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iLEAPS India: Recent work on indoor air

This blog post discusses some recent work by iLEAPS Early Career Committee Member Dr. Pallavi Saxena who is an Assistant Professor at Department of Environmental Sciences, Hindu College, University of Delhi, Delhi, India.

How Ornamental Plants Helps in Removal of Ozone in Indoor Environment by Dr. Pallavi Saxena

Indoor air pollution is considered as more harmful for human health than outdoor air pollution. As per UNEP, more than 3 million humans died each year due to poor indoor air quality. It has also been reported that 16 times more deaths occur globally due to poor indoor air quality as compared to outdoor air pollution. While, analyzing the general lifestyle of people, particularly in urban or suburban areas, approximately 80% to 90% of their time, they spent in indoors and therefore, deleterious impacts can be seen in the cases related to poor indoor air quality.

Ozone is a very strong oxidizing agent. It is one of the secondary pollutants and component of photochemical smog, which produces ill effects on human health and property. It is produced by chemical reactions with precursors like NOx, VOCs, CO in the presence of sunlight. In the outdoors, ozone plays an important role in the chemistry of the atmosphere. Ozone also has a major role in heterogeneous reactions which often gave rise to the generation of volatile organic products. Indoor ozone is generated by photocopiers, air purifiers, corona discharge and exchange of outdoor and indoor ozone by ventilation and infiltration. When indoor ozone reacts with substances or materials like flooring, paints, and metals, may result in the formation of more secondary products which probably be more dangerous than ozone. indoor air contains 10 to 50% of outdoor pollutant concentrations and hence indoor air is almost 7-8 times more harmful than ambient air present in an urban environment.

There are usually two ways which can reduce the indoor ozone concentrations. The very simplistic one is to stop the entry of ozone in air, which is present in the building while the second one is to trim down the levels of ozone once present in indoors. Saxena and Sonwani, 2020.The most economically fit methods for indoor ozone removal is remediation through plant species. Studies on indoor plants confirms their role in removal of ozone. Very few studies have been reported on ozone removal by indoor plant species, particularly by highlighting their deposition velocities and ozone removal effectiveness. Thus, there is a stringent need to perform more studies on ozone removal so that health risks can be reduced. Therefore, this study was conducted during 2017-18 in the vicinity of University of Delhi campus area with my another fellow researcher, Dr. Saurabh Sonwani, University of Delhi.

This type of study is directly reflecting about land-atmosphere exchange science to better understand their concepts and physiology and also helpful in playing the role more significantly as an early career committee member for iLEAPS. We had analyzed and estimated the ozone removal effectiveness of three indoor ornamental plant species (Dracaena deremensis, Tagetes erecta and Lilium candidum) in an indoor environment.

We have found that Dracaena deremensis has got the highest value of 7.7m/h at the time of first exposure test while Lilium candidum has got the lowest value of 0.5m/h during third exposure. Moreover, on average, ozone deposition velocities were found to highest in a first exposure followed by second and then third exposure. In addition to that Ozone Deposition Velocity was decreased by 46% and 29% after second exposure for Dracaena deremensis and Lilium candidum respectively. It was also found that ozone removal effectiveness will be in the range of 0.1-1% for all selected plants for 0.01/m leaf area to volume ratio and 4-13% for 0.1/m leaf area to volume ratio. Therefore, among all selected plant species, Dracaena deremensis has got highest ozone deposition velocity as well as ozone removal effectiveness and Lilium candidum has got the lowest values.

This study can act as a cost-effective and most sustainable solution to reduce indoor ozone concentrations. Such remediation studies are very much helpful for policymakers and other scientific and government organizations to implement plans for the welfare of health and society.

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