Phytoremediation of Indoor Organic Air Pollution Using House Plants
By: Dr. Seemaa Ghate
Degradation of indoor air by harmful chemicals and other particulate matter is called as Indoor Air Pollution. It is up to 12 times higher than the outdoor air pollution. Indoor air pollution in India may contribute to 22-52 % of the overall pollution as per UNEP (United Nations Environmental Programme) studies. Their recommendations include reduction of household pollutant sources to improve indoor air quality. As stated in the report, around 93% of the world’s children under the age of 15 years are at risk due to polluted indoor air.
The main source of air pollution can be different household sources like kitchen exhaust, smoke from mosquito coil, phenyls, room fresheners, heavy-smelling incense sticks, paper towels, plastic bags, wooden furniture, paints, cement walls etc. Pollutants emitted through these sources may have adverse effect on our health. Some of the organic pollutants like formaldehyde, xylene, toluene, volatile and semi-volatile compounds are produced from household sources. Some biological pollutants like pollens, moulds and dust mites also contribute adversely to Indoor environment.
Research states that there are about two million premature deaths per year, 54% due to Chronic Obstructive Pulmonary Disease (COPD), 44% due to pneumonia and 2% due to lung cancer. It is observed that most affected category due to indoor pollution are women and children as they spend most of the time at home. There are many ways to overcome indoor pollution. Using air filtration systems and air purifiers are some examples of the same. People keep on using these to reduce Indoor air pollution. A more reliable way to reduce this problem is using greenhouse plants. Many of indoor pollutants can be remediated with green plants surviving in low light. This technology is called as “phytoremediation” which aims at solving and reducing indoor air pollution problem aesthetically, naturally and technically.
Phytoremediation technology works on simple principle of selecting various plant species having capacity of absorbing different types of pollutants through distinct plant parts; and helping in eradicating as well as minimizing these pollutants. These absorbed pollutants can either be stored in the plant (phytoextraction), volatized by the plant (phytovolatization), metabolized by the plant (phytodegradation) or any combination of the above. Absorbed pollutants are degraded by plants cells. The daughter compounds which are non-poisonous, can be either volatized or stored in the plant. This technology is to be used to safeguard health of people spending time in the non-ventilated indoor spaces to protect human beings from harmful indoor pollutants.
Phytoremediation is an aesthetically pleasing, solar-energy driven, novel, efficient, environmentally friendly, low-cost and passive technique that can be used at sites with low to moderate levels of contamination. It is well suited for problems involving indoor pollution. House plants can absorb indoor volatile organic compounds, metabolize them into simpler compounds. In this process bacteria from rhizosphere help to absorb and metabolize pollutants.
In a close chamber study was performed during research project sanctioned by Department of Science and Technology (D.S.T.), New Delhi. Many indoor plant species were exposed to different pollutants released through various household sources like mosquito coil, naphthalene balls and heavy smelling incense sticks. It was observed that these plant species absorb different hazardous indoor pollutants. The observations were confirmed by GLC and GCMS studies. Five plant species were exposed to pollutants released through smoke from mosquito coil. Smoke from the coil releases ‘Allethrin’, a poisonous pesticide used to kill mosquitoes. It was observed that plants absorb Allethrin successfully. The range of absorption varies from plant to plant. Chlorophytum comosum shows highest absorption of Allethrin which is 1075 ppb. The lowest absorption was observed in Aglaonema commutatum plant which is 23.111 ppb. To speed up absorption, activated charcoal was added to the potting mixture. The activity of phytoremediation was accelerated by adding a consortium of Sphingomonasin the growth medium. Activated charcoal increases the absorption surface and bacteria help to metabolize pollutants endophytically and in the rhizosphere. Quantification of pollutants absorbed was done on a Triple Quadrupole GC/MS/MS with Electrospray Ionisation (ESI).
List of some indoor plants studied for their phytoremediation activity of indoor pollutants:
Syngonium (Syngonium podophyllum) ‘Maza Red’,
Green spider plant (Chlorphytum comosum),
Chinese evergreen (Aglonema commutatum),
Peperomia (Peperomia meridiana),
Ficus (Ficus benjamina)
Ming Aralia (Polyscias fructicosa)
Agave (Sansevieria trifasciata)
Peace lily (Spathiphyllum wallisii)
In future, absorption of gaseous pollutants per unit leaf area as well as per unit volume of room will be calculated. Pollution removal rate of each species will be calculated. With the help of results obtained, standards of phyto-remediators will be established e.g. potting mixture, size of the plant and number of leaves required to achieve specific levels of phytoremediation in the presence of specific pollutants.
Communities which are benefitted due to this technology are common households, IT parks, shopping malls, banks, hospitals, schools, R&D laboratories, telecom industries, production industries, food processing units etc.
*Women Scientist, D.S.T., New Delhi, Know How Foundation, Bavdhan, Pune.