower dosages. The results of these two studies together demonstrate that the potted-plant microcosm can provide an effective, self-regulating, sustainable bioremediation or phytoremediation system for VOC pollution in indoor air. © 2006 Springer Science+Business Media, Inc

Potted-plant/growth media interactions and capacities for removal of volatiles from indoor air

Results are presented of an investigation into the capacity of the indoor potted-plant/growth medium microcosm to remove air-borne volatile organic compounds (VOCs) which contaminate the indoor environment, using three plant species, Howea forsteriana (Becc. (Kentia palm), Spathiphyllum wallisii Schott. 'Petite' (Peace Lily) and Dracaena deremensis Engl. 'Janet Craig'. The selected VOCs were benzene and n-hexane, both common contaminants of indoor air. The findings provide the first comprehensive demonstration of the ability of the potted-plant system to act as an integrated biofilter in removing these contaminants. Under the test conditions used, it was found that the microorganisms of the growth medium were the "rapid-response" agents of VOC removal, the role of the plants apparently being mainly in sustaining the root microorganisms. The use of potted-plants as a sustainable biofiltration system to help improve indoor air quality can now be confidently promoted. The results are a first step towards developing varieties of plants and associated microflora with enhanced air-cleaning capacities, while continuing to make an important contribution to the aesthetics and psychological comfort of the indoor environment

The potted-plant microcosm substantially reduces indoor air VOC pollution: I. Office field-study

Volatile organic compounds (VOCs) are major contaminants of indoor air, with concentrations often several times higher than outdoors. They are recognized as causative agents of "building-related illness" or "sick-building syndrome". Our previous laboratory test-chamber studies have shown that the potted-plant/root-zone microorganism microcosm can eliminate high concentrations of air-borne VOCs within 24 hours, once the removal response has been induced by an initial dose. However, the effectiveness of the potted-plant microcosm in 'real-world' indoor spaces has never previously been tested experimentally. This paper reports the results of a field-study on the effects of potted-plant presence on total VOC (TVOC) levels, measured in 60 offices (12 per treatment), over two 5-9 week periods, using three planting regimes, with two 'international indoor-plant' species. Fourteen VOCs were identified in the office air. When TVOC loads in reference offices rose above 100 ppb, large reductions, of from 50 to 75% (to <100 ppb), were found in planted offices, under all planting regimes The results indicate that air-borne TVOC levels above a threshold of about 100 ppb stimulate the graded induction of an efficient metabolic VOC-removal mechanism in the microcosm. Follow-up laboratory dose-response experiments, reported in the following paper, confirm the graded induction response, over a wide range of VOC concentrations. The findings together demonstrate that potted-plants can provide an efficient, self-regulating, low-cost, sustainable, bioremediation system for indoor air pollution, which can effectively complement engineering measures to reduce indoor air pollution, and hence improve human wellbeing and productivity. © Springer 2006