Effectiveness of Houseplants in Reducing the Indoor Air Pollutant
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as a result of increased input of the Effectiveness of Houseplants in Reducing precursors of ozone into the atmos- the Indoor Air Pollutant Ozone phere (Mustafa, 1990). Automobiles are the principal contributors to sec- ondary tropospheric ozone genera- Heather L. Papinchak1, E. Jay Holcomb2,4, tion (Maroni et al., 1995). Teodora Orendovici Best3, and Dennis R. Decoteau2 Ozone as an indoor air pollutant can be prevalent in homes and offices due to infiltration of outdoor ambient ADDITIONAL INDEX WORDS. mitigation, depletion rates, foliage air indoors (Weschler, 2000). Ozone- emitting equipment such as copy UMMARY Sansevieria trifasciata S . Three common indoor houseplants, snake plant ( ), machines, laser printers, ultraviolet spider plant (Chlorophytum comosum), and golden pothos (Epipremnum aureum), were evaluated for their species effectiveness in reducing ozone concentrations in a lighting, and some electrostatic air simulated indoor environment. Continuously stirred tank reactor (CSTR) chambers purification systems may also contrib- housed within a greenhouse equipped with a charcoal filtration air supply system ute to indoor ozone levels (Maroni were used to simulate an indoor environment in which ozone concentrations could et al., 1995; Weschler, 2000). Ozone be measured and regulated. Ozone was injected into the chambers and when generation from appliances such as concentrations reached 200 ± 5 ppb, the ozone-generating system was turned off photocopiers on average yield 5.2 and ozone concentrations over time (ozone was monitored every 5–6 min in each mgÁh–1 and laser printers on average chamber) were recorded until about <5 ppb were measured in the treatment produce 1.2 mgÁh–1; however, con- chamber. On average, ozone depletion time (time from when the ozone generating centrations could vary based on < system was turned off at 200 ppb to 5 ppb in the chamber) ranged from 38 to equipment maintenance (Black and 120 min per evaluation. Ozone depletion rates were higher within chambers that contained plants than within control chambers without plants, but there were no Worthan, 1999; Weschler, 2000). plant species differences. Depending on the air exchange rates between outdoor and indoor envi- ronments, indoor air has been ndoor air pollution is ranked as appear to be equal for developing reported to contain from 10% to one of the world’s greatest public and developed countries. Australia’s 50% of outdoor values (Weschler, Ihealth risks (Wolverton, 1997). Commonwealth Science Council has 2006) to five to seven times the The United Nations Development suggested that 9 of 10 deaths due to contaminant concentrations of ambi- Program estimated in 1998 that over indoor air are experienced by the ent urban air (Brown et al., 1994; 2 million humans die each year due to developing world (Brennan and With- Orwell et al., 2004). the persistence of deleterious indoor gott, 2005). The principal groups at risk to air (Brennan and Withgott, 2005). It Ozone (O3), a photochemical ozone toxicity are organisms in which has also been estimated that globally oxidant with a redox potential of the primary route of exposure is via 14 times as many deaths occur from +2.07 V, is one of the most powerful inhalation (Wright and Welbourn, poor indoor air quality compared naturally occurring oxidants (Maroni 2002). Daily inhalation of indoor with ambient air pollution (Brennan et al., 1995; Mustafa, 1990). It is ozone for these organisms (such as and Withgott, 2005). considered a secondary ambient pol- humans) are estimated to be between Because humans in industrialized lutant and one of the components 25% and 60% of total ozone intake countries spend about of 80% to 90% of tropospheric smog, which can (Weschler, 2006). Major toxic effects of their time indoors (Orwell et al., adversely affect human health and of ozone in humans include altera- 2004; Wolverton, 1997), negative property (Mustafa, 1990). Ozone is tions in pulmonary function in addi- societal consequences due to polluted produced within the troposphere by tion to cellular and biochemical indoor air can be great (Fisk and Rose- chemical reactions involving free rad- endpoints (Wright and Welbourn, nfeld, 1997). For example, the cost of icals. It is formed during the reaction 2002). Exposure to ozone also may unhealthy indoor air in Australia has of carbon monoxide (CO) and vola- result in pulmonary edema, hemor- been estimated at $12 billion annually tile organic compounds (VOCs) in rhage, inflammation, and extensive due to losses in productivity, higher the presence of nitrogen oxides lesions on the lung tissue, trachea, medical costs, more absenteeism, and (NOX), oxygen and sunlight. There and upper bronchi (Mehlman and lower earnings (Wood, 2003). In is strong evidence to suggest that Borek, 1987). addition, the health burden associated average ozone concentrations have Indoor exposures to ozone are with indoor air pollution does not been rising during the past century often accompanied by exposure to the We thank James Savage and Jonathan Ferdinand for providing technical assistance. 1Department of Economics, Environmental Resources Units Management, The Pennsylvania State University, To convert U.S. to SI, To convert SI to U.S., University Park, PA 16802 multiply by U.S. unit SI unit multiply by 2 Department of Horticulture, The Pennsylvania State 0.0283 ft3 m3 35.3147 University, University Park, PA 16802 6.4516 inch2 cm2 0.1550 3School of Forest Resources, The Pennsylvania State 28,350 Oz mg 3.5274 · 10–5 University, University Park, PA 16802 1 ppb nLÁL–1 1 4Corresponding author. E-mail: [email protected]. (°F – 32) O 1.8 °F °C (1.8 ·C) + 32 286 • April–June 2009 19(2) products of ozone-initiated oxidative of ozone within a simulated indoor recorded at approximate 5- to 6-min reactions (such as isoprenes, styrenes, environment. intervals. This depletion rate was used terpenes, sesquiterpenes, and unsatu- as an indicator that the aerial portion rated fatty acids) (Weschler, 2004). Materials and methods of the plant was assisting in ozone The average daily intakes of ozone PLANT MATERIAL AND GROWING mitigation. Air circulation within the oxidative products are roughly one- CONDITIONS. Three plants species, chambers continued during all trials. third to twice the average daily intake snake plant, spider plant, and golden Five spider plants, five golden of ozone alone (Brown et al., 1994). pothos, were evaluated for their effec- pothos plants, and two snake plants Some of the oxidative products of tiveness in reducing ozone concen- (because of their larger size) per rep- ozone that are known or suspected trations in a simulated indoor lication were used in this evaluation. to adversely affect human health environment. These plant species During the evaluations, the top part include formaldehyde, acrolein, were chosen because of their popular- of each pot was enclosed with plastic hydrogen peroxides, and fine and ity as indoor houseplants (primarily sheeting in such a manner that only ultrafine particles (Weschler, 2004). due to their low cost, low mainte- the aerial portion of the plants was Common indoor sources of reactive nance, and rich foliage) and their exposed to ozone. One chamber that chemicals to ozone include occupants previously reported ability to reduce did not contain any plants served as themselves, soft woods, linoleums, air pollutants other than ozone (Wol- control. certain paints, polishes, cleaning verton, 1986, 1997). At the completion of the evalua- products, soiled fabrics, and soiled Plants were grown in greenhouse tions, leaf surface area and stomatal ventilation filters. Indirect evidence pots (one plant per pot) containing conductance (gS) of the plants were supports connections between human peatlite commercial growing mix measured. Leaf surface area (cm2) was morbidity/mortality and exposures (Sunshine #4; Sun Gro Horticulture, measured via an area meter (LI-3100; to indoor ozone and its oxidative Bellevue, WA) in a greenhouse at The LI-COR, Lincoln, NE) on all the products (Weschler, 2006). Pennsylvania State University campus plants within the individual chambers As indoor air pollution poses in University Park. Watering, fertil- and is reported as leaf area per cham- –2 –1 concerns for human health, cost- ization, and pest control were con- ber. GS [water (molÁm Ás )] was effective and easy-to-implement meth- ducted according to recommendations measured midleaf on representative ods are needed to eliminate or reduce and ensured good healthy plant growth midaged leaves (while avoiding large concentrations. Activated charcoal fil- before and during the experiments. veins or any patterns of variegation) ters reduce air pollutants but installa- OZONE EXPOSURE AND MONIT- on individual plants via a portable tion and maintenance costs can be ORING. Four continuously stirred photosynthesis system (LI-6400; LI- high (Wolverton, 1997). As an alter- tank reactor (CSTR) chambers (2 COR) equipped with a leaf chamber 3 native, foliage plants could be used to m volume) covered with clear Tef- fluorometer and is reported as gS sequester some types of air pollution, lonÒ film and situated within a green- average per chamber. although their effectiveness appears house equipped with a charcoal STATISTICAL DESIGN AND ANALYSIS. to be plant species specific and air filtration air supply system (resulting The experiment was conducted as a pollutant dependent (Wolverton, in ambient levels of ozone within the completely randomized design with 1986). greenhouse of <5 ppb) were used to plant