Chennai Study Shows Indoor Plants Can Mitigate Air Pollution in Homes
Vehicular emissions and indoor sources such as cleaning products can significantly elevate pollution levels within homes and apartments that lack proper ventilation. However, a recent pilot study conducted in Chennai has discovered that strategically placed native indoor plants and common species can help reduce common air pollutants, albeit to a limited extent.
Research Methodology and Key Findings
Researchers monitored two identical apartment balconies over a one-month period. One balcony featured a curated mix of 17 plants, while the other remained plant-free. Using IoT-based sensors, the team tracked levels of carbon dioxide (CO2), carbon monoxide (CO), total volatile organic compounds (TVOCs), benzene, and formaldehyde. The results consistently showed lower pollutant concentrations in the planted balcony.
During evening peak hours, CO2 levels measured 984 parts per million (ppm) in the non-planted balcony, compared to 919 ppm in the planted space. Carbon monoxide dropped from 392 micrograms per cubic meter (μg/m³) to 335 μg/m³, and TVOCs decreased from 75 μg/m³ to 71 μg/m³. The absorption rates varied throughout the day, with the highest CO2 reduction reaching 161 ppm in the morning and the lowest at 58 ppm at night. TVOC reduction ranged from 1 to 11 μg/m³, indicating a measurable but limited impact.
Benzene levels returned to permissible limits within eight hours in the planted balcony, whereas it took approximately one and a half days without plants. Formaldehyde concentrations reduced within two hours after cleaning activities in the planted space, compared to three hours in the non-planted area. According to the Central Pollution Control Board (CPCB), the maximum permissible annual average concentrations are 500 μg/m³ for VOCs, 50 μg/m³ for formaldehyde, 5 μg/m³ for benzene, 1000 μg/m³ for CO2, and 2000 μg/m³ for CO.
Expert Insights and Plant Selection
Swetha Madhusudanan, the first author of the study, emphasized, "Plants as a natural medium are inexpensive and best at absorbing air pollutants, thereby improving the quality of the indoor environment. The absorption by the plant palette is not uniform throughout the day and varies with environmental conditions and human activity." This multi-institutional study, led by the Dr M G R Educational and Research Institute, was published in the journal Environmental Science and Pollution Research.
The planting palette included species such as areca palm, peace lily, Boston fern, tulsi, golden pothos, aloe vera, spider plant, and jade plant. These plants contributed to reducing CO2, CO, benzene, and VOCs. Notably, aloe vera demonstrated night-time CO2 uptake, while spider and jade plants helped regulate indoor humidity. Researchers also highlighted that Bougainvillea and vertical creepers can assist in reducing heat gain by blocking incoming radiation at balcony openings.
Limitations and Practical Implications
Indoor pollution levels were highest during peak traffic hours, particularly between 8-10 am and 6-8 pm, reflecting the influence of vehicular emissions. Activities like floor cleaning and indoor painting temporarily increased formaldehyde and benzene levels. While plants can act as passive filters at entry points such as balconies, their impact remains modest. Researchers caution that they cannot replace mechanical ventilation or air filtration systems, underscoring the need for comprehensive air quality management strategies in urban homes.
