Nanotechnology has been offering various innovative products in biomedical, pharmaceutical, cosmetics, and semiconductor industries, to name a few. The apparel products have not escaped this trend, as seen in antimicrobial clothes and anti-odor socks. Unfortunately, these products that have been gaining popularity to hygiene-conscious consumers, could severely damage the agricultural lands, and consequently, harm the plants.
In his doctoral thesis at Chalmers University of Technology, Rickard Arvidsson has developed new methods to assess the risks associated with nanomaterials and applied them on some specific materials such as silver nanoparticles.
Among the metals that have antimicrobial property, also known as ‘oligodynamic effect’, silver is the most potent and least toxic to most animal cells. For this reason, the apparel industry has started incorporating them into the fabrics to knock out body odors caused by microbes during sweating.
The idea, undoubtedly, is brilliant enough that it has caught a lot of attention from the consumers. The downside to it, however, is that when these clothes are washed, the nanoparticles release silver ions that go with the laundry water. These ions that are now present in wastewaters are left unrecovered and remain in the sludge, which is routinely sent to agricultural land as fertilizers as it is full of phosphorus. Antimicrobial silver ions will then kill the microbes present in the soil that are responsible for plant growth.
Arvidsson explains, “Clothing is considered to be a large source of nanosilver emissions already. If silver usage in clothing continues to increase, the consequences for the environment can be major. For example, silver can accumulate in soil if sludge from waste water treatment plants is used as fertilizer, which can result in long-term damage to soil ecosystems.”
How much silver ions that may accrue in the sludge is dependent on the concentration of ions that the manufacturers use. The lowest concentration, 0.003 mg/kg, will have an unobservable effect on sludge and soils. “With the highest concentration, however,” says Arvidsson, “it would suffice if all of the city’s residents bought and used one silver nanoparticle-treated sock a year for the silver concentration in waste water treatment plant sludge to double.
“Using silver in clothing is a new technology, and it is still difficult to ascertain patterns for how much is being used. However, if the negative environmental impact is to be avoided, either the silver concentration in clothing or consumption of silver nanoparticle-treated clothing must be limited.”
Metal recovery using the cheap metal-selective resins that were recently featured in a previous article, could be a solution to removing the silver ions in wastewaters. How good the intentions could be in making these products, the manufacturers, and consumers as well, could not just let things be as they are and act only when things get worse. In defense of the nanomaterials, they do open new beginnings in search of solutions and improvements. Nevertheless, as the saying goes, “balance is the key to everything.”