Extract from the May issue, By Gabrielle Stannus
A recent research paper claims that artificial plants may act as a sink for particulate matter polluting indoor environments. However, this study ignores the potential for these “plants” to add to indoor pollution.
Writing “A breath of fresh air in the green wall industry!” for the April 2018 edition of Hort Journal, I came across some research that literally left me gasping.
In this research, environmental engineers in Thailand sought to assess the performance of both artificial and living houseplants in capturing fine particulate matter (PM) smaller than 2.5 μm (PM2.5). Removing PM from indoors is a worthy aim as it causes damage to to the circulatory and respiratory systems.
The researchers’ rationale for including artificial plants was that they are increasingly used for interior decoration due to their supposed long life. Indeed, they are available in all shapes and sizes, including fake bamboos, palms, cycads, agaves, ferns, orchids and fruit trees constructed from dead trunks are also popular.
So what were the research results? Not surprising, living and artificial plants were both found to serve as indoor PM “sinks”. Dr Peter Irga from the University of Technology Sydney (UTS) says that PM deposition is largely driven by leaf micro-structural features including leaf surface roughness, pubescence (leaf hairs), thick waxy epicuticles and stomatal densities. The leaves of many living plants can absorb or adsorb PM, excepting smooth-leaved species. Can artificial plant leaves bind PM this way? If not, PM will probably become resuspended, once again polluting the interior in which it is situated.
Most importantly, the researchers failed to address the potential for artificial plants to possibly contribute to, rather than ameliorate, indoor air pollution. Dr Fraser Torpy (UTS) says that plastic plants would be expected to release at least some dangerous volatile organic compounds (VOCs). Whilst living plants will release (biological) VOCs too, these are generally regarded as harmless. And living plants are able to take up “stuffiness-inducing” CO2 through photosynthesis. Artificial plants inserted into non-living “substrate” lack the advantage of soil bacteria that can break down any biodegradable parts of the trapped particles, which includes most of the dangerous chemicals. And what about the environmental, social and economic impacts associated with the production, distribution and eventual disposal of artificial plants?